Problems on Capacitors & Direct Current Circuits

http://www.esnips.com/web/Physics3

Problems used in former tests about Capacitors & Direct Current Circuits.
[Download the file PruebaFisica3_CapacitanciaCircuitos.pdf]

Physics 3-06. The Electric Field II

Physics 3-06. The Electric Field I

Physics 1-01. Kinematics - Motion in 1 Dimension

Building a Better Battery

http://www.wired.com/wired/archive/14.11/battery.html

By John Hockenberry
They run out of juice – or burst into flames – at exactly the wrong time. Can't anyone make a battery that doesn't suck?
Issue 14.11 - November 2006

How Gene Silencing May Provide Cures

http://www.technologyreview.com/read_article.aspx?id=17652&ch=biotech

By Katherine Bourzac

RNA interference was first discovered by Andrew Fire and Craig Mello through their work on C. elegans worms, shown above. (Credit: James King-Holmes / Science Photo Library)

Recent Nobel laureate Andrew Fire talks about the evolving understanding of RNA interference's natural roles in development and disease.

Wednesday, October 25, 2006

3M's Safer, Lithium-Ion Batteries

http://www.technologyreview.com/read_article.aspx?id=17653&ch=energy

By Kevin Bullis

New electrodes and electrolytes could mean higher energy and less danger from lithium-ion batteries. 

Wednesday, October 25, 2006

A Practical Fuel-Cell Power Plant

http://www.technologyreview.com/read_article.aspx?id=17644&ch=energy

By David Talbot



GE's advance allows for a solid-oxide fuel cell to use coal-based fuels at costs approaching that of conventional power plants.

Monday, October 23, 2006

Printing Fuel Cells

http://www.technologyreview.com/read_article.aspx?id=17626&ch=energy

By Kevin Bullis 

A new printing process could cheaply make complex fuel-cell reformers, and other microscale devices.

Tuesday, October 17, 2006

Safer, Higher-Capacity Batteries

http://www.technologyreview.com/read_article.aspx?id=17603&ch=energy

By Kevin Bullis 

Silver-zinc battery chemistry could replace lithium ion in laptops and other electronics--if such batteries can be made cheaply enough.

Wednesday, October 11, 2006

Assessing GM's Fuel Cell Strategy

http://www.technologyreview.com/read_article.aspx?id=17586&ch=energy

By Kevin Bullis

The automaker plans to begin rolling out a test fleet of fuel-cell cars, but some experts say it's a mistake.

Friday, October 06, 2006

Will Silicon Light Illuminate the Future?

http://www.technologyreview.com/read_article.aspx?id=17588&ch=energy

By Tyler Hamilton

A startup says it can make silicon-based lighting that will compete with conventional incandescent bulbs and existing LED-based lighting. 

Friday, October 06, 2006

More Efficient Solar Cells

 http://www.technologyreview.com/read_article.aspx?id=17577&ch=energy

By Prachi Patel-Predd

A semiconductor material with three energy bands uses more sunlight, by trapping low-energy photons.

Wednesday, October 04, 2006

Powerful Batteries That Assemble Themselves

http://www.technologyreview.com/read_article.aspx?id=17553&ch=energy

By Kevin Bullis

MIT researchers are developing low-cost manufacturing methods based on the rapid reproduction of viruses. Angela Belcher explains.

Thursday, September 28, 2006

Virus-Assembled Batteries

http://www.technologyreview.com/read_article.aspx?id=16673&ch=biztech&sc=&pg=1

By Kevin Bullis

A biological template ramps up electrode performance and scales down size.

Images courtesy of Angela Belcher, MIT.Copyright Technology Review 2006

Recipe for using viruses to make an electrode:

Dip a polymer electrolyte in a solution of genetically engineered viruses.

These form a uniform coating on the electrolyte.

Dip the coated polymer into a solution of battery materials.

The viruses coat themselves with the battery material, transforming into nanowires with a regular crystal structure good for high-energy batteries.

Friday, April 07, 2006

Special Report: Facing Global Warming

http://www.technologyreview.com/special/oil/index.aspx









Readily available energy technologies could be put in use today to forestall global warming. Technology Review examines some of these technologies and argues that they require not further refinement but a considered, long-term deployment strategy.

BMW's Hydrogen Hopes

http://www.technologyreview.com/read_article.aspx?id=17526&ch=energy

By David Talbot

Hydrogen may never be feasible as a fuel for vehicles, but BMW is pushing ahead anyway with an advanced hydrogen-gas combustion hybrid.

The internal combustion engine in BMW’s new hydrogen-gasoline hybrid engine can switch seamlessly between the two fuels. And control systems optimize the concentrations of hydrogen being burned, which can minimize or eliminate one of the downsides of hydrogen combustion: the formation of nitrogen oxides. While BMW hopes its new model will help drive the adoption of hydrogen in vehicles, experts are skeptical. (Credit: BMW)

Friday, September 22, 2006

Lithium Ion Hybrid Batteries

http://www.hybridcars.com/lithium-ion-hybrid-batteries.html

A Laptop in Every Garage
The emergence of small lightweight long-running lithium-ion batteries has helped create a market for notebook computers, cell phones, and other portable devices from the iPod to the BlackBerry. Now, efforts to scale that technology for use in car batteries could do for the automotive industry what it did for computer and phone companies. The benefit for consumers could be revolutionary: hybrid or pure electric cars with great efficiency, acceleration and range—at the same price or cheaper than today's conventional cars.

Ultracapacitors & Hybrid Electric Vehicles

http://maxwell.com/ultracapacitors/applications/transportation.html

Application: Hybrid Electric Vehicles (HEV)

Key Customer Requirements

Manufacturers of HEV's are looking at relieving battery's load during high power times, such as initial acceleration and braking. These are the instances when the batteries see the highest current levels. By load leveling these spikes the batteries will last longer, saving the customer money.

Maxwell Solution

Maxwell Technologies ultracapacitors were designed to work with system batteries to improve power management and relieve peak load times stress on batteries. Our ultracapacitor technology protects the battery. It allows the battery to handle the energy requirements while the caps handle the high power requirements.

Customer Benefits

Ultracapacitors significantly improved power management in the hybrid electric vehicles and extended battery life. In addition, ultracapacitors allow for lower emissions, better fuel-efficiency and advanced electrical drive capabilities. The new power system using ultracapacitors allowed the HEV to recapture and reuse braking energy. Compared to conventional diesel engines: reduction of fuel consumption was estimated at greater than 50%; reduction in particulate emissions was greater than 90%; and reduction of nitrogen oxide emissions was 50%.

Ultracapacitors & Medical Applications

http://maxwell.com/ultracapacitors/applications/medical.html

Application
High reliability Medical equipment that requires Medical grade electrical isolation, conditioned and/or backup power.

Key Customer Requirements
Reliable distribution of Medical grade conditioned power to Medical Imaging, Diagnostic and Treatment equipment that requires high reliability and availability. Power systems that integrate seamlessly with the entire system and provide power protection and conditioning for worldwide voltages and frequencies.

Maxwell Solution
POWERCACHE® System can be engineered to provide worldwide industry leading noise suppression, Medical grade voltage regulation and transformation along with custom power distribution.

Customer Benefits
Power engineering expertise that can help develop and integrate power systems seamlessly into their entire system. Increased reliability and continued operation of their systems.

Ultracapacitors & Space

http://maxwell.com/ultracapacitors/applications/space.html

Application: Satellites

Customer Requirements

Satellites require efficient power solutions. As with any other system that uses power, satellites have a need for reliable and efficient power delivery. In addition, satellites often require large busts of power to perform processor-intensive operations, which may be for a limited amount of time. Or, during a power outage it is often critical to maintain some electrical functions, such as the memory contents, that may require a small amount of current.

Maxwell's Solution

The high reliability of BOOSTCAP ultracapacitors makes them an ideal solution for mission critical electronics that must operate consistently, even during power outages. Although originally designed for terrestrial power needs, recent studies of Maxwell's ultracapacitors show that their performance remains the same when subjected to the unique environment of space. The PC5 has survived the environmental tests for MIL-STD-810 while our PC10, PC100 and PC1000 ultracapacitors continued to perform within spec while being exposed to gamma doses up to 200 Krad(Si).

Customer Benefits

Based on the results of these studies, BOOSTCAP® ultracapacitors are a viable option for power needs in low earth orbit satellite applications and pending further testing, may also be suitable for deep space missions. The smaller size and weight of BOOSTCAP ultracapacitors, as compared to traditional batteries and other power packs of similar performance, allows for a greater packaging efficiency which is essential for satellite applications.

These capacitors are used in the International Space Station PEEK (Portable Electrical Equipment Kit). The PEEK hardware provides electrical power extension cables and outlets as well as 120 to 28Vdc converter units to power portable electrical hardware on the ISS.

Evaluation of Maxwell Technologies PC-5 Ultracapacitor, by The Parts Analysis and Assurance group at the Johnson Space Center:

http://maxwell.com/ultracapacitors/support/papers/PC5_evaluation.html

http://maxwell.com/ultracapacitors/support/papers/PC5_evaluation.pdf

Ultracapacitors & Entertainment

http://maxwell.com/ultracapacitors/applications/toys.html

Application: Battery Operated Toys

Customer Requirements

Price is key in this industry. Toy companies will explore every option to reduce expenses and increase their overall margins. After price, the toy manufacture business requirements include product availability and performance.

Maxwell Solution

Maxwell Technologies PC5 and PC10 cells both have the performance and footprint characteristics to be applied in capacitor toys. The toy market has embraced the use of ultracapacitor technology. Toy manufactures can benefit by placing a permanent ultracapacitor on board in place of a battery. A clear advantage is the capacitor is much lighter which awards performance advantages. It can be re-charged hundreds of times by a battery pack.

Customer Benefits

Our small cells are a flat design that provides the designer with a new option for developing a toy application. The use of ultracapacitor technology also has more energy per gram than other solutions available on the market. This provides our toy designers with more run time.

Ultracapacitors & Digital Cameras

http://maxwell.com/ultracapacitors/applications/electronics.html

Application: Digital Cameras

Customer Requirements

Manufacturers of digital cameras are looking at options to relieve battery load during high power times, such as microprocessor, zoom and flash, and extend battery life. These activities create high peak demand functions of the camera. By leveling out the load the battery is spared and will last longer resulting in limited battery replacement that is results in cost savings and enhanced convenience to the consumer.

Maxwell's Solution

Maxwell Technologies ultracapacitors were designed to work with system batteries to improve power management. Digital cameras are perfect candidates for ultracapacitor technology because of their energy and peak power demands. By using the ultracapacitors for all peak power demands, the battery is protected from the big current draws that shorten their overall lifespan.

Customer Benefits

Ultracapacitors significantly improved power management in the digital cameras and extended battery life. In addition, ultracapacitors allows consumers of digital camera to easily install replaceable alkaline batteries so they do not have to rely on inconvenient, and often hard-to-find re-chargeable batteries-making cameras smaller, lighter, and user-friendlier. Ultimately resulting in sales and increased customer satisfaction.

ISE Corporation - Hybrid Electric Vehicle

http://maxwell.com/ultracapacitors/applications/ise.html

ISE Corporation Case Study

The depletion of natural resources, air pollution and the rocketing price of gas are all issues that impact the automotive industry. Fortunately, something is being done about it. “Transportation for a clean planet” is the motto of the ISE Corporation, which has been building hybrid and electric vehicles since 1996.

The Problem

ISE's Hybrid Electric Vehicle (HEV) technology combines the best characteristics of fuel-driven engines, electric motor drives and energy storage components. Their solution has been designed with a combustion engine that functions as the primary power source, and an electric motor with a power storage system that functions as the secondary power source. Designers are able to size the combustion engine for cruising power requirements thanks to the presence of the secondary power source that handles the peak power demands for acceleration. Additionally, regenerative braking energy is captured by the secondary power system and that energy is applied for further acceleration or for the basic energy needs of supplementary electrical systems by using the secondary source.

Using only batteries to provide the electrical power storage has drawbacks in the hybrid application. These deficiencies are multiple, and they create many design challenges for automotive engineers. Firstly, batteries have difficulty functioning in cold weather. Secondly, batteries require a sophisticated charge equalization management. Thirdly, batteries have limited cycle life under extreme conditions, which results in high cost replacement throughout the life of the vehicle. A new battery has to be purchased and installed; the old battery has to be removed and disposed. Battery disposal can be problematic unless the manufacturer has a recycling program. All of this adds to the cost of a battery-based system.

Perhaps most importantly though, batteries are limited in their ability to capture and provide bursts of high power during short duration events such as acceleration and regenerative braking. This high power limitation reduces the efficiency of the hybrid electric drive system design.

The Solution

ISE's solution to the above stated problems has been to think beyond batteries; to the reliable technology of ultracapacitors. An ultracapacitor can fulfill many of the functions of batteries in this application, but with dramatically higher reliability and overall performance.

Compared to batteries, the key benefits offered by BOOSTCAP ultracapacitors are as follows.

• Ultracapacitors function well in cold weather, down to –40° Celsius, whereas, without heating, batteries do not operate reliably below 0° degrees Celsius.
• Ultracapacitors are a safe solution as a pack with equalization is discharged over night.
• Ultracapacitors have a long life cycle, basically built to last the lifetime of the machine into which they are incorporated and as they are maintenance-free, that ultimately results in cost savings.
• Ultracapacitors are more efficient than batteries; 84-95% as compared to an average of below 70% for batteries in this application as measured by ISE.
• Ultracapacitors are very earth-friendly as they are 70% recyclable and do not include any heavy metals which are detrimental to the environment.
• Ultracapacitors offer up to 10x the power of batteries and in terms of acceleration of a vehicle, this plays an important role.

ISE Corporation - ThunderPack:

http://www.isecorp.com/ise_products_services/components_subsystems/ultracapacitor-packs.php

Combat Survivor Evader Locator

http://www.boeing.com/defense-space/ic/csel/userequip.html

The CSEL Radio

The User Equipment Segment consists of the multifunction hand-held radio and theater mission planningcomputers, including GPS key loaders. The Boeing multifunction hand-held radio is very user friendly and supports data communication for all OTH Relay modes; aircraft interrogation, precise geopositioning, and SAR aircraft-compatible LOS voice and beacon. The hand-held radio is designed to keep the operator informed withdescriptive status messages and a reassuring LED indicating proper unit operation and message validation.

Boeing's Combat Survivor Evader Locator (CSEL) communication system with ultracapacitor technology

http://editors.maxwell.com/ultracapacitors/applications/boeing.html

Maxwell Technologies Ultracapacitors – Applications

Case Study

Customer Requirements

The loss of a downed pilot is never an acceptable mission outcome. Even in the recent past, we have seen images on television of the agony of family and friends as they wondered as to the whereabouts of their loved ones in Southeast Asia, Bosnia and the Middle East. Often rescue missions experienced low recovery rates and exposed rescue forces to very high enemy threats. Boeing has addressed these issues with the introduction of its new and revolutionary Combat Survivor Evader Locator (CSEL) communication system. This "locator radio" is based on flexible, modular communication architecture that utilize multiple satellite links, a state-of-the-art military GPS Receiver and is fully integrated into the Global Command and Control System.

One of the key challenges in the design of the CSEL system was the requirement for backup power in the event the 21-day battery needs to be replaced during a mission. Boeing looked to Maxwell Technologies and its ultracapacitor technology. Ultracapacitors offer a small, reliable solution for the short-term power needs of the system during battery replacement, or in the case of battery failure.

Maxwell Solution

Maxwell's ultracapacitors are an excellent solution for this application - storing energy when not needed, and providing power to the CSEL radio while the soldier swaps out the battery. Battery life is always a concern in all hand held devices, but is especially crucial when loss of power can result in and interruption of vital data transmissions, and the loss of crucial mission information. Boeing needed something that would last the life of the product, and the high reliability and long life of ultracapacitors provide the longevity they needed, and are robust enough to withstand the harshest of conditions faced by a soldier in the field. Ultracapacitors are turning up in a wide variety of hand held devices ranging from digital cameras to children's toys. In the case of the CSEL, they are providing a critical function that may one day help to bring a soldier back home.

Customer Solution

Needed was the design and development of a device using ultracapacitor component to offer uninterrupted backup power for Critical Lifesaving Communication System (CSEL). The CSEL is an amazing device with an incredible amount of functionality and, surprisingly, it is contained in a very small package. One of the keys to the program's success was it's minimal size, and ultracapacitors contributed to the small form factor due do their compact, flat design.

Maxwell Technologies is proud to be a component in Boeing's state of the art radio locator. These systems are already being deployed to selected branches of the United States military and will soon be used worldwide.

Ultracapacitors – Technology Overview

http://www.maxwell.com/ultracapacitors/support/overview.html

Ultracapacitors are an innovative energy storage technology ideally suited for applications needing repeated bursts of power for fractions of a second to several minutes. They pack up to 100 times the energy of conventional capacitors and deliver ten times the power of ordinary batteries.

To make power available when needed by the application, the ultracapacitor "caches" power from any energy source. This power is then discharged from the ultracapacitor at rates demanded by the application. The ultracapacitor can be repeatedly charged and discharged at rates optimized for the application.

Using ultracapacitors for power bursts maximizes the life and efficiency of the system's energy source. The ultracapacitor allows the entire system to be tailored to optimally meet both power and energy requirements.

Maxwell Technologies: Ultracapacitors

http://www.maxwell.com/ultracapacitors/index.html

As compared to batteries, ultracapacitors deliver up to 10 times the power, last up to 10 times as long, operate more reliably in high- and low-temperature conditions, require far less maintenance and reduce environmental issues associated with battery disposal.

Extremely high electrical energy storage capacity and the ability to deliver bursts of high power and recharge rapidly from any energy source over hundreds of thousands of cycles make ultracapacitors an ideal solution for a wide variety of applications.

Postage stamp-size small cell ultracapacitors extend battery life and enhance the performance and functionality of hand-held electronic devices, remote transmitting devices and toys.

Large cells are also available and can be linked together to form power packs of up to 500 cells to power initial acceleration, operate electrical subsystems and recapture energy from braking for cleaner, more fuel-efficient hybrid electric/internal combustion buses, trucks and automobiles. Maxwell offers several integrated module and pack solutions that are available with active or passive voltage balancing.

Ultracapacitors offer also highly reliable solutions for bridge power applications requiring “zero downtime” power reliability.

Ultracapacitor’s key characteristics:

• High reliability and cycle life 100,000 cycles plus
• Rapid recharge capability within minutes
• High power density
• Wider temperature range versus batteries
• No maintenance

How an Ultracapacitor Works

http://www.nrel.gov/vehiclesandfuels/energystorage/ultracapacitors.html

Ultracapacitors

Like batteries, ultracapacitors are energy storage devices. They use electrolytes and configure various-sized cells into modules to meet the power, energy, and voltage requirements for a wide range of applications. But batteries store charges chemically, whereas ultracapacitors store them electrostatically. Currently, ultracapacitors are more expensive (per energy unit) than batteries. Ultracapacitors are true capacitors in that energy is stored via charge separation at the electrode-electrolyte interface, and they can withstand hundreds of thousands of charge/discharge cycles without degrading. They provide quick bursts of energy.

NREL – National Renewable Energy Laboratory

Advanced Vehicles and Fuels Research

Energy Storage

How a Battery Works

http://www.nrel.gov/vehiclesandfuels/energystorage/batteries.html

Batteries

A conventional vehicle uses a lead acid battery to start the engine and power auxillary loads (lighting, electronics, etc.). Hybrid electric, electric, and fuel cell vehicles (HEVs, EVs, and FCVs) have conventional lead acid batteries, but also have propulsion batteries, which are constructed quite differently—they are built for high power, high energy, and long cycle lives. Some low-voltage hybrid vehicles use advanced lead acid batteries, known as valve regulated lead acid (VRLA) batteries.

NREL – National Renewable Energy Laboratory

Advanced Vehicles and Fuels Research

Energy Storage

Safer Lithium-Ion Batteries

http://www.technologyreview.com/read_article.aspx?id=17362&ch=energy

By Kevin Bullis

In light of Apple's and Dell's massive recalls, will computer makers opt for batteries that are less prone to catching fire?

Friday, August 25, 2006

Safer, Longer-Lasting Batteries

http://www.technologyreview.com/read_article.aspx?id=17513&ch=biztech

By Kevin Bullis

Thin-film technology is still expensive, but it could soon run remote sensors and medical implants--and one day electric vehicles.

Tuesday, September 19, 2006

Better Fuel Cells for Laptops

http://www.technologyreview.com/read_article.aspx?id=17495&ch=energy

By Kate Greene

Adding a chemical found in antifreeze to fuel cells could provide a longer-lasting alternative to batteries in portable electronics.

Wednesday, September 13, 2006

Solar Cells for Cheap

http://www.technologyreview.com/read_article.aspx?id=17490&ch=energy

By Kevin Bullis

Not everyone gets a solar cell named after them: but Michael Gratzel did. He says his novel technology, which promises electricity-generating windows and low manufacturing costs, is ready for the market.

Tuesday, September 12, 2006

How Future Batteries Will Be Longer-Lasting and Safer

http://www.technologyreview.com/read_article.aspx?id=17382&ch=energy

By Kevin Bullis

An MIT battery expert says advances in materials and engineering can realistically double capacities in the next 10 years, without sacrificing safety.

Wednesday, August 30, 2006

An Alternative to your Alternator

http://www.technologyreview.com/read_article.aspx?id=16945&ch=nanotech

By Kevin Bullis

New thermophotovoltaic materials could replace alternators in cars and save fuel.

Thursday, June 1, 2006

Better Fuel Cells Using Bacteria

http://www.technologyreview.com/read_article.aspx?id=16921&ch=biztech

By Emily Singer

Bioengineer Tim Gardner says synthetic biology could create bacteria that produce electricity from waste more efficiently.

Wednesday, May 24 2006

More Powerful Hybrid Batteries

http://www.technologyreview.com/read_article.aspx?id=16894&ch=biztech#

By Kevin Bullis

A123 Systems has built a powerful, lightweight lithium-ion battery pack that could lower the price of hybrid vehicles.

Friday, May 19, 2006

Plug-In Hybrids Are on the Way

http://www.technologyreview.com/read_article.aspx?id=16922&ch=biztech

By Kevin Bullis

Cars with advanced batteries get 100 mpg and boast far greater range than all-electric vehicles.

Wednesday, May 24, 2006

Better than Hybrids

http://www.technologyreview.com/read_article.aspx?id=16727&ch=biztech

By Kevin Bullis

A proposed engine design approaches the efficiency of gas-electric hybrids, but could be far cheaper.

Monday, April 24, 2006

Finally, Better Batteries

http://www.technologyreview.com/NanoTech/wtr_16455,318,p1.html

By Kevin Bullis

Graphite “foam,” nanotech-enabled lithium surge to market.

March/April 2006

The Lithium-Ion Car

http://www.technologyreview.com/BizTech/wtr_16624,295,p1.html

By Kevin Bullis

Altair Nanotechnologies plans to road test an advanced electric vehicle prototype.

Friday, March 24, 2006

Practical Fuel-Cell Vehicles

http://www.technologyreview.com/BizTech/wtr_16504,296,p1.html

By Kevin Bullis

Hybrid vehicles operating in an unusual environment are lifting the prospects of fuel cells.

Friday, March 03, 2006

The Ultra Battery

http://www.techreview.com/NanoTech-Devices/wtr_16326,303,p1.html

By Kevin Bullis

A new type of ultracapacitor could eventually have you throwing out your conventional batteries.

Monday, February 13, 2006

Battery Breakthrough – An Update

http://www.techreview.com/BizTech/wtr_16410,295,p1.html

By Kevin Bullis

As President Bush talks up the need for more research, scientists are making advances in hybrids and all-electric vehicles.

Wednesday, February 22, 2006

Battery Breakthrough

http://www.technologyreview.com/NanoTech/wtr_16384,318,p1.html

By Kevin Bullis

A new material could mean batteries that finally make electric cars practical.

Tuesday, February 21, 2006

Batteries that Don't Die

http://www.techreview.com/Devices/wtr_16278,303,p1.html

By Kevin Bullis

New technologies are transforming an old workhorse, promising all-electric lawnmowers and hybrid military vehicles.

Friday, February 03, 2006

More Powerful Batteries

http://www.technologyreview.com/read_article.aspx?id=14548&ch=infotech

By Kevin Bullis

A new, fast-charging battery will make drills and hybrid cars more powerful.

Monday, November 21, 2005

The Atomic Battery

http://www.technologyreview.com/read_article.aspx?id=14548&ch=infotech

By Eric S. Brown

A breakthrough in betavoltaics could mean a 10-year battery life for sensors and medical implants.

June 16, 2005

A Fuel Cell in Your Phone

http://www.technologyreview.com/read_article.aspx?id=12668&ch=biztech

By David Voss

Tired of short-lived batteries? Methanol-powered micro fuel cells are racing toward market, promising up to 20 hours of cell-phone talk time.

November 2001