text:
A method of growing a thin film onto a substrate. A precursor of the film is fed into a reaction space in the form of a vapor phase pulse causing the precursor to adsorb onto the surface of the substrate to form a layer thereof. A catalyst is susequently fed into the reaction space in an amount to substantially convert the layer of the precursor to the desired thin film. The above steps may be repeated to achieve the desired film thickness.
1. A method for depositing a metal-containing film to a substrate within a process chamber by an atomic layer deposition technique, comprising:
introducing a precursor to the process chamber;
adsorbing the precursor to the substrate;
purging the process chamber with a purge gas;
introducing a process gas comprising the precursor and a reactant;
reacting the adsorbed precursor with the process gas to deposit the metal-containing film; and
purging the process chamber with the purge gas.
2. The method of
3. The method of
4. The method of
5. The method of
6. The method of
7. A method for depositing a metal-containing film to a substrate within a process chamber by an atomic layer deposition technique, comprising:
introducing a metal-containing precursor to the process chamber;
adsorbing the metal-containing precursor to the substrate;
purging the process chamber with a purge gas;
introducing a process gas comprising the metal-containing precursor and a gaseous catalyst;
chemically reducing the adsorbed metal-containing precursor with the process gas to deposit the metal-containing film; and
purging the process chamber with the purge gas.
8. The method of
9. The method of
10. The method of
11. The method of
12. The method of
13. A method for depositing a copper-containing film to a substrate within a process chamber by an atomic layer deposition technique, comprising:
introducing a copper precursor to the process chamber;
adsorbing the copper precursor to the substrate;
purging the process chamber with a purge gas;
introducing a process gas comprising the copper precursor and a reactant;
reacting the adsorbed copper precursor with the process gas; and
purging the process chamber with the purge gas.
14. The method of
15. The method of
16. The method of
17. The method of
18. A method of growing a thin film onto a substrate located with a reaction chamber comprising feeding a precursor of the film into the reaction chamber, causing the precursor to adsorb onto the surface of the substrate to form a layer thereof, and feeding a catalyst and the precursor into the reaction chamber in amounts to substantially convert the layer of the precursor to the thin film, wherein the precursor comprises copperhexafluoracetylacetonate trimethylvinylsilane.
19. The method of
This application claims benefit of provisional application No. 60/261,946, filed Jan. 16, 2001.
The present invention relates to a method of growing thin films on substrates in a reaction space being subjected to alternately repeated steps of feeding a precursor followed by feeding a catalyst for the precursor to grow the desired thin film.
There are a variety of methods employed in the art of growing thin films. For example, chemical vapor deposition (CVD) has been used for many years to deposit solid thin films for a variety of commercial products including integrated circuits. The CVD method consists of exposing a substrate in a reaction chamber to one or more gaseous species that react to form a solid thin film on the substrate surface. CVD may be carried out at atmospheric or sub-atmospheric pressures, and usually requires that the reactivity of the gases be enhanced by heating the substrate or by creating a glow discharge in the reaction chamber. One of the disadvantages of the CVD method is that the gases may take part in undesired gas phase reactions. These undesired gas phase reactions may lead to the formation of particulates, and may also deplete the seed gases before they can reach all areas of the substrate. Thus, the undesired gas phase reactions can impact the quality and uniformity of the thin film being deposited.
An example of a specific CVD process is disclosed in U.S. Pat. No. 6,110,530 assigned to the assignee of the present application. The '530 patent discloses a CVD process for depositing a solid thin film of copper that employs a single gaseous precursor to form the copper layer. Although that precursor, hexafluoracetylacetonate-Cu-trimethylvinylsilane (hereinafter hfac-Cu-TMVS), is sufficiently reactive to deposit copper at temperatures below 200� C., the copper deposition rate is undesirably slow. It is, however, undesirable to raise the processing temperature to increase the reaction rate because, among other reasons, higher processing temperatures may degrade previously deposited layers on the substrate. It was found that the slow deposition rate at lower temperatures could be increased by adding water to the hfac-Cu-TMVS precursor. It appears that the water may act as a catalyst, facilitating the decomposition of hfac-Cu-TMVS at lower temperatures. Although the addition of water avoids the need to carry out the CVD deposition at higher temperatures, the problem of undesired gas phase reactions remains. Specifically, the addition of water also facilitates the decomposition of hfac-Cu-TMVS in the gas phase, which can lead to problems such as particulate formation. In other words, catalytically converting the copper precursor to elemental copper with water during a single processing step within the reaction chamber, although having certain advantages, suffers from processing limitations to which the present invention is intended to address.
When a CVD reaction requires more than one gaseous reactant, undesired gas phase reactions between them can by avoided by separately and sequentially introducing the gaseous reactants into the reaction chamber. One method that employs the separate and sequential introduction of gaseous reactants is the Atomic Layer Deposition (ALD) method, one version of which is described in U.S. Pat. No. 4,058,430. In ALD, the substrate is heated to a temperature such that when a first gas is introduced into a reaction chamber, it chemisorbs on the substrate surface, forming a monolayer. An exact monolayer can be formed because the first layer of the gaseous species is relatively strongly bonded to the surface of the substrate by the chemisorption reaction while any excess reactant is relatively weakly bonded to the chemisorbed monolayer. The excess first gaseous reactant can then be removed from the reaction chamber. This removal may take place by, for example, evacuating the reaction chamber with a vacuum pump or by purging the reaction chamber with an inert gas. Ideally, the monolayer of the first gaseous species remains on the heated substrate surface after the removal of the excess reactant. Next, a second gaseous reactant is introduced into the reaction chamber. The second gaseous reactant reacts with the monolayer to produce the desired solid thin film. The excess of the second reactant, along with any reaction by-products, are then removed from the reaction chamber. Again, the removal may take place by means of evacuating the reaction chamber or purging the reaction chamber with an inert gas. A distinguishing characteristic of the ALD process is that it deposits a precise layer thickness each time the above sequence of steps is repeated. A precise layer thickness is obtained because of the formation of an exact monolayer of the first precursor. The above sequence of steps can be repeated until a thin film of desired thickness is created.
Although ALD may eliminate undesired gas phase reactions between multiple CVD precursors, ALD has a number of disadvantages that limit its utility. One of those disadvantages is that the ALD process can only be used with gaseous species that react with the substrate and with each other within a "temperature window". The temperature window is defined by the constraints that the substrate temperature must be high enough for the second gaseous reactant to react with the chemisorbed monolayer of the first gaseous reactant, but the substrate temperature cannot be so high that the monolayer of the first reactant desorbs. This temperature window severely limits the number of species that are compatible with the ALD process. Furthermore, the temperature window limitation of ALD means that ALD cannot be used to deposit a film from a single gaseous species. The use of a single species is incompatible with ALD because the substrate temperature would have to be high enough for the species to react to form a solid film. Since the film formation reaction would consume any of the species introduced into the reactor, the precise thickness control characteristic of ALD would not be possible. In other words, the deposition process would degrade into CVD with a single reactant. Thus the precise layer control obtainable in ALD, which is made possible by separating the introduction of the gaseous reactants, cannot be achieved in a single species system.
The present invention is directed to a method of growing a thin film onto a substrate. The method comprises feeding a single gaseous precursor into a reaction space. The precursor is caused to adsorb onto the surface of the substrate to form a layer. A catalyst is then fed into the reaction space in an amount to substantially convert the layer of the precursor into the desired thin film. Embodiments of the present invention overcome the shortcomings of previously available CVD and ALD methods.
It is now proposed to employ a catalyst in a process that employs a single gaseous precursor in such a manner that the precise layer thickness control of the ALD process can be obtained. Specifically, the process comprises the steps of introducing a single gaseous precursor into a reaction chamber under conditions such that a portion of the precursor adsorbs on the substrate and subsequently converting the adsorbed precursor to the desired thin film through the use of a suitable catalyst.
As illustrative of the present invention, reference is made once again to the creation of a thin film of copper metal on a substrate through the use of the precursor hfac-Cu-TMVS.
The copper film is produced pursuant to the following reaction:
It is known that water will catalytically promote this reaction. As such, the present invention contemplates introducing the precursor hfac-Cu-TMVS, into a reaction chamber, generally maintained at low pressure, causing the precursor to adsorb onto the substrate, which may be heated and which is located within the reaction chamber. Like in an ALD process, the adsorption may take place by means of chemisorbing an exact monolayer of the precursor onto the substrate. Formation of a monolayer in this manner will produce the type of precise layer control characteristic of an ALD process. On the other hand, it is also possible to carry out the claimed method under conditions in which the precursor physisorbs onto the substrate. When the precursor physisorbs onto the substrate, layer thickness control may be achieved, for example, by controlling the amount of precursor introduced into the reaction chamber. It is to be appreciated that the substrate temperature may be modified to facilitate the appropriate type of adsorption, which may differ for different applications of the claimed process.
After the precursor adsorbs onto the substrate in the appropriate manner, a catalyst is introduced into the chamber. The catalyst is chosen so that the adsorbed precursor reacts to form the desired thin film at the substrate temperature. The use of a catalyst allows the film formation reaction to occur at lower temperatures, so that the problem of high temperature desorption of the precursor can be ameliorated. Where the precursor is hfac-Cu-TMVS, a suitable catalyst is water. The introduction of water lowers the temperature required for hfac-Cu-TMVS to decompose into elemental copper. Specifically, the addition of water allows the substrate temperature to be less than about 150� C., and possibly as low as 100� C. The addition of a catalyst with a single precursor allows the deposition process to be carried out at temperatures low enough to prevent desorption of the precursor, yet high enough, due to the addition of the catalyst, to permit the film-formation reaction. Thus it is possible to extend some of the advantages of ALD to a single precursor system, while overcoming the disadvantages of prior art techniques.
The precursor and the catalyst may be introduced into the reaction chamber by any appropriate method. For example, the precursor could be introduced in the form of a gaseous stream of pure precursor, or the precursor entrained within a flow of a carrier gas. Similarly, the catalyst could be introduced alone or mixed with a carrier gas. The choice of carrier gas would be dictated by the precursor and catalyst chemistries. For the example system of hfac-Cu-TMVS and water, examples of suitable carrier gases are H2, Ar and N2.
After the precursor is adsorbed onto the substrate surface, but before the introduction of the catalyst into the reactor, if any excess non-adsorbed precursor exists, it may be removed from the proximity of the substrate. This removal of the precursor may be desirable in order to control the amount of precursor adsorbing on the substrate, or to prevent the precursor from reacting in the gas phase when catalyst is introduced into the reactor. In an alternative embodiment of the claimed method, however, precursor may continue to be introduced into the reaction chamber while the catalyst is introduced. This embodiment may be useful when the stoichiometry of the deposition reaction requires more than one precursor molecule. For example, in the deposition of copper from hfac-Cu-TMVS, two molecules of the precursor are needed to apply a single molecule of copper. As such, introducing additional precursor with the water catalyst encourages production of the final film.
When it is desired to remove excess or non-adsorbed precursor from the proximity of the substrate before introduction of the catalyst, any suitable method may be used to accomplish the removal. For example, the precursor could be removed by evacuating the reaction chamber with a vacuum pump. Alternatively, removal could occur by purging the reaction chamber with a gas. The purge could consist of flowing the gas between the introduction into the reaction chamber of flows of pure precursor and catalyst, or the purge could consist of flowing just the carrier gas while ceasing to introduce precursor or catalyst into the flow of carrier gas. The gas could be an inert gas such as Ar and N2, or a gas that is not necessarily inert such as H2. It is to be appreciated that when the precursor is removed by purging the reaction chamber, the extent of the purge may be varied. In other words, in some embodiments it may be desirable to purge the reaction chamber with a sufficient volume of purge gas so that the excess precursor, if any, is essentially completely removed from the reaction chamber. The volume of purge gas could be adjusted by varying the purge gas volumetric flow rate, the amount of time the purge gas flows through the reactor, or by varying the reactor pressure. In alternative embodiments, a smaller volume of purge gas could be used to remove the precursor from each localized area of the substrate before the catalyst arrives at that localized area. Using a smaller volume of purge gas in this manner could reduce the cycle time required for the process.
After the desired film-formation reactions have occurred, it may be desirable to remove the catalyst and any reaction products from the proximity of the substrate. The same removal techniques described above are also suitable for removing the catalyst and reaction products from the reaction chamber. The above sequence of steps, namely, the introduction of the precursor, the optional removal of excess precursor, introduction of catalyst, and the optional removal of catalyst and reaction products, may be repeated to achieve the desired film thickness.
An apparatus useful in carrying out the proposed method could be the same apparatuses generally employed in the formation of thin films by CVD or by ALD. For example, the exemplary process for copper deposition can be carried out on an xZ-series CVD reactor, which is marketed by Applied Materials, Inc. of Santa Clara, Calif.
It should be noted that although the present invention has been described with respect to the precursor, hfac-Cu-TMVS, employed together with water as the catalyst, this example is intended to be merely illustrative of the present invention directed to method of cyclically introducing a precursor and a catalyst into a reaction chamber in order to create a suitable film.
Although the present invention has been illustrated using a specific embodiment, the invention is not meant to be so limited. It is intended that the present invention be defined solely by the appended claims.
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The Scroll Recipe Series: Pimentón Lamb
Talking to BuzzFeed about my favorite lamb recipe
While we were away in Poland, Friend-of-The-Scroll Emily Fleischaker prepared one of my favorite recipes for a feature she does at BuzzFeed. She even asked me for advice about how make it, which is hilarious since she graduated from culinary school and I am addicted to Taco Bell.
Now that BuzzFeed has smiled upon it, I wanted to share the dish with you. It's Pimentón Rack of Lamb and the origins of the recipe are near and dear to me: I pilfered it a few years ago from the Times Dining Section and have been passing it off as my own culinary brilliance ever since.
As the article points out, it is the laziest way to make lamb. All you need is 30 minutes (or, for me, 40), a pan, and maybe a food processor. My favorite thing about the dish itself is the pimentón (smoked paprika) and Jewish rye topping, which gives it a little heat on the finish.
Plus, if you end up overcooking it a little, the topping will give you cover so you won't feel sheepish (wakka wakka).
Earlier: The Kosher Prairie Oyster
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subset: commoncrawl


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Six tourists from Andhra Pradesh were injured when a truck collided with a tourist bus near Darlong in Saraikela-Kharswan district of Jharkhand late Thursday, police said.
The tourists from Vijayawada in Andhra Pradesh were returning home from Haridwar when the truck collided with the bus on National Highway 33, the police said.
The officer-in-charge of Chowka police station, Ramawadh Singh, who rushed to the spot, said the injured, were shifted to MGM hospital in Jamshedpur, from where five seriously injured tourists were shifted to Tata Main Hospital.
One of the injured was discharged after first aid.
Keywords: Bus-truck collision, Darlong, Saraikela-Kharswan district
More In: Other States | National | Vijayawada | States | News | Andhra Pradesh


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Which Bruce (claw) anchor to buy?
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Please enlighten us
Originally Posted by
An Outstanding product will advertise by itself. Wait and then you could learn more about « new products » => on other nautical forums !!!
Can you enlighten us as to which forums invite free advertising of product?
Here's a quick list of the forums I use and their commercial interest policy on advertising. All these forums allow commercial vendors to participate but NOT advertise.
Sailboatowners.com = NO
Cape Dory Forums = NO
Plastic Classic Forums = NO
Cruisers Forums = NO
Cruisers Log's = NO
SSCA Forums = NO
Boat US Forums = NO
Cruising World Forums = NO
Maine Coast Forums = NO
If you want to go play over at SA feel free!!!
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Atacama Weekender
- Color:
- brown
Please select an available size.
Please select a size.
Description: Recycled nylon zip top weekender.
- Dual adjustable leather carry handles with leather snap grip and an adjustable and removable shoulder strap.
- Exterior zip pocket and logo tag.
- Leather trim throughout.
- Fully lined with an interior zip pocket.
- Approximate measurements: length: 20¾", width: 9.05", height: 12.4", handle drop: 8".
Material: 100% Recycled Nylon, Leather
Brand: Ecoalf
Origin: Imported


text:
Photos of Brad Pitt on His Motorcycle in LA 2009-06-22 08:18:05
Brad Pitt's Moneyball Movie Runs Into Trouble
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Brad Pitt went for another ride around LA on his motorcycle on Friday. Production on Brad's latest project, Moneyball, was scheduled to start today in Phoenix but has been stalled because Columbia Pictures didn't like the latest copy of the script. The movie still has the clout of Brad as well as director Steven Soderbergh, both of whose agents met this weekend to discuss the future of the film. Moneyball, which is based on the bestselling book of the same name, still could be picked up by another studio, but if not Brad might be looking at some extra free time this Summer.
Read More Brad Pitt
5 years
WOW! Maybe he just needs a brake from the children...Angy and Brad are cool peps. love their movies ;)
Lyllie 5 years
#11 really should read stories before commenting. The studio didn't back out because of Brad but because of the script. These "Brad and Angelina are bad parents" are stupid. Nobody knows how the kids are raised so why people act like they do is baffling. Entertainers spend more time with their kids than the average person. Celebrities work whenever they want. Brad didn't work for six months and Angelina didn't work for 14 months before Salt. They also have the luxury of bringing kids on to sets, concert tours, etc. Most non-celebrity kids grow up in households where both parents work a minimum 40hrs a week, 48-50 weeks a year. Or they live in single-parent households where, in many situations, see one parent only every weekend or every other weekend. If that parent is in their life at all. I also don't understand why people only have a problem with only Brad and Angelina when most celebrities work just as much if not more than they do.
5 years
Brad couldn't care less if this movie never gets made. He still walks away with his $15 million up front and gets to spend the summer in Miraval with his family. Wish somebody would pay me $15 million for doing nothing all summer long.
5 years
Studios waste money on Big Stars like Brad. Just hire Chris Pine or Bradley Cooper for half the price and better acting and be done with it.
5 years
This is apparently a highly unusal move by a studio so close to the films start date. They didn't read the script until Friday? Is this Amy Casals woman close friends to his EX? Just wondering.
5 years
Other than comment #7 I don't see where anyone called Brangelina "baabsolutely despicable parents" who should be thrown in jail. But then again, Brangelunatics are prone to hysterical exaggeration.
5 years
What ? if Brangelina are bad parents for not spending enough time with their kids, what are the 'normal' parents, you know the ones that constituted 99,99 % of the world and the american society, the ones who work from 9 to 5 at minimum, sometimes combining two jobs, as welll as single parents ? Monsters who should be checked for their parenthood skills ? I guess all in here who are parents are bad parents according that same logic since they spend their spare time on the internet criticizing other parents who spend 100 x more times with their kids that they do with theirs. Oh, and probably those criticizing the amount of time Brangelina spend with their broads have been illraised by both of their own parents who probably spent more time working than taking care of them. No wonder that their uneducated kid turned adults are now spouting nonsense on parents who spedt at least 6 months a year taking care of their child day and night. 99,9999 % of men don't even have the luxury of spending 1/10 of the time he spend with his kids, with their own kids. Throw them in jail, since they are baabsolutely despicable parents !
5 years
I like Brad, but a movie about baseball strategy and politics is not so interesting to me. I'm sure it'll get picked up by another studio. Soderbergh and Pitt may be too hard to pass up. And what's the deal with the comments about parenting? For f*cks sake, stay on the subject.
5 years
brangelina are not very good parents. they certainly don't spend enough time with their children on a consistent basis.
ilanac13 5 years
that would suck big time if the movie is axed. and if the chatter is true then i'm sure that jen will be sad (but angie will be happy)


text:
Trees in the Reiser4 Filesystem, Part I
Reiser4 includes many different kinds of items designed to hold different types of information:
static_stat_data: holds the owner, permissions, last access time, creation time, last modification time, size and the number of links (names) to the file.
cmpnd_dir_item: holds directory entries and the keys of the files they link to.
extent pointers: explained above.
node pointers: explained above.
bodies: hold parts of files not large enough to be stored in unfleaves.
We call a unit that which we must place as a whole into an item, without splitting it across multiple items. When traversing an item's contents, it is often convenient to do so in units:
For body items the units are bytes.
For directory items the units are directory entries. The directory entries contain a name and a key of the file named (in practice the name and key may be compressed).
For extent items the units are extents. Extent items contain only extents from the same file.
For static_stat_data the whole stat data item is one indivisible unit of fixed size.
I have explained the basic structures of the Reiser4 tree, but the fun stuff is yet to come. I have not yet explained how other researchers structure their trees. Nor did you learn why object contents are stored at the bottom of the tree, why high fanout is important or what are the different kinds of balancing. No hint have I yet given as to why balanced trees are better and dancing trees are best. What I have most especially not done is explain how a subtle and controversial tree structure change, which you can see in the trees depicted in this article, doubled Reiser4 read speed compared to Reiser3. This will (space permitting) be in Part II in next month's issue of Linux Journal.
Hans Reiser (firstname.lastname@example.com) entered UC Berkeley in 1979 after completing the eigth grade and majored in "Systematizing", an individual major based on the study of how theoretical models are developed. His senior thesis discussed how the philosophy of the hard sciences differs from that of computer science, with the development of a naming system as a case study. He is still implementing that naming system, of which Reiser4 is the storage layer. In 1993 he went to Russia and hired a team of programmers to develop ReiserFS. He worked full-time to pay their salaries while spending nights and weekends arguing over algorithms. In 1999 it began to work well enough that his mother stopped suggesting a salaried job at a nice big company.
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text:
The photorefractive effect results in a change in the refractive index of bulk chalcogenide glass when it is exposed to certain wavelengths of light, in particular, sub-band-gap light. The effect results in a variety of device structures including a fiber optic faceplate; an optical waveguide; a fiber tap; a lens and a Bragg grating. Methods for fabricating the various devices are described.
1. A fiber optic faceplate comprising: a disk-like plate having a thickness greater than about 200μ formed of bulk chalcogenide glass having an absorption coefficient of about 103 cm-1 at a wavelength defined as the band-gap, said plate having a plurality of regions of altered refractive index formed by exposure of the plate to a selectively applied beam of sub-band-gap light for a time sufficient to result in the alteration of said refractive index of the glass.
2. The fiber optic faceplate of claim 1 wherein the beam of light is applied through an aperture mask.
3. The fiber optic faceplate of claim 1 wherein the beam of light is selectively applied in individual locations by a focused laser beam.
4. The fiber optic faceplate of claim 1 wherein the beam penetrates the plate to a depth of at least a millimeter.
5. The fiber optic faceplate of claim 1 further comprising an overcoat of glass on at least one face of the plate, wherein the overcoat of glass has an absorption coefficient greater than that of the plate.
6. The fiber optic faceplate of claim 5 wherein the overcoat is a chalcogenide glass.
7. The fiber optic faceplate of claim 5 wherein the overcoat is transparent to light in an operating range of the bulk glass.
8. The fiber optic face plate of claim 1 wherein the glass has an absorption coefficient of about 1 cm-1 at about 0.6 micrometers.
9. An optical waveguide comprising: a fiber having a diameter greater than a thin film, formed of a chalcogenide glass having an absorption coefficient of about 103 cm-1 at a wave length defined as the band-gap, said fiber having a core and cladding, said core having an index of refraction higher than the cladding, said core formed by exposure of the fiber to sub-band-gap light for a time sufficient to result in the alteration of said refractive index of the glass.
10. The optical waveguide of claim 9 wherein the fiber is drawn from a bulk preform and exposure of the fiber occurs on the draw.
11. The optical waveguide of claim 9 wherein during the draw a central portion of the fiber is molten and the light is produced by a laser beam focused at the central portion downstream of where it is molten.
12. The optical waveguide of claim 9 wherein the light is produced by a pair of focused laser beams intersecting in the core for producing a Bragg grating.
13. The optical waveguide of claim 12 wherein the intersecting laser beams interfere.
14. The optical waveguide of claim 9 wherein the exposure occurs during drawing of the fiber from a melt.
15. The optical waveguide of claim 14 wherein the melt is a molten tip of a homogeneous preform.
16. The optical waveguide of claim 9 wherein the light is tuned sub-band-gap light.
17. The optical waveguide of claim 9 wherein the light is sub-band-gap light inversely varied with time for producing a graded index in said core.
18. An optical waveguide comprising: a fiber having a diameter greater than a thin film formed of chalcogenide glass having an absorption coefficient of about 103 cm-1 at a wavelength defined as the band-gap, said fiber having a core and a cladding, said core having an index of refraction higher than that of the cladding and wherein the cladding has a region of altered index of refraction formed by exposure of the cladding to sub-band-gap light for producing a radial light path therein in communication with the core.
19. An optical waveguide comprising: a chalcogenide glass fiber having an absorption coefficient of about 103 cm-1 at a wavelength defined as the band-gap, said fiber having a core, a cladding and an end face portion extending axially of the fiber to a depth greater than a thin film, said core having an index of refraction higher than the cladding and said end face portion of the fiber having an index of refraction higher than the core formed by exposure to sub-band-gap light for forming a lens at said end face portion.
20. An optical device comprising a bulk glass having an absorption coefficient of about 103 cm-1 at a wavelength defined as the band-gap and having a thickness greater than a thin film, said glass exhibiting a photorefractive effect at a location therein resulting from alteration of the refractive effect at a location therein resulting from alteration of the refractive index of the glass at the location, said alteration of the refractive index resulting from exposure of the glass to at least one beam of sub-band-gap light for a time sufficient to effect the alteration.
21. The optical device of claim 20 wherein the beam of sub-band-gap light includes at interfering beams within the device for producing said alteration in the form of a Bragg grating.
22. The optical device of claim 20 wherein the glass is a photorefractive chalcogenide.
This application is a divisional application of application Ser. No. 454,646, filed Dec. 21, 1989 (U.S. Pat. No. 5,028,105).
The invention relates to the photorefractive effect in glass. In particular, the invention relates to the application of the photorefractive effect to the fabrication of optical devices based on chalcogenide glasses.
The Fiber Optic Faceplate (FOFP) is an important product, finding applications in various technologies, e.g., night vision devices and CRT displays. FOFPs are manufactured by heating and drawing a core/clad preform into thin canes, bundling the canes, and redrawing them to yield a multifiber bundle. After several such redraws, the thin bundles, each consisting of many individual optical fibers, are heated and fused into a block. The block is cut and polished to yield a thin plate, cylinder, or other configuration which can serve as an image transfer device. In effect, the finished FOFP is a fused array of many thousands of very small optical fibers. The process is time consuming and labor and materials intensive.
The FOFP and other fused fiber devices made by this process are designed to operate at light wavelengths in and around the visible portion of the spectrum, where the glasses used to make them are transparent. In particular, infrared (IR) transparent optical fibers derived from materials known as chalcogenide glasses have emerged as important new materials having a variety of desirable applications.
The term chalcogenide glasses defines a large family of vitreous materials fabricated from metals (e.g., As, Ge, Sb) in conjunction with the heavier elements in the oxygen family (i.e., the calcogens S, Se, Te). There are literally hundreds of such glass-forming chalcogenide compositions; one well studied example is the glass known as arsenic trisulfide or As2 S3. Generally speaking, chalcogenide glasses have low glass transition temperatures (typically 180�-300� C.) and high refractive indices (typically 2.5). While dependent on composition, the transparency range of these glasses spans (roughly) the 0.8 to 15 micron region.
Optical fibers drawn from chalcogenide glasses are known. It is also known to draw and fuse many such fibers into a bundle and use them to transmit simple IR images. There are problems, however, in maintaining the circular cross-section of the individual fiber elements, which tend to distort during the fusing process.
In another approach to making an IR image transmitting device, a thin metal plate containing an array of many small holes (made via lithography and etching) is dipped into a molten chalcogenide glass and then removed. The glass coats the plate and fills the holes. The plate is then polished to remove the surface glass. The result is an IR faceplate in which each glass-filled hole acts a like a fiber element. This technique is difficult to implement and is expensive. Moreover, the faceplate has limited applications.
In many chalcogenide glasses, the refractive index of the material may be increased by illuminating the material with light of an appropriate wavelength and intensity. This light-induced refractive index increase is referred to in the art by a variety of names such as photorefractive effect; photostructural transformation; photodarkening or photoinduced refractive index change (PRC). For simplicity, the designation PRC shall be used in this disclosure to describe the effect. Various PRC effects are summarized below.
It is important to note that the vast majority of PRC related results have been derived from experiments on chalcogenide glass thin films whose thickness is typically 1 to 10 microns. These are often prepared by laborious processes employing thermal evaporation or sputtering from crushed glass or bulk glass targets (discs) in a high vacuum system.
The physical origins of PRC are not well understood and are the subject of ongoing theoretical discussions in the literature. It is generally agreed, however, that the effect occurs in many chalcogenide glasses with the largest effect occurring in vitreous As2 S3 i.e., this glass exhibits the largest increase in index upon irradiation with light. The applications outlined in this disclosure are not limited to a particular chalcogenide composition, but arsenic trisulfide, As2 S3, will be used as an example.
In FIG. 1 curve A generally shows the estimated average of the absorption coefficient of As2 S3 within a range of values represented by the shaded area about the curve as a function of wavelength (or photon energy) in the visible portion of the spectrum. The data from which curve A was prepared is available from standard references, journal papers and measurements on glasses made by the applicant. There is generally good agreement among these various sources. At high values of the absorption coefficient (e.g., >1 cm-1) the material is considered opaque. At lower values it is progressively more transparent in the longer wave lengths, >0.6 μm. The arsenic trisulfide thus appears red in color. Over much of the range of FIG. 1, the logarithm of the absorption coefficient is linear with wavelength as is apparent from the curve. Above about 0.6 microns, curve A bends. The origin of this "bend" is still debated, with some authors believing it due to iron impurities in the glass while others suggest that it is intrinsic (inherent) to the glass structure. Curve B is a plot of the measured absortion coefficient for a Ge-Sb-Se glass which is shifted by about 0.1 μm towards the longer wavelengths.
The band-gap of the glass shown in FIG. 1 is loosely defined as the wavelength region where the absorption coefficient has a value of 103 cm-1. The art refers to wavelengths shorter than this as band-gap light. Such wavelengths are almost entirely absorbed before light can progress more than a few microns into the material. Light of wavelengths longer than the band-gap is referred to as sub-band-gap light. Depending on wavelength, such light can penetrate millimeters to centimeters into the material without suffering a significant decrease in intensity.
There are several PRC effects which can occur when a chalcogenide glass is illuminated with light in the wavelength region spanned by FIG. 1. All such PRC effects produce an increase in the refractive index. These effects are referred to in the art by a variety of (partially self-explanatory) names: irreversible PRC; reversible PRC; dynamical PRC and transitory PRC. Which of these effects is operative depends on the wavelength of illumination, the prior thermal history and/or the illumination history of the glass sample.
For clarity, it should be noted that irreversible PRC occurs only in freshly deposited thin films whose structure is much different from that of bulk glasses made by melting and casting. When such fresh films are exposed to band-gap light, their structure photopolymerizes or densifies resulting in a large permanent increase in the refractive index, which cannot be reversed by heating. The same effect can be produced by heating an unexposed freshly deposited thin film. Heating causes densification and an increase in refractive index. Such a heat-treated or annealed film has an index (and other properties) which is considered to be representative of the bulk glass. These annealed films are often used as a starting point for experiments on other PRC effects.
Dynamical and transitory PRC phenomena are less permanent and/or are of smaller magnitude than the thermally reversible effects. They are of interest because they are switchable in one of two ways. In dynamical effects, illumination with one wavelength can increase the index slightly. Illumination with a different wavelength decreases the index to its original value. A transitory effect occurs upon illumination with band-gap light whereby the index increases during illumination but relaxes (decreases) slightly to a lower, but permanent, value when the light is turned off.
In considering the prior art it must be reemphasized that, the application of PRC effects has been limited to very thin chalcogenide glass films or platelets and employs comparatively short wavelengths in the region marked band-gap in FIG. 1. While the term bulk glass is occasionally used in certain references in the art, careful analysis of such references shows the term to have a subtle and often confusing meaning. For example, what appear to be small reversible PRC effects in bulk glasses were obtained when slices from a large ingot (made by conventional melting) were cut and polished to thickness of 10-30 microns for illumination with band-gap region light. Others have looked for reversible PRC in annealed thin films and compared their behavior with that of bulk ingots which were never illuminated. The implicit presumption is that the annealed film properties are representative of bulk glasses behavior. These results conclude that, there is no measurable change (Δn<0.01) in the refractive index which accompanies illumination of such annealed films. A further example is contained in work which attempts to compare the reversible PRC behavior of film and so called bulk samples. Unfortunately, no information is available about the preparative conditions or size of the specimens. The work shows that irreversible index changes may occur in bulk samples, but only at cryogenic temperatures. Heating to room temperature eliminates the effect.
Despite the apparent confusion, some practical applications of PRC effects have been reported in the art. One important example is the use of PRC to store holographic images in thin films of chalcogenide glass. Although the glass layers used are only about 10-50 microns thick these have been referred to as volume or 3-dimensional holograms. The films are prepared either by evaporation or by squeezing a molten glass to minimal thickness between two cold plates. In these applications, the glass film serves as photographic medium. The holographic interference pattern is stored in the film as localized increases in the refractive index. The image can be erased or bleached either by heating or by uniformly exposing the plate to light of an appropriate wavelength. The latter has the effect of increasing the index of previously unexposed regions of the plate, such that the stored information, in effect, fades into the background. Such light-induced bleaching is an important concern.
The use of transitory and dynamical PRC effects to fabricate thin film optical signal processing devices has been investigated. These include switches, modulators, and light deflectors in which the propagation of one light beam is controlled by another via local (and temporary) changes in refractive index.
Reversible PRC effects have also been employed to write optical waveguides into evaporated thin glass films. A focused argon laser near 0.514 microns or an electron beam is scanned across the surface of a glass thin film. The beam creates a channel of increased refractive index in the surrounding glass whose width and depth is dependent on the beam spot size and intensity. The channel is thus a waveguide or optical fiber embedded in the film. The technique offers the prospect for fabricating thin film optical integrated circuits containing a variety of devices such as fiber couplers and signal splitters.
Chalcogenide thin films have also found application to the field of optical recording discs. This technology, however, makes use of optically induced (and reversible) crystallization in such glassy films.
Others have described applications for PRC effects in certain bulk plastics in which a cylindrical filament of high refractive index may be optically written deep within the body of a plastic cube by exposing the region to high intensity ultraviolet light. The end use appears to be optical integrated circuits in 3-dimensional bulk form, as opposed to the basically 2-dimensional thin film application outlined above. The concepts have not been extended to multiple filament applications or to glasses.
It would be desirable to have a method which could produce a device consisting of an array of many hundreds or thousands of individual fibers or fiber like structures which could be prepared without use of the draw/redraw/fuse or other mechanical approaches. It would also be desirable that the device operate at wavelengths in the infrared (IR) which is difficult to access with current technology. IR wavelengths of 3-11 microns, are of special interest as many imaging, thermal detection, and analytic systems operate in this region.
FIG. 1 are logarithmic plots of absorption coefficient (cm-1) v. wavelength (μm) for As2 S3 glass (curve A) and for Ge-Sb-Se glass (curve B);
FIGS. 2A-2E illustrate in step wise form the fabrication of a fiber optic faceplate (FOFP) according to one embodiment of the invention;
FIG. 3A is a perspective view of a FOFP manufactured in accordance with the method steps illustrated in FIGS. 2A-2E;
FIGS. 3B and 3C illustrate the manufacture of FOFPs according to alternative methods;
FIGS. 4 and 4A are respective side sectional and end views of an optical fiber in which the index of refraction of the core and cladding have been altered by PRC effects;
FIGS. 5, 5A and 5B illustrate a method of manufacture of an optical fiber according to the present invention in which the fiber is shown in cross-section before and after application of a laser light source; and
FIG. 6 illustrates a Bragg grating formed in a bulk glass sample in accordance with the present invention.
The present invention makes use of the photorefractive effect in bulk chalcogenide glasses. In particular, such glasses exhibit a permanent, but reversible change in the index of refraction deep within the sample by exposure to sub-band-gap light.
The invention can be manifested as a variety of 3-dimensional device structures including fiber optic faceplates, optical fibers, lenses and fiber taps and Bragg gratings. The invention also is manifested in a method of manufacturing an optical fiber.
A unique aspect of the invention is that it extends the use of PRC to bulk chalcogenide glasses, such as objects having a thickness>1 mm and fibers having a diameter>10 microns.
In accordance with the present invention there is provided a method of altering the refractive index of bulk chalcogenide glasses. In particular, the invention permits a greatly simplified manufacture of a variety of devices. In one embodiment the manufacture of a fiber optic faceplate for use in the infrared spectral region is described.
This concept is illustrated in FIGS. 2A-2D. The starting material is a suitably polished plate or disc 10 of well-annealed bulk chalcogenide glass made by known glass melting/preparation methods. The thickness of the disc 10 may be on the order of hundreds of microns to several millimeters. Using known photolithography techniques, an optically opaque mask 12 containing a plurality of holes 14 is applied to one surface (FIG. 2B). The diameter d of the holes 14 is selected based on the desired optical performance of the finished article. For example, the holes 14 may be a few to several 10's of microns in size. The masked plate 10 is then uniformly illuminated with sub-band-gap light 16 (FIG. 2C). The wavelength of the light 16 is chosen on the basis of an absorption curve similar to FIG. 1. Each hole 14 in the mask 12 allows the light 16 to penetrate and illuminate a roughly cylindrical volume of glass 18. PRC effects cause the refractive index of these regions 18 to increase (FIG. 2D). The selected wavelength would be such that there is good penetration into the disc 10. In the case of an As2 S3 plate a few millimeters thick, for example, one would choose a wavelength near the bend of curve A in FIG. 1 (e.g. 0.60-0.65 μm) so that PRC occurs throughout the sample thickness and not simply in a thin layer near the surface. According to the invention, exposure of the disc 10 with sub-band-gap light 16 is effected for a time sufficient to result in permanent PRC in the cylindrical volumes 18, such that the disc 10 has a plurality of high index filaments 22 optically formed therein (FIG. 2D). The result is a fiber optic faceplate structure 24. The photomask 12 is thereafter removed.
As noted earlier various PRC effects generated in some structures are susceptible to reversal or bleaching and/or relaxation or fading with time. These effects occur because ambient lighting contains wavelengths which can cause PRC effects to occur. Bleaching and fading may be overcome by coating the opposite faces 26 of the faceplate structure 24 with a thin layer or overcoat 28 of a different chalcogenide glass composition (FIG. 2E). For example, if the disc 10 of the faceplate 24 is fabricated from As2 S3, the overcoat 28 may be a Ge-Sb-Se glass. The latter glass has, (like all chalcogenide glasses), has an absorption edge characteristic (curve B) similar to curve A shown in FIG. 1 except that it is shifted to longer wavelengths. For example, at a given wavelength, the absorption coefficient, curve B, of the overcoat 28 is several orders of magnitude higher than the absorption coefficient represented by curve A of the faceplate glass, thus protecting it from short wavelength bleaching radiation. These faceplates are designed to operate in the 4-11 μm region and both glasses are transparent at these wavelengths. The long wavelengths in this region do not produce any measurable PRC as the energy of their photons is too weak. The finished device 36 employing a disc 10 of As2 S3 glass and overcoat 38 of Ge-Sb-Se glass 28 is shown in FIG. 3A.
In accordance with another embodiment of the invention illustrated in FIG. 3B, the starting material is identical to the disc 10 shown in FIGS. 2A-2D. In this approach, an appropriately focused laser beam 40 is employed to write or burn in high index channels 42 through the thickness T of the disk 10. The beam 40 is stepped across the surface 44 from point to point and turned on and off to create the individual filaments 42. The laser wavelength is selected in accordance with the criteria outlined above. After exposure the overcoat 28 (FIG. 3A) is applied.
A variant of the above technique is shown in FIG. 3C. A large array (e.g. 100�100) of uniform intensity (small circular) spots 46 is generated by directing a single laser beam 40 through a binary phase grating 48. The array 46 is projected onto the surface 44 of the chalcogenide glass plate 10 to form groups of high index channels 49 simultaneously.
In accordance with the present invention, another application of PRC effects is described in FIGS. 4 and 4A, in which an optical fiber 50 made from chalcogenide glasses is illustrated in respective side sectional and end views. Such fibers are typically 100 to 600 micrometers in diameter (D), and typically consist of a high index core glass 52 surrounded by lower index cladding glass 54. In accordance with the invention the core 52 and cladding 54 may be altered by PRC effects. Higher index regions 56 and 58 represented by the shaded areas may be optically written on such fibers 50 using a finely focused sub-band-gap laser 60. As shown, the core light 62 in unaltered portions of the fiber 50 typically propagates along the core 52 via a series of total internal reflections 61 at the core/clad interface 63. If the index of the cladding 54 is raised in the shaded region 56 via PRC, a fraction 64 of the core light 62 is not totally internally reflected and escapes. The escaping light 64 may be collected by an external device (not shown) and/or coupled to another fiber resulting in a signal splitter (not shown).
Alternatively, the index of the core 52 may be raised locally in the region 58 at the fiber endface 66. The effect is a solid state lens at the fiber end 66. In the altered region 58 the core light 62 becomes focused light 70. The foregoing are two examples of the present invention using PRC to locally modify the index distribution of an already drawn optical fiber to produce optical devices, e.g., a coupler, signal splitter, sensor end tip, etc.
In yet another embodiment of the present invention illustrated in FIGS. 5, 5A and 5B, a chalcogenide optical fiber 80 is prepared by drawing glass from the tip 82 of a preform 84 (FIG. 5) (or by pulling directly from molten glass using a crucible technique, not shown). If the preform 84 (or melt) is homogeneous, the fiber 80 is produced having a generally uniform refractive index across its diameter (D) (FIG. 5A), and along its length (L). In accordance with the invention during the drawing process, a beam 86 of sub-band-gap laser light 86 is aimed at the moving fiber 80 through lens 88 (FIG. 5). The sub-band-gap light 86 is focused by the lens 88 at a point 90 within the fiber 80 resulting in a high light intensity near the center (C) of the fiber 80. PRC effects occur within the region 90, and as the fiber 80 moves, a high index region 92 is produced along its length (L') downstream of the location of the applied laser beam 86. In effect, the high index region thus produced is a light guiding core 92 which is written as the fiber 80 is drawn (FIG. 5B).
The concept shown in FIGS. 5, 5A and 5B may be extended by employing a tunable laser (not shown), or one whose intensity varies with time. In this way a spatially varying refractive index profile can be created across the fiber diameter D or along the length L'. Alternatively a second laser beam (not shown), may be applied perpendicular to the beam 86. As will become apparent hereinafter with respect to FIG. 6, optical interference effects occur in the region where two such beams cross, resulting in a Bragg grating. These provide further flexibility in generating unique fiber structures.
The optical technique used to test for the existence of PRC in a test piece or disk 100 is schematically illustrated in FIG. 6. An arsenic trisulfide glass melt was prepared, and several 1.5 cm diameter disks 100 with thicknesses of 0.2 to 1.0 cm were cut from the resulting rod and polished. A (red) laser (not shown) having a wavelength of 0.637 microns was selected. Referring to FIG. 1 curve A, the absorption coefficient of the glass disk 100 is about 1 cm-1 so that a substantial fraction of the light traverses a specimen near 1 cm thick.
Using a beam splitter (not shown), the light emanating from the laser was divided into two beams 106A and 106B of roughly equal intensities (e.g., a few milliwatts). With the aid of mirrors (not shown), the beams 106A and 106B were directed such that they intersected at a cross-over region 108 about 5 mm inside the 10 mm thick sample 100. The beams 106A and 106B then diverged, i.e. exited the sample 100, and fell on a paper screen 110 some 30 cm from the sample.
Within the cross-over region 108, the light intensity was higher than that of the individual beams 106A, 106B. More importantly, the light waves in the beams 106A, 106B generated an interference pattern in this region; i.e., their amplitudes either add together or cancel one another out. This generated a periodic spatial variation which is a special type of diffraction grating called a "Bragg grating" 112, and it can act as a mirror. In other words, the interference caused by the crossed laser beams 106A, 106B created an equivalent variation in refractive index within the region 108 resulting in the Bragg grating 112. It was postulated that, if the PRC effect is permanent, the Bragg grating 112 should remain imbedded in the sample 100 after the beams 106A, 106B are turned off. Moreover, it should be possible to look for the grating 112 with a probe beam at a later time.
Qualitatively, the following results were observed. For the first few seconds after the beams 106A, 106B were turned on, a pair of sharp dots were observed at points 114A and 114B on the screen 112. Within about 30 sec to 1 min the spots 114A, 114B began to enlarge or bloom. (The PRC effect produced high index waveguide channels 116A, 116B, shown as dotted lines. In the cross-over region 108 the interfering light 106A, 106B produced the Bragg grating 112.) At the low intensities used, the blooming reached equilibrium in about 15-20 minutes, indicating that a steady state value of index was achieved. Confirmation of the effect was observed when one beam (e.g., 106A) was blocked. Whereupon a bright spot appeared near point 114A, with a much dimmer spot near point 114B.
Were there no Bragg grating in the sample 100 (i.e., no permanent index change) the remaining beam 106B would continue to generate only spot 114B on the screen 110. However, due to the PRC-induced Bragg grating 112 the beam 106B was largely reflected within the chalcogenide glass sample 100. Equally important, the sample 100 was removed from its holder (not shown) and replaced at a later time. The grating 112 was readily found by scanning the sample 100 with a probe beam until a strong beam deflection was observed on the screen 110. Using this method, several gratings which are now several weeks old have been examined. The gratings still exist and it appears that they are permanent on this time scale.
The significance of the observation and effects illustrated in FIG. 6 is twofold: first it demonstrates that it is possible to create an apparently long-lived region of increased refractive index via a photorefractive effect deep within a bulk chalcogenide glass using sub-band-gap light; and second it demonstrates that a relatively complex high resolution structure (i.e., a periodic diffraction grating) can be created via PRC.
While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications. This application is intended to cover any variations, uses or adaptations of the invention following, in general, the principles of the invention, and including such departures from the present disclosure as come within known and customary practice within the art to which the invention pertains.
Patent Citations
Non-Patent Citations
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CBSE is thinking of making vocational subjects compulsory for students to pass the 10th and 12th standard examinations.
Right now 40 optional vocational courses are included in the curriculam. The board on the government's instruction is finalising a strategy to have skill-based professional courses so that those leaving school midway don't depend on the government for jobs.
"India has only 5% skilled workforce. But the need for skilled workers will grow by 2% or more a year over the next five years," a senior CBSE official said. "We want children to pick up real life applications at an early stage so that their skills can be honed over time and developed for the country's better future."
The CBSE is exploring options to start teaching the basics of accountancy and auditing, banking, electrical and automobile technology, IT application, health care sciences, fashion designing from the 6th standard.
At present, these courses start from the 9th standard. "By exploring a student's interest at an early age, the board will determine orientation of students to prepare them to face future challenges in life," the official said.
At present, CBSE offers 40 vocational courses at the senior secondary level and four at the secondary level as optional subjects. Schools have the option of offering a vocational subject as an optional sixth subject, along with the existing five regular subjects at the secondary level.
The other option is to offer a vocational subject as a compulsory sixth subject in the 9th and 10th standards. Most school follow the first option. On completion, CBSE issues a "National Certificate for Work Preparation". This certificate is in addition to the regular Continuos and Comprehensive Evaluation (CCE) certificate issued to students.


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I took a photo an hour on the last day in August. I will probably way this ten more times but I can't believe it is September! Milo will be three months old in no time and it still totally feels like he was born yesterday. Anyways, this photo an hour day we went up to visit my Dad's family for their annual corn roast which was also a bit of a baby shower for Milo. We had a great day.
10 am :: We were actually up at 8 something but had a bit of a busy morning so I forgot to take any photos before 10. This was Milo's morning nap after a little soak in the tub. Don't worry, with all those blankets around him you better believe this was a fully supervised nap. I got dressed and put on my makeup right beside him as he snoozed.
This week is going to be over before I know it. I am planning on looking into a few more group activities that Milo and I can go do. I'm thinking of swimming lessons/playtime in a few more months and some free city programs. I'm excited!


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Krist: Full tanks, empty bellies
American fuel demands send food prices soaring
Residents of Louisiana, Texas and Mississippi are still feeling the effects of hurricanes Katrina and Rita, which stomped, hacked and slashed their way through hundreds of Gulf Coast communities in August and September of 2005. Thousands of people remain displaced nearly 18 months later, occupying trailers and wondering when or even if they might rebuild.
But the storms also had a direct effect on people much farther away. Katrina and Rita altered the lives of people in Iowa and Montana, Vermont and California, Kansas and the Dakotas. And fallout from the storms' destructive tour of the American South has not remained within the borders of the United States; it has affected the daily lives of nearly every human being in North, Central and South America.
The catalytic agent that has made this possible is corn, the most widely planted crop in the United States. To understand how corn could entwine the lives of Mexican peasants and New Orleans jazz musicians is to understand something profoundly disturbing about the global food system, which each day looks more and more like the global petroleum business.
Three weeks before Katrina came ashore, President Bush signed the Energy Policy Act of 2005. Among other provisions, the law required refineries to incorporate a minimum of 7.5 billion gallons of renewable fuels in the nation's highway fuel supply by 2012. The energy bill also contained tax incentives intended to boost production and keep the retail price artificially low.
In practical terms, the only renewable fuel available in mass quantities in the United States is ethanol, and the only commercially viable feed stock for U.S. ethanol production is corn.
Katrina and Rita significantly magnified the appeal of the Energy Policy Act subsidies. Within the storms' overlapping footprints was the densest collection of oil and gas wells, pipelines and refineries in the nation. Between the shutdowns ordered in anticipation of the storms' arrival and the damage inflicted by their passage, the United States abruptly lost a quarter of its crude oil supply and 20 percent of its natural gas production. Energy prices particularly the retail price of gasoline quickly soared.
The combination of federal subsidies and skyrocketing pump prices proved irresistible, and private investment capital flooded into the ethanol industry. According to the Renewable Fuels Association, an industry trade group, there were 93 ethanol refineries at the time Hurricane Katrina struck, with another 23 under construction. Less than 18 months later, there are 116 operating ethanol refineries and 78 under construction. Capacity has risen from 4.2 billion gallons annually to 5.8 billion gallons.
Skyrocketing demand for corn to feed those refineries has had two effects: U.S. farmers this year planted more acres in corn than ever before, and corn prices are at record highs. For the first time in human history, the market price of a staple food crop is being determined by its value as a vehicle fuel rather than its value as something to eat.
Because the United States is a major exporter of corn to the world, rising corn prices here translate into increased food prices everywhere. That's the principal reason 75,000 people marched in Mexico City three months ago to protest tortilla prices, which have doubled in a year. Subsidized American corn production in the past artificially lowered global prices, driving many Mexican farmers off their land often to seek work illegally north of the border and now subsidized American fuel production threatens to deprive Mexico's poor of a dietary staple.
Americans are not immune. Because corn is a major component of poultry and livestock feed, rising corn prices mean higher meat, egg and dairy prices. Corn derivatives also are in nearly every processed food product in a modern supermarket, so the ripples touch almost every meal.
According to a study issued last week by the Center for Agricultural and Rural Development at Iowa State University, ethanol-related price increases have added $14 billion annually to the nation's food bill already. The study also projects that the combination of high crude-oil prices and continued subsidies could boost ethanol production to more than 30 billion gallons a year by 2016, at which point it would consume half the U.S. corn crop and add $20 billion a year to the nation's food bill.
Most Americans can afford it; we spend a smaller percentage of our household income on food than anyone in the world. But we are not likely to make any friends in the global community if we force poor people elsewhere to endure empty bellies so we can keep our gas tanks full.
John Krist is a senior editor and Opinion page columnist for the Star. To read previous columns, visit http://www.johnkrist.com. His e-mail address is firstname.lastname@example.com.
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text:
A while back, Steve Rogers, Google's director for Europe, Middle East and Africa officially opened the iHub UX lab. He also gave an amazing talk on User experience in emerging markets that received rave reviews for those who attended this talk.
Steve is back and has been kind enough to prepare another session for the community. This is an even more interesting hands on session in which he shall be sharing how to develop ideas into actual viable products.
Come test your idea against this approach. What are you working on at the moment? Do you have a business or product idea? Wouldn't it be nice to learn new methods of dealing with your ideas?
WhereIhub main space
Bishop Magua Building, 4th floor
Ngong Road, Opposite Uchumi Hyper
Time10:00 a.m – 12:00 p.m.
Friday 18th October
Come test your idea! Join us for 2 hours and improve your skills. You will not regret it!


text:
|Dec 26, 2012, 09:06 PM
Remote Shutter - Camera Timer with Lens Filter
Hi Everyone,
If you looking for a photography app for help you take a group photo, Remote Shutter is a good choice for everyone. Remote Shutter allow you to connect your iPhone, iPod, and iPad using one as camera and one as remote to see live stream preview.
This happy holiday, you will never be left out of the frame any more.
>>Download here<<
- Connect 2 devices use one as camera and one as REMOTE.
- Bluetooth connection, no need internet connection you can take a shot while you are outdoor.
- LIVE PREVIEW STREAM, remote sees what camera see(available in full version).
- FILTER, customize photo with color and filter(available in full version).
- Full-Featured Camera DSLR design.
- Front/Rear Camera.
- Photo Quality adjust Low, Medium, Hight.
- Auto Focus on/off
- Auto White Balance on/off
- Exposure on/off
- Flash light and Torch for night shot.
- Multiple Shots(available in full version).
- Self Timer.
- Photo save in to both devices.
How to use
- Connect 2 devices by tap at Blue tooth sign.
- Choose your device to be Remote or Camera.
- Switch Your device for remote or camera in the blue tooth connection page.
- In Live preview you are fully control the camera.
- Put your camera device in right location.
- Look at live preview in your remote to adjust your location.
- Take photo
- Picture will save in to both devices.
What are you waiting for? Try it now in free version. If you love this app please support us in full version.
Remote Shutter is now available for iPhone and iPad.
>>Download here<<
Thank you everyone. Merry Christmas and Happy New Year.
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1854-O $3 AU55 NGC. Variety 2....
2011 December 8-11 US Coins Signature Auction- New York #1162
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Ukrainian Institute of America at The Fletcher-Sinclair Mansion
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New York, NY 10075
|Printable auction results for all items in the 2011 December 8-11 US Coins Signature Auction- New York.
Choice AU 1854-O Three Dollar Gold1854-O $3 AU55 NGC. Variety 2. The 1854-O is the only three dollar gold piece struck at the New Orleans Mint, with a mintage of 24,000 pieces. The issue is very rare in Mint State grades. Much detail is lacking on Variety 2 examples because of die lapping (note the upper portion of the ribbon bow seems almost detached from the knot on this piece). The lightly abraded greenish-gold surfaces retain traces of satiny luster.(Registry values: N2998) (NGC ID# 25M5, PCGS# 7971)
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Only O-Mint Three
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text: Do You Know the Basics About Migraines?By Erinn Connor, Everyday Health Staff Writer The National Headache Foundation (NHF) estimates that more than 37 million Americans suffer from migraines. The pain from a migraine headache is so severe it can be debilitating. Yet, as common as migraines are, misconceptions about the condition persist. Test your migraine knowledge and find out how they're diagnosed and what their symptoms are. What is NOT part of the criteria for diagnosing a migraine? At least five previous headachesNausea and/or light and sound sensitivityFamily history of migrainePain that throbs or pounds at one side of the head A migraine with aura typically involves disturbances to which sense? VisionSmellTasteHearing True or false: Medications can only be taken for migraines once the migraine has already started. TrueFalse What is a trigger for migraines? Hormone levelsStressChanges in sleep patternsAll of the above What is most important for a doctor rule out before diagnosing a patient with a migraine? A bad head coldBrain tumorPregnancy True or false: Women are more prone to migraines than men. TrueFalse Which is not a symptom of a migraine? Pain on one side or one part of the headSensitivity to lightGreen or yellow discharge from noseNausea True or false: People having a migraine can still function normally at work, home, etc. TrueFalse Which of these non-medication techniques can help a person manage their migraines? MeditationKeeping a journal to track symptomsDrinking more waterEating less salty foods During which stage of life do migraine symptoms typically get better? Teen yearsMiddle agePost-menopausalNone. Migraine symptoms remain the same throughout a person's life. Please answer all questions. Please enter a valid e-mail address. Take me directly to my results or enter your e-mail address below to get your results and sign up for our free Healthy Living newsletter. You will also be eligible to receive special content and promotions we think you'll like. By clicking "Get Results," I agree to the Everyday Health Privacy Policy.


text:
Manufacturer: Farnam
Model: Tri-Tec 14
Category: Fly Control
Purchase: I have been using this fly spray for years, and it has worked great. Kept the flys off for up to 2 days in good weather.... And I liked the fact it included sunscreen However, as of the spring of 2010, it seems they have changed their formulation along with the packaging. Causing a reaction in my horse!
Likes: Loved it up until this year ( 2010)
Dislikes: I noticed the new packaging/ bottle design and didn't think anything of it. However, soon after using the new bottle, my paint horse started breaking out in hives!! I ruled out feeds/supplements/ and tried a different spray, the hives cleared up. But as soon as I used the new Tri-Tec again, the hives returned ! I have contacted Farnam, and am waiting for a response to see if they had made any formulation changes.
Quality: Typical spray bottle
Summary: Please go back to the original formula !!!!
Rating: 1
Author: Lee
Date: 2010-08-06
Usefulness Rating: 1.66667 out of 5.
3 reader(s) voted.
Kensington Protective Products KFM300 / Fly Mask with Fleece Trim with Ears Fly Control
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Cashel Crusader Fly Mask Fly Control
Farnam Mosquito Halt Fly Control
Cashel Fly Mask with ears Fly Control
Absorbine Ultrashield Bonnet w/ears Fly Control
Zephyr's Garden No-Fly Zone Healving Salve Fly Control
Flyarmor mane and tail band Fly Control
Kensington Bug Eye Fly Mask (long w/ears) Fly Control
Schneiders Dura-Mesh Fly Mask with Halter Combo Fly Control
Dumor Fly Spray Fly Control
Manna Pro Calm Coat Fly Spray Fly Control
Farnam Endure Fly Spray Fly Control
Guardian Masks Guardian Fly Mask Fly Control
Top Horse Handy Helpers Fly Spray Fly Control
Gordon's Horse & Pony Spray Fly Control
Rambo Fly Buster Sheet with Neck Attachment Fly Control
Pyranah Spray & Wipe Fly Spray Fly Control


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Comments about SHOW ME YOUR MUMU BACHELORETTE BLOSSOM DRESS:
this dress is really pretty, but the sleeves are definitely true bell sleeves. Also, for some reason my lining hung slightly lower than the outer layer. But the color and fabric are great, and the length is perfect (5'5 & 110lbs - got a size small)


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who would win?
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#2 Posted by Captain_Awesome85 (476 posts) - - Show Bio
Hard to compare Marvel v Amine,I want to say Hiei opens the first level and cuts his head off but thats only because they seem to move so much faster in anime. Average fighters in these shows look like the move as fast as the flash.
@Cosmic Mancer said:
who would win?
Unfortunately, anime/mana vs. comics is not allowed unless it's in a tourney or possibly even a challenge a viner match (I dunno if that's allowed in CaV, gotta get clarification on that). And I know manga and comics are pretty much the same thing (in fact, in japan they refer to comic books as manga), but it's just not allowed.
Welcome to the vine! Enjoy your stay!
Thanks for reading,
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UK lawmakers on Tuesday voted in favor of a law that would make the UK the first country to allow an in vitro fertilization (IVF) technique that uses DNA from two women and one man. In the House of Commons, members of Parliament voted 382 in favor of passing the law and 128 opposing it. The ...[read more]
The French Court of Cassation ruled on Monday that a woman is allowed to adopt the child of her same-sex spouse conceived through in vitro fertilization (IVF). The ruling by the French high court comes following recently enacted laws regarding same-sex marriage rights. The court held each spouse ...[read more]
The Inter-American Court of Human Rights ruled Thursday that Costa Rica's ban on in vitro fertilization (IVF) violates the rights to privacy, liberty, personal integrity and to form a family, as recognized under international law. The challenge was filed in July 2011 on behalf of 50 Costa Rican ...[read more]
The Italian government on Wednesday announced that it has appealed a recent decision by the European Court of Human Rights (ECHR) that the country violated the rights of a couple with cystic fibrosis by preventing them from screening in vitro fertilization (IVF) embryos. The couple, who already ...[read more]
The US Supreme Court ruled unanimously Monday in Astrue v. Capato that children conceived by in vitro fertilization (IVF) after a parent's death are not entitled to that parent's social security benefits. Justice Ruth Bader Ginsburg announced the decision, which agreed with the Social Security ...[read more]
The US Court of Appeals for the Eighth Circuit ruled Monday that an Iowa girl born two years after her father's death was not entitled to his Social Security benefits. After the death of her husband, Patti Beeler used in vitro fertilization (IVF) to conceive the child, known as BEB, with her late ...[read more]
The Inter-American Commission on Human Rights (IACHR) on Monday filed suit in the Inter-American Court of Human Rights to challenge Costa Rica's longstanding ban on in vitro fertilization (IVF). The suit will be filed on behalf of 50 Costa Rican couples who have had to seek IVF procedures in ...[read more]
The Grand Chamber of the European Court of Human Rights (ECHR) in Strasbourg ruled Tuesday that a British woman could not have frozen embryos conceived with a former partner implanted without his consent. Natallie Evans and Howard Johnston entered an in vitro fertilization (IVF) program in 2001 ...[read more]
The European Court of Human Rights (ECHR) announced Monday that it will hear the appeal of a British woman trying to use frozen embryos despite objections from her former partner who fertilized the eggs. The ECHR ruled in March that Natallie Evans could not use the embryos resulting from a 2001 ...[read more]
Australian Prime Minister John Howard agreed Wednesday to hold a conscience vote on a stem cell research bill allowing therapeutic cloning if a private bill is offered to parliament. A conscience vote is a free parliamentary vote in which members are not bound by party policy. In 2002, following ...[read more]


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GeForce 4 Ti 128 on Mandrake 8.2 ???
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Registered User
Join Date: Oct 2002
Posts: 9
I found what was wrong in my installation. It was easier than I thought. The problem was that once the nvidia rpm's installed and the XF86Config-4 file edited as said in the manual, there was still a modifiction missing in that configuration file. That modification has not been done automaticaly by the system because the Video Card is not recognized by Mandrake 8.2. Well, here is the solution :
You have to specify after having changed every line in the XF86Config-4 file the Device used by your Screen setting in the "Screen section".
Here's the sample of my XF86Config-4 configuration file for those who don't want to lose any more time searching for a solution installing their new and beautiful GeForce 4
first of all you have the X server have to load the GLX acceleration, this is done by specifying the folowing line in the
' Section "modules" '
Load "glx" #just add this line in the Module section
Then you have to specify wich card you have and wich driver to use, this is done in the ' Section "device" ' by replacing the existing configuration by the following :
Identifier "Geforce4" #this identifer can ben whatever you like
VendorName "unknown" #just write whatever you like lol
BoardName "unknown" #idem
Driver "nividia" #here you must write "nvidia"
Till here it is like in the manual or README file distributed by Nvidia. But now comes the clue (or whatever you call this
, I'm sorry, my english is not very good). The identifier "Geforce" you have written in the ' Section "Device" ' is used by the screen configuration. As I understood, the screen configuration is given for your video board and so I thought that I maybe had to give the indentifier name somewhere. And it was what I thought !! God I'm good !
Here is what you have to do :
In the ' Section "screen" ' just go to the line beginning with "Device" and write down "Geforce4" between the brackets. In fact, there, the X server uses the string you used as Identifier in the ' Section "device" ' and so you have to specifie it there to to make the X server know what video card you use for that specific screen configuration.
Here is what you should have if you've used "Geforce4" as identifier (note : if you used another identifier name, you just have to use that other particular name here).
Section "screen"
Identifier "screen1" #by default so called.
Device "Geforce4" #as used in the Section "Device"
... just leave the rest of the section as it was.
Now you save the whole operation, exit your root user and start X by typing "startx". There it is ! You are now able to install UT2003 (or whatever you want lol) and play play play play ! By the way you can notice the difference in speed when you move a window. It's the prove that even the 2D display has been updated.
What do we say ? WE LOVE LINUX !!!!!! Yeah !
See ya !
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