Gigabit Wi-Fi gear to arrive in 2014 but data rates will vary

Companies will be able to buy plenty of Gigabit Wi-Fi gear in 2014, but they may not get Gigabit Wi-Fi data rates.

Gigabit Wi-Fi, which refers to the IEEE 802.11ac almost-standard, can vary widely in data rates depending not only on its implementation in a radio, but also on how far a client is from an access point or hotspot. It runs only in the 5-GHz band, which in theory propagates less well compared to the crowded, channel-challenged 2.4-GHz band.

Network World - Companies will be able to buy plenty of Gigabit Wi-Fi gear in 2014, but they may not get Gigabit Wi-Fi data rates.

Gigabit Wi-Fi, which refers to the IEEE 802.11ac almost-standard, can vary widely in data rates depending not only on its implementation in a radio, but also on how far a client is from an access point or hotspot. It runs only in the 5-GHz band, which in theory propagates less well compared to the crowded, channel-challenged 2.4-GHz band.

+Also on Network World: Getting ready for gigabit Wi-Fi | First Look: Gigabit Wi-Fi adapters | Your best 'Gigabit Wi-Fi' resources+

Eric Geier reviewed a selection of 11ac USB adapters and a PCI Express card for Network World, and his tests vividly show the range issues. “In terms of performance, when tested at a distance of 25 feet from our access point, with one wall in between, our top performer was the ASUS [PCIE] card, with a maximum throughput of 280Mbps and an average of 169Mbps,” he writes. “That’s pretty fast, but not close to the Gigabit speeds promised by the 802.11ac standard. However, when we moved the laptop to within a foot of the access point, performance skyrocketed to 800Mbps.”

(Related: Geier also reviewed a group of consumer-grade 11ac access points) 

Enterprise WLAN vendors are introducing aggressively priced 802.11ac access points, and more and more dongles and mobile devices have this newest version of Wi-Fi. Market researchers are forecasting rapid growth in 2014.

IDC says about 249,000 11ac enterprise-class access points shipped in 2013, with revenues of about $130 million. “That’s barely a dent in the market,” says Nolan Greene, IDC research analyst. The dent will be much bigger in 2014: IDC forecasts 1.6 million units, and about $700 million in revenues.

Enterprise 11ac access points will constitute about 10% of the market in 2014, compared to below 5% in 2013, says Chris DePuy, vice president of wireless LAN research for Dell’Oro Group. Third quarter 2013 sales jumped 10% with new entrants, such as Ubiquiti Networks.

Full list of stories looking ahead to 2014 in the tech industry.

The bulk of the buying will be what’s called “Wave 1” 11ac, with a maximum data rate of 1.3Gbps if the radios support three spatial streams, use 80-MHz channels, and are pretty close together. However, most of the early client-side implementations in laptops (and potentially tablets) support two or, in the case of smartphones, one spatial stream. As a result, performance is well under 1.3Gbps but still up to roughly double what’s possible today with 802.11n connections in optimal conditions.

Wave 2 products, due out late in 2014, will include a number of tweaks and additions, including multi-user MIMO, that will double the maximum possible data rate to 6.9Gbps.

View the original article here

Vitamin D linked to lower rates of tooth decay

View the original article here

Book explains allergies, asthma; magazine rates teen TV shows for safe-sex info

Healthy Kids

Help for 'sneezers and wheezers' "Allergies and Asthma" (American Academy of Pediatrics, $14.95)

The second edition of "Allergies and Asthma" is an important resource for parents because of the authority of the publisher: the American Academy of Pediatrics, an organization of 60,000 pediatricians. The paperback guide, which is dedicated to "the sneezers and wheezers â?¦ the scratchers and rashers," covers the basics of what allergies and asthma are, how to test for them and how to live with them. This edition includes new medications and the most up-to-date recommendations on topics such as environmental factors that can cause asthma symptoms. But it doesn't go into new research about how or when to introduce potentially allergenic foods to infants or whether avoiding certain foods during pregnancy can reduce the incidence of allergies in your child.

Safe sex on tv

Some teen shows neglect protection POZ, January/February issue

Teens having sex on TV shows isn't new, but in 2011 you might hope that the shows would at least encourage safe sex. POZ, the lifestyle magazine for people with HIV/AIDS, evaluated a variety of teen TV shows for how often characters took actions or talked about the need to protect themselves against sexually transmitted diseases or unwanted pregnancies. "Glee" got the lowest rating because Artie and cheerleader Brittany had no such discussion before hopping into the sack. "Gossip Girl" and "90210" were in the middle of the pack. The ABC Family series "The Secret Life of the American Teenager" earned the top rating for the safe-sex PSAs that follow each episode.

- Rachel Saslow

View the original article here

Scientists measure reaction rates of second key atmospheric component (Update)

Researchers at Sandia National Laboratories' Combustion Research Facility, the University of Manchester, Bristol University, University of Southampton and Hong Kong Polytechnic have successfully measured reaction rates of a second Criegee intermediate, CH3CHOO, and proven that the reactivity of the atmospheric chemical depends strongly on which way the molecule is twisted.

The measurements will provide further insight into hydrocarbon combustion and atmospheric chemistry. A paper describing the research findings titled "Direct Measurements of Conformer-Dependent Reactivity of the Criegee Intermediate CH3CHOO" is featured in the April 12 edition of Science magazine.

Criegee intermediates—carbonyl oxides—are considered to be pivotal atmospheric reactants, but only indirect knowledge of their reaction kinetics had previously been available. Last year, Sandia and its UK-based partners reported, for the first time, direct measurements of reactions of the smallest gas-phase Criegee intermediate using photoionization mass spectrometry. That research was featured in the January 13, 2012, edition of Science. A short video featuring two Sandia researchers describing the work can be seen below:

This video is not supported by your browser at this time.

New findings include confirmed fast reactions, first-time measurements with water

Sandia combustion chemist Craig Taatjes, the lead author on the Science papers, said there are several significant aspects about the new research findings.

In particular, the measurements show that the reaction rate depends dramatically on whether the CH3CHOO is bent, with the CH3– and –OO ends pointing toward the same side, a conformation called "syn–" or more straightened, with the CH3– and –OO ends pointing away from each other, called "anti–".

"Observing conformer-dependent reactivity represents the first direct experimental test of theoretical predictions," said Taatjes. "The work will be of tremendous importance in validating the theoretical methods that are needed to accurately predict the kinetics for reactions of Criegee intermediates that still cannot be measured directly."

In fact, said Taatjes, the latest results supply one of the most critical targets for such validation. Because of the large concentration of water in Earth's atmosphere, Criegee concentrations—and, hence, the tropospheric implications of all Criegee intermediate reactions—depend on knowing the rate constant for reaction with water.

Although the reactions for most Criegee intermediates, including the syn- conformer of CH3CHOO, with water may simply be too slow to be measured by the research team's methods, anti-CH3CHOO has been predicted to have a vastly enhanced reactivity with water. Taatjes and his colleagues confirmed this prediction and made the first experimental determination of the reaction rate of a Criegee intermediate with water. "A Criegee intermediate's reaction with water determines what the concentration of these intermediates in the atmosphere is going to be. This is a significant benchmark," he said.

Taatjes said one of the questions remaining after the first direct measurement of Criegee reactions was whether the remarkably fast reaction of CH2OO with SO2 was representative of other Criegee intermediates.

"This measurement of a second intermediate—which we found to react just about as fast with sulfur dioxide as the intermediate we measured last year—supports the notion that the reactions of all Criegee intermediates with SO2 will occur easily," said Taatjes "It also confirms that Criegee intermediate reactions are likely to make a contribution to sulfate and nitrate chemistry in the troposphere." This increase in reactivity, he said, provides additional evidence that Criegee intermediates will play a significant role in the oxidation of sulfur dioxide in the atmosphere.

Unraveling the mysteries, complexities of Criegee intermediates

Hydrocarbons that are emitted into Earth's troposphere, either naturally or by humans, are removed by many reactive atmospheric species. For unsaturated hydrocarbons—molecules with at least one C=C double bond—a prominent removal mechanism is reaction with ozone, called ozonolysis. It is accepted that ozonolysis produces other reactive species, including carbonyl oxides, which are known as Criegee intermediates. Rudolf Criegee, a German chemist, first proposed the mechanism of ozonolysis in the 1950s.

Because so much ozonolysis happens in the atmosphere, the reactions of Criegee intermediates are thought to be very important in a wide range of tropospheric processes like secondary organic aerosol formation and nighttime production of highly reactive OH radicals. As a result, the chemistry of these reactive Criegee intermediates has been the subject of intense investigation for decades, but without any direct measurement of their reaction rates until last year's published work by Sandia and its collaborators.

More information: "Infrared Absorption Spectrum of the Simplest Criegee Intermediate CH2OO," by Y.-T. Su, Science, 2013. www.sciencemag.org/content/335/6065/204

Journal reference: Science

Provided by Sandia National Laboratories

View the original article here