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By Admin (from 02/05/2011 @ 08:00:51, in en - Science and Society, read 1560 times)

Researchers at the National Institute of Standards and Technology (NIST) have for the first time used an apparatus that relies on the "noise" of jiggling electrons to make highly accurate measurements of the Boltzmann constant, an important value for many scientific calculations. The technique is simpler and more compact than other methods for measuring the constant and could advance international efforts to revamp the world’s scientific measurement system.

The Boltzmann constant relates energy to temperature for individual particles such as atoms. The currently accepted value of the Boltzmann Constant is 1.380 6504 x 10-23 joules/kelvin. The accepted value of this constant is based mainly on a 1988 NIST measurement performed using acoustic gas thermometry, with a relative standard uncertainty of less than 2 parts per million (ppm). The technique is highly accurate but the experiment is complex and difficult to perform. To assure that the Boltzmann constant can be determined accurately around the world, scientists have been trying to develop different methods that can reproduce this value with comparable uncertainty.

The latest NIST experiment used an electronic technique called Johnson noise thermometry (JNT) to measure the Boltzmann constant with an uncertainty of 12 ppm. The results are consistent with the currently recommended value for this constant. NIST researchers aim to make additional JNT measurements with improved uncertainties of 5 ppm or less, a level of precision that would help update crucial underpinnings of science, including the definition of the Kelvin, the international unit of temperature.

The international metrology community is expected to soon fix the value of the Boltzmann constant, which would then redefine the Kelvin as part of a larger effort to link all units to fundamental constants. This approach would be the most stable and universal way to define measurement units, in contrast to traditional measurement unit standards based on physical objects or substances. The Kelvin is now defined in terms of the triple-point temperature of water (273.16 K, or about 0 degrees C and 32 degrees F), or the temperature and pressure at which water’s solid, liquid and vapor forms coexist in balance. This value may vary slightly depending on chemical impurities.

The NIST JNT system measures very small electrical noise in resistors, a common electronic component, when they are cooled to the water triple point temperature. This “Johnson noise” is created by the random motion of electrons, and the signals they generate are directly proportional to temperature. The electronic devices measuring the noise power are calibrated with electrical signals synthesized by a superconducting voltage source based on fundamental principles of quantum mechanics. This unique feature enables the JNT system to match electrical power and thermal-noise power at the triple point of water, and assures that copies of the system will produce identical results. NIST researchers recently improved the apparatus to reduce the statistical uncertainty, systematic errors and electromagnetic interference. Additional improvements in the electronics are expected to further reduce measurement uncertainties.

The new measurements were made in collaboration with guest researchers from the Politecnico di Torino, Italy; the National Institute of Metrology, China; the University of Twente, The Netherlands; the National Metrology Institute of Japan, Tsukuba, Japan; and the Measurement Standards Laboratory, New Zealand.

Source: PhysOrg

More information: S.P. Benz, et al. An electronic measurement of the Boltzmann Constant. Metrologia. Published online March 30, 2011.

Provided by National Institute of Standards and Technology

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By Admin (from 01/05/2011 @ 21:10:44, in en - Video Alert, read 3194 times)
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By Admin (from 01/05/2011 @ 14:00:24, in ro - Observator Global, read 1560 times)

Imagini care au surprins momente cutremuratoare, impresionante, emblematice, imprimate in memoria noastra afectiva, au fost realizate de fotografi extraordinari ale caror nume, de obicei, nu sunt retinute. Sa ne reamintim de ei si de imaginile care au facut inconjurul lumii.

1. Jeff Widener - Omul din fata tancurilor, in piata Tienamnen, Beijing

Pe 5 iunie 1989, cand protestele de la Beijing au atins apogeul, zeci de tancuri au invadat piata Tienanmen, insa un singur om a avut curajul sa stea in fata lor. Identitatea lui a ramas necunoscuta. Se spune ca patru fotografi au imortalizat momentul, insa doar imaginea realizata de Jeff Widener a facut inconjurul lumii.

2. Kevin Carter - vultur pandind un copil sudanez mort de foame

La trei luni dupa ce a realizat aceasta imagine, pentru care a castigat un premiu Pulitzer, Kevin Carter s-a sinucis. Fotograful a fost acuzat ca a stat 20 de minute in fata acelui spectacol de cosmar, in care copilul sudanez subnutrit era pandit de un vultur, ca sa isi realizeze imaginea, in loc sa sara in ajutorul bietului neputincios.

3. Alberto Korda - Che Guevara

Imaginea simbol cu Guevara, imprimata si pe bancnota de trei pesos cubanezi, a fost realizata in timpul unui eveniment organizat in memoria victimelor exploziei de la La Coubre.


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By Admin (from 01/05/2011 @ 11:00:18, in it - Scienze e Societa, read 1440 times)

Vi avvisiamo: non provateci. O, se proprio volte farlo, affidatevi a un esperto. Di cosa stiamo parlando? Di far passare corrente elettrica nel cervello: un buon modo per diventare più bravi in matematica. Parola di ricercatore di Oxford.

Bastano 15 minuti di una leggera stimolazione elettrica del cervello per migliorare le proprie capacità matematiche per almeno 6 mesi: è la singolare conclusione di uno studio recentemente condotto  nei laboratori di Oxford su alcuni volontari.

Utilizzando un metodo non invasivo noto come stimolazione elettrica transcranica diretta gli scienziati britannici hanno fatto passare una leggera corrente nel cranio di alcuni volontari, stimolando in questo modo il lobo parietale, sede dell’elaborazione numerica.

La matematica? Elettrizzante...

Ai pazienti è stato chiesto di imparare dei nuovi simboli da sostituire ai comuni numeri, poi, durante la stimolazione elettrica, è stato chiesto loro di compiere delle operazioni con le nuove cifre. Le loro performance sono state nettamente migliori di quelle fatte registrare prima della elettrizzante esperienza. Non solo: il test è stato ripetuto dopo 6 mesi e le alte performance si sono mantenute. Secondo i ricercatori la corrente aiuta le terminazioni nervose coinvolte nel ragionamento matematico ad accendersi in tempi più rapidi, rendendo più semplice la memorizzazione delle informazioni.
Il prossimo passo dello studio coinvolgerà persone con capacità matematiche più basse della media. Gli scienziati di Oxford sperano di riuscire a mettere a punto un dispositivo che consenta una pratica somministrazione della stimolazione elettrica transcranica per aiutare quel 20% della popolazione che ha difficoltà più o meno gravi nel maneggiare i numeri. Ma prima di poter parlare di una terapia passeranno ancora diversi anni.


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By Admin (from 01/05/2011 @ 08:00:23, in en - Global Observatory, read 1592 times)

Future buildings may use heat to cool off more efficiently, using new materials developed at Pacific Northwest National Laboratory. The materials could enable compact adsorption chillers inside homes and office buildings.

Adsorption chillers are a type of air conditioner that runs on waste heat, requiring very little electricity. But they’re big and expensive, which has limited their use to large, hot places like power plants or industrial spaces, as Technology Review explains.

PNNL received a grant last summer from the DOE’s Advanced Research Projects Agency, ARPA-E, to build smaller adsorption chillers based on PNNL-developed nanostructured metal-organic heat carriers, or MOHCs. The material is more porous than existing adsorption materials, which makes them more efficient. PNNL researchers displayed the new material at a recent conference.

Adsorption is the binding of molecules or particles to a surface. In an adsorption chiller, hot water drives the cooling process instead of electricity. An evaporated refrigerant (in this case, water) binds to the surface of silica gel. The gel acts as a sponge for water vapor, and when the gel is heated, the water molecules are released, condensing into water droplets when the pressure rises.

The nanostructured MOHCs are even better sponges, trapping three or four times more water by weight, which can reduce the size of the system. They are also more efficient at releasing the water molecules, further reducing the chiller’s size; Tech Review gives the full breakdown here.

PNNL says a variety of heat sources can be used to warm up the MOHCs and free the water vapor, such as burning natural gas or other fuels, heating with solar thermal, or capturing engine or fuel cell system waste heat.

Source: Technology Review

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By Admin (from 30/04/2011 @ 20:35:20, in en - Science and Society, read 13820 times)

Marijuana plants are either male or female . The male Marijuana plants produce pollen which pollinates the flowers  of  the  female  Marijuana plant, which once pollenized, produce seeds . If the female Marijuana plant  isn't  pollenized  (if  there  are  no  male  Mariuana plants  nearby  producing pollen), the flower/buds continue to develop and produce THC. Female Marijuana plants  which  are  not  pollenized  are  referred  to  as sinsemilla (without seeds). Usually 30-50% of the Marijuana plants are male.

What's the Difference you ask?

Males are often, but not always, tall with stout stems ,  sporadic  branching  and  few  leaves.  Males  are  usually  harvested except those used for breeding,  after  their  sex  has  been  determined,  but  before  the  pollen  is  shed.  When  harvesting, especially if close to females, cut the Marijuana plant off at the base, taking  care  to  shake  the  male  as  little  as  possible.  This  helps prevent any accidental pollination by an unnoticed, open male flower.

When a male enters the stage of flower development, the tips  of  the  branches  where  a  bud  would  develop  will  start  to grow what looks like a little bud (little balls) but it will have no white hairs coming  out  of  it.  Females  will  have  no  balls  and will have small white hairs. Read More about Male marijuana plants.

Male marijuana plant 


Cannabis in temperate climates begin to show his sexual identity by the end of July (end of January in the southern hemisphere) in different dates according to the varieties, Marijuana being the resinous flower of female cannabis plants intended for seed production, in absence of pollen buds turns out pure sensimilla weed and is gentle and sweet to smoke.

It is very important to get rid of male plants on time, as they are unwanted pollen carriers. By the early flowering stage male cannabis, if compared to female's, shows quite a different structure but the characteristic excrescencies would be the sex indicator this are called primordia and will emerge by the side of the third or fourth internodes in the main stem.

Female cannabis are completely revealed when the characteristic "V" shaped pistils become visible, all this to a close observation. Outdoors males will uncover themselves approximately three weeks before the females, indoors sexing of both males and females happens within a week to ten days according to the variety.

Female marijuana plant 


We've heard of urban legends about environmental conditions, age of seeds, added chemicals and even lunar stages having an influence on sexual differentiation of Cannabis; you might take note of those suggestions as personal communications, but a good handbook or an internet surf works the best if you lack in experience when sexing.

What is a Hermaphrodite plant?
An hermaphrodite, or hermie, is a Marijuana plant of one sex that develops the sexual organs of the other sex. Most commonly, a flowering female  Marijuana plant  will  develop  staminate flowers, though the reverse is also true. Primarily male hermaphrodites are  not  as well  recognized  only  because  few   growers  let  their  males  reach  a  point  of flowering where the pistillate would be expressed.

Hermaphrodites are generally viewed with disfavor. First, they  will  release  pollen and ruin a sinsemelia crop, pollinating themselves and all of the other females in the room. Second, the resulting seeds are worthless, because hermaphrodite  parents tend to pass on the tendency to their offspring.

Please note that occassionally specious staminate  flowers  will  appear  in  the  last  days  of  flowering  of  a  female  Marijuana plant. These do not drop pollen and their appearance is not considered evidence of deleterious hermaphroditism.

Hermaphrodite marijuana plant 


Here's an image of a hermaphrodite, specifically a female Marijuana plant with staminate flowers.


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By Admin (from 30/04/2011 @ 14:00:06, in en - Science and Society, read 1881 times)

An Oxford University study suggests that people living in countries with 'free market' regimes are more likely to become obese due to the stress of being exposed to economic insecurity.

The researchers believe that the stress of living in a competitive social system without a strong welfare state could be causing people to overeat. According to the study published in the latest issue of the journal Economics and Human Biology, Americans and Britons are much more likely to be obese than Norwegians and Swedes.

Oxford researchers compared 11 affluent countries and found that those with a liberal market regime (strong market incentives and relatively weak welfare states) experienced one-third more obesity on average. Their analysis of nearly 100 surveys, carried out between 1994 and 2004, revealed that the highest prevalence of obesity reported in a single survey was in the United States where one-third of the population was classed as obese. By contrast, Norway had the lowest prevalence of obesity in a single survey at just five per cent.

The study compared 'market-liberal' countries (United States, Britain, Canada and Australia) with seven relatively affluent European countries that have systems that traditionally offer stronger social protection (Finland, France, Germany, Italy, Norway, Spain and Sweden). It concludes that economic security plays a significant role in determining levels of obesity. Countries with higher levels of job and income security were associated with lower levels of obesity.

In the past, the rise of obesity in affluent societies has frequently been attributed to the ready supply of cheap, accessible, high-energy, pre-processed food in fast food outlets and supermarkets. This cause is known by researchers as the 'fast food shock'. Oxford researchers measured the impact of fast food by using a price index, constructed by The Economist magazine*, showing the international variation in the cost of the McDonald's Big Mac hamburger. They found that the availability of fast food may not be as significant as previously thought, as they calculated it had half as much an effect on the prevalence of obesity as the effects of economic insecurity.

Lead author Professor Avner Offer, Chichele Professor of Economic History at the University of Oxford, said: 'Policies to reduce levels of obesity tend to focus on encouraging people to look after themselves but this study suggests that obesity has larger social causes. The onset and increase of large-scale obesity began during the 1980s, and coincided with the rise of market-liberalism in the English-speaking countries.

'It may be that the economic benefits of flexible and open markets come at a price to personal and public health which is rarely taken into account. Basically, our hypothesis is that market-liberal reforms have stimulated competition in both the work environment and in what we consume, and this has undermined personal stability and security.'

The Oxford research team based this study on observations in academic literature about animal behaviour. Animals, both in captivity and in the wild, have been found to increase their food intake when they are faced with uncertainty about their future food supply.

These latest findings suggest that obesity in affluent societies is a response to the stress of economic insecurity. The researchers found that the effects of economic security were considerably greater in causing obesity than other factors measured (the existence of a market-liberal regime; inequality, the price of fast food, and the passage of time).

'Obesity under affluence varies by welfare regimes: The effect of fast food, insecurity, and inequality' is by Avner Offer, Rachel Pechey and Stanley Ulijaszek.

Source: ScienceDaily

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By Admin (from 30/04/2011 @ 11:00:39, in ro - Observator Global, read 2302 times)

 Aflat la 84 kilometri nord-vest de Londra, pe malul raului Chervel, Oxfordul este un oras vechi si elegant, vestit mai ales pentru celebra sa Universitate. Mentionat documentar in 912, orasul s-a grupat in jurul acestui asezamant de cultura fondat in 1168. Farmecul orasului este renumit in intreaga lume. Peste tot esti intampinat de turle, cupole, ziduri medievale, multe dintre ele inecate in iedera.

Galeriile acoperite ale manastirilor, cele 65 de biserici fac din orasul inconjurat de dealuri un loc fascinant cu o arhitectura unica in lume. Universitatea ca emblema a orasului este la fel de cunoscuta si la fel de veche precum cele de la Paris, Bologna, Padova si Salamanca. Multi dintre oamenii de seama ai Marii Britanii si nu numai au studiat aici sau la Cambridge, celalalt oras universitar al tarii situat in nord-estul capitalei. De fapt cele doua universitati sunt cunoscute sub numele comun Oxbridge. Oxfordul a servit ca decor de film pentru numeroase pelicule printre care cele realizate dupa romanele politiste ale lui Colin Dexter, al caror erou este inspectorul Morse.

Un colorit aparte il ofera orasului multimea studentilor imbracati in robele largi si purtand toci in culoarea colegiului respectiv. Colegiile au un aspect specific. Fiecare are o poarta prin care se intra in curtea interioara (patrulaterul) in jurul careia se inalta capela, sala mare, dormitoarele si camerele de studiu. Toate se mandresc cu gradini, banci de piatra, cadrane solare si arbori seculari.

Cel mai frumos dintre acestea este Christ Church, a carui catedrala, Sfantul Frideswide a fost ridicata intre 1170-1180 si completata in 1225. Colegiul se mandreste cu numeroase tablouri de Titian, Leonardo da Vinci si Rubens. La colegiul Merton, inaltat in 1264, exista o biblioteca in timpul Renasterii iar la Colegiul Hertford un pod venetian reconstruit, care leaga aripa noua de cea veche. Fiecare colegiu are viata lui proprie, este o organizatie independenta si are o avere considerabila, provenita in special din donatii si dispozitii testamentare.

Colegiile au fost puternic ancorate in istorie. Oxfordul era unul dintre locurile preferate de plimbare ale reginei Elisabeta care discuta si glumea aici cu profesorii in engleza si latina. Tot aici Carol I si-a tinut curtea in timpul Razboiului Civil, in timp ce farfuriile de argint ale colegiilor erau topite pentru a servi cauzei regale.

Una dintre cladirile si institutiile incarcate de traditii este Biblioteca Bodleiana care adaposteste peste 6.000.000 de volume, pe langa inestimabilele manuscrise si tiparituri din secolul al XV-lea. Ea a pornit din donatia testamentara de 256 manuscrise ale ducelui de Gloucester si finantata ulterior de Sir Thomas Bodley. Farmecul orasului este sporit de teatre, muzee, de strazile intortocheate, totul amintind un tablou realizat de un mare maestru.


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By Admin (from 30/04/2011 @ 08:00:15, in it - Scienze e Societa, read 2718 times)

Baveno si trova ad un’altitudine di mt. 205 s.l.m. e conta poco meno di 5.000 abitanti. È una cittadina posta sulla sponda occidentale  del Lago Maggiore, di fronte al golfo Borromeo, in un territorio insieme rivierasco e montuoso. In agevole comunicazione con i maggiori centri del nord Italia e con la Svizzera, grazie all’importante linea ferroviaria internazionale del Sempione ed all’autostrada A26 Voltri-Gravellona Toce.

Rinomata stazione di villeggiatura già dal secolo scorso, come testimoniano le sontuose ville sparse sul suo territorio, tra cui: Villa Henfrey (oggi nota come Villa Branca) dove sono stati ospiti la Regina Vittoria d`Inghilterra e lord Byron e Villa Fedora , appartenuta al noto compositore Umberto Giordano, in cui onore ogni estate si tiene un festival di musica lirica e classica. Nel centro storico del paese interessante è la visita della parrocchiale dei SS. Gervaso e Protaso, risalente ai secc. X-XI, con attiguo Battistero ottagonale e campanile romanico. Particolarmente apprezzata dai turisti è la piccola frazione di Feriolo, antica stazione di transito delle truppe romane dirette ai valichi alpini, che mantiene ancora oggi il suo caratteristico aspetto di villaggio di pescatori e scalpellini.

L’economia di Baveno è di tipo turistico-industriale,  oltre alla buona struttura ricettiva degli alberghi e dei campeggi, vi sono piccole e medie industrie, è sviluppato l’artigianato e l’estrazione del famoso granito rosa, con il quale sono state realizzate la Galleria Vittorio Emanuele a Milano ed il celebre colonnato della Basilica di San Paolo a Roma.
Baveno è ricca di angoli suggestivi, di spiaggette, tra le quali quella di Villa Fedora e di giardini lussureggianti, impreziosita dal grazioso centro storico e dalla Chiesa Parrocchiale, un complesso monumentale che risale all’anno Mille, comprendente anche il Battistero con origini paleocristiane, il campanile, il sagrato e la Via Crucis. Esistono in Baveno centro, due nuclei abitati che hanno almeno in parte conservato le caratteristiche del borgo antico. Questi agglomerati sembrano riproporre un modo di abitare molto diverso dall’attuale. I due nuclei si chiamano “Domo” e “Baitone”. Il nucleo di “Baitone” a nord della chiesa, si articola in una serie di viuzze che scendono verso la strada del Sempione, dove vi è un edificio (ora restaurato) che fu nell’ottocento il più antico albergo del lago: “l’Albergo della Posta”, con la sosta dei cavalli. Qui soggiornavano quanti scendevano verso l’Italia dal Valico del Sempione. Si ricordano anche alcuni nomi celebri come Napoleone I, Schubert e Dumas, Churchill. Dal Sagrato della Chiesa (XII sec.), dedicata ai SS. Gervasio e Protasio, ci si addentra nel quartiere “Domo”, un agglomerato di case addossate l’una all’altra. I cortili interni, i piccoli portici, i lunghi ballatoi di legno, i vicoli stretti e tortuosi, le ripide scale, le piazzette, le cappelle e i dipinti votivi, sono tutte parti integranti dell’alloggio, non inteso come uno spazio chiuso al mondo esterno. Qui può essere più facile incontrarsi, partecipare ad una vita di comunità. Oltre il torrente Selvaspessa si trova la frazione di Oltrefiume; il borgo deve la sua origine agli insediamenti dei cavapietre e degli scalpellini addetti all’estrazione ed alla lavorazione del granito rosa. Nel nucleo più antico, recentemente restaurato,  restano a testimoniare questo passato operoso, molti manufatti in granito inseriti come elementi architettonici delle case.  Da non perdere, infine, la frazione di Feriolo che, pur mantendo ancora oggi il suo caratteristico aspetto di villaggio di pescatori e scalpellini, è divenuto uno dei poli del turismo all’aria aperta.

Fonte: Sito del Comune di Baveno

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By Admin (from 29/04/2011 @ 14:00:44, in en - Science and Society, read 1686 times)

The world has waited with bated breath for three decades, and now finally a group of academics, engineers, and math geeks have finally found the magic number. That number is 20, and it's the maximum number of moves it takes to solve a Rubik's Cube.

Known as "God's Number", the magic number required about 35 CPU-years and a good deal of man-hours to solve. Why? Because there's 43,252,003,274,489,856,000 possible positions of the cube, and the computer algorithm that finally cracked God's Algorithm had to solve them all. (The terms "God's Number/Algorithm are derived from the fact that if God was solving a Cube, he/she/it would always do it in the most efficient way possible.)

A full breakdown of the history of God's Number as well as a full breakdown of the math is available here, but summarily the team broke the possible positions down into sets, then drastically cut the number of possible positions they had to solve for through symmetry (if you scramble a Cube randomly and then turn it upside down, you haven't changed the solution).

They then borrowed some computing time from Google (one of the principals is an engineer there) and burned about 35 core-years to solve all the possible positions. The number 20 has been the lower limit for God's Number for more than a decade, but the team was finally able to whittle away at the upper limit (which was trimmed back to 22 in 2008).

So far the algorithm has identified some 12 million distance-20 positions, though there are definitely many more than that. Click on this link if you want to see what some of the hardest positions are, and how they exactly tackled this problem.

Source: PopSci

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