Model copes with chaos to deliver relief Computer program helps responders transport supplies in tough conditions
By Rachel Ehrenberg Science News, Web edition: Monday, February 21st, 2011
WASHINGTON — Getting blood or other perishable supplies to an area that’s been struck by an earthquake or hurricane isn’t as simple as asking what brown can do for you. But a new model quickly determines the best routes and means for delivering humanitarian aid, even in situations where bridges are out or airport tarmacs are clogged with planes.
The research, presented February 18 at the annual meeting of the American Association for the Advancement of Science, could help get supplies to areas which have experienced natural disasters or help prepare for efficient distribution of vaccines when the flu hits.
Efficient supply chains have long been a goal of manufacturers, but transport in fragile networks — where supply, demand and delivery routes may be in extremely rapid flux — requires a different approach, said Anna Nagurney of the University of Massachusetts Amherst, who presented the new work. Rather than considering the shortest path from one place to another to maximize profit, her system aims for the cleanest path at minimum cost, while capturing factors such as the perishability of the product and the uncertainty of supply routes. ‘You don’t know where demand is, so it’s tricky,’ said Nagurney. ‘It’s a multicriteria decision-making problem.’
By calculating the total cost associated with each link in a network, accounting for congestion and incorporating penalties for time and products that are lost, the computer model calculates the best supply chain in situations where standard routes may be disrupted.
‘Mathematical tools are essential to develop formal means to predict, and to respond to, such critical perturbations,’ said Iain Couzin of Princeton University, who uses similar computational tools to study collective animal behavior. ‘This is particularly important where response must be rapid and effective, such as during disaster scenarios … or during epidemics or breaches of national security.
’ The work can be applied to immediate, pressing situations, such as getting blood, food or medication to a disaster site, or to longer-term problems such as determining the best locations for manufacturing flu vaccines. . Retrieved April 7th, 2011.

Para responder às questões de números 26 a 31, considere o texto abaixo.

January 23, 2009
Worm Infects Millions of Computers Worldwide
By JOHN MARKOFF

A new digital plague has hit the Internet, infecting millions of personal and usiness computers in what seems to be the first step of a multistage attack. The world's eading computer security experts do not yet know who programmed the infection, or what the next stage will be.
In recent weeks a worm, a malicious software program, has swept through corporate, educational and public computer networks around the world. Known as Conficker or Downandup, it is spread by a recently discovered Microsoft Windows vulnerability, by guessing network passwords and by hand-carried consumer gadgets like USB keys.
Experts say it is the infection since the Slammer worm exploded through the Internet in January 2003, and it may have infected as many as nine million personal computers around the world.
Worms like Conficker not only ricochet around the Internet at lightning speed, they harness infected computers into unified systems called botnets, which can then accept programming instructions from their clandestine masters.
Many computer users may not notice that their machines have been infected, and computer security researchers said they were waiting for the instructions to materialize, to determine what impact the botnet will have on PC users. It might operate in the background, using the infected computer to send spam or infect other computers, or it might steal the PC user's personal information.
Microsoft rushed an emergency patch to defend the Windows operating systems against this vulnerability in October, yet the worm has continued to spread even as the level of warnings has grown in recent weeks.
Earlier this week, security researchers at Qualys, a Silicon Valley security firm, estimated that about 30 percent of Windows-based computers attached to the Internet remain vulnerable to infection because they have not been updated with the patch, despite the fact that it was made available in October.
Unraveling the program has been particularly challenging because it comes with encryption mechanisms that hide its internal workings from those seeking to disable it.
The program uses an elaborate shell-game-style technique to permit someone to command it remotely. Each day it generates a new list of 250 domain names. Instructions from any one of these domain names would be obeyed. To control the botnet, an attacker would need only to register a single domain to send instructions to the botnet globally, greatly complicating the task of law enforcement and security companies trying to intervene and block the activation of the botnet.
Several computer security firms said that although Conficker appeared to have been written from scratch, it had parallels to the work of a suspected Eastern European criminal gang that has profited by sending programs known as "scareware" to personal computers that seem to warn users of an infection and ask for credit card numbers to pay for bogus antivirus software that actually further infects their computer.
One intriguing clue left by the malware authors is that the first version of the program checked to see if the computer had a Ukrainian keyboard layout. If it found it had such a keyboard, it would not infect the machine, according to Phillip Porras, a security investigator at SRI International who has disassembled the program to determine how it functioned.

(Adapted from The New York Times)

Read text I and answer questions 31 to 36.

TEXT I

Beware the power of the blog

Companies may not like blogs, but if they ignore them
they may be inviting some PR disasters


The number of blogs on the internet is doubling every five
months, according to blog-tracking site Technorati. The total is
now around 20 million, with around 1.3 million posts made each
day. Most are no more interesting than overhearing another
person's telephone call, but there are exceptions that can have a
remarkable impact.



(from http://www.computing.co.uk/itweek/comment/ 2145491/beware-power-blog, retrieved on September 24th, 2008)