text:
A process for authenticating a user to control remote access to a service, data base or data network is provided, in which during an enrollment step, an initial voice sample provided by the user is analyzed to obtain an initial user-specific voice profile and, in a later verification step, a current voice sample of the user is analyzed and compared to the initial voice profile to generate an access control signal. An additional user-dedicated authentication is generated in a pre-enrollment period, and the additional authentication is used to authenticate the user in the enrollment step and/or in an access control step prior to and independent on the enrollment step, in a provisional or supplementary authentication procedure.
1. A process for authenticating a user, to control his remote access to a service, data base or data network using a computer system or electronic computing device, comprising: in an enrolment step, providing an identification and an initial voice sample by the user and analyzing the initial voice sample to obtain an initial user-specific voice profile and, in a later verification step, providing the identification and a current voice sample by the user and analyzing the current voice sample to obtain a current voice profile which is compared to the initial user-specific voice profile to generate an access control signal in response to a result of the comparison step, generating an additional user-dedicated authenticating means in a pre-enrolment period, using the additional user-dedicated authenticating means to authenticate the user in the enrolment step and/or in an access control step prior to and independent of the enrolment step, in a provisional or supplementary authentication procedure,
wherein the additional authenticating means comprises a system-specific ID card, with the system-specific ID card displaying a unique system specific PIN or similar code, and the method further comprises system-internally linking the PIN or the code to the user and corresponding data of the user, and shipping the system-specific ID card as a blank card and activating the blank card upon request of the user and in response to an input of the system-specific PIN or similar code at a data or telecommunication terminal of the user.
2. The process according to
3. The process according to
4. The process according to
5. The process according to
6. The process according to
7. The process according to
8. The process of
9. The process of
10. An arrangement for authenticating a user and controlling his remote access to a service, data base or data network, the arrangement comprising
a user data and telecommunication terminal comprising a data input device and a speech input device for inputting a user's voice sample, an authentication server for processing data and voice samples input by the user and an at least temporary network connection of the user terminal to the authentication server, wherein the authentication server comprises a user identification recognition stage that recognizes a user identification, a voice profile generator, a voice processor to analyse user's voice samples to obtain a respective user-specific voice profile, a voice profile storage device for storing processed user's voice samples, and a voice profile comparator for comparing a current voice profile evaluated from a user's current voice sample with an initial voice profile stored in the voice profile storage device for obtaining a first authentication output based on a voice sample input by the user, and a user data processor, user data storage device for storing corresponding reference data of the user, and a user data comparator for comparing the referenced user data with data currently received from the user terminal for obtaining a second authentication output from data input by the user and an access control signal generator to generate an access control signal only after receiving the first and second authentication outputs,
an ID Card generator for generating a physical system-specific ID card comprising a system-specific ID or similar code being unambiguously assigned to a user-specific set of information items, the user-specific set of information items including at least one of a user ID or an ID storage device for storing the system-specific ID or similar code in unambiguous assignment to the user-specific set of information items, wherein the ID storage device acts as a user data storage device and is connected to an input of the user data comparator, and
a user card activating device for activating a previously generated and distributed system-specific ID card in response to an input of the system-specific ID or similar code via a data or telecommunication terminal.
11. The arrangement according to
12. The arrangement according to
a voice sample input instruction device for instructing the user to input a PIN or similar code or predetermined information items as the user's voice sample via the speech input device, and a text sample storage device for storing text samples which are subject of the user's voice sample input by the user, in response to instructions obtained from the authentication server, wherein the text sample storage device is connected to the voice processor to enable processing of the user's voice sample without an automatic speech recognition step.
13. The arrangement according to
14. The arrangement according to
This invention refers to a process and arrangement for authenticating a user of facilities, a service, a database or a data network.
In conventional access control systems, as applied to data networks, identification or authentication means, respectively, of the knowledge-based type are being used to fulfil the security requirements. In particular, for decades password-based or PIN based identification/authentication schemes are known and generally used. More specifically, in spy- or fraud-sensitive applications, such as home banking applications, supplementary security measures like the provision and obligatory use of individual transaction codes or TANs, respectively, are known and widely used. Even such supplementary security-enhancing schemes are knowledge based and suffer, therefore, from the typical disadvantages of all knowledge based schemes, i.e. problems related to the loss of the relevant information by the authorized user on one hand and risk arising from the access to such information by an unauthorized user on the other hand.
Therefore, in recent years considerable efforts have been made to include other types of identification/authentication schemes into the security mechanisms of data networks. In particular, approaches to add "possession-based" (tokens) and/or "being-based" (biometry-based) schemes to the well-known knowledge-based schemes, or even to substitute the latter schemes with such new ones, have been tried. For example, in automatic cash dispensers, biometrical authentication schemes based on fingerprint or retina recognition, respectively, have been proposed for controlling the access to bank accounts. Furthermore, the meanwhile well-established fingerprint-based access control means of notebooks and other personal computers should be mentioned as some kind of means for controlling the access to data networks.
More recently, voice-based authentication solutions, as a specific type of biometry-based identifications/authentications, have widely been introduced by firms to supplement their internal knowledge-based access control schemes.
In internet and mobile based services and activities, in particular in internet market places like ebay or internet financial transaction systems like PayPal, with the rapidly growing worldwide user base the number of fraudulent attacks increases significantly. The probability of a successful attack on accounts of a worldwide internet-based service with millions of users is much higher than with phishing attacks on local banks.
Thus, voice-based authentication is also being discussed as a security scheme for internet and mobile network based services and data access systems.
Facing this type of sophisticated application on a huge scale, voice biometric solutions have to cope with several technological challenges and to achieve a high level of user acceptance. Specific challenges are linked to the enrolment procedure, cross-channel problems, security requirements, flexibility and scalability demands.
For the enrolment process, a unique user ID is required to identify the user. However, there is no universal form of user IDs to identify users of voice biometric systems. The formatting varies from company to company. In the enterprise market the personal number of the employees is often used for identification, whereas in the consumer market the name of a person or any other substitute to the name (login name, e-mail address, mobile number) are used or can be used to identify the user, at least with a certain degree of reliability.
Today, for this step, automatic speech recognition (ASR) is used. However, basically the integration of ASR in a voice verification solution is limiting its scalability. ASR solutions are not available in all languages or suffer from several problems in a number of languages. This means: Although a voice verification solution could, in principle, be offered to customers in these specific countries, the solution as it is offered now (including a speech recognition and a voice verification part) cannot be provided to customers in these countries due to the missing or sub-optimal ASR component.
The elimination of the ASR component would make the system easier to use and easier to scale, but until now there is no solution to avoid the integration of the speech recognition component into a voice profile based authentication system.
Furthermore, security is a big issue for customers. Until now, most voice biometric security solutions exclusively rely on voice authentication as the only real security layer besides the user ID (checked with voice recognition). However, this means that the threshold of the voice authentication security layer had to be set high to ensure a high resulting level of security. This can result in limitations during the usage of the system.
The usage of different types of phones (fixed line (wired), fixed line (DECT), mobile phone, VoIP) results in problems in the usage of voice biometric solutions. As the bandwidth of the different telephony channels is ranging from 8 kbit/s (VoiP) to 64 kbit/s (ISDN) and even much more, the quality of the voice sample differs. A user enrolled with a VoIP phone can have problems with verification on a wired fixed line phone, as the voice sample provided on the fixed line phone differs from the voice sample provided during enrolment on the VoIP phone. A solution for this problem would be to decrease the threshold which determines the sensitivity of the system.
Combined with the security requirements, the cross-channel problems may lead to an inconvenience factor in the usage of voice authentication products, related to higher false rejection rates (FRR) and problems during enrolment and usage of the solution.
As already mentioned above, to use a voice biometric system each user has to register in the system, storing his/her voiceprint in the database. Only after the user has enrolled in the system he/she can use the system. A problem linked with the enrolment process is that most voice biometric systems try to achieve a 100% enrolment level of the users in the start period of the system implementation. This results in a high load on the voice channels in the first weeks/months after the installation. A higher number of voice channels are needed to handle the high number of enrolling users. If a system is only used with the number of voice ports, which are needed to guarantee a convenient daily usage after the enrolment phase, some of the users, which want to enrol, may not be served as the voice ports are blocked.
It is an object of the invention to provide an improved process and apparatus for controlling the access of a user to a service provided in a data network which is, in particular, relatively easy to implement and to use, as well as acceptable under cost aspects.
This object is, under process aspects, solved by a process according to the invention and, under device aspects, by an arrangement according to the invention. Preferred embodiments of the invention are subject of dependent claims.
The invention intends to improve a process for authenticating a user, to control his remote access to a service, data base or data network, wherein, in an enrolment step, an initial voice sample provided by the user is analyzed to obtain an initial user-specific voice profile and, in a later verification step, a current voice sample provided by the user is analyzed to obtain a current voice profile which is compared to the initial voice profile to generate an access control signal in response to the result of the comparison step. The improvement includes the idea to provide additional user-dedicated authenticating means which are generated in a pre-enrolment period, the additional authenticating means being used to authenticate the user in the enrolment step and/or in an access control step prior to and independent on the enrolment step, in a provisional or supplementary authentication procedure.
Correspondingly, under apparatus aspects the invention intends to improve an arrangement for carrying out this process and for this purpose comprising an authentication server in so far as the authentication server comprises voice profile generation means, voice profile storing means and voice profile comparing means for obtaining a first authentication output based on voice sample input by the user and user data processing means, user data storing means and user data comparing means for obtaining a second authentication output from data input by the user and access control signal generation means to generate an access control signal in response to the first and second authentication outputs.
A key difference with regard to existing voice biometric solutions is that the proposed 2nd factor authentication procedure does not rely on voice biometrics as the only security layer, but combines in one security solution an additional out-of-band security layer with the voice authentication.
This makes it possible to accept a decrease in the threshold of the voice verification part, as the integration of the 2nd security layer can compensate for such decrease in the FRR of the voice authentication and even raise the level of security. The relevant information (or hardware authentication means) of the 2nd layer is linked to a single user. Therefore it can only be used by this specific user. In the case of loss of a hardware component (ID card), no other user can access the system, as the voice authentication-security level is still present. A new card can be issued and used without any problems, as the enrolled voice sample remains the same and only the second security layer has to be replaced. No repeated enrolment is necessary and the user can use the system immediately after getting the new card.
The ultimate goal of a voice biometric system should not be a 100% enrolment level, but a 100% automation level. Users do only enroll in the system once they are in need of a service. The enrolment and the provision of the service providing will be preferably included in one single process. This results in a lower load on the voice channels as the number of users, enrolling in the system basically at the same time may be reduced dramatically. The so-called "On-Demand-Enrolment" solves many existing problems: The users do not have to enrol in the system within a given time frame. The number of ports does not have to be extended only to serve the higher number of enrolling users, and the enrolment and first services procedures may be combined in one single process, thus increasing the user acceptance.
Further advantages and aspects of the invention result from the following description of preferred embodiments with reference to the figures. Of these:
The system server 1 has a user prompting output interface 9, a user input interface 11 (which simultaneously acts as a voice sample input interface) for temporary connection to the mobile phone 3 of the user, and a control signal output interface 13 for connection to the data management server 5 for the output of control signals to it.
According to the functional structure (shown in a simplified form in the figure for improved clarity) of the system server 1, the user input interface 11 is simultaneously designed as an input signal branch which permits feeding of input signals (for example the MSISDN) transmitted automatically by the mobile phone 3 to subsequent processing units over a first signal path a and of voice inputs of the user to subsequent components via a second signal path b. In the first signal path a digital input classification stage 20 is provided to route records generated automatically in the mobile phone along a first partial signal path a1 to a mobile number recognition stage 15, while data entered digitally by the user is routed over a second partial signal path a2 to a user data processing stage 19 and in parallel to a user input switch-through stage 35.
The mobile number recognition unit 15 issues a control signal to a user prompting unit 17 in response to acquisition of the user's mobile phone number. This unit 17 realises all user prompting during enrolment or authentication processes executed with the system presented and outputs corresponding elements of user prompting through the user prompting output interface 9. The acquired MSISDN is supplied by the mobile number recognition unit 15 to a user data processing stage 19 which, in total, is designed for input-end processing of all manner of user data. There, the data is initially buffered for later processing.
In response to the output of a user prompt providing guidance through the further procedure by the user prompting unit 17 (with details described further below), the user will speak some voice sample. The voice samples are routed via the signal path b to a voice profile computing unit 25, to obtain a current voice profile of the user.
A voice profile successfully computed by the voice profile computing unit 25 is routed to a voice profile comparison unit 27, where it is subjected to a comparison with a previously stored voice profile of the same user, which is loaded for this purpose out of a voice profile storage unit 29. Corresponding addressing of the voice profile storage unit 29 is ensured via the output signal of the mobile number recognition unit 15, which supplies the relevant indicator for the user's identity. If conformity transpires from the comparison of the voice profiles in the comparison unit 27 to an adequate degree of reliability, this unit outputs a corresponding confirmation signal to a first input of an OR stage 31.
The user data processing stage 19 acquires relevant user information from a data stream received through the user input interface 11 and isolates relevant authentication data for authenticating the user independent on its voice profile therefrom. Stage 19 compares such data with corresponding comparison data stored in the user data storage unit 33 and can (besides other functions which have been omitted in the simplified functionality presented here) output a confirmation signal to a second input of the OR stage 31 as a result of the comparison.
Further user inputs routed via the branch 20 (for example, a required access address of a memory area, the designation of a service retrieved by the user or a recharging amount for a prepaid card) can be routed to the input of a user input switch-through stage 35. The user input switch-through stage 35 is connected via a control input to the output of the OR stage 31, which sets stage 35 to a user input switch-through state provided a positive confirmation signal is present at at least one of its inputs that identifies successful authentication of the user via his or her voice profile or via other inputs (i.e. in a substitute authentication procedure). In this case the user input present at the input end is routed into the control signal output interface 13 and ultimately leads to access enabling in the database 7 via the data management server 5 (or to the execution of a comparable operation, for example the provision of a required service or the execution of a required transaction due to transaction data stored in the database 7).
At the same time, a control signal indicating switching through of the user inputs is sent to the user prompting unit 17, which outputs corresponding confirmation information for display/output on the mobile phone 3.
One of ordinary skill in the art can derive details of the special processes for specific application scenarios easily from the description above and so an explanation of one single example as given below will suffice. It also transpires from the following description that the voice profile computation and voice recognition for the purpose of 2nd factor authentication shown as parallel processing in a simplified form in
In the following, exemplary embodiments of the enrolment and verification procedures according to the invention are described, which embodiments include the integration of an additional security layer to the voice-authentication based security layer and the elimination of an automatic speech recognition from the voice-authentication security layer.
Each user of the voice biometric solution will receive a physical ID card. He will only be able to activate the card using a PIN code, which will be sent to the user via a different way than the ID card and which is used later on to verify his identity during the enrolment step.
Optionally, the user can use the received PIN code to obtain his ID card online, in entering the PIN code on a specific website. After entering some credentials including the PIN Code, the user can download the Virtual Voice Card as a pdf or any non-changeable data file to his computer and print it.
As another option, the user can use the received PIN code to obtain his/her ID card via a mobile phone, in accessing a specific "mobile page" of the system provider. After entering some credentials including the PIN Code, the user can download the card as a Java Bean or any file which can be executed on a mobile phone. Afterwards, a secret table shown on the card in
This ID card includes a user ID, which is linked to a person and a VT code, which is linked to the person's company to identify the user. Besides these two codes, the user ID card includes an N�N matrix with numbers uniquely linked to the owner of the card. These numbers or the secret table, respectively, are used as the second authentication layer. Optionally, the matrix numbers can be covered with a protection layer, which has to be rubbed away to use the numbers—in this case these numbers would be PINs for single, temporary use, which become invalid after one time usage.
1. The user calls the system for enrolment. Other than in the case of an ASR solution, where the user has to say his user ID, in the case of a user ID card based enrolment, the user has to type in his/her user ID and his/her VT code on the touchpad, using the DTMF functionality of the phone.
With the elimination of the ASR, it is ensured that
a) the voice biometric solution remains flexible and scalable even to countries where ASR solutions are not available in respective languages and
b) the inconvenience factor, which results from potential non-recognition of the user ID, is decreased. The user has to enter the ID on the touchpad of the phone or on the keyboard of the computer—only little misusage happens.
2. The system asks the user to enter specific numbers from the secret table on the back of the ID card which, optionally, the user has to rub away before he can see it. E.g. in the example as shown in
3. To ensure that only the real user enrols, a PIN is provided to the user on a separate way. This PIN is used to verify the user during the enrolment.
4. In a next step, the user has to speak numbers delivered by the system. E.g., the system might ask the user to count from zero to nine or asks the user to repeat four numbers in a row twice. This procedure is based on text-independent voice authentication, as the user can enrol with other numbers than used for verification. E.g., the user enrols with a digit queue of 1-2-3-4 and verifies with a digit queue of 4-3-2-1.
5. After enough data is collected to create a speaker's voice profile, the user is successfully enrolled in the system.
1. The user calls the system for verification. The system asks the user to enter his/her user ID and the VT code on the touchpad.
2. The system asks the user to enter specific numbers from the secret table on the back of his user ID card, which optionally, the user has to rub away before he can see it. E.g. in the example above: Please enter D2→User has to read 69, Please read C5→User has to read 12. Depending on the security standard required, one or more challenge-response sequences are used.
3. In a next step, the user has to repeat (speak) numbers given by the system. Different from in the enrolment procedure, less data are required to verify the user. E.g. the system asks to repeat 4 numbers in a row twice. This procedure is based on text-independent voice verification, as the user can enrol with other numbers than used for verification.
The user won't be informed about the result of the single authentication steps. E.g. if the first authentication fails, the user still has to go through the second authentication and will only be informed about the result after two authentication steps. This ensures that potential attackers to the system will only get limited feedback about success and failure of the several authentication layers.
An alternative to the above described 2nd factor authentication based on a token-like hardware component is the implementation of a second factor based on shared secrets. Like in the above-explained scenario the ASR is no longer needed. The enrolment and authentication process is based on DTMF and voice verification technology. The following scenario exemplifies a banking environment:
1. The user calls the system for using the service and enrolling in the system. For identification, the user has to type in his/her bank account number or any other use-unique identification, followed by the used PIN or any other user-unique authentication. These two factors are used for the initial identification and authentication of the user.
2. The user has to do a voice enrolment. In a challenge-response procedure the user has to answer certain challenge questions. These challenges are e.g. the user's name or shared secrets. E.g. the user has to repeat his/her name and to tell as a shared secret his/her mother's maiden name or the date/place of birth.
3. After enough data is collected to create a speaker's model, the user is successfully enrolled in the system.
4. After passing the voice enrolment step the user can immediately use the service within the same service call. E.g., the user can immediately reset a password or instruct some financial transaction etc. without having to call the system a second time.
1. The user calls the system for using the service. For identification, the user has to type in his/her bank account number or any other user-unique identification. As the user is already enrolled in the system, a PIN is no longer needed.
2. In the next step, the user has to do a voice verification based on the information provided in the enrolment step (user's name+shared secrets).
3. After the user is successfully authenticated, he/she can use the service.
The combination of voice biometrics with shared secrets increases the level of convenience and still guarantees a certain level of security as the user has to pass an authentication step and has to know the shared secrets. The system thereby tests something the user is and something the user knows.
A further development to the 2nd factor authentication procedures as explained above is an extension to the shared secret scenario. The embodiment explained above demands a secure authentication of the user in the enrolment phase. If the system cannot identify and authenticate the user in the enrolment, a potential intruder might, in principle, enrol in the system without being allowed to do so. In the example, this was checked by asking the bank account number and PIN. In other scenarios the secure authentication of the user based on an existing trust chain is more difficult. In such cases the following scenario, as illustrated in
Enrolment (Part 1)
1. The user is informed by the relevant authority that a voice biometrics system is introduced. Different from today's schemes, the user doesn't have to go through the complete voice authentication enrolment procedure in the beginning. The user only has to execute a first step of web-registration. The voice enrolment, which is needed to authenticate the user for any future transaction, will be done later on.
2. The user has to access an internal website, authenticating with his existing user name and PIN/password or an additional Registration PIN. After successful identification and authentication of the user, he/she will be asked to provide answers to a list of secret questions. These answers will be stored in the system and used later on to authenticate the user for voice enrolment and a password reset process.
Option 1: The secret answers have to be typed in.
Option 2: The secret answers have to be chosen out of a selection of answers offered to the user by the system (as exemplified in
3. After the user has provided the demanded information, the first registration step is completed. The user can now call e.g. the service any time he/she is in need of and finish the enrolment procedure with the voice enrolment steps.
Enrolment (Part 2)
4. If the user is in need of a new password or wants to use any other voice-authentication based service, he/she calls a given phone number and identifies with his/her user ID or any other given unique identity.
5. Based on the information given in the first step of the registration the user will be asked, either to speak (Option 1) or to type in (Option 2) the answers to a pre-registered challenge question. In Option 1, the spoken answers are being used to execute the voice profile evaluation and create a current speaker's voice model, whereas, if Option 2 is valid, the system will request that the user speaks pre-defined text pieces (numbers, names etc.), as explained further above in the first embodiment. In this latter case, the procedure takes somewhat more time and requires more activity from the user so that Option 1 should, at least in principle, be preferred from the point of view of user acceptance.
6. After enough data is collected to create a speaker's model, the user is successfully enrolled in the system.
7. After successful voice enrolment the user can immediately use the password reset or the other voice-authentication based service and does not have to call again—everything is handled in one call.
By following this challenge-response dialogue with a combination of shared secrets and voice biometrics, the system ensures a high level of convenience and security. On the one hand, the correctness of the given answers is checked, on the other hand a voice model is generated for the him/her to re-use the service.
1. For every further action, the user calls the system for using a voice service. For identification, the user has to type in his/her bank account number or any other unique user ID using DTMF.
2. In the next step, the user has to do a voice verification based on the information provided in the enrolment steps (user's name+shared secrets). As the user is already enrolled in the system he no longer needs to choose between different optional answers in the challenge—response procedure. He only needs to provide the right answer to the question asked by the system.
Now a further embodiment of the invention will be explained, referring to
On the front surface of the card (
On the back surface of the "Voice Card" (
An important advantage is that the user does not have to keep in mind his user-ID as it is linked in the database to the number shown ("system-specific ID") on the card. Especially in companies where multiple user IDs exist it is difficult for employees to keep in mind their user IDs. Compared to existing solutions, there are many further advantages: First of all, even without an access to a computer (which is not available in most situations when a user has forgotten his/her password) a user can reset his/her password, even without having registered his/her voice profile before. In prior solutions, a PIN code is sent via E-Mail to the user, which step is needed for voice enrolment. Having locked out of the system, the user cannot use the password reset service if he/she hasn't completed the voice enrolment. The problem many voice biometric solutions face is that it is hard to convince a user to do a voice enrolment before he/she actually needs the system. This can be solved by the on-demand enrolment procedure the "Voice Card" is based on.
Furthermore, in the case of "Voice Card" there is no visible linkage to a user and no user-specific data on the card. If the card gets lost or is stolen on the way, a possible fraudulent user cannot enrol in the system as the card can only be activated by that user who should receive the card. The activation will be based on an existing trust chain. This means that the card can only be activated after the user has logged on a certain service or system for which confidential user data are needed.
Now, important steps when using the "Voice Card" will be described.
1. Pre-Linkage of Card to User Data
Before the card is distributed among the users, each card (i.e. the system-specific ID displayed on the Voice Card) will be linked to users' details (e.g. user-ID) in the database. E.g. this means that card number 000000000000001 can be matched to user-ID aaa0001. There could be a linkage to multiple user-IDs as well. However, this linkage will only be in the database, there is no visible linkage of a certain "Voice Card" number to a specific user.
2. Activation of "Voice Card"
After the card has been delivered to a user, he/she has to activate it to make sure that the right user has received the right card. This activation procedure is based on an existing trust chain. E.g. after the user logs on to his/her computer he/she will be asked to activate his/her Voice Card. E.g. "You have received your voice card to do automated passwords resets based on voice authentication in the future. Your card number is: 000000000000001. If this is correct, please press "OK" to activate your card." For this purpose, by the authentication system a user-specific log in scheme is provided, i.e. a scheme which is determined for a specific user and accessible only by this user beforehand, on the basis of data which are pre-stored in a data base of the system.
Once the user has activated his/her card he/she can use the card for enrolment and verification of any password reset or other services. If the card is lost on the way or a wrong user has received a wrong number, no activation will be initiated and take place and therefore no voice enrolment and no password reset for a specific user is possible.
3. 1st Time Usage: Voice Enrolment
After having activated the "Voice Card" the user can do the voice enrolment and password reset at any time he/she wants to. After calling a dedicated number, the user will be asked to enter his/her "Voice Card" number via DTMF, optionally via voice recognition. In the database the system-specific ID will be matched with the user ID. If the user hasn't enrolled his/her voice so far he/she will be asked to go through a challenge/response procedure for voice enrolment. In a first step the user will have to say his/her name, respectively repeat his/her name a couple of times. This step serves as a shared secret, as the name is not visible anywhere on the Voice Card and is not directly linkable for fraudsters. This means that the there is a 3-factor authentication once the user is enrolled.
Optionally, the "Voice Card" number (system-specific ID) will be matched to the user-ID in the database. The user-ID or any other user-specific information will be prompted on the telephone and the user has to repeat it for future usage a couple of times. This means that there is a 2-factor authentication once the user is enrolled.
For further voice enrolment the user will be asked to repeat a given word or number sequence multiple times until enough voice material is available to create a voice model.
After the voice profile has been stored on the server and linked to the user, the user can immediately reset a password for a chosen target system or use any other service.
4. Normal Usage
For normal usage the procedure is not different from the voice enrolment step, except for the fact that the voice samples don't have to be repeated a couple of times to create a voice print. First of all, the user has to type in his/her system-specific ID number using DTMF or via voice recognition. As a next step, the user has either to answer a shared secret question (e.g. his/her name) or repeat immediately the prompted information (e.g. user ID). In the following steps the user has to go through a challenge/response procedure to verify his/her voice. After successful voice verification the user is allowed to reset the password for a chosen target system or to use any other service.
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Save space with the Graco Swing By Me Swing, the multi-purpose swing that offers two products in one. Designed to allow you to bring baby with you from room to room at home and when you are traveling, this swing includes a comfortable seat, multiple swing speeds, and an overhead toy bar with soft detachable toys to keep her engaged. This swing's compact, folding frame makes for easy storage and provides on-the-go convenience. Features:
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33 year old woman | Fair Oaks, CA, USA | Seeking men 33-41 within 50 miles
I never lie to any man, because I don't fear anyone. You only lie when you are afraid.
I'm friendly, caring, honest, trustworthy and love to enjoy life. I am looking for someone similar to me. I love the outdoors but I also love relaxing at home and enjoying an evening in. I"m adventurous and country... Hope to find someone that is the same,
Camping , Coffee and conversation , Cooking , Dining out , Fishing/Hunting , Hobbies and crafts , Movies/Videos , Museums and art , Music and concerts , Exploring new areas , Playing cards , Playing sports , Travel/Sightseeing , Video games , Watching sports , Wine tasting
Auto racing / Motorcross, Baseball, Billiards / Pool, Bowling, Cycling, Football, Hockey, Martial arts, Swimming, Walking / Hiking, Weights / Machines
I exercise 3-4 times per week.
I like Dogs, Fish, Horses, Other
Some other viewpoint
Anywhere outside.
I love Country music, old and some new. Southern Rock, Rock n Roll.. and some other random genres. TV, I like cartoons... always love a good laugh, and Sons of Anarchy, Justified, also love to watch some shows on Disc, Hist, TLC, speed, espn
I love camping, fishing, rock crawling, mudding, motorcycles, muscle cars. Most anything outdoors. Kayaking, hiking, bike riding. Road trips, love the ocean, mountains, the snow.
I"m reading a book right now titled Plum Island, author Nelson Demille.
Z{{Cta}} {{#if HasMoreInfo}} ?{{CtaSecondary}} {{/if}}
|What she is looking for
|5'6" (167cms)
|5'10" (177cms) to 6'10" (208cms)
|Body type:
|Slender, About average, Athletic and toned, A few extra pounds
|Blue, Brown, Green, Hazel
|Light brown
|Light brown, Dark brown, Salt and pepper
|No Way, Occasionally
|Social Drinker
|Never, Social Drinker, Moderately
|Administrative / Secretarial
|No preference
|Less Than $25,000
|$25,001 to $35,000, $35,001 to $50,000, $50,001 to $75,000, $75,001 to $100,000, $100,001 to $150,000, $150,001+
|Never Married
|Never Married, Widow / Widower, Currently Separated, Divorced
|Have kids:
|Yes, and they sometimes live at home, No, Yes, and they live away from home, Yes, and they live at home
|Wants kids:
|Definitely, Someday
|White / Caucasian
|White / Caucasian
|Spiritual but not religious
|Spiritual but not religious, Other, Christian / Other
|High school
|High school, Some college, Associates degree, Bachelors degree, Graduate degree, PhD / Post Doctoral


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Visitor Information
- Opening Times
Iceland is a cheap, major national supermarket chain specialising in frozen foods. It offers good, multi-buy deals on frozen meals, fresh snacks and alcoholic drinks. It also stocks the usual assortment of fresh foods, drinks, condiments and household goods. The fresh fruit and vegetables tend to be disappointing and overpriced.
Opening and closing times for Iceland
Today (Tuesday) Iceland closes at 20.00
Underground Stations
Railway Stations
Further articles featuring Iceland on LondonTown.com
The Scandinavia Show Earls Court Exhibition Centre, SW5 9TA 6th October 2012 - 8th October 2012 Scandinavia compiles some of the most beautiful and stylish destinations in the...
Chelsea Fishmonger 10 Cale Street, SW3 3QU The Chelsea Fishmonger is a labour of love for Rex Goldsmith who has been in the fish trade since...
With an exciting calendar of entertainment, 2015 is another special year in London. Find out what's happening throughout the capital with our thorough guide to the best 2015 London events.
Hotels near Iceland
London > Hotels > Mid-Range Chain Hotel from £83 30% off
53 Upper Street, N1 | 4.3 miles from Iceland
The Business Design Centre next door is the obvious attraction for many of the guests at this smart, efficient Hilton Hotel, but Islington's excellent restaurants and ... More
London > Hotels > Mid-Range Chain Hotel from £58 23% off
419 to 437 Hackney Road, E2 | 4.3 miles from Iceland
This hotel is modern, clean and very convenient if you want to explore the sights and bright lights of trendy Shoreditch. Although close to the City, ... More
London > Apartment > Apartment from £112 37% off
Patriot Square, E2 | 4.4 miles from Iceland
The Town Hall building in Bethnal Green has been beautifully restored creating a unique designer hotel which fuses old and new. With a mix of bedrooms, ... More
Alternative Food and Drink Shops nearest Iceland
London > Shopping > Food and Drink Shops
32-40 Stoke Newington Church Street, N16 | 2.2 miles from Iceland
Whole Foods Market specialises in organically grown and good-for-you foods with an emphasis on foods that are free of artificial preservatives, colours, flavours, sweeteners and hydrogenated ... More
London > Shopping > Food and Drink Shops
17 The Broadway, Crouch End, N8 | 2.6 miles from Iceland
The century-old smokehouse at the rear of Walter Purkis provides excellent, and reasonably priced, smoked salmon to both branches (the other is in (Muswell Hill) of ... More
London > Shopping > Food and Drink Shops
30 Highbury Park, N5 | 3.1 miles from Iceland
Consistently recognised and awarded for being a very special place to indulge your cheese addiction, La Fromagerie is one of the best cheese shops in London ... More
Shopping near Iceland
London > Shopping > Specialists
Finsbury Park North-West Gate, Junction of Upper Tollington Road and Endymion Road, N4 | 2 miles from Iceland
Offering an urban forest on eight farm-style sites around London, the Christmas Forest is London's largest independent "treetailer" ensuring that Londoners can enjoy their tree-browsing experience ... More
London > Shopping >
84 Stoke Newington Church Street, N16 | 2.2 miles from Iceland
Olive Loves Alfie is a wonderful children's store in Stoke Newington where you can find inspiring and imaginative toys, games, clothes and accessories that are both ... More
London > Shopping > Supermarkets
581C Green Lanes, N8 | 30 minutes from Iceland
Harringay locals, couple Ebony and Paul Harding, are behind this supermarket with a difference. Harringay Local Store unites their two passions, stocking locally made products and ... More
Events near Iceland
London > Events > Film Events Dates: 3rd to 9th Jul 2015
Bernie Grant Arts Centre, Town Hall Approach Road, N15 | 10 minutes from Iceland
London > Events > Film Events Dates: 3rd to 9th Jul 2015
Bernie Grant Arts Centre, Town Hall Approach Road, N15 | 10 minutes from Iceland
London > Events > Film Events Dates: 3rd to 9th Jul 2015
Bernie Grant Arts Centre, Town Hall Approach Road, N15 | 10 minutes from Iceland
Entertainment near Iceland
London > Entertainment > Theatres
1-15 Leswin Place, N16 | 2.5 miles from Iceland
No airplanes take off from Stoke Newington International Airport. And there's no point looking up departure times here. Instead turn up for live performances by local ... More
London > Entertainment > Theatres
11 Clifton Terrace, N4 | 2.6 miles from Iceland
The £2.2 million Park Theatre is situated two minutes' walk from Finsbury Park tube station and houses a two-tier 200 seat and a 90 seat theatre, ... More
London > Entertainment > Live Music
Alexandra Palace Way, Wood Green, N22 | 2.6 miles from Iceland
After a shaky start - destroyed by fire 16 days after 'The People's Palace' first opened in 1873 - Alexandra Palace re-opened again two years later ... More
Sights and Attractions near Iceland
London > Attractions > Art Galleries
Lloyd Park, Forest Road, E17 | 2.2 miles from Iceland
The Grade II-listed William Morris Gallery, housed in the mid-18th century boyhood home of artist and designer William Morris, has a permanent exhibition on his ... More
London > Attractions > Activities
Stoke Newington West Reservoir, Green Lanes, N4 | 2.3 miles from Iceland
The purpose-built environmental education and watersports centre is a wonderfully tranquil place on the edge of the city. Based at a decommissioned reservoir in Stoke Newington, ... More
London > Attractions > Attractions for Kids
Spring Lane, E5 | 35 minutes from Iceland
The KIDS Adventure Playground in Hackney provides a stimulating, inclusive play centre for disabled children and young people aged 5 to 19 years. The playground, situated ... More
Restaurants near Iceland
London > Restaurants > Eastern European restaurants
488 West Green Road, N15 | 26 minutes from Iceland
Eastern European Cuisine... More
London > Restaurants > South American restaurants
Hollywood Green, Redvers Road, N22 | 32 minutes from Iceland
... More
London > Restaurants >
429 Green Lanes, Harringay, N4 | 33 minutes from Iceland
... More
Education near Iceland
London > Education > Evening Classes
Unit 207, Belgravia Workshop, 157-163 Marlborough Road, N19 | 3 miles from Iceland
Only the French could come up with an art form so bizarrely fascinating. Mime is as relaxing as Tai Chi, as healthy as yoga, and as ... More
London > Education > Careers Services
27B Dalston Lane, E8 | 3.3 miles from Iceland
Connexions is a countrywide information and advisory service for 13-19 year olds and people with special learning needs or disabilities under 25. They offer an array ... More
London > Education > Cookery Courses
Unit 8 The Islington Studios, 6 Hornsey Road, N7 | 3.5 miles from Iceland
Islington cafe-cum-deli Jenius Social isn't just a place to enjoy fine food and carefully sourced balsamic vinegar, artisan chocolates and cured meats. It's also a ... More
Leisure near Iceland
London > Leisure > Parks and Gardens
Forest Road, E17 | 2.1 miles from Iceland
The 12.5 hectare Lloyd Park is a lovely green space in Walthamstow, opened in 1900 and restored in 2012, with a children's ... More
London > Leisure > Parks and Gardens
Stoke Newington High Street, N16 | 2.2 miles from Iceland
Non-denominational cemetery, arboretum and nature reserve. Hidden away in the north-east corner of London, lies this highly influential, pioneering and yet relatively unknown beauty spot. Part nature ... More
London > Leisure > Parks and Gardens
Upper Clapton Road, E5 | 32 minutes from Iceland
Springfield Park was formed in 1905 from the grounds of three private houses, one of which still survives and serves as a delightful cafe. The grade ... More
Pubs near Iceland
London > Nightlife > Pubs
105 Stoke Newington Church Street, N16 | 2.3 miles from Iceland
The Guinness in this soothingly dark little Celtic den is nothing short of exceptional. Smooth, bitter, creamy and rich they serve up divine pints ... More
London > Restaurants > Gastropub
59 Kynaston Road, N16 | 2.4 miles from Iceland
Gastropub ... More
London > Nightlife > Pubs
69 Stoke Newington High Street, N16 | 2.5 miles from Iceland
Stoke Newington's extremely likable White Hart seems to cater for just about anyone. Inside, it's spacious and comfortable, with low-slung sofas and comfy chairs the order ... More
Nightlife near Iceland
London > Nightlife > Nightclubs
Amhurst Road, E8 | 3.3 miles from Iceland
Hackney's freshest venue is a converted railway station with a plush bar / restaurant on the ground floor and a nightclub upstairs. The kitchen serves excellent ... More
London > Nightlife > Bars
18 Ashwin Street, E8 | 3.3 miles from Iceland
On the roof of The Print House, a former factory for catalogues, crayons and pencils, sits Dalston Roof Park, an urban oasis four floors ... More
London > Nightlife > Bars
312 Archway Road, N6 | 3.4 miles from Iceland
The Boogaloo has succeeded in breaking the all pervasive contemporary pub blueprint, fashioning a popular alternative with a great atmosphere - and not an inch of ... More
Meeting venue hire near Iceland
London > Business > Venue Hire
The Vestry, Union Chapel, Compton Avenue, N1 | 3.8 miles from Iceland
... More
London > Business > Venue Hire
14 Dagmar Passage off Cross Street, Islington, Islington, London N1 | 4.1 miles from Iceland
A teeny, tiny and wonderful puppet theatre located in a hidden side road backing onto a green church yard ideal for spontaneous picnics with goodies from ... More
London > Business > Venue Hire
23-27 Wadeson Street, Hackney, London E2 | 4.2 miles from Iceland
... More
Also in High Road
Our recommendations in the same street as Iceland
Hotels near Iceland
From cheap budget hotels to luxury 5 star suites see our deals for Iceland hotels, including The RE London Shoreditch Hotel from 87% off.


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Snafu comics - comics based movies, games, music, , Comics based on movies, games, music, and pop culture.. Sugarscape: stop shop boys, bands, books, We love hot guys, celeb gossip, boys in bands, film, tv, fashion, beauty, books, and snacks. also we will try and make you laugh. try.. Home « blood sugar basics, Blood sugar basics: get to your goals is a simple, step-by-step plan designed to help you understand the importance of working with your healthcare team to set….
Is sugar toxic? - york times, Refined sugar ( , sucrose) molecule carbohydrate glucose, bonded molecule carbohydrate fructose — 50-50. http://www.nytimes.com/2011/04/17/magazine/mag-17Sugar-t.html Blood sugar - wikipedia, free encyclopedia, The blood sugar concentration blood glucose level amount glucose (sugar) present blood human animal. body naturally tightly regulates. http://en.wikipedia.org/wiki/Blood_sugar Brown sugar - rolling stones - youtube, Amazing brown sugar https://www.facebook./chelseabootsofficial. http://www.youtube.com/watch?v=Rx07A9LWBJA


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Crimson Apartments1100 17th St, Tuscaloosa, AL 35401
- $499 - $865
- 1 - 4 Beds
Note : Prices & Availability Subject To Change
Note : Prices & Availability Subject To Change
Note : Prices & Availability Subject To Change
Tuscaloosa off campus housing at its finest! Crimson Student Living offers fully furnished apartments in Tuscaloosa, AL, near the University of Alabama campus, with all the fun UA has to offer! With affordable rates, and a great student lifestyle ??? Crimson Student Living is much better than living in the dorms.
If your looking for Tuscaloosa apartment rentals near UA with over-the-top amenities, come live at Crimson. We feature a great lounge pool, 24-hour fitness center, 24-hour computer center, free indoor tanning making us the ideal spot to call home while attending college. Plus, we are a quick drive or complimentary Tide Ride shuttle trip to campus. Crimson also provides a great Students First residence life program designed to meet your needs as an active college student. Students First is built to enhance your UA experience and promote a positive sense of community between residents. Beautiful student apartments close to University of Alabama are available right now at great affordable prices. Call us today for more information about living at the best Tuscaloosa student apartments - Crimson Student Living! Please call for an appointment today.
Crimson is located in the Tuscaloosa Area in the 35401 zip code. View this apartment on a map.
Professionally Managed By: Campus Advantage
Community Features
- The Courts: Basketball and Sand Volleyball Courts
- Dog Daze: Pet Friendly with Two Pet Parks
- Gate
- Playground
- Wired: 24-Hour Computer Lab
- Tide Ride: Complimentary Shuttle to Bama
- Jitters: Cyber Cafe with Gourmet Coffee Bar
- Fitness/Health Center
- Convenient: 24-Hour Maintenance Staff
- Think Tank: 24-Hour Study Rooms
- You: Students First Residence Life Program
- Aqua: Lounge Pool and Entertainment Areas
*Note: In Select Units


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In this video, Keyboard magazine's Stephen Fortner visits Dave Smith for an extended demo of the new all-discrete analog Sequential Prophet 6 synthesizer. Continue reading
Tag Archives: Sequential Circuits
Sequential Six-Trak iPad Editor (Sneak Preview)
This video, via keyboardmag1, is a sneak preview of Bill Mitsakos' upcoming real-time touchscreen editor for the vintage Sequential Circuits Six-Trak synthesizer. Continue reading
Dave Smith Explains The Return Of Sequential
In this video, via Future Music, Dave Smith tells the story of the return of Sequential.
Smith explains how he got rights to the 'Sequential' name back and introduces the new Sequential Prophet 6 analog synthesizer. Continue reading
Dave Smith Intros State Of The Art Vintage Sequential Prophet 6
At the 2015 NAMM Show, Dave Smith introduce the new Sequential
Circuits Prophet 6 analog synthesizer. Continue reading
Sequential Circuits Is Back!
Dave Smith Instruments announce today the return of the Sequential Circuits brand: Continue reading
Inside A Sequential Circuits Model 800 Step Sequencer
This video, via Synth Keith, takes a look at an early version of the rare Sequential Circuits Model 800 step sequencer. Continue reading
Dave Smith Interview At RBMA Tokyo
Synth designer Dave Smith (Sequential Circuits, Dave Smith Instruments) is featured in this new interview/lecture from Red Bull Music Academy Tokyo 2014. Continue reading
Arturia iProphet Synthesizer On The iOS Update
In the latest episode of Sweetwater's iOS Update, host Mitch Gallagher takes a look at the new Arturia iProphet software synthesizer. Continue reading


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This is my second Father's Day as a father myself. I always liked this holiday, but it became extra special when I became a father in late 2013. This Father's Day is significant to me, and I think to all other responsible marijuana consuming fathers in Oregon, because it is the last Father's Day that I'm celebrating while marijuana is still prohibited. This time next year, I will be celebrating Father's Day as a truly free marijuana consumer. That may not seem like a big deal to someone that doesn't consume marijuana, but to a marijuana consumer, being a parentRead More
I just saw a video of former MVP of the National Basketball League (NBA) Kevin Durant which shows him entering a vehicle, where what appears to be a container of marijuana falls out of the vehicle as he opens the door to it. The media is already ramping up, with some of them condemning Kevin Durant, others cracking jokes, and all kinds of other commentary. For starters, no one even knows if it is marijuana in the container. And two, even if it was marijuana, who cares? Below is a picture of the container in question, via TMZ: Could the containerRead More
4/20 is already an international holiday celebrated by the masses. But until Bill Maher gets his wish, neither America nor the rest of the world will recognize 4/20 as a national or international day to celebrate the freedom of cannabis. And that's foolish, because whether cannabis consumers and college stoners have 4/20 off or not, many of us will either take the day off or find time for a smoke break or 10. What makes 4/20 special is that it's the one day a year that the person you'd least expect to smoke weed will likely ask you for aRead More
How Do You Determine If Cannabis Concentrates Are Good Or Bad? Are you new to the marijuana concentrates world? Do you know what 'dabs' are? If you consume marijuana often enough, chances are you have taken at least one dab hit by now. For those of you that have yet to take a dab hit, maybe due to unavailability in your area or because you are a new consumer, you should really check it out. They say a dab will do ya, which is true. If you are like me, and you like to ride the 'higher high', dabs areRead More
I'm off work today, and hopefully you are too. Hopefully you are enjoying the holiday with friends and family and didn't party too hard last night. If you are from Oregon like me, chances are you are watching the Oregon Ducks face Florida State, and will be rooting for a Ducks victory! This is is the fifth New Year's Day since The Weed Blog was started in 2010. A lot has happened in the last five years in the world of marijuana, and it has been an honor to have such great support from our readers throughout the years. IRead More
It's a brand new year. 2014 is history and 2015 is a mystery. People all across the globe made New Year's resolutions leading up to the new year. Where you one of those? I had some interesting conversations with social media friends last night about marijuana related New Year's resolutions. Did your New Year's resolution or resolutions involve marijuana? Below are some of the ones that were brought up last night during my conversations: No bammer weed – I was surprised to learn that there are still a lot of people out there smoking brick weed. It's likely because people haveRead More
The year 2014 saw a lot of things happen in the marijuana world. There are now more legalized states since last year, and people are more interested in all things marijuana than ever before. Marijuana has truly gone mainstream, and the marijuana reform movement has proven itself to be a force in politics. After reviewing people's e-mails and social media messages, and talking things over with some of my friends and colleagues, I have compiled the official winners of the 2014 Weed Blog Awards. Below are the categories (in bold) and winners of this year's awards. We don't have prizes toRead More
There a handful of reasons why people take a break from consuming marijuana. The most likely reason is that you need to get a job, and that your desired employer drug tests. The second most common reason is that the break from consuming marijuana is court ordered do to forced rehab or probation or some other unfair reason. But another reason is what many refer to as a 'marijuana tolerance break.' A marijuana tolerance break is a good idea if you are not getting as high as you used to, and wish to get more out of the experience ofRead More
Happy Thanksgiving from us here at The Weed Blog! We are very, very thankful for all of our readers because with out you guys, we would just be posting articles into the digital abyss. I hope that all of you are safe, and with people that you care about, and that you get to eat as much as you can with a happy heart. This is the fifth Thanksgiving since the Weed Blog was created in 2010, and there is a lot to be thankful for, but I am most thankful for your support! As long as you guys keepRead More
Last year was the first year that The Weed Blog released the 'Weed Blog Awards.' We didn't have a fancy event or make sweet trophies because quite honestly, we just didn't have the resources for that. However, I still felt the need to give respect where respect was due, and acknowledge people that made a difference in the marijuana world in 2013. I'm making it an annual thing here at TWB, and I want readers to nominate people in the comments section that they feel should win an award for their work in 2014. Below is a list of categories thatRead More


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The Journal Sentinel sports staff brings Milwaukee Bucks fans the latest news, notes and analysis
Comparing Yi and Dirk
The one player in the National Basketball Association that Milwaukee Bucks' rookie Yi Jianlian has been compared to most is probably German star Dirk Nowitzki of the Dallas Mavericks.
The Bucks had Yi matched up against Nowitzki Saturday night at the
"I don't know that anyone matches up really well with Dirk," said Krystkowiak. "He's a special player. They're both close to 7 feet tall and long and they shoot the ball well. It may be the guy that everybody in the league wants to compare Yi to because he's a skilled 7-foot guy."
Nowitzki went into the game averaging 20.7 points and he scored 20 against the Bucks. It wasn't the first time that Yi had gone up against Nowitzki since they have played against each other in international play. Krystkowiak said before Saturday's game that he hadn't been aware of that fact.
"I just assume that Yi doesn't know anybody," said Krystkowiak. "We watch a lot of personnel and individual film and he didn't share with me that he's familiar with him. Yi spends a lot of time in the film room because every game he plays, it's at least two or three (new) people that he may see that he may be matched up against. So he's becoming a student of the game. He has to understand tendencies and other team's personnel."
Nowitzki struggled at times adjusting to the NBA early in his career and Yi, too, has experienced some peaks and valleys this season.
"You can look at Dirk's rookie year and even second year …it wasn't like we talk about Dirk now," said Krystkowiak. "He struggled at times. That's what we're talking about with the process with a rookie…it's hard. Confidence in the NBA is probably the biggest key. I know Dirk didn't have a lot of confidence his rookie year in the league and he started to find his way and the rim gets bigger and you start making shots.
"He's confident now and he's excelled like a lot of stars in the NBA do. The reason he was here to begin with was because he was very skilled and he was in international basketball, similar to Yi. You're 7 feet tall and you have a lot of skill – footwork and hands and agility – it's become a pretty popular thing in the NBA to find those kinds of players."
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Final: Knicks 100, Spurs 83
Final: Knicks 100, Spurs 83 The Spurs (26-9) hung in for three quarters in their fourth game in five nights, but ultimately were no match for the Knicks. Specifically, they were no match for the Knicks (22-10) in the fourth quarter. Coming off a disappointing home loss to Portland, the Knicks made their first eight […] [Read More]
Scouting the Knicks
Opening tip: 6:30 p.m., Madison Square Garden At a glance Record: 21-10 overall, 12-3 at home Offensive rating: 111.7 points per 100 possessions, 2nd Defensive rating: 106.3 points per 100 possessions, 20th Pace: 91.2 possessions per game, 21st Margin of victory: 4.97, 4th Strength of schedule: 26th Last 10: 5-5 Previous meetings: The Knicks won […] [Read More]
Recap: Spurs 117, Bucks 110
Summing it up: The Spurs (26-8) engineered another offensive masterpiece in their seventh straight victory, but there was a blemish with tomorrow's game at New York looming. Leading by 23 late in the third quarter, they were forced to bring back the starters when the Bucks rallied within nine early in the fourth. That's probably […] [Read More]
Final: Spurs 117, Bucks 110
Final: Spurs 117, Bucks 110 The game wasn't quite as close as the final score would suggest, but the Spurs (26-8) had to work a bit harder than they would have liked for their seventh straight win after leading by 23 late in the third quarter. The Bucks (16-14) got within nine early in the […] [Read More]
Recap: Spurs 104, Nets 73
Summing it up: As you'd expect, Gregg Popovich circumvented a question about his team's dominant third quarter. So we'll have to provide an assessment for him — it was pretty impressive. Or from P.J. Carlesimo's point of view, "abominable." Aided by the Nets' inability to do anything well, the Spurs (25-8) held them to just […] [Read More]
Final: Spurs 104, Nets 73
Final: Spurs 104, Nets 73 The Spurs celebrated New Year's a few hours early, holding the Nets to only four points in the third quarter — just one more than the franchise record — en route to their fourth victory by at least 20 in the past five games. Limited in similar measures by San […] [Read More]
The Weekly Primer
A visit home for the holidays did the Spurs good. Having spent most of the previous weeks living out of a suitcase, they swept their four-game home stand before heading out to saddle Dallas with another beating Sunday. At 24-8, the Spurs half a game behind Oklahoma City and a game and a half behind […] [Read More]
Scouting the Mavericks
Opening tip: 7:30 p.m. tonight, AT&T Center At a glance Record: 12-18 overall, 8-5 at home Offensive rating: 102.8 points per 100 possessions, 24th Defensive rating: 106.7 points per 100 possessions, 22nd Margin of victory: minus 4.13, 24th Strength of schedule: 11th Last 10: 2-8 Previous meetings: The Spurs won 129-91 at San Antonio on […] [Read More]
Recap: Spurs 122, Rockets 116
Summing it up: The Spurs (23-8) were about as poor on defense as they've been all season. But what little they did play made all the difference in the world. Holding the Rockets (16-13) to just seven points for nearly eight minutes to start the fourth quarter, the Spurs blew open what had been an ABA-style […] [Read More]
Final: Spurs 122, Rockets 116
Final: Spurs 122, Rockets 116 It took the better part of three quarters. But, with a healthy assist from Rockets coach Kevin McHale, the Spurs (23-8) finally figured the Rockets out offensively. With James Harden limited by five fouls after McHale left him in late in the third with No. 4, the Rockets (16-13) went […] [Read More]
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Thrash veterans DEATH ANGEL will release The Bay Calls for Blood – Live in San Francisco on LP exclusively through Nuclear Blast mail-order on July 24th. The release will also be made available in the digital format and as a bonus CD with their upcoming DVD entitled a thrashumentary. Artwork for the LP version was created by Joey James Hernandez.
"Joey James Hernandez has created designs for most of our tour merch over the past few years," commented guitarist Rob Cavestany."We love his style and felt it the perfect fit with this record!


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New York, NYUSA
June 8, 2014
Not yet
Front end developer interested in learning Swift
About us…
Help support your Meetup
Apple unveiled their new programming language at WWDC that has been secretly in development for 4 years by the guy that created LLVM. It promises to introduce a modern language without sacrificing performance.
This Meetup has 3 goals:
1) Help existing Objective-C developers transition smoothly to Swift 2) Introduce new developers to the world of iOS and OS X development 3) Create a community where iOS and OS X developers can meet and collaborate on projects
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NZ tax hike lifts interest in home-grown tobacco
In the city of Tauranga, New Zealand, smokers who grow their own leaf tobacco are making money by using websites and social media pages to sell tobacco plant seeds to others looking to reduce their costs of smoking following a recent 10 percent tax hike.
According to a story by Rebecca Savory for the Bay of Plenty Times; while it is illegal in New Zealand to sell or gift home-grown tobacco plants, people can legally grow tobacco for their own use and sell and buy the seeds.
Individuals may process up to 15 kg of home-grown tobacco per adult per year for personal use. This equates to between 50 and 100 cigarettes per person per day, depending on tobacco content.
Savory reported that searches for tobacco seeds on Trade Me had recently increased by 10 percent on those of a year ago and that tobacco seeds comprised the top tobacco-related search during the past 12 months.
Commercial tobacco manufacturers are unlikely to take fright, however. Searches for tobacco seeds in New Zealand routinely increase through December and peak in the middle of January.
And interest in growing tobacco at home regularly increases with tobacco price hikes.
The main problem is that it is difficult to process a palatable tobacco product from home grown plants.
Whether or not home grown tobacco offers a health benefit or deficit is another story.


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week ending PRL 103, 226401 (2009) PHYSICAL REVIEW LETTERS 27 NOVEMBER 2009 Band Gap Narrowing of Titanium Oxide Semiconductors by Noncompensated Anion-Cation Codoping for Enhanced Visible-Light Photoactivity Wenguang Zhu,1,2 Xiaofeng Qiu,3 Violeta Iancu,2 Xing-Qiu Chen,1 Hui Pan,4 Wei Wang,4 Nada M. Dimitrijevic,5,6 Tijana Rajh,5 Harry M. Meyer III,1 M. Parans Paranthaman,3 G. M. Stocks,1 Hanno H. Weitering,2,1 Baohua Gu,4 Gyula Eres,1 and Zhenyu Zhang1,2 1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 2 Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA 3 Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 4 Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 5 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, USA 6 Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA (Received 11 September 2009; published 23 November 2009) ''Noncompensated n-p codoping'' is established as an enabling concept for enhancing the visible-light photoactivity of TiO2 by narrowing its band gap. The concept embodies two crucial ingredients: The electrostatic attraction within the n-p dopant pair enhances both the thermodynamic and kinetic solubilities, and the noncompensated nature ensures the creation of tunable intermediate bands that effectively narrow the band gap. The concept is demonstrated using first-principles calculations, and is validated by direct measurements of band gap narrowing using scanning tunneling spectroscopy, dramatically redshifted optical absorbance, and enhanced photoactivity manifested by efficient electron-hole separation in the visible-light region. This concept is broadly applicable to the synthesis of other advanced functional materials that demand optimal dopant control. DOI: 10.1103/PhysRevLett.103.226401 PACS numbers: 71.20.Nr, 61.72.SÀ, 84.60.Àh The development of advanced materials for alternative TiO2 is extremely low for most dopants, especially for and sustainable energy applications is an extremely active p-type doping [4,6]. As a result, most of the dopants reside research area of great visibility and importance. In particu- at undesirable interstitial sites, which not only compromise lar, much effort has been devoted to searching for new the effectiveness of band gap narrowing but also provide types of catalytic materials that can readily split water to numerous recombination centers that are responsible for generate hydrogen as an environmentally friendly fuel via the loss of photogenerated electron-hole pairs [13,14]. photolysis using the abundant energy from sunlight. In In this Letter, we report a noncompensated n-p co- such efforts of property optimization, one often encounters doping concept to overcome these fundamental limitations. the challenging need to control precisely the concentration First, the Columbic attraction between the n- and p-type and the location of foreign dopants in a host system. dopants with opposite charge state substantially enhances Similar issues are also frequently encountered in other both the thermodynamic and, in particular, the kinetic areas, such as control of magnetic dopants in diluted solubilities of the dopant pairs in concerted substitutional magnetic semiconductors for spintronic applications. doping. More profoundly, the noncompensated nature of TiO2 is one of the most promising photocatalysts for the n-p pairs consisting, for example, of a single acceptor solar energy utilization and environmental cleanup [1–8]. and a double donor ensures the creation of intermediate However, the photoreaction efficiency of TiO2 is severely electronic bands in the gap region, effectively narrowing limited by its large intrinsic band gap (>3 eV) capable of the band gap. Controlled creation of such intermediate absorbing only the ultraviolet portion of the solar spectrum bands is also highly desirable for solar cell applications [3,5]. A crucial prerequisite for enhancing the solar energy [15]. We further show that the position and magnitude of conversion efficiency is to enable TiO2 to absorb the more the intermediate bands can be tuned by choosing different abundant visible light by reducing its band gap below 2 eV combinations and concentrations of the noncompensated [5,9]. Since the seminal discovery of Fujishima and Honda n-p pairs. These findings establish the noncompensated [1], numerous attempts have been made to optimize the n-p codoping concept as a powerful guiding principle in band gap of TiO2 by different doping schemes [5,6,10–12]. future design of photocatalysts and other functional However, an overwhelming body of the literature reported materials. efforts of trial-and-error nature, lacking a major conceptual The concept is first demonstrated quantitatively using breakthrough as the guiding principle. This standing ob- first-principles calculations, focusing on the band gap stacle is inherently tied to the fundamental limitations that narrowing and the enhanced thermodynamic and kinetic the thermodynamic solubility in substitutional doping of solubilities. These studies predict Cr-N as the preferred 0031-9007=09=103(22)=226401(4) 226401-1 Ó 2009 The American Physical Society week ending PRL 103, 226401 (2009) PHYSICAL REVIEW LETTERS 27 NOVEMBER 2009 codopant pair. We then use a wet chemistry method to synthesize Cr-N codoped TiO2 nanocrystals, which exhibit substantially narrowed band gaps, as well as dramatically enhanced photoabsorption and photoactivity in the visible spectral region. The calculations were performed using the VASP code [16], based on density functional theory (DFT) using the projector augmented wave (PAW) method [17,18] and the generalized gradient approximation (PBE-GGA) [19] for exchange correlation. We used a 3 Â 3 Â 1 supercell con- taining 36 Ti atoms and 72 O atoms to model bulk anatase TiO2 . To overcome the well-known band gap problem, we used the GGA þ U method to treat the 3d electrons of the transition metals [20], producing an intrinsic band gap of 3.2 eV. The ''climbing image nudged elastic band'' method [21] is used for the calculation of kinetic barriers. In a comparative study, we first consider bulk anatase TiO2 codoped with four different n-p pairs: Cr-N (net n-type), V-C (net p-type), Cr-C (compensated), and V-N (compensated). The dopants are incorporated substitution- ally into anatase TiO2 by replacing a host Ti atom with an n-type dopant, V or Cr, and a neighboring O atom with a p-type dopant, C or N. For each case, total energy calcu- lations reveal that the n-type and p-type dopants exhibit a strong tendency to form a pair occupying neighboring lattice sites. The energy lowering from the pairing is FIG. 1 (color online). Density of states (DOS) of anatase TiO2 for different n-p codoping pairs: (a) Cr-N resulting in net n-type 1.85 eV, 1.52 eV, 1.89 eV, and 2.44 eV for the Cr-N, doping; (b) V-C resulting in net p-type doping; (c) V-N resulting V-C, V-N, and Cr-C pair, respectively. Figure 1 illustrates in compensated codoping; and (d) Cr-C resulting in compensated the effect of different codoping combinations on the den- codoping. The dashed lines designate pure anatase TiO2 . sity of states, as compared with that of intrinsic anatase TiO2 . The appearance of new electronic levels in the intrinsic band gap is tied to the noncompensated nature of the codopants. In particular, due to strong hybridiza- anatase TiO2 , respectively. These results indicate that it tion, the new levels are substantially broader than the is energetically unfavorable to dope both V and C into localized impurity levels contributed by either Cr or N as substitutional sites, but simultaneous substitutional doping a dopant alone, forming intermediate bands. As a conse- of Cr and N are favored at O-rich conditions, making Cr-N quence, the intrinsic band gap is narrowed to 1.6 eV and the preferred noncompensated n-p codoping pair. 0.9 eV for Cr-N [Fig. 1(a)] and V-C [Fig. 1(b)] codoped The third crucial aspect to be examined is the kinetic TiO2 , respectively. Compensated n-p codoping using solubility [24], as reflected by how the noncompensated V-N as the codopants does not change the basic electronic n-p codoping changes the kinetic barriers of the dopants structure, but generates levels at the band edges [Fig. 1(c)]. going from interstitial to substitutional sites [Fig. 2(c)]. An Impurity bands with lower spectral weights could also be isolated interstitial Cr atom has to overcome an energy generated in the gap for the compensated Cr-C co- barrier $2 eV to become a substitutional dopant. For an doped system [Fig. 1(d)], where the extra charge associated isolated interstitial N atom, the barrier against converting with the two dopants cannot be completely compensated into substitutional is even higher, 2.34 eV, and the reverse with each other because the Cr d levels are strongly local- process only has an energy barrier of 0.51 eV, indicating ized [22]. The distinctive merit of noncompensated n-p that N strongly prefers interstitial sites. These results also codoping is that it ensures the formation of intermediate explain why it has been exceptionally difficult to dope bands in the gap, while compensated n-p codoping does sufficiently high concentrations of substitutional N into not [23]. TiO2 [25]. In contrast, for a Cr-N pair, the interstitial Cr In search for optimal growth conditions, we next com- and N atoms can undergo concerted atomic processes to pare the formation energies of the n-p codoped systems reach simultaneous substitutional sites by pushing out a Ti with different configurations of the dopants occupying and an O atom to interstitial sites, and the overall energy interstitial or substitutional sites. The relative formation barrier along the kinetic pathway is much lower than that energies vary as a function of the chemical potentials of the for doping with either element alone. Furthermore, the two host elements [4]. Figures 2(a) and 2(b) show the final state for Cr-N codoping is lowered by about 0.71 eV results for the noncompensated Cr-N and V-C codoped from that of N dopant alone. Therefore, both the kinetic 226401-2 week ending PRL 103, 226401 (2009) PHYSICAL REVIEW LETTERS 27 NOVEMBER 2009 (a) (c) Cr-N in TiO2 FIG. 2 (color online). (a) and (b) Cal- Relative formation energy (eV) )N (i) culated relative formation energy for all r(s possible combinations of interstitial and C Energy (eV) Cr(i)N(i) substitutional configurations of Cr-N and 2.00 2.34 V-C in anatase TiO2 as a function of the 1.83 1.52 1.12 Cr( chemical potential of Ti and O. (c) Cal- 1.57 i)N (s) s) culated kinetic barriers for a single Cr 0.56 N( Cr (s) 0.19 (the blue dashed line), a single N (the red O rich Ti rich Cr(i) N(i) Cr(i)N(i) Cr(s)N(i) Cr(s)N(i) Cr(s)N(s) Chemical potential dashed line), and a Cr-N pair (the black (b) (d) Cr-N-TiO2-1 (e) Cr-N-TiO2-1 solid line) going from interstitial to sub- V-C in TiO2 Cr-N-TiO2-3 Cr-N-TiO2-3 stitutional sites in anatase TiO2 . (d) and Relative formation energy (eV) V(i)C(i) Cr-N-TiO2-5 Cr-N-TiO2-5 Cr-TiO2-3 N-TiO2 (e) X-ray photoelectron spectroscopy Cr atomic % N atomic % Cr-TiO2-5 )C( s) measurements of the Cr and N concen- V(s V(i) C(s ) trations in anatase TiO2 nanocrystals as a function of the annealing temperature. (i) C The numbers in the legend designate s) V( the nominal at.% of Cr in the precursor. O rich Ti rich Chemical potential Sintering temperature (˚C) Sintering temperature (˚C) and thermodynamic solubilities of the dopants in the host ture, the STS spectra show that single element doping semiconductor are substantially enhanced by noncompen- fails to reduce substantially the band gap of TiO2 sated n-p codoping. [30,31]. In contrast, striking band gap narrowing to 1:5 Æ Next we present compelling experimental evidence that 0:2 eV was observed in Cr-N codoped TiO2 samples. The either directly supports or is consistent with the predictions reproducibility of this finding was confirmed on many for TiO2 codoped with Cr and N. A wet chemical technique nanocrystals from different batches and with different was used to synthesize TiO2 and doped TiO2 nanocrystals by hydrolysis from titanium (IV) tetra-isopropoxide in the (a) (c) absence or presence of ethylenediamine for N and chro- TiO2 Cr-TiO2-3 Cr5+ N-TiO2 Cr-N-TiO2-1 mium acetylacetonate for Cr [26,27]. X-ray powder dif- Cr-N-TiO2-3 fraction (XRD) shows that the dried precipitate crystallizes Absorbance into anatase particles of 10 to 20 nm size when annealed in air at 500 C. The amount of Cr and N dopants remaining Dark in the particles after crystallization was determined by Illuminated After light OFF x-ray photoelectron spectroscopy. Compared with single element doping with Cr or N, the signal from the same 320 330 340 350 Wavelength (nm) Field (mT) element is significantly higher in the codoped samples (b) [010] (d) [Figs. 2(d) and 2(e)]. In particular, Cr-N codoping appears Tunneling current (nA) Cr 5% 4.5 effective in retaining N that if doped alone is rapidly lost Cr-N 1% 2.8 soon after annealing at 400 C in air [26]. Cr-N-TiO2 Cr-N 2.5% 3.0 1.5 eV N-TiO2 The unprecedented magnitude of both absorbance and 2.6 eV redshift in the visible-light absorption spectra in Fig. 3(a) Cr-TiO2 2.8 eV serves as initial indication that Cr-N doping creates new TiO2 and accessible electronic states in the band gap of TiO2 . In 3.2 eV contrast, Cr doping alone creates only localized electronic Bias Voltage (V) 334 336 338 Field (mT) 340 states in the band gap of TiO2 that are known to induce visible-light absorption without affecting the band gap. FIG. 3 (color online). (a) UV-vis diffuse reflectance spectra of Similarly, numerous papers report visible-light absorption pure and doped anatase TiO2 nanocrystals annealed at 500 C. resulting from N doping alone, but the characteristics of The numbers in the legend designate the nominal at.% of Cr in the N electronic states are currently the subject of intense the precursor. (b) STS spectra of pure and doped anatase TiO2 . debate [13,14,25,28,29]. The I-V curves are shifted vertically for better visualization. The Scanning tunneling spectroscopy (STS) demonstrates inset displays a STM image of undoped TiO2 nanocrystal surface. (c) The red line shows the effect of charge generation the central message of this work that noncompensated on the EPR signal from 1 at.% Cr-N codoped anatase TiO2 n-p codoping effectively narrows the band gap of TiO2 . nanocrystals induced by 2:5 eV light illumination. The green The STS spectra were measured by recording the tunneling line shows the recovery of the EPR signal after the light is turned current while ramping the tunneling bias at specific lo- off. (d) The narrower EPR linewidth Á for 1, and 2.5 at.% Cr-N cations on the nanocrystals as illustrated in the inset of codoping than for Cr only doping is indication of enhanced Fig. 3(b). In agreement with recent reports in the litera- photocatalytic efficiency in Cr-N codoping. 226401-3 week ending PRL 103, 226401 (2009) PHYSICAL REVIEW LETTERS 27 NOVEMBER 2009 STM tips. The STS spectrum of Cr-N codoped TiO2 is [1] A. Fujishima and K. Honda, Nature (London) 238, 37 also in excellent agreement with the calculated density of (1972). states [Fig. 1(a)]. The DFT results show that when N is [2] A. L. Linsebigler, G. Lu, and J. T. Yates, Jr., Chem. Rev. doped into TiO2 with the assistance of codoped Cr, the 95, 735 (1995). ¨ [3] M. Gratzel, Nature (London) 414, 338 (2001). hybridization of the Cr and N electronic states substan- [4] S. B. Zhang, J. Phys. Condens. Matter 14, R881 (2002). tially broadens the impurity levels, thereby enhancing [5] R. Asahi et al., Science 293, 269 (2001). the formation of extended intermediate bands. This broad- [6] For recent reviews, see special issue Doping and ening, in turn, explains the enhanced optical absorption Functionalization of Photoactive Semiconducting Metal and the band gap narrowing observed in Cr-N codoped Oxides, edited by C. Di Valentin, U. Diebold, and A. TiO2 . Selloni [Chem. Phys. 339, 1 (2007)]. Band gap narrowing in Cr-N doped TiO2 was further [7] A. Fujishima, X. T. Zhang, and D. A. Tryk, Surf. Sci. Rep. confirmed by demonstration of visible-light induced 63, 515 (2008). electron-hole separation using low temperature electron [8] M. R. Hoffmann et al., Chem. Rev. 95, 69 (1995). paramagnetic resonance (EPR) spectroscopy [Figs. 3(c) [9] A. Mills and S. Le Hunte, J. Photochem. Photobiol., A and 3(d)]. The EPR signal from nonilluminated (black 108, 1 (1997). [10] T. L. Thompson and J. T. Yates, Jr., Chem. Rev. 106, 4428 line) samples shows that Cr-N codoping generates para- (2006). magnetic species that are absent in undoped TiO2 . The [11] C. C. Pan and J. C. S. Wu, Mater. Chem. Phys. 100, 102 EPR signal consists of an intense surface component at (2006). g ¼ 1:97, corresponding to Cr5þ surface species that is [12] S. U. M. Khan, M. Al-Shahry, and W. B. Ingler, Jr., attributed to formation of Cr-O-Ti bridging complexes Science 297, 2243 (2002). [Fig. 3(c)], and a broad weak component at g $ 4:6 (not [13] N. Serpone, J. Phys. Chem. B 110, 24 287 (2006). shown), originating from isolated Cr3þ ions in substitu- [14] Y. Nakano et al., Chem. Phys. 339, 20 (2007). tional TiO2 lattice sites [32,33]. The signal from N radicals [15] A. Luque and A. Marti, Phys. Rev. Lett. 78, 5014 (1997). could not be resolved because it is obscured by the strong ¨ [16] G. Kresse and J. Furthmuller, Phys. Rev. B 54, 11 169 Cr signal [25]. Continuous irradiation with photons of (1996). ¨ [17] P. E. Blochl, Phys. Rev. B 50, 17 953 (1994). subband gap (<2:5 eV) energy causes a drop in the EPR [18] G. Kresse and D. Joubert, Phys. Rev. B 59, 1758 (1999). signal shown in Fig. 3(c) by the red line because of [19] J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. reduction of Cr ions by photogenerated electrons. The 77, 3865 (1996). efficient charge separation is followed by recombination [20] V. I. Anisimov, F. Aryasetiawan, and A. I. Lichtenstein, of charges and recovery of the EPR signal shown by the J. Phys. Condens. Matter 9, 767 (1997). green line after the light is turned off. The sharper and more ´ [21] G. Henkelman, B. P. Uberuaga, and H. Jonsson, J. Chem. intense Cr signal in Cr-N codoped samples compared to Phys. 113, 9901 (2000). that in the Cr only doped sample in Fig. 3(d) suggests that [22] L. H. Ye and A. J. Freeman, Phys. Rev. B 73, 081304(R) the presence of N breaks up clustering of Cr ions resulting (2006). in a more efficient photocatalyst. [23] Y. Gai et al., Phys. Rev. Lett. 102, 036402 (2009). In summary, we describe first-principles calculations [24] S. B. Zhang and S. H. Wei, Phys. Rev. Lett. 86, 1789 (2001). and present compelling experimental evidence that vali- [25] C. Di Valentin et al., Chem. Phys. 339, 44 (2007). date the concept of noncompensated n-p codoping for [26] X. F. Qiu, Y. X. Zhao, and C. Burda, Adv. Mater. 19, 3995 narrowing the band gap of TiO2 by simultaneously incor- (2007). porating n- and p-type dopants with unequal charge states. [27] X. F. Qiu and C. Burda, Chem. Phys. 339, 1 (2007). This concept is particularly important for the development [28] C. Di Valentin, G. Pacchioni, and A. Selloni, Phys. Rev. B of a new class of TiO2 -based photocatalysts for solar 70, 085116 (2004). energy conversion, hydrogen generation from water, and [29] J.-Y. Lee, J. Park, and J.-H. Cho, Appl. Phys. Lett. 87, a variety of industrial and environmental applications. 011904 (2005). Because the ideas have a broad significance they are also [30] O. Diwald et al., J. Phys. Chem. B 108, 52 (2004). expected to impact related areas demanding optimal dop- [31] M. Batzill, E. H. Morales, and U. Diebold, Phys. Rev. Lett. 96, 026103 (2006). ant control [34–36]. ´ [32] D. Dvoranova et al., Appl. Catal., B 37, 91 (2002). This work was supported by the Division of Materials ¨ [33] K. Kohler et al., J. Catal. 143, 201 (1993). Science and Engineering, Office of Basic Energy Sciences, [34] X. H. Xu et al., New J. Phys. 8, 135 (2006). Department of Energy, and in part by the LDRD Program [35] W. G. Zhu, Z. Y. Zhang, and E. Kaxiras, Phys. Rev. Lett. of ORNL. The calculations were performed at NERSC of 100, 027205 (2008). DOE. The EPR experiments were performed at Argonne [36] L. G. Wang and A. Zunger, Phys. Rev. Lett. 90, 256401 under DOE BES Contract No. DE-AC02-06CH11357. (2003). 226401-4
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