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2013年9月28日星期六

A step up in wavelength to reduce size of short-distance communication systems

Millimeter waves are a type of radiofrequency electromagnetic radiation with wavelengths between 0.1 and 10 millimeters long. Because they are susceptible to absorption by water in the atmosphere, they travel short distances only. Despite this limitation, their short wavelength makes them a useful technology for small-distance applications. Examples include short-range, secure wireless communication and automotive-radar technology, which lets self-driving cars sense their environment.

Electronic components that can manipulate millimeter waves are vital for realizing this potential in commercial applications. Specifically, it is important to change the wavelength of such waves from, for example, one that is optimal for sending information across short distances to one that is more easily processed electronically.

Rui Li and co‐workers at the A*STAR Institute of Microelectronics, Singapore, have designed and fabricated an electronic module that can convert a millimeter wave from one wavelength to another. The device, called a subharmonic passive mixer, mixes an incoming millimeter wave that has a wavelength of 2.2 millimeters with a local source of 4.3-millimeter waves to generate a 1.1-millimeter signal. A signal of this wavelength means that the device operates at a frequency of 273 gigahertz; that is, 273 billion oscillations per second. Operation at such a high frequency allows a large number of potential transmission channels.

Importantly, the researchers' device is based on a technology called 'system-on-package', where the components are attached to a package. "It is the first time that [an on-package] converter has operated at such a high frequency," says Li. In contrast, conventional electronic devices, such as laptops and phones, are miniaturized by combining hundreds of electrical devices on a silicon chip. This approach becomes problematic when dealing with electronic components that operate at radiofrequencies. The low electrical resistivity of silicon results in an energy loss that degrades the overall system performance. The manufacturing cost is also high because the components occupy a large area.

The device developed by Li and her co-workers comprised three stacked thin films of metal, and the choice of material to separate these layers was crucial to it's efficient operation. The researchers used benzocyclobutene -- a polymer that, unlike silicon, is known to have good electrical performance, even in the millimeter-wave region. Thorough electrical testing confirmed the high-performance of their design.

"We are currently in the process of designing and implementing numerous similar types of millimeter-wave passive components in various types of package," says Li. "We hope this will reduce the chip area as compared to 'on-chip'-based approaches."

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Laser treatments yield smoother metal surfaces

Sep. 26, 2013 — Ever since the Bronze Age, metals have been cast in different shapes for different applications. Smooth surfaces that are resistant to corrosion are crucial for many of the present-day uses of cast metals, ranging from bio-implants to automotive parts. Yingchun Guan, from the A*STAR Singapore Institute of Manufacturing Technology (SIMTech) and her co-workers have shown how different laser-processing methods improve metal surfaces and protect them against corrosion.

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Laser processing involves scanning a high-intensity laser beam multiple times across the surface of a metal. Each scan by the laser beam 'writes' a track in the surface, which partially melts the metal. Consecutive tracks can overlap -- the degree to which affects how well the melting caused by these tracks will smooth the surface of the metal. The scanning speed can also affect the surface melt.

Guan and co-workers investigated how different degrees of overlap between the tracks affect the surface properties of AZ91D -- a common magnesium alloy. "AZ91D is the most widely used magnesium alloy for the production of high-volume components for the automotive, electronics and telecommunications industries," Guan explains.

By examining cross-sections of AZ91D samples post-melt, the researchers found that the greater the degree of overlap between the tracks, the fewer the number of small cracks that developed during solidification (see image). According to Guan, this finding should be considered when processing metals destined for exposure to fluids, such as those that will be used in bio-implants.

The researchers also detected alterations in the alloy's composition through changes in the degree of laser-track overlap. Melted magnesium evaporates more readily than aluminum, and as the degree of laser-track overlap increased, it changed the composition of the alloy -- particularly in the larger areas of melt. Theoretical calculations by Guan and her co-workers described these kinetics accurately.

According to the team's model, a greater level of overlap provided a greater amount of heat, which improved the convection of the metals within the molten liquid and yielded a more homogeneous surface. Electrochemical tests by the team also confirmed that the more homogeneous the surface of a material, the more resistant it was to corrosion.

The team's approach, particularly the theoretical model, is applicable to assess laser processing of other alloys and compounds, Guan notes. As the surface structures affect not only the mechanical and chemical properties but also the electronic, thermal and optical parameters, these findings will be of relevance to metals used in a variety of applications.

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2013年9月27日星期五

Power 10W charger chip from Dialog/iWatt

2013/09/27

Dialog Semiconductor has introduced a 10W ac-dc power controller that can use an npn bipolar transistor (BJT) – a transitor option first pioneered by CamSemi – instead of needing a mosfet.

“The use of BJTs is prevalent in 5W and lower power supplies,” said Dialog v-p Ron Edgerton. “We are bringing this to higher power applications.”

Called iW1679 (Dialog bought iWatt recently) the chip is a pulse width modulation and pulse frequency modulation (PWM/PFM) controller intended for 5V/2A smartphone adapters and chargers.

Claimed average active efficiency is 83% and no-load stand-by is <30mW.

“This enables designers to meet or exceed emerging global energy standards, including the European CoC version 5, which is anticipated to require 76% active average efficiency and high light load efficiency down to 10% loads, as well as the proposed US DoE regulation, expected to require 79% active average efficiency, and the Energy Star EPS 2.0, which will require 73% active average efficiency,” said the firm.

Base drive requirements for a BTT are more complex than needed at the gate of a mosfet.

Dialog has has proprietary base-drive techniques – which involve switching in and out parallel current sources – to modulate drive.

“This optimises performance and improves efficiency by keeping the BJT out of saturation,” said the firm, adding: “Since BJTs have softer switching compared to FETs, they generate less noise and, therefore, have inherently lower EMI.”

Valley-mode switching is another technique used to cut EMI. “It also includes a proprietary switching mode that results in no audible noise from the controller,” said Dialog.

Four-level cable drop compensation is included, as is protection from output short-circuit, output over-voltage, output over-current, and over-temperature.

The package is an 8-lead SOIC.

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General Nokia may seek wireless tie-up with Alcatel-Lu

2013/09/26

Nokia, shortly to be reduced to an infrastructure company, is pondering a tie-up with Alcatel-Lucent, reports Reuters.

Nokia’s infrastructure business has annual revenues of $18 billion and the company
still has net cash of over €4 billion.

Recently it bought out Siemens’ share of the business.

Alcatel-Lucent has lost an average of $934 million every year since the disastrous takeover of Lucent in 2006.

Recently Qualcomm bought a stake in the company and started a small cell joint development programme with it.

Alcatel-lucent’s new CEO, Michel Combes, is looking for similar i.e. R&D plus minority stake deals.

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Test and Measurement Agilent creates a new and more aggressive test business

2013/09/26

Agilent Technologies test and measurement business is separating from the larger life sciences and chemical analysis system business.

This will create a ‘new’ test system supplier with an established portfolio of test and measurement products, but with a new brand name.

image002_low But what will be different about this new test brand to convince the market that separation from the other half of Agilent Technologies is a positive step?

“The two businesses, the electronic measurement group and the life sciences group, were pulling in different directions from a shareholder point of view,” said Jim Armentrout, European marketing manager for Agilent’s test and measure business.

“The overlap between the two businesses was very small, they operated in different industries and different markets,” said Armentrout.

“Both sets of products are about measurements, but both are measuring very different things,” said Armentrout.

The decision to split the group seems to have been determined in part by the strong growth of the life sciences arm over the last few years.

“The life sciences business has grown into a self-sustaining business,” said Armentrout.

The test and measurement business had sales of $2.9bn in this last financial year. The life sciences and chemical analysis systems business is more profitable and larger with sales of $3.9bn.

“It was apparent that both businesses could stand on their own as independent companies. They have the size and financial stability to do this,” said Armentrout.

“We will not be competing for investment within the group,” said Armentrout.

But it will be a smaller company. Is Armentrouit confident that the new company will have the same level of R&D behind it?

“It is true the R&D activity was shared between the two groups,” said Armentrout. “But effectively the research activity was split internally between the businesses. Now it will be split externally, so there will be no reduction in R&D.”

It is likely that the new Agilent test business, under its new name, will slowly change in character. Part of this could be changes to product strategies.

Armentrout ensures me that nothing will really change. “The new company will have the same product roadmap, the same staff and its own R&D laboratories,” said Armentrout.

“But what will be different is a new focus on electronic measurement as a pure-play test and measurement company,” said Armentrout.

This is the interesting part.

The new business will have to compete in the test market by its own financial and product strategies. There will be no corporate safety net.

My guess is this will make the ‘new Agilent’ more opportunistic in its product plans and more aggressive on price than the ‘old’ company was.

For example, the modular PC-based instrument business will become a new focus for the company.

It entered the market in a big way just three years ago when it launched over 100 instrument modules based on the industry standard PXI platform.

Positioning the modular product strategy has not been easy in a business which makes most of its money from traditional standalone rack and benchtop instruments.

But now there are signs that the new company has found a way to blend the PXI modular and benchtop products together. This is based on common hardware and software which are shared by both PXI and benchtop instruments.

“We will create reference design test systems using a combination of PXI and benchtop instruments running common test applications software,” said Phil Lorch, sales manager for the software and modular product business at Agilent.

The company is also prepared to incorporate PXI modules from other vendors in the system, if necessary.

“It is not about selling a single PXI module anymore, but meeting a specific test application,” said Lorch.

The new approach to the logic analyser product line also gives us a clue that the ‘new’ company will be more flexible and price-aggressive in its product plans.

Logic analysers are a product line which the ‘old’ Agilent was a little undecided about.

“We had a focus on high-end logic analysers, but we neglected mid-range products,” said Yoram Shimoni, market development manager for the Agilent scope and protocol division in EMEA.

Like with PXI, there are signs that this is changing. The company has introduced its first mid-range logic analyser.

The company has identified the sweet spot for logic analysis is FPGA-based designs and it has adjusted the specification of the 16850 analyser to appeal to this application.

It has doubled the sample memory size to 128M samples. It has also developed a software-based probing technology which can be embedded in the netlist of the FPGA.

The new company has also given the new logic analyser a mid-range price tag of around $12k.

For the ‘new’ Agilent the challenge is to shake off the shackles of ‘big company’ culture but protect its most ambitious product plans.

These are early days, but there are first indications this may already be starting to happen.

I imagine Agilent’s test rivals will be watching closely to see if the new company, whatever it is called, will be able to do this.

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Water glides freely across 'nanodrapes' made from the world's thinnest material

These "nanodrapes" are less than a nanometer thick, chemically inert, and provide a layer of protection without changing the properties of the underlying material. The team of researchers, led by Rensselaer Professor Nikhil Koratkar, demonstrated how droplets of water encounter significantly less friction when moving across a surface covered with a nanodrape.

This innovation holds the potential to benefit lab-on-chip devices, high-throughput assays, self-cleaning surfaces, and many other applications requiring the motion of liquid drops on solid surfaces.

"Graphene nanodrapes are the thinnest, most sheer drapes we can imagine. Other than providing a barrier against water, these drapes are optically transparent and cause minimal changes to the topology of the underlying surface," said Koratkar, the John A. Clark and Edward T. Crossan Professor of Engineering at Rensselaer. "We found this ultrasheer drape prevents the penetration of water into textured surfaces, which has interesting and potentially important technological implications for many applications in micro- and nanofluidics."

Drops of water can get easily stuck or "pinned" to a material with a nanotextured rough surface. When the droplet falls onto the material, the energy from the fall pushes out or displaces the tiny amounts of air trapped in the textured surface. Once in this pinned state, it is difficult to unpin the droplet and move it around the surface.

Covering the surface with an impermeable graphene drape, however, prevents a droplet from getting pinned to the surface. The nanodrape creates a barrier that prevents the water drop from penetrating into and displacing the air from the textured surface. Instead, the droplet sits on top of the drape, with reduced friction between them, which in turn makes it easier to move the droplet around on the surface, Koratkar said. While helping to minimize this friction, the ultrasheer nanodrape causes minimal disruption to the underlying surface.

The square nanodrapes measure several inches in length, and once applied to a surface are only detectable with a powerful microscope. Koratkar and the research team dropped small amounts of water on a surface of copper nanorods, and the same surface covered with a nanodrape. Water dropped on the bare surface spread out to form large flat drops indicative of a hydrophilic surface, while water dropped on nanodraped surfaces formed a much rounder or spherical drop indicative of a water-repellant or hydrophobic surface. The researchers also used high-speed cameras to observe and measure the shape of the drops as they impacted the surface, spread out, contracted, and finally settled. Once settled, the wettability of the surface was characterized by measuring the angle at which the liquid drop contacted the solid surface.

Koratkar said the water-resistant properties are apparent after the application of a single nanodrape, but the properties are enhanced with the addition of a few additional layers. Nanometer-size cracks and wrinkles likely form in the first layer as it is applied and settles onto the surface. The second and subsequent layers likely suffer from fewer defects, and help to cover up defects on the first layer.

Koratkar and his research team create the nanodrapes by growing graphene -- a single layer of carbon atoms arranged like a nanoscale chicken-wire fence -- on top of a copper substrate. They then coat the graphene with a polymer film, and use weak acids to remove or etch away the copper, which leaves the polymer layer with the graphene film underneath floating on the top of the liquid acids. The polymer layer with graphene sheet is then transferred to a surface, and the polymer layer is gently washed away using acetone. What remains is a single-carbon-atom thick, ultra-sheer, impermeable graphene drape.

This study is the latest from Koratkar, whose research is positioned at the intersections of nanotechnology, energy, and sustainability. His work has focused on the synthesis, characterization, and application of nanoscale material systems, including graphene. His research group uses different techniques to investigate ways of incorporating these materials into various composites, coatings, and device applications.

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Hidden genetic code for better designer genes

Sep. 26, 2013 — Scientists routinely seek to reprogram bacteria to produce proteins for drugs, biofuels and more, but they have struggled to get those bugs to follow orders. But a hidden feature of the genetic code, it turns out, could get bugs with the program. The feature controls how much of the desired protein bacteria produce, a team from the Wyss Institute for Biologically Inspired Engineering at Harvard University reported in the September 26 online issue of Science.

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The findings could be a boon for biotechnologists, and they could help synthetic biologists reprogram bacteria to make new drugs and biological devices.

By combining high-speed "next-generation" DNA sequencing and DNA synthesis technologies, Sri Kosuri, Ph.D., a Wyss Institute staff scientist, George Church, Ph.D., a core faculty member at the Wyss Institute and professor of genetics at Harvard Medical School, and Daniel Goodman, a Wyss Institute graduate research fellow, found that using more rare words, or codons, near the start of a gene removes roadblocks to protein production.

"Now that we understand how rare codons control gene expression, we can better predict how to synthesize genes that make enzymes, drugs, or whatever you want to make in a cell," Kosuri said.

To produce a protein, a cell must first make working copies of the gene encoding it. These copies, called messenger RNA (mRNA), consist of a specific string of words, or codons. Each codon represents one of the 20 different amino acids that cells use to assemble proteins. But since the cell uses 61 codons to represent 20 amino acids, many codons have synonyms that represent the same amino acid.

In bacteria, as in books, some words are used more often than others, and molecular biologists have noticed over the last few years that rare codons appear more frequently near the start of a gene. What's more, genes whose opening sequences have more rare codons produce more protein than genes whose opening sequences do not.

No one knew for sure why rare codons had these effects, but many biologists suspected that they function as a highway on-ramp for ribosomes, the molecular machines that build proteins. According to this idea, called the codon ramp hypothesis, ribosomes wait on the on-ramp, then accelerate slowly along the mRNA highway, allowing the cell to make proteins with all deliberate speed. But without the on-ramp, the ribosomes gun it down the mRNA highway, then collide like bumper cars, causing traffic accidents that slow protein production. Other biologists suspected rare codons acted via different mechanisms. These include mRNA folding, which could create roadblocks for ribosomes that block the highway and slow protein production.

To see which ideas were correct, the three researchers used a high-speed, multiplexed method that they'd reported in August in The Proceedings of the National Academy of Sciences.

First, they tested how well rare codons activated genes by mass-producing 14,000 snippets of DNA with either common or rare codons; splicing them near the start of a gene that makes cells glow green, and inserting each of those hybrid genes into different bacteria. Then they grew those bugs, sorted them into bins based on how intensely they glowed, and sequenced the snippets to look for rare codons.

They found that genes that opened with rare codons consistently made more protein, and a single codon change could spur cells to make 60 times more protein.

"That's a big deal for the cell, especially if you want to pump out a lot of the protein you're making," Goodman said.

The results were also consistent with the codon-ramp hypothesis, which predicts that rare codons themselves, rather than folded mRNA, slow protein production. But the researchers also found that the more mRNA folded, the less of the corresponding protein it produced -- a result that undermined the hypothesis.

To put the hypothesis to a definitive test, the Wyss team made and tested more than 14,000 mRNAs -- including some with rare codons that didn't fold well, and others that folded well but had no rare codons. By quickly measuring protein production from each mRNA and analyzing the results statistically, they could separate the two effects.

The results showed clearly that RNA folding, not rare codons, controlled protein production, and that scientists can increase protein production by altering folding, Goodman said.

The new method could help resolve other thorny debates in molecular biology. "The combination of high-throughput synthesis and next-gen sequencing allows us to answer big, complicated questions that were previously impossible to tease apart," Church said.

"These findings on codon use could help scientists engineer bacteria more precisely than ever before, which is tremendous in itself, and they provide a way to greatly increase the efficiency of microbial manufacturing, which could have huge commercial value as well," said Wyss Institute Founding Director Don Ingber, M.D., Ph.D. "They also underscore the incredible value of the new automated technologies that have emerged from the Synthetic Biology Platform that George leads, which enable us to synthesize and analyze genes more rapidly than ever before."

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How viral infection disrupts neural development in offspring, increasing risk of autism

The research, "MHCI Requires MEF2 Transcription Factors to Negatively Regulate Synapse Density during Development and in Disease," is published in the Journal of Neuroscience.

The study's senior author is Kimberley McAllister, professor in the Center for Neuroscience with appointments in the departments of Neurology and Neurobiology, Physiology and Behavior, and a researcher with the UC Davis MIND Institute.

"This is the first evidence that neurons in the developing brain of newborn offspring are altered by maternal immune activation," McAllister said. "Until now, very little has been known about how maternal immune activation leads to autism spectrum disorder and schizophrenia-like pathophysiology and behaviors in the offspring."

The study was conducted in mice and rats and compared the brains of the offspring of rodents whose immune systems had been activated and those of animals whose immune systems had not been activated. The pups of animals that were exposed to viral infection had much higher brain levels of immune molecules known as the major histocompatibility complex I (MHCI) molecules.

"This is the first evidence that MHCI levels on the surface of young cortical neurons in offspring are altered by maternal immune activation," McAllister said.

The researchers found that the high MHCI levels impaired the ability of the neurons from the newborn mice's brains to form synapses, the tiny gaps separating brain cells through which signals are transmitted. Earlier research has suggested that ASD and schizophrenia may be caused by changes in the development of connections in the brain, especially the cerebral cortex.

The researchers experimentally reduced MHCI to normal levels in neurons from offspring following maternal immune activation.

"Remarkably, synapse density returned to normal levels in those neurons," McAllister said.

"These results indicate that maternal immune activation does indeed alter connectivity during prenatal development, causing a profound deficit in the ability of cortical neurons to form synapses that is caused by changes in levels of MHCI on the neurons," she said.

MHCI did not work alone to limit the development of synapses. In a series of experiments, the UC Davis researchers determined that MHCI interacted with calcineurin and myocyte enhancer factor-2 (Mef2), a protein that is a critical determinant of neuronal specialization.

MHCI, calcineurin and Mef2 form a biological signaling pathway that had not been previously identified. McAllister's team showed that in the offspring of the maternal immune activation mothers, this novel signaling pathway was much more active than it was in the offspring of non-MIA animals.

"This finding provides a potential mechanism linking maternal immune activation to disease-linked behaviors," McAllister said.

It also is a mechanism that may help McAllister and other scientists to develop diagnostic tests and eventually therapies to improve the lives of individuals with these neurodevelopmental disorders.

Other study authors are Bradford M. Elmer, Myka L. Estes and Stephanie L. Barrow, all of UC Davis.

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General Infineon keeps No.1 power slot

2013/09/27

Infineon remained the leading supplier of power semiconductor discretes and modules last year, reports IHS.

The company held an 11.8 percent share of global market revenue, almost unchanged from 12 percent in 2011. Infineon led No. 2 player Toshiba Corp. by 4.7 percentage points.

“Infineon maintained its leadership in the total discrete market and in the discrete insulated-gate bipolar transistor (IGBT) segments,” says IHS’ Victoria Fodale, “the company also continued to increase its share in Mosfets.”

Toshiba had the second strongest growth among the Top ten players with growth of 0.6 percentage points.

No. 3 Mitsubishi Electric maintained leadership in power modules, although the company’s share of the market declined.

ON Semiconductor achieved a more than 1 percentage point increase in share in 2012, partially driven by its acquisition of Sanyo.

Power semiconductors had a bad 2012. Power modules fell 27% and discretes fell 16%, says IHS

Blame for the collapse was put on falling consumer demand in Europe and the US, a slowdown in Asian energy projects and reduced demand in industrial and automotive markets.

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Abuse, lack of parental warmth in childhood linked to multiple health risks in adulthood

Sep. 26, 2013 — The effects of childhood abuse and lack of parental affection can last a lifetime, taking a toll both emotionally and physically.

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There are many reports assessing the psychological damage resulting from childhood abuse, and the effects on physical health have also been well documented. For instance, this "toxic" stress has been linked to elevated cholesterol, cardiovascular disease, metabolic syndrome and other physical conditions posing a significant health risk. The research into the physical effects of abuse, however, has focused on separate, individual systems.

A new UCLA-led study for the first time examines the effects of abuse and lack of parental affection across the body's entire regulatory system, and finds a strong biological link for how negative early life experiences affect physical health. The study is published online by the Proceedings of the National Academy of Sciences.

"Our findings suggest that there may be a way to reduce the impact abuse has, at least in terms of physical health," said Judith E. Carroll, a research scientist at the Cousins Center for Psychoneuroimmunology at UCLA, and the study's lead author. "If the child has love from parental figures they may be more protected from the impact of abuse on adult biological risk for health problems than those who don't have that loving adult in their life."

The researchers studied 756 adults who had participated in a study called Coronary Artery Risk Development in Young Adults (CARDIA). They measured 18 biological markers of health risk, such as blood pressure, heart rate, stress hormone, cholesterol, waist circumference, inflammation, and blood sugar regulation, and added up their risks across these markers to create a summary index called "allostatic load." Values at the upper range across these markers indicated they were at higher biological risk for disease. Previous research has shown that higher levels of allostatic load are associated with increased likelihood of a negative health event such as a heart attack or stroke, or show declines in physical or cognitive functioning.

To determine the study subjects' childhood stress the researchers used a well-validated self-report scale called the Risky Families Questionnaire.

They found a significant link between reports of childhood abuse and multisystem health risks But those who reported higher amounts of parental warmth and affection in their childhood had lower multisystem health risks The researchers also found a significant interaction of abuse and warmth, so that individuals reporting low levels of love and affection and high levels of abuse in childhood had the highest multisystem risk in adulthood.

The researchers suggest that toxic childhood stress alters neural responses to stress, boosting the emotional and physical arousal to threat and making it more difficult for that reaction to be shut off.

"Our findings highlight the extent to which these early childhood experiences are associated with evidence of increased biological risks across nearly all of the body's major regulatory systems" said Teresa Seeman, professor of medicine in the division of geriatrics at the David Geffen School of Medicine and of epidemiology at the Fielding School of Public Health at UCLA, and the paper's senior author. "If we only look at individual biological parameters such as blood pressure or cholesterol, we would miss the fact that the early childhood experiences are related to a much broader set of biological risk indicators -- suggesting the range of health risks that may result from such adverse childhood exposures."

The authors note that the findings are based on a cross-sectional analysis and do not prove causation. It used information provided by the participants, so there may be some recall bias. Also, the analysis may not have captured other factors affecting regulatory systems, such as poor nutrition or environmental pollution.

But the findings suggest that parental warmth and affection protect one against the harmful effects of toxic childhood stress. Also, the lingering effects of childhood abuse can be linked to age-related diseases such as cardiovascular disease. Among other things, this could have an effect on long-term health care costs.

"It is our hope that this will encourage public policy support for early interventions," Carroll said. "If we intervene early in risky families and at places that provide care for children by educating and training parents, teachers, and other caregivers in how to provide a loving and nurturing environment, we may also improve the long term health trajectories of those kids."

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