Osservando il cielo, può capitare di vedere strane formazioni nuvolose con un buco al centro. Sono le cosiddette hole punch clouds, oggetto di studio sin dagli anni Quaranta e fonte di leggende per chi vi leggeva un segnale extraterrestre. Poi, un anno fa, una ricerca ha svelato il mistero: sono gli aerei che, volando attraverso le nubi, le scavano letteralmente. E ora sappiamo anche che da quei tunnel possono scatenarsi tempeste di pioggia e neve. Come e perché lo spiega su Science un gruppo di ricerca coordinato da Andrew Heymsfield del National Center for Atmospheric Research (Usa), che ha approfondito il fenomeno svelandone ogni dettaglio.
Quando un aereo passa attraverso una nuvola modifica la pressione e abbassa la temperatura dell’aria anche di 20-30°C. In questo modo, promuove la condensazione delle gocce d’acqua in cristalli di ghiaccio, fenomeno che dà luogo ai caratteristici fori.
Man mano, i cristalli attirano altra gocce d’acqua e i buchi si ingrandiscono sempre più: è un processo che può durare oltre un’ora arrivando a creare tunnel lunghi anche cento chilometri. Quando infine i cristalli di ghiaccio diventano troppo pesanti, precipitano sotto forma di pioggia o neve.
Heymsfield e colleghi sono giunti a queste conclusioni analizzando 20 immagini satellitari di hole punch clouds raccolte il 29 gennaio del 2007 nei cieli del Texas. Spulciando negli archivi della U.S. Federal Aviation Administration, i ricercatori hanno quindi ricostruito il traffico aereo della giornata e, usando un modello meteorologico per studiare formazione e l’evoluzione delle nubi, hanno scoperto che molti degli aerei in volo quel giorno avrebbero potuto bucare le nuvole scatenando le precipitazioni poi verificatesi.
Le conseguenze, a quanto pare, sono solo locali, perché il fenomeno non sembra influenzare il clima globale; come è noto, però, può aumentare le precipitazione sugli aeroporti in particolari condizioni meteorologiche.
In periplul sau prin vechiul imperiu incas, conchistadorul si cronicarul Pedro Cieza de Leon descopera in spatiul sacru din cetatea Tihuanaco, monumente, temple si piramide impresionante. Tihuanaco e situat la sud-est de lacul Titicaca, la 3870 metri altitudine, in jurul caruia se intind pajisti populate de lame. La estul sitului se inalta un lant muntos, cel mai semet si impozant varf fiind Illimani, extrem de fertil, venerat si in zilele noastre. La o distanta relativ apropiata se afla vaile tropicale (yunga) unde se cultiva, printre altele, coca.
Cetatea Tihuanaco ce se intinde pe o suprafata de 10 kilometri patrati, avea in perioada sa de inflorire intre 30 si 60 de mii de locuitori devenind un mare centru ceremonial. O incinta sacra din piatra – Kalasasaya – in care se afla monoliti dispusi la intervale regulate, delimiteaza un spatiu sacru, prevazut cu numeroase temple. Remarcabile sunt piramida Akapana, monolitii Ponce si Bennet (dupa numele celor care i-au descoperit) si celebra Poarta a Soarelui.
Akapana e o piramida cu 7 terase, in fiecare unghi regasindu-se un monolit construit in acelasi stil cu cei din Kalasasaya. In varful piramidei se afla o curte in jurul careia sunt dispuse mici locuinte despre a caror utilizare nu se stie nimic. Mai jos de Akapana se afla un templu semi-subteran, ce contrasteaza cu piramida. In zidurile sale se afla inserate capete antropomorfe cu ochi patrati, de o expresivitate inspaimantatoare. Caracteristica cea mai remarcabila a piramidei o constituie sistemul de canalizare care traverseaza interiorul acesteia, prin care se scurgea apa de pe o terasa pe alta producand un efect de fantana. In cetate se afla un al doilea centru situat la o distanta de 1 kilometru, denumit Puma Punku. Aici se regasesc aceleasi elemente arhitecturale si aceeasi calitate a taierii blocurilor de piatra.
Poarta Soarelui e, incontestabil, monumentul cel mai impresionant din Tihuanaco. E taiata intr-un singur bloc de piatra, in varful caruia se afla un lintou decorat cu sculpturi in jurul unui personaj central care tine in fiecare mana un sceptru. Efigia zeului e inconjurata de o multime de „servitori” inaripati, pe jumatate inclinati spre el. Aceasta iconografie a fost comparata cu alte reprezentari arheologice dupa ce s-a cautat in documentele istorice si etnologice corespondentele stilistice si simbolice. Au fost astfel identificati zeul central, Tunupa, confundat cu Viracocha, varianta incasa.
Printre elementele semnificative se pot cita sceptrul care se termina printr-un sarpe bicefal, coroana si colierul, care reprezinta razele Soarelui. Legenda spune ca primii oameni traiau intr-o lume a tenebrelor pana cand marele creator Kon Tici Viracocha a zamislit Soarele si Ziua, Luna si stelele. Apoi a transformat oamenii in pietre pentru a-i pedepsi pentru faptul ca l-au batjocorit. Din aceste pietre a creat, insufletindu-le, o noua umanitate compusa din mai multe populatii. Imaginea acestui zeu a fost modificata de incasi care au incercat sa legitimeze originea lor solara facand apel la credintele seculare ale popoarelor de pe inaltele platouri.
While many people may assume the answer to that provocative and unsettling question is zero, the creators of a new Web site want to demonstrate how forced labor, especially overseas, is tantamount to slavery.
A nonprofit group, with funding from the State Department, will unveil the new site, www.slaveryfootprint.org, on Thursday in an effort to show that forced laborers are tied to all kinds of everyday products, from electronics and jewelry to the shirt on your back.
Ideally, they hope to get consumers engaged enough in the issue to do something about it, primarily hoping people demand that companies carefully audit supply chains to ensure, as best as they can determine, that no “slave labor” was used to manufacture its products.
“What we are trying to do is make it so it’s not just someone else’s business, it’s everyone’s business,” said Luis CdeBaca, ambassador at large for the State Department’s Office to Monitor and Combat Trafficking in Persons. “There’s a horror about it when they figure out what is going on.”
The slavery footprint is a twist on the more commonly known carbon footprint, and the new site tries to point out areas of a consumer’s life where the organization believes slavery is most likely used to manufacture products.
Slavery Footprint defines a slave as “anyone who is forced to work without pay, being economically exploited and is unable to walk away.” The State Department estimates that there are 27 million slaves globally. The Web site steers users through a set of prompts, where they can define where they live, the type of dwelling they live in, how many children they have, how many cars they use, what they eat and what types of things they have bought.
Sprinkled throughout are grim notations about slave labor and human trafficking, like this one: “In China, soccer ball manufacturers work up to 21 hours in a day, for a month straight. Even the toughest American coaches wouldn’t ask that from their squads.”
Or this claim: “Every day tens of thousands of American women buy makeup. Every day tens of thousands of Indian children mine mica, which is the little sparkles in the makeup.”
The site also asks users how many times they have paid for sex. While there is no way to answer, the site notes that people who pay for sex contribute to the demand for sexual trafficking.
Although the Web site had a few kinks before its official introduction, it informed me that I had 76 slaves working on my behalf, well above the average of 55.
The site was created by the Fair Trade Fund, a California-based nonprofit group that uses media to promote advocacy on issues, particularly human slavery. Among its projects are “Call + Response,” a documentary on the slave trade, and chainstorereaction.com, a Web site that encourages consumers to send electronic letters to companies challenging them to define their policies on human trafficking.
The companies’ responses, or lack thereof, are posted on the Web site.
Based on the movie and the Web site, the State Department sought out the Fair Trade Fund to create the Slavery Footprint site and provided it with a $200,000 grant.
Justin Dillon, 42, the organization’s chief executive, said the Slavery Footprint site did not make specific companies its targets. Instead, it shows consumers which products they use are most likely to involve forced labor.
He said a mobile application would allow consumers to find information on products at the point of purchase, and send companies electronic letters asking about their policies on slave labor. Those letters will also be sent to all of the consumers’ Facebook friends, in the hopes of applying consumer pressure for changes in practices. “Really the goal is to amplify the conversation between the consumer and the producer,” Mr. Dillon said. “Our torches and pitchforks are out for the slave traders, not the multinationals.”
Ideally, he said companies would hire third-party auditors to determine if their supply chains were employing slave labor.
The Slavery Footprint application is being started nearly a year after California passed a law that requires companies with global sales in excess of $100 million who do business in the state to disclose what efforts they have made to eliminate forced labor from their supply chains.
Some business groups opposed the measure, saying it unfairly tagged companies for “failing” on an issue they were powerless to change.
On Wednesday, a spokesman for the United States Chamber of Commerce said he would not comment because officials at the organization had not yet seen the Slavery Footprint Web site. Mr. CdeBaca said the new grant recognized the need to encourage consumers to put pressure on the marketplace.
“Without some kind of demand, the traffickers wouldn’t be rushing to meet that through coercion and threats,” he said.
Casa de moda Hugo Boss a fabricat uniforme pentru membrii Partidului National Socialist, lucru care a salvat compania de la faliment, potrivit Realitatea TV.
Companiile germane Hugo Boss si BMW isi cer scuze pentru ca au colaborat cu nazistii. Supranumit "croitorul lui Hitler", patronul Hugo Boss, Ferdinand, a folosit muncitori cu forta, in timpul celui de-al Doilea Razboi Mondial. Casa de moda a fabricat uniforme pentru membrii Partidului National Socialist, lucru care a salvat compania de la faliment.
Cat priveste producatorul BMW, acesta a utilizat 50.000 muncitori, cu forta. Cateva mii dintre acestia proveneau din lagarele de concentrare. Pana acum, proprietarul BMW a fost discret in privinta acestui subiect, insa acum a decis sa-si infrunte trecutul, scrie presa germana.
A new kind of sensor could warn emergency workers when carbon filters in the respirators they wear to avoid inhaling toxic fumes have become dangerously saturated.
In a recent issue of the journal Advanced Materials, a team of researchers from the University of California, San Diego and Tyco Electronics describe how they made the carbon nanostructures and demonstrate their potential use as microsensors for volatile organic compounds.
IMAGE: Porous photonic crystal microsensor particles on the ends of optical fibers can detect organic pollutants.
First responders protect themselves from such vapors, whose composition is often unknown, by breathing through a canister filled with activated charcoal – a gas mask. Airborne toxins stick to the carbon in the filter, trapping the dangerous materials.
As the filters become saturated, chemicals will begin to pass through. The respirator can then do more harm than good by providing an illusion of safety. But there is no easy way to determine when the filter is spent. Current safety protocols base the timing of filter changes on how long the user has worn the mask.
"The new sensors would provide a more accurate reading of how much material the carbon in the filters has actually absorbed," said team leader Michael Sailor, professor of chemistry and biochemistry and bioengineering at UC San Diego. "Because these carbon nanofibers have the same chemical properties as the activated charcoal used in respirators, they have a similar ability to absorb organic pollutants."
Sailor's team assembled the nanofibers into repeating structures called photonic crystals that reflect specific wavelengths, or colors, of light. The wing scales of the Morpho butterfly, which give the insect its brilliant iridescent coloration, are natural examples of this kind of structure.
Caption: Repeating bands of greater density give this bundle of carbon nanofiber photonic crystals a characteristic color. When the porous fibers absorb chemicals, they change color, making the material a sensitive optical sensor for chemical vapors.
Credit: Timothy Kelly, UCSD Chemistry and Biochemistry
The sensors are an iridescent color too, rather than black like ordinary carbon. That color changes when the fibers absorb toxins – a visible indication of their capacity for absorbing additional chemicals.
The agency that certifies respirators in the U.S., the National Institute of Occupational Safety and Health, has long sought such a sensor but the design requirements for a tiny, sensitive, inexpensive device that requires little power, have proved difficult to meet.
The materials that the team fabricated are very thin – less than half the width of a human hair. Sailor's group has previously placed similar photonic sensors on the tips of optical fibers less than a millimeter across and shown that they can be inserted into respirator cartridges. And the crystals are sensitive enough to detect chemicals such as toluene at concentrations as low as one part per million.
Per le rivolte vale una regola comune a pressoché tutte le attività umane: il tempo necessario per portare a conclusione un’operazione diminuisce man mano che questa viene ripetuta, seguendo con una buona approssimazione una “legge di potenza”. A trovare la relazione matematica è stato un gruppo di fisici dell’Università di Miami, guidato da Neil Johnson. In tempi caldi come quelli che stiamo vivendo, la possibilità di comprendere le dinamiche delle sommosse e degli episodi di violenza fin dai primissimi scontri sta a cuore a diversi governi, e sul tema si sono cimentati molti gruppi di ricerca in tutto il mondo (vedi Galileo, La legge matematica della guerra). Ultimo quello di Johnson, che ha pubblicato i suoi risultati su Science.
Secondo gli studiosi, le tempistiche degli attacchi più cruenti e delle controffensive tra due opposte fazioni seguono uno schema ben preciso, che può essere previsto a tavolino, a partire dal tempo intercorso tra i primi due attacchi. I ricercatori si sono basati sui dati storici degli eventi avvenuti durante le guerre in Iraq e in Afghanistan e sull'analisi di 3.143 atti terroristici avvenuti tra il 1968 e il 2008. Analizzando l’intensificarsi degli atti di violenza, il gruppo ha constatato che per le operazioni di rivolta è facile osservare un aumento delle perdite di vite umane man mano che le due forze in opposizione si scontrano e affilano le proprie armi.
“Quello che ci dicono i dati – ha spiegato Johnson – è che ci troviamo di fronte a una situazione simile a quella nota in biologia evolutiva come ‘della Regina Rossa’”. Secondo questa ipotesi, ispirata dal secondo capitolo di Alice nel Paese delle Meraviglie, per quanto una fazione si sforzi di avere la meglio sull’altra, l’abilità di reagire dell’avversario porta tendenzialmente a un nulla di fatto. Così, parallelamente all’aumentare delle capacità dei ribelli nell’organizzare azioni violente, si osserva una simile abilità delle forze contrarie a prevenire e ridurre l’esito di tali azioni.
Per gli autori, la scoperta dovrebbe permettere di prevedere come evolveranno le rivolte sulla base del tempo intercorso tra i primi due attacchi. La relazione, infatti, sembra essere immutabile: “È un po’ come per il traffico nelle ore di punta - ha spiegato Johnson - per la maggior parte delle persone c’è un solo orario possibile a cui accompagnare i figli a scuola e andare al lavoro”. Sulla carta i conti tornano, e lo studio potrebbe servire alle organizzazioni internazionali come strumento di previsione dei conflitti armati.
One theory of the origin of AIDS is that it developed from contaminated vaccines used in the world's first mass immunisation for polio. There are a number of reasons why this theory is plausible enough to be worthy of further investigation.
The location coincides dramatically. The earliest known cases of AIDS occurred in central Africa, in the same regions where Koprowski's polio vaccine was given to over a million people in 1957-1960.
The timing coincides. There is no documented case of HIV infection or AIDS before 1959. Centuries of the slave trade and European exploitation of Africa exposed Africans and others to all other diseases then known; it is implausible that HIV could have been present and spreading in Africa without being recognised.
Polio vaccines are grown (cultured) on monkey kidneys which could have been contaminated by SIVs. Polio vaccines could not be screened for SIV contamination before 1985.
Another monkey virus, SV-40, is known to have been passed to humans through polio vaccines. A specific pool of Koprowski's vaccine was later shown to have been contaminated by an unknown virus.
In order for a virus to infect a different species, it is helpful to reduce the resistance of the new host's immune system. Koprowski's polio vaccine was given to many children less than one month old, before their immune systems were fully developed. Indeed, in one trial, infants were given 15 times the standard dose in order to ensure effective immunisation.
If this theory is correct, it has serious ethical, health and policy implications. In particular, it points to the danger of interspecies transfer of material through vaccinations, organ transplants, etc., which could lead to new variants of AIDS as well as other new diseases. As well, studying the theory may lead to insights about responding to AIDS and preventing new diseases.
On several occasions, critics have claimed that the theory has been refuted. The Wistar Committee in 1992 said the death of a British sailor in 1959, whose tissues later tested positive for HIV, made the theory implausible. However, several years later, more sensitive tests showed no HIV in the tissues.
In 2001, reports were published that polio vaccine samples held in Philadelphia from the 1950s showed no immunodeficiency viruses. This was trumpeted as a refutation of the theory. Edward Hooper later produced evidence that US-produced vaccines had been amplified in Africa using chimpanzees as a substrate, thus showing the theory could be correct.
Scientists have spent a lot of effort trying to refute the polio-vaccine theory of the origin of AIDS, but very little trying to refute the conventional view, that blood from an SIV-infected chimpanzee got into humans via hunting or eating. There is very little direct evidence to support the conventional view, which explains neither the timing nor the location of the origin.
Scientific journals have been reluctant to publish articles about the polio-vaccine theory. For example,Naturehas received substantial submissions about the theory from at least six scholars but has not published any of them. Opponents of the theory have used defamation threats and legal actions to discourage publication. The result is that editorial prerogative and legal action have given the false impression that critics of the theory have been unanswered.
To help rectify this situation, key documents presenting the theory and commenting on it are provided here. Also given is a list of publications about the theory. This material is provided byBrian Martinwho as a social scientist has been following the origins debate since 1991. It is part of a page onsuppression of dissent. Comments and additional contributions are welcome.
Some key publications about the theory (in reverse chronological order)
BOOKS
Edward Hooper,The River: A Journey Back to the Source of HIV and AIDS(Harmondsworth: Penguin; Boston: Little, Brown, 1999; revised edition, Penguin, 2000). This is an enormous but highly readable scientific blockbuster, providing the most detailed examination of the polio vaccine theory yet available, including many new findings. It has generated widespread discussion and debate and has established the polio-vaccine theory of the origin of AIDS as by far the strongest contender to the cut-hunter orthodoxy.
Omar Bagasra,HIV and Molecular Immunity: Prospects for the AIDS Vaccine(Natick, MA: Biotechniques Books, 1999). This technical scientific book presents a new theory of molecular immunity for the origin and history of HIV-1, which, it is argued, most likely derived from polio vaccinations in Africa. Kiley R. Prillimanreviews the bookin the prestigious journalCell.Julian Cribb has providedinsightful comments on the bookfor nonspecialists. The author, Omar Bagasra, can be contacted atomarb@sc.rr.com. The book is available fromEaton Publishing, 154 East Central Street, Natick MA 01760, USA, phone 508-653 6272, fax 508-653 2706.
Julian Cribb,The White Death(Sydney: Angus & Robertson, 1996). An engaging book focussing on both the polio-vaccine-AIDS theory and its reception by the scientific community.Full text available.
New material about the origin of AIDSpublished in November 2005 inNarrow Roads of Gene Land: The Collected Papers of W. D. Hamilton, Volume 3: Last Words,edited by Mark Ridley, Oxford University Press.
Stanley A. Plotkin,"Chimpanzees and journalists"(editorial),Vaccine,Vol. 22, 2004, pp. 1829-1830. Introduction to Osterrieth's article.
Paul Osterrieth,"Oral polio vaccine: fact versus fiction",Vaccine,Vol. 22, 2004, pp. 1831-1835. Denial of Hooper's claims about production of polio vaccine in Africa.
Lincei meeting papers Origin of HIV and Emerging Persistent Viruses, Rome, 28-29 September 2001 Published asAtti dei Convegni Lincei,2003, Vol. 187, ISBN 88-218-0885-8
Edward Hooper,"Dephlogistication, Imperial Display, Apes, Angels, and the Return of Monsieur Émile Zola", pp. 27-230. This massive paper is a response to criticisms ofThe River,plus new evidence.
2.The Marx/Drucker theoryof iatrogenic spread through unsterile needles, and the recent intervention by Professor David Gisselquist, who claims that most HIV infections in Africa are caused through this same route
Royal Society Discussion Meeting(and subsequent events) Origins of HIV and the AIDS Epidemic, London, 11-12 September 2000 Papers, press releases, media stories and responses
Blaine F. Elswood and Raphael B. Stricker,"Polio vaccines and the origins of AIDS",Medical Hypotheses, vol. 42, 1994, pp. 347-354 and Correspondence, vol. 44, 1995, p. 226. This is the first major paper in the scientific literature presenting the theory. Blaine Elswood can be contacted atBlaine.Elswood@snow.edu.
W. D. Hamilton,unpublished letter toScience, 27 January 1994. Hamilton attempted to publish a letter inScienceresponding to Koprowski's 1992 letter. Included here is both the letter itself and Hamilton's correspondence withScience.
Rolling Stone,"'Origin of AIDS' update", 9 December 1993, p. 39. Publication of this "Clarification" was part of the settlement of Koprowski's defamation action againstRolling Stoneand Tom Curtis.
B. F. Elswood and R. B. Stricker,"Polio vaccines and the origin of AIDS",Research in Virology, vol. 144, 1993, pp. 175-177. A letter to the editor presenting the theory plus a critical reply from the editorial board. Blaine Elswood can be contacted atBlaine.Elswood@snow.edu.
Tom Curtis,unpublished letter toScience, 30 September 1992. This letter rejected bySciencewas a response to Koprowski's letter inScienceattacking the polio-vaccine theory.
Claudio Basilico et al.,Report from the AIDS/Poliovirus Advisory Committee, 18 September 1992. Stimulated by Curtis's article inRolling Stone, the Wistar Institute set up an independent committee to examine the theory. This is its report, which was never formally published.
Hilary Koprowski,"AIDS and the polio vaccine"(letter),Science, vol. 257, 21 August 1992, pp. 1024, 1026-1027; correction, 11 September 1992, p. 1463. This is a reply to Tom Curtis's article inRolling Stoneand is one of the few published critiques of the theory.
Tom Curtis,"The origin of AIDS",Rolling Stone, Issue 626, 19 March 1992, pp. 54-59, 61, 106, 108. This article gave the theory its first wide visibility. Based on a version of the theory developed independently by Blaine Elswood, it was investigated and reported on by Tom Curtis. Tom Curtis can be contacted attcurtis@utmb.edu.
Louis Pascal,"What happens when science goes bad", Science and Technology Analysis Working Paper #9, University of Wollongong, December 1991. This was the first major published account of the theory. Hard copies are available free from Brian Martin,bmartin@uow.edu.au, on request. Please include your postal address.
O echipa de cercetatori francezi de la Institutul Pasteur a demonstrat faptul ca numeroase zone ale creierului sunt capabile sa produca noi neuroni cu ajutorul celulelor gliale. Celulele gliale au fost descoperite in 1891 de medicul spaniol Santiago Ramon Y Cajal. Acest cercetator deosebit de prolific a pus in evidenta caracterul celular al neuronilor. Studiile sale, recompensate cu Premiul Nobel pentru Medicina in 1906, au scos in evidenta existenta celulelor gliale, de 9 ori mai numeroase decat neuronii, care joaca un rol important in transmisia influxului nervos si care, contrar neuronilor, sunt capabile sa se reproduca. Proportia dintre celulele gliale si neuroni a dat nastere, in urma unei erori jurnalistice, ideii care s-a infiltrat in opinia publica, conform careia oamenii folosesc doar 10% din creier.
Functiile celulelor gliale sunt putin cunoscute. Li se atribuie rolul organizarii conexiunilor neuronale, adica, facultatii neuronilor de a produce noi sinapse. In acest sens s-a demonstrat recent ca practica intensiva a jocului la micile mamifere duce la o crestere a numarului celulelor gliale in raport cu subiectii care nu practica acest „sport”. Cat priveste fiintele umane, e de semnalat faptul ca creierul lui Einstein avea un numar anormal de mare de celule gliale la nivelul lobilor parietali.
Prabusirea unei dogme
Cercetatorii (neurobiologi) erau convinsi ca neuronii creierului uman sunt capabili sa se multiplice. Pana in 2003, cand o echipa de cercetatori francezi a descoperit faptul ca unele categorii de celule gliale se puteau transforma in neuroni capabili sa se insereze in tesutul neuronal existent. In 2004, aceeasi echipa, in colaborare cu specialisti germani, a demonstrat ca o molecula secretata de bulbul olfactiv (tenascina) are facultatea de a atrage neuronii imaturi, care se transforma in veritabili neuroni.
Dispozitive de regenerare
O noua etapa in descifrarea activitatii cerebrale a fost astfel parcursa. Aceeasi echipa de cercetatori a mai demonstrat faptul ca celulele suse (stem) gliale se repartizeaza nu doar in zona de formare ci si de-a lungul unui tunel prin care migreaza noii neuroni si in bulbul olfactiv. Demonstratia a fost facuta utilizandu-se un marcator fluorescent vehiculat de un vector viral capabil sa vizeze celulele gliale. Transformarea acestora in neuroni era intensificata in urma unei leziuni care ducea la pierderea simturilor olfactive, o dovada clara a capacitatii de autoreparare a creierului. Deturnandu-se neuronii nou formati din zona lor germinativa spre regiunile lezate, constituie o strategie terapeutica extraordinara si o speranta pentru tratarea unor patologii neurodegenerative ale sistemului nervos central.
Brate miscate prin puterea gandului
In urma realizarii unei conexiuni artificiale intre creier si mana, o maimuta macac afectata de o paralizie temporara a unui brat, a reusit intr-un timp foarte scurt sa-si reia miscarea bratului. Pentru a conferi mobilitate unui brat paralizat in urma sectiunii unei legaturi nervoase sau dupa un soc care a atins coloana vertebrala, se poate imagina o noua conexiune intre zona motrice a creierului (legata de maduva spinarii) si muschi, asa cum un electrician ar instala un nou fir electric. Deocamdata medicii sunt departe de a realiza aceasta minune. Primele incercari in acest sens au fost insa facute. Acum e posibil, de pilda, sa se detecteze semnalul care parcurge o legatura nervoasa sau care parvine din activitatea neuronilor creierului.
Unele experimente realizate au avut ca scop controlul unor proteze sau a calculatorului prin forta gandului. Pe acest drum extrem de dificil s-a inscris cu succes o echipa de cercetatori americani de la Universitatea din Washington care a pus la punct un dispozitiv ce conecteaza prin intermediul calculatorului, cortexul motor al creierului de muschii mainii. Realizata in cazul a doua maimute cu un brat temporar paralizat (sub anestezie locala), experienta le-a permis, dupa mai multe incercari, ca muschii mainii sa fie comandati de creier.
Electrozii au fost bransati pe neuroni izolati din cortexul maimutelor care nu aveau functia de a comanda muschii! Pentru a verifica functionarea acestora, cercetatorii au cuplat sistemul la un monitor. Prin semnalele trimise de electrozi, detectate de calculator, a fost posibila deplasarea cursorului pe ecran. Experimentul a fost transformat intr-un joc in care maimutele trebuiau sa dirijeze cursorul spre un patrat, reusita fiind recompensata cu dulciuri.
Dependenta de droguri
Mecanismele cerebrale ale dependentei nu sunt, probabil, cele stiute. Recentele studii ale unui specialist francez (Jean-Paul Tassin) repun in discutie aceasta problema. Este vorba de o noua viziune care permite reconsiderarea procesului de dependenta de tutun, alcool, droguri, jocuri de noroc etc. In 1998, in urma studiilor a doi cercetatori italieni, s-a ajuns la concluzia ca toate drogurile provoaca eliberarea de dopamina intr-o regiune a creierului denumita nucleu acumbens. Dependenta era pusa pe seama faptului ca circuitul cerebral asa zis „al recompensei”, care gestioneaza satisfacerea nevoilor noastre vitale, e total perturbat de eliberarea masiva a mesagerului ei principal, dopamina. In acest caz, creierul nostru considera drogul ca fiind esential in satisfacerea nevoilor.
Echipa de cercetatori francezi propune o alta teorie care ar putea revolutiona acest domeniu permitand totodata sa rezolve „fragilitatea” modelului „oficial” al dopaminei. Tassin considera ca toate drogurile – alcool, morfina, amfetamine, cocaina etc. – distrug legatura intre cei doi neurotransmitatori, noradrenalina si serotonina, doua molecule care se gasesc din abundenta in cortex si in sistemul limbic, perturband activitatea acestora, ceea ce face ca orice emotie traita de toxicoman sa fie foarte puternica. Cand noradrenalina se epuizeaza in urma nevoii de drog, moralul toxicomanului se prabuseste iar interesul social dispare.
Dependenta apare in momentul in care se produce o decuplare intre acesti doi neurotransmitatori. Decuplat, sistemul nu mai poate asigura controlul emotiilor, provocand o hiperemotivitate care il impinge pe subiect spre drog.
The question they may want to ask instead is how can they prevent their child from becoming a bully.
New research to be presented on Sunday, May 1, at the Pediatric Academic Societies (PAS) annual meeting in Denver shows that parents can play a key role in decreasing the chances that their son or daughter will harass or intimidate other children.
Researchers, led by Rashmi Shetgiri, MD, FAAP, examined the prevalence of bullying reported by parents who took part in the National Survey of Children's Health from 2003-2007. They also looked at factors that were associated with an increased or decreased risk that a child bullied others.
The survey showed nearly one in six youths 10-17 years old bullied others frequently in 2007, according to Dr. Shetgiri, assistant professor of pediatrics at University of Texas Southwestern Medical Center and Children's Medical Center, Dallas. While the rates of parents who reported that their children harassed others frequently (defined as sometimes, usually or always) decreased from 2003 to 2007, these rates remain high, Dr. Shetgiri said.
Survey results also showed that 23 percent of children had bullied another youngster in 2003 compared to 35 percent in 2007.
Some factors that increase the likelihood that a child will bully others have persisted from 2003 to 2007. For example, children are more likely to be bullies if their parents frequently feel angry with them or feel their child bothers them a lot. In addition, children with an emotional, developmental or behavioral problem and those whose mothers report less than very good mental health also are more likely to be bullies. In fact, about one in five bullies has an emotional, developmental or behavioral problem, more than three times the rate in non-bullies, Dr. Shetgiri noted.
Other factors that seem to protect a child from becoming a bully also have persisted from 2003 to 2007. Parents who share ideas and talk with their child, and who have met most or all of their child's friends are less likely to have children who bully, Dr. Shetgiri said.
"Targeting interventions to decrease these persistent risk factors and increase the persistent protective factors could lead to decreased bullying," she said.
For example, parents can increase involvement with their children by meeting their friends and by spending time talking and sharing ideas with their children, Dr. Shetgiri suggested. "They also can find effective ways to manage any feelings of anger toward their child and can work with health care providers to make sure any emotional or behavioral concerns they have about their child, as well as their own mental health, are addressed."
Le isole Andamane, in India, sono una meta sempre più popolare. Spiagge bianche, mare cristallino, barriere coralline. Ma il turismo, in questa parte di mondo, ha un che di kafkiano. Ogni mese, migliaia di visitatori non solo indiani, ma provenienti da tutto il mondo, percorrono la Andaman Trunk Road attratti dalla possibilità di vedere la tribù dei Jarawa, in quello che somiglia molto a uno zoo safari umano. I tour operator locali, infatti, attirano fuori dalla foresta i Jarawa con biscotti e dolciumi, per permettere ai turisti di vederli e fotografarli. Con il risultato di esporre la popolazione, che conta solo 365 individui, al rischio di malattie e di incidenti stradali.
Contro l’assurdità di queste escursioni organizzate, Survival International ha lanciato una campagna di boicottaggio. Da quando fu realizzata negli anni Settanta, la superstrada Andaman Trunk ha semplificato la vita di bracconieri, coloni e taglialegna che depredano la selvaggina della tribù e ne minacciano la sopravvivenza. I cacciatori-raccoglitori Jarawa, infatti, sono in contatto con l’esterno solo dal 1998 e hanno poche difese immunitarie contro le malattie più comuni, a causa del lungo isolamento. Non è tutto: come sottolinea Survival, nella riserva sono stati denunciati anche casi di abuso sessuale e il safari è l’ultimo di una serie di affronti inumani a questa popolazione.
Per proteggere gli Jarawa, nel 2002 la Corte Suprema dell’India ha ordinato la chiusura della strada, che però risulta tuttora aperta illegalmente, e rappresenta una meta ambita per i villeggianti. “Il viaggio nella riserva tribale era come un vero e proprio safari: stavamo nel mezzo della foresta tropicale in attesa di vedere gli animali selvatici o, per essere precisi, i Jarawa”, ha riportato un turista. I più attratti dal cibo lanciato dai passeggeri dei veicoli in marcia sulla strada sono i bambini, che spesso restano coinvolti in incidenti stradali. Per questo Survival, insieme all’associazione locale Search, chiede ai turisti di boicottare queste escursioni.
La campagna, lanciata già lo scorso anno, finora ha ottenuto un discreto successo e diversi tour operator hanno smesso di promuovere gite nella riserva degli Jarawa; autisti indipendenti e altre compagnie, però, continuano a usare la terra nativa di questa tribù come un parco safari. “Oggi chiediamo a tutti i turisti di rifiutarsi di percorrere la strada delle Andamane, tenuta aperta dall’amministrazione locale in palese sprezzo dell’ordine della Corte Suprema dell’India”, ha dichiarato Stephen Corry, direttore generale di Survival. “Nonostante le direttive, i turisti continuano a invadere il territorio dei Jarawa mettendo a rischio le loro vite e trattandoli come animali. Se la situazione non cambierà, promuoveremo un boicottaggio del turismo in tutte le Isole Andamane”, ha aggiunto Corry.
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