Libros a Descargar Gratis

Cell Immortalization

Autor: Alvaro Macieira-coelho

Número de Páginas: 224

The problem of the long-term proliferation of cells is a seminal one. It has always been a hot subject in biology, a source of far-reaching hypotheses, even more so now when explanations for the mechanisms of cell prolifera tive mortality or immortality seem within our reach. A question which is still debated is whether an infinite division potential can be a normal trait or is always the result of modifications leading to abnormal cell growth and escape from homeostasis. In general, investigators have been advocates of one of the two extremes, universal limited or unlim ited normal proliferative potential. Since the long-term proliferative potential of cells concerns regulation of development, regeneration of tissues, and homeostatic control of cell growth, in brief survival of living organisms, and since the regulation of these processes is so different along the evolutionary scale, it is not surpris ing that there does not seem to be any universal trait. The question of whether cells are endowed with finite or infinite prolifera tive phenotypes has to be seen using the perspective of comparative biology.

Epstein Barr Virus Volume 2

Autor: Christian Münz

Número de Páginas: 493

Epstein Barr virus (EBV) was discovered as the first human tumor virus around 50 years ago. Since its discovery in Burkitt’s lymphoma it has been associated with various other malignancies, infectious mononucleosis and even autoimmune diseases. The two book volumes on EBV summarize the first 50 years of research on this tumor virus, starting with historical perspectives on discovery, oncogenicity and immune control, reviewing the role that the virus plays in the various associated diseases and concluding with a discussion on how the immune system keeps persistent EBV infection under control in healthy EBV carriers and can be used to treat EBV associated diseases. The respective 32 chapters are written by international experts from three continents for health care providers, biomedical researchers and patients that are affected by EBV. The assembled knowledge should help to understand EBV associated diseases better and to develop EBV specific vaccination in the near future.

Encyclopaedia Londinensis, Or, Universal Dictionary of Arts, Sciences, and Literature

Número de Páginas: 1076

Cellular Aging and Cell Death

Autor: Nikki J. Holbrook , George R. Martin , Richard A. Lockshin

Número de Páginas: 344

Cellular AGING AND CELL DEATH Edited by Nikki J. Holbrook, George R. Martin, and Richard A.Lockshin Cellular Aging and Cell Death provides a thorough understanding ofthe mechanisms responsible for cellular aging, covering the recentresearch on programmed cell death and senescence, and describingtheir role in the control of cell proliferation and the agingprocess. This one-of-a-kind book is the first to combine the twohottest research areas of cell biology into one comprehensivetext. Leading experts contribute to give readers an authoritativeoverview of the distinct fields of cellular aging and programmedcell death, as well as to demonstrate how both fields are criticalto understanding the aging process. They address the large andgrowing interest in apoptosis, especially with regard to themolecular signals that induce and regulate programmed cell death,and the role of apoptosis in a variety of age-associated diseasesand disabilities. Throughout the book, a strong emphasis is placedon the interrelationship of the molecular, cellular, andphysiological aspects of senescence. Individual chapters discuss such topics as the role and regulationof apoptosis in development, the potential...

Culture of Animal Cells

Autor: R. Ian Freshney

Número de Páginas: 766

This is the sixth edition of the leading text in the basic methodology of cell culture, worldwide. Rigorously revised, it features updates on specialized techniques in stem cell research and tissue engineering; updates on molecular hybridization, somatic cell fusion, hybridomas, and DNA transfer; new sections on vitrification and Organotypic Culture, and new chapters on epithelial, mesenchymal, neurectodermal, and hematopoietic cells; germs cells/stemcells/amniocytes; and non-mammalian/avian cells. It is written for graduate students, research and clinical scientists, and technicians and laboratory managers in cell and molecular biology labs and genetics labs. PowerPoint slides of the figures as well as other supplementary materials are available at a companion website: www.wiley.com/go/freshney/cellculture

Human Papilloma Viruses

Autor: D.j. Mccance

Número de Páginas: 212

This book describes up-to-date information on the pathogenesis and molecular biology of human papillomaviruses and describes the mechanistic role of the viruses in epithelial cancers. Included in the book are chapters on the epidemiology of human papillomaviruses, the factors that control replication and transcription and the viral proteins, which are involved in modulating the biology of the host cell leading to cancer. Details of the immune response to the viruses and potential vaccine strategies are discussed.

A Dictionnary of the English Language

Autor: Samuel Johnson

Número de Páginas: 498

A Dictionary of the English Language

Autor: Samuel Johnson

Número de Páginas: 1186

Medea

Autor: James J. Clauss , Sarah Iles Johnston

Número de Páginas: 391

From the dawn of European literature, the figure of Medea--best known as the helpmate of Jason and murderer of her own children--has inspired artists in all fields throughout all centuries. Euripides, Seneca, Corneille, Delacroix, Anouilh, Pasolini, Maria Callas, Martha Graham, Samuel Barber, and Diana Rigg are among the many who have given Medea life on stage, film, and canvas, through music and dance, from ancient Greek drama to Broadway. In seeking to understand the powerful hold Medea has had on our imaginations for nearly three millennia, a group of renowned scholars here examines the major representations of Medea in myth, art, and ancient and contemporary literature, as well as the philosophical, psychological, and cultural questions these portrayals raise. The result is a comprehensive and nuanced look at one of the most captivating mythic figures of all time. Unlike most mythic figures, whose attributes remain constant throughout mythology, Medea is continually changing in the wide variety of stories that circulated during antiquity. She appears as enchantress, helper-maiden, infanticide, fratricide, kidnapper, founder of cities, and foreigner. Not only does Medea's...

Total Freedom

Autor: Jiddu Krishnamurti

Número de Páginas: 385

Counted among his admirers are Jonas Salk, Aldous Huxley, David Hockney, and Van Morrison, along with countless other philosophers, artist, writers and students of the spiritual path. Now the trustees of Krishnamurti’s work have gathered his very best and most illuminating writings and talks to present in one volume the truly essential ideas of this great spiritual thinker.Total Freedom includes selections from Krishnamurti’s early works, his ‘Commentaries on Living’, and his discourses on life, the self, meditation, sex and love. These writings reveal Krishnamuri’s core teachings in their full eloquence and power: the nature of personal freedom; the mysteries of life and death; and the ‘pathless land’, the personal search for truth and peace. Warning readers away from blind obedience to creeds or teachers – including himself – Krishnamurti celebrated the individual quest for truth, and thus became on of the most influential guides for independent-minded seekers of the twentieth century – and beyond.

The Spanish Verb Finder

Autor: Kenneth P. Theda

Número de Páginas: 536

Approximately 2,243 irregular Spanish verbs, 34,550 irregular verb forms, 40,500 definitions including 4,850 regular Spanish verbs arranged alphabetically with definitions identified. This revised version also includes the identification of each irregular verb form by mode, person, and number.

Guide to Reporting Verbs

Autor: Grant Eckstein , Jacob D. Rawlins , Elizabeth Hanks

Número de Páginas: 403

Guide to Reporting Verbs is an accessible guide to citing sources in academic writing across the disciplines. The way writers introduce previous literature is essential to authorial voice. Specifically, the effective use of reporting verbs can highlight important details about the cited work while allowing writers to present themselves as experts in their field. This reference guide lists the most common reporting verbs across various disciplines in the hard and soft sciences and provides important information about how they can be used in academic writing. The book: lists prevalent reporting verbs across six disciplines: applied linguistics, biology, history, philosophy, political science, and physics provides information on authorial voice for each reporting verb highlights effective use of each reporting verb through inclusion of a definition, the lemma along with a few members of the word family, stance act(s), common contextual environments, example sentences from academic sources, the verb’s frequency in academic writing (based on two corpora, or databases), and the verb’s relative frequencies across disciplines offers practical tasks and exercises for students as online ...

A Dictionary of the English Language

Autor: Johnson

Número de Páginas: 742

Great Dictionary of Atomic Typographical Errors in English. Omission of a Single Letter – III.2 E-L

Autor: Cornéliu Tocan

Número de Páginas: 213

(20,602 lemmata – 27,086 Atomic Typographical Errors – 212 pages)

Xenotransplantation

Autor: Carolyn Wilson , Daniel R. Salomon

Número de Páginas: 261

Xenotransplantation could have an impact on at least three aspects of medicine. The first is as a means of overcoming a severe shortage of human donor organs for the treatment of organ failure. The second aspect relates to the possibility that a xenogeneic organ would not be susceptible to infection by a "human" virus and thus the xenograft might resist injury caused by such viruses. The third and, as of yet, unexplored aspect relates to a means of delivering genes for therapeutic purposes thus overcoming some of the limitations of "conventional" gene therapy.

The Homeric Hymn to Demeter

Autor: Helene P. Foley

Número de Páginas: 322

The Homeric Hymn to Demeter, composed in the late seventh or early sixth century B.C.E., is a key to understanding the psychological and religious world of ancient Greek women. The poem tells how Hades, lord of the underworld, abducted the goddess Persephone and how her grieving mother, Demeter, the goddess of grain, forced the gods to allow Persephone to return to her for part of each year. Helene Foley presents the Greek text and an annotated translation of this poem, together with selected essays that give the reader a rich understanding of the Hymn's structure and artistry, its role in the religious life of the ancient world, and its meaning for the modern world.

Biology of Aging

Autor: Alvaro Macieira-coelho

Número de Páginas: 198

The survival of the human species has improved significantly in modern times. During the last century, the mean survival of human populations in developed countries has increased more than during the preceding 5000 years. This improvement in survival was accompanied by an increase in the number of active years. In other words, the increase in mean life span was accompanied by an increase in health span. This is now accentuated by progress in medicine reducing the impact of physiologic events such as menopause and of patho logical processes such as atherosclerosis. Up to now,research on aging, whether theoretical or experimental, has not contributed to improvement in human survival. Actually, there is a striking contrast between these significant modifications in survival and the present knowledge of the mechanisms of human aging. Revealed by this state of affairs are the profound disagreements between gerontologists in regard to the way oflooking at the aging process. The definition of aging itself is difficult to begin with because of the variability of how it occurs in different organisms.

Our Indifferent Universe

Autor: Surazeus Astarius

Número de Páginas: 366

"Our Indifferent Universe" presents 903 poems written 2015-2017 by Surazeus that explore what it means to be a human in our indifferent universe.

A Text Book of British Poetry and Drama: 14th to 17th Centuries MJC Major Core Paper-English Semester-III-Under CBCS Paper-IV

Autor: Umar Farooque

Número de Páginas: 139

The history of British poetry and drama is a rich and dynamic journey that mirrors the evolution of society, culture, and thought in the United Kingdom. This textbook, A Textbook of British Poetry and Drama: 14th to 17th Centuries, aims to provide students and enthusiasts of English literature with a comprehensive understanding of the literary masterpieces that shaped the course of British literary tradition from the medieval period through the early modern era. Spanning from the 14th to the 17th centuries, this period encompasses the rise of the English Renaissance, the flourishing of poetic forms, and the development of drama that would lay the foundation for the works of Shakespeare and his contemporaries. It begins with the age of Geoffrey Chaucer, whose Canterbury Tales captured the spirit of medieval England, and follows the trajectory through the Elizabethan and Jacobean periods, where poetry and drama reached unparalleled heights of sophistication.

Freshney's Culture of Animal Cells

Autor: Amanda Capes-davis , R. Ian Freshney

Número de Páginas: 1756

FRESHNEY’S CULTURE OF ANIMAL CELLS THE NEW EDITION OF THE LEADING TEXT ON THE BASIC METHODOLOGY OF CELL CULTURE, FULLY UPDATED TO REFLECT NEW APPLICATIONS INCLUDING IPSCS, CRISPR, AND ORGAN-ON-CHIP TECHNOLOGIES Freshney’s Culture of Animal Cells is the most comprehensive and up-to-date resource on the principles, techniques, equipment, and applications in the field of cell and tissue culture. Explaining both how to do tissue culture and why a technique is done in a particular way, this classic text covers the biology of cultured cells, how to select media and substrates, regulatory requirements, laboratory protocols, aseptic technique, experimental manipulation of animal cells, and much more. The eighth edition contains extensively revised material that reflects the latest techniques and emerging applications in cell culture, such as the use of CRISPR/Cas9 for gene editing and the adoption of chemically defined conditions for stem cell culture. A brand-new chapter examines the origin and evolution of cell lines, joined by a dedicated chapter on irreproducible research, its causes, and the importance of reproducibility and good cell culture practice. Throughout the book,...

Viral Messenger RNA

Autor: Yechiel Becker

Número de Páginas: 386

The nucleotide sequence of the gene from which messenger RNA mole cules are transcribed is in a form that can be translated by cellular ribosomes into the amino acid sequence of a particular polypeptide, the product of the gene. The discovery of messenger RNA more than twenty years ago led to a series of studies on its organization and function in cells in the presence of infecting viruses. This volume is devoted to current studies in the field of cellular and viral messenger RNA. The studies presented provide an insight into molecular and genetic aspects of messenger RNA. Special attention was paid by the authors to the molecular organization of mRNA species, to the processing of mRNA molecules, and to the different strategies employed by DNA and RNA viruses in the synthesis of their mRNA. The ability of a virus to take over the protein-synthesizing mechanisms of an infected cell depends on its ability to produce mRNA molecules which can affect the host mRNA or utilize cellular components more efficiently. The differences between, and similarities of, the strategies of mRNA synthesis devised by various DNA and RNA viruses are described herein. This book should be of interest to...

Annual Report, Intramural Activities

Autor: National Cancer Institute (u.s.). Division Of Cancer Etiology

Número de Páginas: 584

Neoplastic Transformation in Human Cell Culture

Autor: Johng S. Rhim , Anatoly Dritschilo

Número de Páginas: 405

The role of carcinogenic agents in the deveolopment of human cancers is now being defined using a variety of human cells as experi mental model systems. A workshop on "neoplastic transformation in human cell systems in vitro: mechanisms of carcinogenesis" was held at the Georgetown University Medical Center, Washington, DC, on April 25-26, 1991. The aims of the workshop were to present the state-of-the art in the transformation of human cells in culture, as well as to provide insight into the molecular and cellular changes involved in the conver sion of normal cells to a neoplastic state of growth. The following topics were closely related to the theme of the workshops: 1. Derivation of in vitro model systems (epithelial, fibroblastic, and hematopoietic). 2. Factors modulating cellular transformation. 3. Usefulness of defined in vitro model systems for viral, chemical, and radiation carcinogenesis. 4. Multistep nature of human cell carcinogenesis. 5. Role of activated and suppressor oncogenes in neoplastic trans formation. The workshop was organized by J. S. Rhim and A. Dritschilo (cochairmen), G. Jay, J. little, M. McCormick, R Tennant, and R R Weischelbaum. There were 32...

Molecular Pathology of Early Cancer

Autor: Sudhir Srivastava , Donald Earl Henson , Adi F. Gazdar

Número de Páginas: 512

This book describes the principles and the application of the existing molecular methodology for the detection of early cancer. Discussion focuses on the molecular changes characterizing preneoplastic lesions; molecular targets for early detection; validation of molecular targets; and new diagnostic technology for early detection. The advantages of molecular detection over current methods are examined, as well as the importance of identifying and characterizing preneoplastic lesions. In addition to the uses of highly specific molecular probes to detect early cancer, this book demonstrates the many ways in which molecular markers serve oncology. While meeting pressing needs in the practice of medicine, molecular detection of early cancer scientifically necessitates a confrontation with the biology of cancer, such as the genetic determinants of progression, regression, dormancy, and invasion. This work not only discusses the diagnostic value of these molecular methods but views their practical benefits against a background of conventional morphology.

Biotherapeutics

Autor: Lyn H Jones , Andrew J Mcknight

Número de Páginas: 331

This book illustrates the successful partnership of chemistry and biology to advance successful biotherapeutic modalities. Molecular design to create function is common to both chemical and molecular biology, and this text highlights recent developments from these disciplines that have delivered drugs, clinical candidates or significantly advanced biotherapeutic approaches. Biotherapeutics are often considered to be beyond the reach of the medicinal chemist, but this book demonstrates that chemistry has an essential role in the future success of this area, by explaining and describing the chemical biology technologies that underpin specific therapeutic advances and demonstrating the unique value of molecular design and understanding. Covering topics such as selective protein modification, immunopharmacotherapy, chemically programmed vaccinations, nanobodies and antibodies, this book provides essential reading for medicinal and pharmaceutical chemists working in both industry and academia.

A Ruling Power for the Crowns and the Crescent; or, Pass to the Camp of a Universal Empire. [Signed, al-Ḥājin.]

Número de Páginas: 52

Planning Power

Autor: Ambe Njoh

Número de Páginas: 513

With a multidisciplinary perspective, Planning Power examines British and French colonial town and country planning efforts in Africa. Drawing out similarities in the colonial administrative and economic strategies of the two powers, rather than emphasizing the differences, the book offers an unusually nuanced view of African planning systems in a time of upheaval and political change. In showing how the colonial authorities sought to gain political and social control in Africa, it can be seen how their will to exert political power influenced every area of planning practice during this era. This unique comparative analysis of British and French colonial town planning – covering the entire sub-Saharan African region – takes theories from a wide range of disciplines, including political science, history, urban and regional planning, economics and geography to paint a comprehensive picture of the subject. Written by a prolific researcher and writer in the political-economy of urban and regional planning in Africa, Planning Power is valuable reading for students and academics in a range of disciplines.

Chattering Courtesans and Other Sardonic Sketches

Autor: Lucian

Número de Páginas: 433

Described by a later Greek historian as "a man seriously committed to raising a laugh", Lucian exulted in the exposure of absurdity and the puncturing of pretension, and was capable of finding a comic angle on almost any subject. In this selection we see him conversing with his literary enemies, railing against hypocrisy and the vanity of human wealth and power, and taking a wry look at the power of lust and the unsatisfactory nature of deviant sexual practices.

Letters Unsent

Autor: Joseph A. Demerchant

Número de Páginas: 106

I’ve led my life, frankly given to chance; I learned of love, yet what of romance? As long as human beings have been writing poetry, it’s been our favorite vehicle to struggle with love and loss—and over the course of a lifetime you tend to accumulate a fair bit of both. Those hard-won lessons and still-unfulfilled yearnings grace the pages of Letters Unsent. Painful vulnerability meets gentle musicality: Joseph A. DeMerchant recalls long-ago romances and faces down present day loneliness in classic rhyming verse. Letters Unsent is the accumulated musings of the last sixty years, thick with joy and sorrow and undergirded with a love of poetry as steady and constant as a heartbeat.

New and Evolving Infections of the 21st Century

Autor: I.w. Fong , Kenneth Alibek

Número de Páginas: 380

The past decade has been highlighted by numerous advances in research of medical scientific knowledge, medical technology and the biological and diagnostic techniques-but somewhat less dramatic changes or improvement in management of medical conditions. This volume in the Emerging Infectious Disease of the 21st century series, addresses some of the emerging issues and controversies in Infectious Diseases. The author has chosen these topics for review based on questions and contentions raised by medical residents, internists, emergency physicians, clinical infectious disease specialists and family physicians. This volume will provide guidance and answers to frequently asked questions in infectious diseases to the researcher, clinician, generalists, specialists and trainees in these areas; thus, facilitating improved patient care, prudent and cost effective management and investigation of these disorders. This volume reviews the research, diagnosis, and treatment of some common infections facing researchers, clinicians and family physicians such as sinusitis, otitis media and asymptomatic bacteriuria. Recent studies and surveys have shown that these conditions are often over...

Building Vocabulary: Level 11 Kit

Autor: Timothy Rasinski, Nancy Padak, Rick M. Newton, And Evangeline Newton

Número de Páginas: 298

Building Vocabulary from Word Roots provides a systematic approach to teaching vocabulary using Greek and Latin prefixes, bases, and suffixes. Over 90% of English words of two or more syllables are of Greek or Latin origin. Instead of learning words and definitions in isolation, students learn key roots and strategies for deciphering words and their meanings across all content areas. Building Vocabulary from Word Roots: Level 11 kit includes: Teacher's Guide; Student Guided Practice Book (Each kit includes a single copy; additional copies may be ordered in quantities of 10 or more); Assessments to support data-driven instruction; and Digital resources including modeled lessons, 50 bonus activities, and more.

Yeast as a Tool in Cancer Research

Autor: John L Nitiss , Joseph Heitman

Número de Páginas: 441

Leland H. Hartwell Director, Fred Hutchinson Cancer Research Center, Nobel Laureate for Medicine, 2001 Yeast has proved to be the most useful single-celled organism for studying the fundamental aspects of cell biology. Resources are now available for yeast that greatly simplify and empower new investigations, like the presence of strains with each gene deleted, each protein tagged and databases on protein–protein interactions, gene regulation, and subcellular protein location. A powerful combination of genetics, cell biology, and biochemistry employed by thousands of yeast researchers has unraveled the complexities of numerous cellular processes from mitosis to secretion and even uncovered new insights into prion diseases and the role of prions in normal biology. These insights have proven, time and again, to foretell the roles of proteins and pathways in human cells. The collection of articles in this volume explores the use of yeast in pathway analysis and drug discovery. Yeast has, of course, supplied mankind’s most ubiquitous drug for thousands of years. In one aspect, the role of yeast in drug discovery is much like the role of yeast in other areas of biology. Yeast...

The Sword and the Pen

Autor: Konrad Eisenbichler

Número de Páginas: 437

In The Sword and the Pen: Women, Politics, and Poetry in Sixteenth-Century Siena, Konrad Eisenbichler analyzes the work of Sienese women poets, in particular, Aurelia Petrucci, Laudomia Forteguerri, and Virginia Salvi, during the first half of the sixteenth century up to the fall of Siena in 1555. Eisenbichler sets forth a complex and original interpretation of the experiences of these three educated noblewomen and their contributions to contemporary culture in Siena by looking at the emergence of a new lyric tradition and the sonnets they exchanged among themselves and with their male contemporaries. Through the analysis of their poems and various book dedications to them, Eisenbichler reveals the intersection of poetry, politics, and sexuality, as well as the gendered dialogue that characterized Siena's literary environment during the late Renaissance. Eisenbichler also examines other little-known women poets and their relationship to the cultural environment of Siena, underlining the exceptional role of the city of Siena as the most important center of women's writing in the first half of the sixteenth century in Italy, and probably in all of Europe. This innovative...

A Few Notes on Sir Charles Lyell's "Antiquity of Man" and on Prof. Huxley's "Evidence as to Man's Place in Nature"

Autor: John Crawfurd

Número de Páginas: 262

Becoming Achilles

Autor: Richard Holway

Número de Páginas: 271

Viewing the Iliad and myth through the lens of modern psychology, in Becoming Achilles: Child-Sacrifice, War, and Misrule in the lliad and Beyond Richard Holway shows how the epic underwrites individual and communal catharsis and denial.Sacrificial childrearing generates but also threatens agonistic, glory-seeking ancient Greek cultures. Not only aggression but knowledge of sacrificial parenting must be purged. Just as Zeus contrives to have threats to his regime play out harmlessly (to him) in the mortal realm, so the Iliad dramatizes threats to Archaic and later Greek cultures in the safe arena of poetic performance. The epic represents in displaced form destructive mother-son and father-daughter liaisons and resulting strifewithin and between generations. Holway calls into question the Iliad's (and many scholars') presentation of Achilles as a hero who speaks truth to power, learns through suffering, and exemplifies kingly virtues that Agamemnon lacks. So too the Iliad's cathartic process, whether conceived as purging innate aggression or arriving at moral clarity. Instead, Holway argues, Achilles (and Socrates) try to prove they are unlike needy, defenseless children, who fear ...

Cell Growth, Differentiation and Senescence

Autor: George P. Studzinski

Número de Páginas: 334

There are three main themes running through this volume. First, basic methods for measurement of cell proliferation are introduced and explained with reference to various systems, primarily in vitro, but in vivo procedures are also illustrated. The second theme is growth signalling, and is exemplified by methods for the analysis of transduction pathways for growth, beginning at the cell membrane and leading to the cell nucleus. The last theme presented here is growth cessation, illustrated by several systems for induction of cell differentiation, and of cell senescence. The emphasis throughout the book is on human cell systems, making it particularly relevant to scientists interested in human disease, especially cancer. Importantly, well proved methods for studying cell growth are supplemented by some novel approaches, e.g., studies of cell cycle checkpoints, cell spheroids, and nuclear architecture. Only two chapters have been retained, in an updated form from Cell Growth and Apoptosis, the predecessor volume. The book is written by a team of scientists highly experienced in procedures they describe, and offer details and hints found valuable in their own laboratories; thus,...

Intimate Depictions

Autor: Walt Mcconville

Número de Páginas: 198

A lifelong love of poetry enlivens this sumptuous banquet of "Rhymes and Reasons" dating from 1927 to 2001, with nostalgic references to memorable Canadian & world events along the way. A hip trip!

Rediscovering Political Friendship

Autor: Paul W. Ludwig

Número de Páginas: 365

Applies Aristotle's argument - that citizenship is like friendship - to the liberal and democratic societies of the present day.