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Scientists from the Morgridge Institute for Research, the University of Wisconsin-Madison, the University of California and the WiCell Research Institute moved gene therapy one step closer to clinical reality by determining that the process of correcting a genetic defect does not substantially increase the number of potentially cancer-causing mutations in induced pluripotent stem cells.

Their work, scheduled for publication the week of April 4 in the online edition of the journal Proceedings of the National Academy of Sciences and funded by a Wynn-Gund Translational Award from the Foundation Fighting Blindness, suggests that human induced pluripotent stem cells altered to correct a genetic defect may be cultured into subsequent generations of cells that remain free of the initial disease. However, although the gene correction itself does not increase the instability or the number of observed mutations in the cells, the study reinforced other recent findings that induced pluripotent stem cells themselves carry a significant number of genetic mutations.

"This study showed that the process of gene correction is compatible with therapeutic use," says Sara Howden, primary author of the study, who serves as a postdoctoral research associate in James Thomson's lab at the Morgridge Institute for Research. "It also was the first to demonstrate that correction of a defective gene in patient-derived cells via homologous recombination is possible."

Like human embryonic stem cells, induced pluripotent stem cells can become any of the 220 mature cell types in the human body. Induced pluripotent stem cells are created when skin or other mature cells are reprogrammed to a pluripotent state through exposure to select combinations of genes or proteins.

Since they can be derived from a patient's own cells, induced pluripotent stem cells may offer some clinical advantages over human embryonic stem cells by avoiding problems with rejection. However, scientists are still working to understand subtle differences between human embryonic and induced pluripotent stem cells, including a higher rate of genetic mutations among the induced pluripotent cells and evidence that the cells may retain some "memory" of their previous lineage.

Gene therapy using induced pluripotent stem cells holds promise for treating many inherited and acquired diseases such as Huntington's disease, degenerative retinal disease or diabetes. The patient in this study suffers from a degenerative eye disease known as gyrate atrophy, which is characterized by progressive loss of visual acuity and night vision leading to eventual blindness.

While diseases such as genetic retinal disorders and diabetes offer attractive targets for induced pluripotent stem cell-based transplant therapies, concerns have been raised over the commonly occurring mutations in the cells and their potential to become cancerous.

Howden says that because gene targeting to correct specific genetic defects typically requires an extended culture period beyond initial induced pluripotent stem cell generation, researchers have been interested to learn whether the process would increase the number of mutations in the cells. The team set out to determine if it was possible to correct defects without introducing a level of mutations that would be incompatible with clinical applications.

In the study, the researchers used a technique called episomal reprogramming to generate the induced pluripotent stem cells. In contrast to techniques that use retroviruses, episomal reprogramming doesn't involve inserting DNA into the genome. This technique allowed them to produce cells that were free of potentially harmful transgene sequences.

The scientists then corrected the actual retinal disease-causing gene defect using a technique called homologous recombination. The stem cells were extensively "characterized" or studied before and after the process to assess whether they developed significant additional mutations or variations. The results showed that the culture conditions required to correct a genetic defect did not substantially increase the number of mutations.

"By showing that the process of correcting a genetic defect in patient-derived induced pluripotent cells is compatible with therapeutic use, we eliminated one barrier to gene therapy based on these cells," Howden says. "There is still much work to be done."

David Gamm, an author of the study and an assistant professor with the Department of Ophthalmology and the Waisman Center Stem Cell Research Program, says the ability to correct gene defects in a patient's own induced pluripotent stem cells should increase the appeal of stem cell technology to researchers striving to improve vision in patients with inherited blinding disorders.

"Although further development certainly is needed before such techniques may reach the clinical trial stage, our findings offer reason for continued hope," Gamm says. "Dr. Howden and our collaborative group have overcome an important hurdle which, when considered in the context of other recent developments, may lead to personalized stem cell therapies that benefit people with genetic visual disorders."

In addition to primary author Howden, who holds joint appointments with the Morgridge Institute for Research, the Department of Cell and Regenerative Biology and the Genome Center of Wisconsin, co-authors of the study included: Thomson, who in addition holds an appointment with the Department of Molecular, Cellular & Developmental Biology, University of California-Santa Barbara; Gamm, who holds joint appointments with the UW-Madison School of Medicine and Public Health's Department of Ophthalmology and Visual Sciences and the Waisman Center Stem Cell Research Program; Jeff Nie, Goukai Chen, Brian McIntosh, Daniel Gulbranson, Nicole Diol and David Vereide with the Morgridge Institute for Research; Athurva Gore, Zhe Li, Ho-Lim Fung and Kun Zhang, of the Department of Bioengineering at the University of California-San Diego; and Benjamin Nisler, Seth Taapken and Karen Dyer Montgomery of WiCell Research Institute.

Source: ScienceDaily

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By Admin (from 09/05/2011 @ 11:00:26, in ro - Stiinta si Societate, read 1250 times)

 Dupa ce fizicianul Drake a enuntat faimoasa sa teorie cu privire la numarul probabil al planetelor din galaxie care ar putea gazdui viata inteligenta, lumea stiintifica a inceput sa viseze cu ochii deschisi la ziua in care mult asteptatul contact cu o civilizatie extraterestra se va produce. Sansele ca acest lucru sa se intample curand cresc pe zi ce trece, adica pe masura ce sunt descoperite noi si noi planete ce ar putea sustine forme de viata.

Un studiu (din 2008) da noi sperante sustinatorii existentei civilizatiilor extraterestre, relevand ca numarul planetelor „apte pentru viata” din galaxia Calea Lactee ar putea fi mult mai ridicat decat s-a crezut pana acum.

Noile descoperiri la care ne referim au fost prezentate la cel mai recent congres al Asociatiei Americane de Stiinta, desfasurat la Boston. Ele sugereaza ca mai  bine de jumatate dintre stelele similare Soarelui ar  putea avea sisteme planetare asemanatoare cu al nostru, ceea ce reprezinta o suma impresionanta. De asemenea, s-a vehiculat ideea ca in afara sistemului nostru solar s-ar putea afla mii de lumi, inca nedescoperite, pe langa cele a caror existenta a fost deja relevata.

„Zona Goldilocks” ar putea gazdui „gemeni” ai Pamantului

Michael Meyer, astronom la Universitatea Arizona, apreciaza ca, gratie noilor metode de investigatie, in urmatorul deceniu, vor fi descoperite mii de stele asemanatoare Soarelui, stele in jurul carora orbiteaza planete din categoria Terrei. „Observatiile noastre ne determina sa afirmam ca intre 20 si 60% dintre stelele apropiate ca masa si dimensiuni Soarelui au, in cadrul sistemelor solare, planete solide, stancoase, in genul Pamantului.

Este o concluzie care pune intr-o lumina mult mai optimista problema existentei vietii in galaxie. Sansele ca aceasta sa existe cresc, din punct de vedere teoretic, considerabil”, spune Meyer. Echipa astronomului american a folosit telescopul spatial Spitzer, apartinand NASA, pentru a examina grupuri de stele cu mase apropiate de ale Soarelui. S-a reusit astfel detectarea unor discuri de praf cosmic in jurul stelelor, la unele dintre cele mai „tinere” grupuri studiate.

Astronomii sustin ca aceasta pulbere ar putea fi rezultatul ciocnirii unor fragmente stancoase, care ulterior se vor uni, formand planete, asemenea procese ducand, in trecut, si la crearea Pamantului. Mai multe indicii referitoare la aceste lumi indepartate va releva, cu siguranta, misiunea spatiala Kepler, pe care NASA o va lansa anul viitor, cu scopul de a cauta in imensitatea universului planete de marimea Pamantului.

Pentru ca o planeta sa poata gazdui forme de viata, ea trebuie insa sa aiba o marime corespunzatoare si sa se gaseasca la o anumita distanta fata de steaua-mama, adica sa se afle in asa-numita „zona Goldilocks”. „Descoperirea unor astfel de planete, avand conditii pentru dezvoltarea vietii, ar fi de o importanta capitala, intrucat le-ar permite colonistilor umani ca in viitor sa le populeze”, a afirmat, in cadrul comunicarii sale, dr. Debra Fischer, de la San Francisco State University.

Un inalt responsabil al NASA, Alan Stern, este de parere ca oamenii n-au vazut decat varful aisbergului, chiar si in privinta propriului nostru sistem solar. „Teoria traditionala, potrivit careia in Sistemul Solar sunt doar noua planete, ar putea fi inlocuita cu o alta, ce afirma ca exista de fapt sute, daca nu mii de planete aici. Multe dintre acestea sunt inghetate, altele stancoase, iar unele ar putea avea mase apropiate de ale Terrei. Ar putea exista planete si in norul lui Oort (o fasie de sfaramaturi cosmice, inconjurand sistemul nostru solar), dar cu siguranta ele sunt inghetate, din cauza prea marii departari fata de Soare”, sustine Stern.

GABRIEL TUDOR - magazin.ro

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Una ricercatrice americana ha scoperto che i pipistrelli sono in grado di selezionare gli stimoli sonori in base alla loro importanza per la sopravvivenza e ipotizza che anche gli uomini utilizzano un meccanismo simile per orientarci nel complesso ambiente sensoriale che ci circonda. (Silvia Artana)

Come facciamo a sentire la sirena di un’ambulanza in mezzo alla confusione del traffico dell’ora di punta, tra i clacson che suonano e la radio accesa? Ce lo spiegano i pipistrelli. La statunitense Bridget Queenan, del Georgetown University Medical Center, ha scoperto che nel cervello dei chirotteri esistono neuroni che “zittiscono” gli altri quando rilevano suoni importanti e neuroni che “gridano più forte” per trasmettere questi suoni al di sopra del rumore di fondo. Un meccanismo che - secondo la ricercatrice - potrebbe essere presente anche negli uomini.

Suoni per orientarsi

La funzione uditiva del cervello dei pipistrelli è da sempre oggetto di studio per la capacità che hanno questi mammiferi di utilizzare i suoni in modo complesso. Infatti, oltre a emettere un’ampia gamma di segnali sonori per comunicare con i propri simili, essi utilizzano i suoni per orientarsi nello spazio e cacciare. Grazie alla ecolocalizzazione, una specie di sonar biologico, i pipistrelli lanciano segnali sonori a frequenze specifiche e ascoltano gli echi che questi producono rimbalzando sulle superfici circostanti per individuare gli oggetti e le prede.
   
E NEGLI UOMINI?

Un meccanismo simile a quello dei neuroni dei pipistrelli sarebbe attivo anche nel cervello degli uomini e spiegherebbe per esempio come fa una madre a sentire la voce di suo figlio in un parco giochi affollato di altri bambini.
Una teoria che, se dimostrata, potrebbe aiutarci a capire come riusciamo a individuare le informazioni che ci servono per vivere e relazionarci con i nostri simili tra tutti gli stimoli sensoriali che ci bombardano quotidianamente. 

Che rumore!

Ma immaginate una colonia di centinaia di pipistrelli che emettono segnali per "vedere" e nel frattempo cercano di comunicare? Come a ecolocalizzare e a sentire contemporaneamente i messaggi sociali nella confusione sonora? La ricercatrice statunitense ha sottoposto alcuni pipistrelli con i baffi (Pteronotus Parnellii) in stato di veglia a differenti combinazioni di segnali di ecolocalizzazione e di comunicazione e ha monitorato l’attività di un’area del loro cervello dove è massima l’acutezza del sistema uditivo.

Neuroni silenziatori

Le rilevazioni hanno evidenziato la presenza di neuroni che “silenziano” letteralmente l’attività di altre cellule neurali quando identificano suoni importanti e di neuroni che amplificano la percezione dei segnali sociali in presenza di rumore di fondo, interagendo in un network che permette ai pipistrelli di sentire le comunicazioni necessarie alla propria sopravvivenza in mezzo all’inquinamento acustico della colonia.

Fonte: Focus.it

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La forza del Movimento Zeitgeist deriva proprio dalla sua natura globale, e come tale ogni realtà va approcciata tenendo conto delle peculiarità di ogni zona geografica e cultura. In Italia ancora in pochi parlano inglese, ma molti si affaticano a leggere i sottotitoli. Inoltre, spesso, si perdono i giochi di parole che rendono una creazione artistica quello che veramente è.


Il GdL video ha iniziato quindi un nuovo progetto collaborativo: "Perché sostengo il Movimento Zeitgeist", sulla scia di quello che sta avvenendo a livello internazionale. Questo progetto sarà fatto da noi italiani, per parlare agli italiani, in modo chiaro e semplice. Dobbiamo dare un volto umano al Movimento, far capire che è fatto di persone, che abbiamo un volto e che non abbiamo paura di mostrarci.

Invitiamo tutti i simpatizzanti del Movimento Zeitgeist, del Venus Project e di una Economia Basata sulle Risorse a partecipare a questo progetto. Sarà realizzato un corto, in cui mostreremo la natura decentralizzata e globale del movimento. Potete prendere spunto da queste domande ed elaborare le risposte:

  1. Perché sosteni il Movimento Zeitgeist?
  2. Quali sono le conseguenze peggiori causate dal sistema monetario?
  3. Perché il profitto è un problema?
  4. Ti piacerebbe vivere in una società egalitaria?
  5. Cosa faresti se non fossi costretto a lavorare?
  6. Quali sono i i vantaggi reali di un'economia basata sulle risorse?
  7. Vedi alternative migliori per il futuro?
  8. Quali sono i problemi mondiali più gravi?
  9. Quali sono le prime cose a cui diresti "BASTA!" in questo momento?

Siamo fiduciosi che aderirete in moltissimi e moltissime, dobbiamo mostrare che noi italiani ci siamo, siamo numerosi, e siamo persone vere!

Buon divertimento! :D

TA

Calendario eventi

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High school students who feel they do not fit in are less likely to attend college — particularly girls who are gay or obese — according to new research from The University of Texas at Austin.

"Because social experiences in high school have such demonstrable effects on academic progress and attending college, the social concerns of teenagers are educational concerns for school," says sociologist Robert Crosnoe.

Crosnoe has completed one of the most comprehensive studies of the long-term effects on teenagers who say they don't fit in. He used national statistics from 132 high schools and spent more than a year inside a high school in Texas with 2,200 students, observing and interviewing teenagers. His findings will be published in his new book "Fitting In, Standing Out" (Cambridge University Press, April 11).

"Kids who have social problems — often because they are overweight or gay are at greater risk of missing out on going to college simply because of the social problems they have and how it affects them emotionally," says Crosnoe, a Sociology Department professor and Population Research Center affiliate. "Not because of anything to do with intelligence or academic progress."

Girls were 57 percent and boys 68 percent less likely than peers of the same race, social class and academic background to attend college if they had feelings of not fitting in, according to the study. Particularly at risk were girls who are obese, who are 78 percent less likely to attend college than non-obese girls, and those who are gay, who are 50 percent less likely to attend.

Crosnoe found feelings of not fitting in led to increased depression, marijuana use and truancy over time. Those coping strategies interrupt the education process — the classes teenagers take, the grades they make — which, in turn, affect their ability to go to college.

"Teenagers cope with the discomforts of not fitting in, including being bullied, in ways that are protective in the short term, but disastrous in the long term," says Crosnoe.

His research, funded by the National Institutes of Health and William T. Grant Foundation, has resulted in recommendations for how parents, teachers and policymakers can ensure that the social side of high school supports, rather than undermines, academics. It comes at a time when state lawmakers and federal policymakers are tackling bullying — often a cause of teenage social problems — as a national crisis.

Source: EurekAlert

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By Admin (from 08/05/2011 @ 11:00:29, in ro - Stiinta si Societate, read 1477 times)

 Dupa ce l-am vazut pe ecrane ca pe un (utopic, in realitate) personaj de film, vom avea ocazia sa-l admiram pe faimosul Spider-Man plimbandu-se chiar pe fatadele blocurilor noastre sau chiar pe tavane. Si noi insine vom putea devenit, temporar, „oameni-paianjen”, destul de curand: cam peste 10 ani. Totusi, ca sa nu nedreptatim alta specie animala, precizam ca incredibilele acrobatii vor fi posibile datorita micutei soparle asiatice gecko tokay.

O soparla... colanta

Reptila amintita traieste in zonele calde si are o caracteristica anatomica uluitoare, considerata multa vreme o enigma. Degetele sale sunt acoperite cu lamele adezive, care ii permit sa se deplaseze cu usurinta pe suprafetele cele mai lunecoase. De pilda, cu un singur deget, ea poate sa se „agate” de o placa de sticla.

Aceasta ciudatenie l-a inspirat pe cercetatorul italian Nicola Pugno, specialist in materiale, care s-a gandit ca si omul poate atinge performante similare, daca este dotat cu incaltari si cu manusi care sa aiba pe suprafata de contact un gen de lamele ca ale soparlei gecko. Pentru a fabrica asemenea particule fine si rezistente, cercetatorul a ales un material la fel de straniu: nanotuburi de carbon. Acestea au diametrul de numai cativa nanometri (o miliardime de metru), formati din atomi dispusi in forma de fagure si sunt de 100.000 de ori mai fine decat firul de par.

Padurile microscopice

Datorita legaturilor solide dintre atomi, minusculele tuburi pot fi de 100 de ori mai rezistente decat otelul, dar de 6 ori mai usoare, deoarece nu contin si atomi de fier. Inventia seamana mult cu lamelele de pe degetele soparlei gecko. Pana la un punct: la animal, lamelele se ramifica spre extremitati, la fel ca ramurile unui copac.

Cand gecko se urca pe un perete, filamentele atrag moleculele de la suprafata, gratie unor forte (Van der Waals), iar cele patru labute ale sale formeaza „paduri” extrem de dense, care multiplica efectul de milioane de ori. Si-atunci, cum se va desprinde de materialul pe care s-a lipit atat de bine? Simplu: isi impinge piciorul in fata, unghiul de contact se modifica si reptila se deplaseaza fara eforturi suplimentare. Iar nanotuburile de carbon actioneaza intr-un mod similar, astfel incat, cu putin antrenament, si un om masiv va putea face plimbari pe tavan!

De la reptile, la astronauti

Senzationala inventie, dar la ce poate folosi? Pugno s-a gandit sa doteze cu nanotuburile sale manusi si incaltari speciale, purtate de cei ce practica activitati dificile, cum este industria forestiera. Dar se-ntelege ca o asemenea minune a atras si specialisti din alte domenii. De exemplu, astronautii si militarii vor folosi cu eficienta echipamente atat de usoare si de performante. In statiile spatiale, imponderabilitatea nu le va mai juca feste celor dintai, mai ales ca, fiind mai putin grele, minusculele particule de carbon vor da rezultate superioare.

Cat despre militari, in cadrul operatiunilor de comando ei vor putea actiona mai rapid, daca vor fi nevoiti sa escaladeze cladiri si sa se deplaseze pe suprafete abrupte. Iar ca sa ne gandim si la noi, ne-am putea imagina un insolit mijloc de locomotie al viitorului, in contextul marilor aglomerari. Asadar, nu ramane decat sa incepem antrenamentele.

ADRIAN-NICOLAE POPESCU - magazin.ro

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38 atomi di anti-idrogeno sono stati creati e per la prima volta "conservati" in un esperimento del Cern.

Un esperimento condotto dal Cern di Ginevra ha prodotto in laboratorio alcuni atomi di antimateria. Fin qui niente di nuovo: gli acceleratori di particelle da anni producono antimateria. Ma nell'esperimento del Cern, i 38 atomi di anti-idrogeno sono stati "imprigionati", immobilizzati per 172 millisecondi (poco meno di 2 decimi di secondo).

E questa è una novità importante, perché conservare l'antimateria anche per così poco tempo permetterà ai ricercatori di studiarne le caratteristiche in modo più approfondito, per confrontare l'antimateria con la materia ordinaria e verificare, per esempio, se l'antimateria è lo specchio esatto della materia. Fino a oggi il tempo di sopravvivenza degli atomi di antimateria non superava pochi microsecondi, dato che entrando in contatto con la materia normale si annichilavano.

Perché è importante questo esperimento?

La speranza è riuscire a risolvere uno dei più grandi rompicapo della fisica contemporanea, ossia perché al momento del Big Bang la natura ha «preferito» la materia ordinaria all'antimateria. Entrambe sono state infatti prodotte nella stessa quantità (in modo simmetrico) e di conseguenza avrebbero dovuto cancellarsi a vicenda; tuttavia questo non è successo perché una certa quantità di materia (calcolata in una particella ogni 10 miliardi di particelle di antimateria) è riuscita a sfuggire e grazie a questa rottura della simmetria si è formato il mondo in cui viviamo.
Che cosa sia successo effettivamente è ancora un mistero, ma adesso i fisici del Cern hanno strumenti senza precedenti per fare un po' di luce.

Fonte: Focus.it

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PRESS RELEASE -

Hundreds of thousands of individuals globally celebrate today (May 5, 2011 - TA note) the confirmation that their efforts to end the torturous pre-trial confinement conditions inflicted upon US Army PFC Bradley Manning have been successful. Manning's lead defense attorney, David E. Coombs of Rhode Island, has personally verified that Manning is indeed being held in Medium Custody confinement at the Joint Regional Corrections Facility (JRCF) at Fort Leavenworth, Kansas, as claimed by the Army last week.

"We won this battle because 600,000 individuals took the time to write letters and sign petitions, because thousands called the White House switchboard, because 300 of America's top legal scholars decried Bradley's pre-trial conditions as a clear violation of our Constitution's 5th and 8th Amendments," declared Jeff Paterson of Courage to Resist and the Bradley Manning Support Network. "We won this battle because over a hundred concerned citizens engaged in civil disobedience at the White House and at Quantico, and because our grassroots campaign shows no sign of slowing."

These new conditions reflect a dramatic improvement for Manning following his transfer to Fort Leavenworth on April 20, 2011, after having suffered extreme solitary-like confinement at US Marine Corps Base Quantico, Virginia. During the nine months at Quantico, Manning was denied meaningful exercise, social interaction, sunlight, and was at times kept completely naked. These conditions were unique to Manning and were illegal under US military law as they clearly amounted to pre-trial punishment.

"I was able to tour the (Fort Leavenworth) facility and meet with PFC Manning last week. PFC Manning is now being held in Medium Custody. He is no longer under.harsh pretrial confinement conditions. Unlike at Quantico, PFC Manning's cell has a large window that provides adequate natural light....PFC Manning is able to have all of his personal items in his cell, which include his clothing, his legal materials, books and letters from family and friends....Each pre-trial area (including PFC Manning's) has four cells, and each pre-trial detainee is assigned to his own cell. The cells are connected to a shared common area, with a table, a treadmill, a television and a shower area....PFC Manning and his group are taken to the outdoor recreation area [for approximately two hours daily]," explained Coombs on his blog at www.armycourtmartialdefense.info hours ago.

"President Obama's recent pronouncement that Bradley Manning 'broke the law' amounts to Unlawful Command Influence, something clearly prohibited because it's devastating to the military justice system. Manning will eventually be judged by a jury of career military officers and noncommissioned officers. Will they be able to set aside the declaration of their commander in chief?" explains attorney Kevin Zeese, a member of the Bradley Manning Support Network. "Along with the illegal pre-trial punishment already inflicted upon Bradley, the government has more than enough legal basis to drop the prosecution. Instead, the death penalty or life in prison hangs over Manning's head."

After nearly a year in confinement, the Army is expected to soon announce Manning's first public hearing, an Article 32 pre-trail proceeding, which will be held in the Washington DC area. Scores of international solidarity events are already being planned.

US Army intelligence analyst Private First Class Bradley E. Manning, 23-years-old, was arrested in Iraq on May 26, 2010. He still awaits his first public court hearing, now expected to begin in June 2011. Over 4,300 individuals have contributed over $333,000 towards PFC Manning's legal fees and related public education efforts. The Bradley Manning Support Network is dedicated to thwarting the military's attempts to hold a secret court martial, and to eventually winning the freedom of PFC Manning.

Source: globalresearch.ca

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Researchers at the Hebrew University of Jerusalem have achieved a breakthrough in the field of nanoscience by successfully altering nanocrystal properties with impurity atoms -- a process called doping – thereby opening the way for the manufacture of improved semiconductor nanocrystals.

Semiconductor nanocrystals consist of tens to thousands of atoms and are 10,000 times smaller than the width of a human hair. These tiny particles have uses in a host of fields, such as solid-state lighting, solar cells and bio-imaging. One of the main potential applications of these remarkable materials is in the semiconductor industry, where intensive miniaturization has been taking place for the last 50 years and is now in the nanometer range.

However, these semiconductors are poor electrical conductors, and in order to use them in electronic circuits, their conductivity must be tuned by the addition of impurities. In this process, foreign atoms, called impurities, are introduced into the semiconductor, causing an improvement in its electrical conductivity.

Today, the semiconductor industry annually spends billions of dollars in efforts to intentionally add impurities into semiconductor products, which is a major step in the manufacturing of numerous electronic products, including computer chips, light emitting diodes and solar cells.

Due to the importance of doping to the semiconductor industry, researchers worldwide have made continuing attempts at doping nanocrystals in order to achieve ever greater miniaturization and to improve production methods for electronic devices. Unfortunately, these tiny crystals are resistant to doping, as their small size causes the impurities to be expelled. An additional problem is the lack of analytical techniques available to study small amounts of dopants in nanocrystals. Due to this limitation, most of the research in this area has focused on introducing magnetic impurities, which can be analyzed more easily. However, the magnetic impurities don't really improve the conductivity of the nanocrystal.

Prof. Uri Banin and his graduate student, David Mocatta, of the Hebrew University Center for Nanoscience and Nanotechnology, have achieved a breakthrough in their development of a straightforward, room- temperature chemical reaction to introduce impurity atoms of metals into the semiconductor nanocrystals. They saw new effects not previously reported. However, when the researchers tried to explain the results, they found that the physics of doped nanocrystals was not very well understood.

Bit by bit, in collaboration with Prof. Oded Millo of the Hebrew University and with Guy Cohen and Prof. Eran Rabani of Tel Aviv University, they built up a comprehensive picture of how the impurities affect the properties of nanocrystals. The initial difficulty in explaining this process proved to be a great opportunity, as they discovered that the impurity affects the nanocrystal in unexpected ways, resulting in new and intriguing physics.

"We had to use a combination of many techniques that when taken together make it obvious that we managed to dope the nanocrystals. It took five years but we got there in the end," said Mocatta.

This breakthrough was reported recently in the prestigious journal Science. It sets the stage for the development of many potential applications with nanocrystals, ranging from electronics to optics, from sensing to alternative energy solutions. Doped nanocrystals can be used to make new types of nanolasers, solar cells, sensors and transistors, meeting the exacting demands of the semiconductor industry.

Source: EurekAlert

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By Admin (from 07/05/2011 @ 11:00:08, in ro - Observator Global, read 1974 times)

 Perioada interbelica a reprezentat, mai ales in conditiile crizei economice mondiale, un teren propice pentru inflorirea unor miscari populiste, extremiste, inclinate spre „vanatoarea de vrajitoare” si pe atribuirea situatiei generale in continua deteriorare fie evreilor, fie politicienilor corupti, fie insesi esentei democratiei, ca o oranduire care nu selecteaza varfurile. Nu este de mirare ca in acest context tendinte totalitariste au aparut chiar si in state democratice cu traditie, ca Marea Britanie si Statele Unite. Si daca toata lumea stie astazi despre dictaturile de sorginte fascista din Germania, Italia, Ungaria, Spania, Bulgaria sau Romania, putini cunosc faptul ca Statele Unite a fost pandita, la un moment dat, de instaurarea unei asemenea dictaturi...

Liga Libertatii dorea dictatura

„Complotul afaceristilor” sau „puciul de la Casa Alba” a fost o conspiratie cu largi ramificatii, menita sa-l rastoarne de la putere pe presedintele democratic ales, Franklin Delano Roosevelt, in anul 1933, adica intr-o perioada cand la Berlin Adolf Hitler isi asuma puteri totale si pornea marsul nebunesc spre aruncarea lumii in haosul celui de-al doilea razboi mondial.

Detalii asupra acestei chestiuni au inceput sa iasa timid la iveala in momentul cand generalul Smedley Butler, fostul sef al Statului Major al Marinei, a depus marturie in fata unei comisii senatoriale, prin care recunostea ca se incercase atragerea lui intr-un complot vizand alungarea de la putere a lui Roosevelt. Butler a depus aceasta marturie, inainte a comisiei McCormack-Dickstein, in 1934.

Desi in final, comisia a recunoscut existenta unei tentative de puci, nimeni nu a fost acuzat, nici o alta investigatie nu a urmat si lucrurile au fost musamalizate. Butler va sustine insa pana la sfarsitul vietii ca problema a fost cat se poate de serioasa si ca o organizatie numita Liga Libertatii s-a aflat in spatele actiunii. Printre membrii acestei organizatii se numarau cei mai bogati magnati americani, patronii de la US Steel, General Motors, Standard Oil, Chase National Bank, Goodyear, ca si membri familiei Du Pont. Un documentar realizat recent de BBC demonstreaza ca si Prescott Bush (in fotografie, alaturi de presedintele Roosevelt) bunicul actualului presedinte al Americii, a fost implicat in complot!

Fascinatia raului

Cum de a fost posibil totusi ca in „tara libertatii” sa se poata urzi un complot vizand instaurarea unei tiranii? Intr-un articol publicat in revista History Today, britanicul Clayton Cramer, specialist in istorie interbelica, sustine ca lipsurile cauzate de Marea Criza din anii 1929-1933, care a afectat grav economia mondiala, i-au facut pe multi americani sa puna la indoiala insesi temeliile democratiei liberale.

„Multi conservatori, din Europa si de peste Atlantic, deveneau atrasi de ideile fasciste si de national-socialism. Altii inclinau mai curand spre socialism si comunism, dar ceea ce a determinat magnatii americani sa puna la cale un complot fascist a fost siguranta ca un astfel de regim, spre deosebire de cel comunist, le-ar fi garantat in continuare privilegiile si nu s-ar fi ajuns la nationalizarea averilor lor, ca in statele comuniste. Nu trebuie uitat ca un curs similar s-a inregistrat in Germania, unde patronii concernelor Krupp sau IG Farbenindustrie l-au sprijinit activ si constant pe Hitler, tocmai pentru a asigura o contrapondere bolsevismului, in continua expansiune”, explica Clayton Cramer.

Un frate geaman al lui Hitler?

Audiat de senatori, incepand cu 20 noiembrie 1934, generalul Butler a marturisit ca primise, din partea complotistilor, propunerea de a conduce o armata de 500.000 de soldati, organizata dupa modelul fascist al lui Mussolini, armata care avea sa marsaluiasca spre Washington, spre a-si impune vointa prin forta, 30 milioane de dolari, drept sprijin financiar si o puternica sustinere mediatica. Este clar ca Butler fusese ales de conspiratori pentru simpatiile sale totalitare, exprimate cu temeritate.

Generalul era privit cu speranta de milioanele de someri si de fosti soldati in timpul primului razboi mondial, ramasi acum pe drumuri. Cel care l-a contactat a fost Gerald MacGuire, mostenitorul fabricilor Singer si un infocat admirator al lui Hitler. De altfel, MacGuire, care ducea o viata luxoasa la Paris, urmarea cu interes evenimentele din Europa si fusese fascinat de reusitele si proiectele lui Mussolini si Hitler in plan economic. MacGuire i-a vorbit despre suferintele indurate din cauza crizei economice de catre fostii lui soldati si i-a aratat ca doar o mana ferma, a sa, poate stavili degringolada spre care se indreapta America.

Lui Butler i s-a propus functia de dictator si a fost asigurat ca Roosevelt nu va pati nimic, ci va ramane presedinte, dar postul sau urma sa fie pur onorific. Adevaratul conducator al Statelor Unite trebuia sa fie Butler, cu conditia sa inceteze politica pacifista a predecesorului sau si sa se implice mai mult in reimpartirea sferelor de influenta, chiar cu pretul unui nou razboi mondial. Temandu-se ca este folosit pentru a scoate din foc castanele, in folosul altora, generalul a dat un raspuns evaziv si s-a adresat imediat autoritatilor. Va imaginati cum ar fi aratat lumea daca un „frate geaman” al lui Hitler ar fi carmuit peste Atlantic?

Roosevelt, adevaratul invingator

Dar marturia sa a fost primita cu ostilitate de presa si elita afaceristilor americani, lucru care n-ar trebui sa ne mire, intrucat magnatii erau si „moguli de presa”, care se vedeau astfel dati in vileag de propriul lor candidat la dictatura. In publicatii precum The New York Times, Philadelphia Post sau Time Magazine  a inceput o campanie agresiva de denigrare a lui Butler si de ridicularizare a afirmatiilor lui. Desi Congresul i-a audiat si pe acuzati, marturiile lor nu au fost niciodata publicate si in 1975, cand s-a incercat limpezirea apelor, s-a ajuns la concluzia ca benzile cu inregistrarea interogatoriilor disparusera fara urma...

Toti cei vizati de dezvaluirile lui Butler au negat vehement ca ar avea vreo vina, singurul care a acceptat sa vorbeasca despre complot, in schimbul unor garantii privind libertatea si siguranta sa, fiind MacGuire. Pe 15 februarie 1935, comisia a prezentat Camerei Reprezentantilor un raport final, prin care respingea toate acuzatiile lui Butler. Complotul, era concluzia raportului, nu existase decat in mintea fostului general... Si totusi, istoricii americani care au studiat acest caz par de acord sa accepte realitatea complotului si faptul ca s-a produs musamalizarea lui.

De fapt, argumenteaza ei, povestea era atat de stanjenitoare pentru multe personalitati influente de la Washington incat aflarea adevarului ar fi dus la distrugerea carierei lor publice. Proprietarii ziarelor americane (magnatii detineau 82% din totalul publicatiilor care apareau in SUA, in anul 1934) au avut tot interesul sa-l discrediteze pe Butler, care le ameninta interesele prin dezvaluirile sale. Chiar si unii dintre consilierii lui Roosevelt erau implicati in complot si au cautat, in mod firesc, sa-si spele rufele murdare in familie.

Istoricul britanic John Buchanan spune ca insusi Roosevelt a fost pus la curent, in cele din urma, cu conspiratia, si a acceptat sa-i ierte pe complotisti, cu conditia ca ei sa-i sprijine grandiosul proiect economic numit New Deal, care nu convenea mai deloc magnatilor capitalisti. Ceea ce, pana la urma, chiar s-a intamplat, schimbarea brusca de macaz a miliardarilor americani, care aveau mai mult de pierdut decat de castigat din reformele economice propuse de Roosevelt, putand constitui un argument in plus in favoarea ipotezei ca fusesera, intr-adevar, prinsi cu mata-n sac...

Autor: GABRIEL TUDOR - Sursa: Magazin.ro

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