2008 Y-12 National Security Complex Annual Illness and Injury Surveillance Report (open access)

2008 Y-12 National Security Complex Annual Illness and Injury Surveillance Report

The U.S. Department of Energy’s (DOE) commitment to assuring the health and safety of its workers includes the conduct of epidemiologic surveillance activities that provide an early warning system for health problems among workers. The Illness and Injury Surveillance Program monitors illnesses and health conditions that result in an absence of workdays, occupational injuries and illnesses, and disabilities and deaths among current workers.
Date: December 11, 2009
Creator: United States. Department of Energy. Office of Illness and Injury Prevention Programs.
Object Type: Report
System: The UNT Digital Library
China's Economic Conditions (open access)

China's Economic Conditions

This report provides background on China's economic rise and current economic structure and the challenges China faces to keep its economy growing strong, and describes Chinese economic policies that are of concern to U.S. policymakers.
Date: December 11, 2009
Creator: Morrison, Wayne M.
Object Type: Report
System: The UNT Digital Library
Choke Flange for High Power RF Components Excited by TE01 Mode (open access)

Choke Flange for High Power RF Components Excited by TE01 Mode

A multifaceted program to study high gradient structures and properties of RF breakdown is under way at SLAC. This program includes testing of simplified versions of traveling wave and standing wave structures at 11.4 GHz. [Dolgashev] RF power is fed into these structures using a TE01 mode-launcher. An RF flange is used to connect the mode-launcher to the test-structure. The rf currents flow through either the stainless steel lip on the flange or, in an alternate assembly, through a copper gasket pressed between the same stainless steel lips. In a recent experiment with a single cell traveling wave structure, a flange with stainless steel lips was irreversibly damaged at RF power about 90 MW and {approx}100 ns pulse length. We suggest an alternative flange that does not rely on metal-to-metal contact in the rf power transfer region. The idea is to use an asymmetric choke flange, where the choke grove is cut into a conflate flange on the mode-launcher. The structures themselves will have a simpler, flat conflate flange with rounded corners on the vacuum side. The Vacuum seal is achieved with a Cu gasket between these two flanges above the RF region. We have designed a flange with a …
Date: December 11, 2009
Creator: Yeremian, A.Dian
Object Type: Report
System: The UNT Digital Library
Comparison of Standard 90.1-2007 and the 2009 IECC with Respect to Commercial Buildings (open access)

Comparison of Standard 90.1-2007 and the 2009 IECC with Respect to Commercial Buildings

The U.S. Department of Energy’s (DOE’s) Building Energy Codes Program (BECP) has been asked by some states and energy code stakeholders to address the comparability of the 2009 International Energy Conservation Code® (IECC) as applied to commercial buildings and ANSI/ASHRAE/IESNA Standard 90.1-2007 (hereinafter referred to as Standard 90.1-07). An assessment of comparability will help states respond to and implement conditions specified in the State Energy Program (SEP) Formula Grants American Recovery and Reinvestment Act Funding Opportunity, Number DE-FOA-0000052, and eliminate the need for the states individually or collectively to perform comparative studies of the 2009 IECC and Standard 90.1-07. The funding opportunity announcement contains the following conditions: (2) The State, or the applicable units of local government that have authority to adopt building codes, will implement the following: (A) A residential building energy code (or codes) that meets or exceeds the most recent International Energy Conservation Code, or achieves equivalent or greater energy savings. (B) A commercial building energy code (or codes) throughout the State that meets or exceeds the ANSI/ASHRAE/IESNA Standard 90.1-2007, or achieves equivalent or greater energy savings . (C) A plan to achieve 90 percent compliance with the above energy codes within eight years. This plan will …
Date: December 11, 2009
Creator: Conover, David R.; Bartlett, Rosemarie & Halverson, Mark A.
Object Type: Report
System: The UNT Digital Library
The Development of the Undulator Controls Module at the Linac Coherent Light Source (open access)

The Development of the Undulator Controls Module at the Linac Coherent Light Source

The Linac Coherent Light Source, LCLS, at the SLAC National Accelerator Laboratory, SNAL, is the first hard x-ray Free Electron Laser. The Undulator Controls Module, UCM, controls five cams and two translation stages that regulate the position of each of the 33 permanent undulator magnet segments within 10 microns. The UCM package, hardware and software, was designed and built by the Advanced Photon Source at Argonne. Important lessons were learned throughout the collaborative design, installation, testing, and commissioning periods that could be invaluable to future similar controls projects.
Date: December 11, 2009
Creator: Alarcon, A. D.
Object Type: Article
System: The UNT Digital Library
Dissecting the Gravitational Lens B1608 656. II. Precision Measurements of the Hubble Constant, Spatial Curvature, and the Dark Energy Equation of State (open access)

Dissecting the Gravitational Lens B1608 656. II. Precision Measurements of the Hubble Constant, Spatial Curvature, and the Dark Energy Equation of State

Strong gravitational lens systems with measured time delays between the multiple images provide a method for measuring the 'time-delay distance' to the lens, and thus the Hubble constant. We present a Bayesian analysis of the strong gravitational lens system B1608+656, incorporating (1) new, deep Hubble Space Telescope (HST) observations, (2) a new velocity dispersion measurement of 260 {+-} 15 km s{sup -1} for the primary lens galaxy, and (3) an updated study of the lens environment. Our analysis of the HST images takes into account the extended source surface brightness, and the dust extinction and optical emission by the interacting lens galaxies. When modeling the stellar dynamics of the primary lens galaxy, the lensing effect, and the environment of the lens, we explicitly include the total mass distribution profile logarithmic slope {gamma}{prime} and the external convergence {kappa}{sub ext}; we marginalize over these parameters, assigning well-motivated priors for them, and so turn the major systematic errors into statistical ones. The HST images provide one such prior, constraining the lens mass density profile logarithmic slope to be {gamma}{prime} = 2.08 {+-} 0.03; a combination of numerical simulations and photometric observations of the B1608+656 field provides an estimate of the prior for {kappa}{sub …
Date: December 11, 2009
Creator: Suyu, S. H.; Marshall, P. J.; Auger, M. W.; Hilbert, S.; Blandford, R. D.; Koopmans, L. V. E. et al.
Object Type: Article
System: The UNT Digital Library
EFFECTS OF TRITIUM GAS EXPOSURE ON EPDM ELASTOMER (open access)

EFFECTS OF TRITIUM GAS EXPOSURE ON EPDM ELASTOMER

Samples of four formulations of ethylene-propylene diene monomer (EPDM) elastomer were exposed to initially pure tritium gas at one atmosphere and ambient temperature for various times up to about 420 days in closed containers. Two formulations were carbon-black-filled commercial formulations, and two were the equivalent formulations without filler synthesized for this work. Tritium effects on the samples were characterized by measuring the sample volume, mass, flexibility, and dynamic mechanical properties and by noting changes in appearance. The glass transition temperature was determined by analysis of the dynamic mechanical properties. The glass transition temperature increased significantly with tritium exposure, and the unfilled formulations ceased to behave as elastomers after the longest tritium exposure. The filled formulations were more resistant to tritium exposure. Tritium exposure made all samples significantly stiffer and therefore much less able to form a reliable seal when employed as O-rings. No consistent change of volume or density was observed; there was a systematic lowering of sample mass with tritium exposure. In addition, the significant radiolytic production of gas, mainly protium (H{sub 2}) and HT, by the samples when exposed to tritium was characterized by measuring total pressure in the container at the end of each exposure and by …
Date: December 11, 2009
Creator: Clark, E.
Object Type: Report
System: The UNT Digital Library
The Endangered Species Act (ESA) in the 111th Congress: Conflicting Values and Difficult Choices (open access)

The Endangered Species Act (ESA) in the 111th Congress: Conflicting Values and Difficult Choices

The Endangered Species Act has been one of the more contentious environmental laws. This may stem from its strict substantive provisions, which can affect the use of both federal and nonfederal lands and resources. This report discusses oversight issues and legislation introduced in the 11th Congress to address Endangered Species Act implementation and management of endangered and threatened species.
Date: December 11, 2009
Creator: Buck, Eugene H.; Corn, M. Lynne; Sheikh, Pervaze A.; Meltz, Robert & Alexander, Kristina
Object Type: Report
System: The UNT Digital Library
Experiences from First Top-Off Injection at the Stanford Synchrotron Radiation Light source (open access)

Experiences from First Top-Off Injection at the Stanford Synchrotron Radiation Light source

As the Stanford Synchrotron Radiation Lightsource (SSRL) of the SLAC National Accelerator Laboratory (SLAC) is moving toward Top-Off injection mode, SLAC's Radiation Protection Department is working with SSRL on minimizing the radiological hazards of this mode. One such hazard is radiation that is created inside the accelerator concrete enclosure by injected beam. Since during Top-Off injection the stoppers that would otherwise isolate the storage ring from the experimental area stay open, the stoppers no longer prevent such radiation from reaching the experimental area. The level of this stray radiation was measured in April 2008 during the first Top-Off injection tests. They revealed radiation dose rates of up to 18 microSv/h (1.8 millirem/h) outside the experimental hutches, significantly higher than our goal of 1 microSv/h (0.1 millirem/h). Non-optimal injection increased the measured dose rates by a factor two. Further tests in 2008 indicated that subsequent improvements by SSRL to the injection system have reduced the dose rates to acceptable levels. This presentation describes the studies performed before the Top-Off tests, the tests themselves and their major results (both under initial conditions and after improvements were implemented), and presents the controls being implemented for full and routine Top-Off injection.
Date: December 11, 2009
Creator: Bauer, J. M.; Liu, J. C.; Prinz, A. & Rokni, S. H.
Object Type: Article
System: The UNT Digital Library
Feasibility Study for a Seeded Hard X-ray Source Based on a Two-Stage Echo-Enabled Harmonic Generation FEL (open access)

Feasibility Study for a Seeded Hard X-ray Source Based on a Two-Stage Echo-Enabled Harmonic Generation FEL

We propose and analyze a scheme to achieve a seeded hard x-ray source based on a two-stage echo-enabled harmonic generation (EEHG) FEL. In the scheme an 180 nm seed laser covering the whole bunch is first used to modulate the beam when beam energy is 2 GeV. After passing through a strong chicane complicated fine structures are introduced into the phase space. The beam is again modulated by a short 180 nm laser that only interacts with the rear part of the beam and accelerated to 6 GeV. A chicane is then used to convert the energy modulation imparted to the rear part of the beam into density modulation. The density-modulated beam is sent through a radiator to generate intense 6 nm radiation which will be used to interact with the front fresh part of the bunch. Finally we generate in the front part of the beam density modulation at the 1199th harmonic of the seed laser. We will discuss the issues related to the realization of the seeded hard x-ray FEL.
Date: December 11, 2009
Creator: Xiang, Dao; Huang, Z.; Ratner, D. & Stupakov, G.
Object Type: Article
System: The UNT Digital Library
Final Report: A Transport Phenomena Based Approach to Probe Evolution of Weld Macro and Microstructures and A Smart Bi-directional Model of Fusion Welding (open access)

Final Report: A Transport Phenomena Based Approach to Probe Evolution of Weld Macro and Microstructures and A Smart Bi-directional Model of Fusion Welding

In recent years, applications of numerical heat transfer and fluid flow models of fusion welding have resulted in improved understanding of both the welding processes and welded materials. They have been used to accurately calculate thermal cycles and fusion zone geometry in many cases. Here we report the following three major advancements from this project. First, we show how microstructures, grain size distribution and topology of welds of several important engineering alloys can be computed starting from better understanding of the fusion welding process through numerical heat transfer and fluid flow calculations. Second, we provide a conclusive proof that the reliability of numerical heat transfer and fluid flow calculations can be significantly improved by optimizing several uncertain model parameters. Third, we demonstrate how the numerical heat transfer and fluid flow models can be combined with a suitable global optimization program such as a genetic algorithm for the tailoring of weld attributes such as attaining a specified weld geometry or a weld thermal cycle. The results of the project have been published in many papers and a listing of these are included together with a list of the graduate thesis that resulted from this project. The work supported by the DOE …
Date: December 11, 2009
Creator: DebRoy, Dr. Tarasankar
Object Type: Report
System: The UNT Digital Library
Generation of Attosecond X-ray Pulses Beyond the Atomic Unit of Time Using Laser Induced Microbunching in Electron Beams (open access)

Generation of Attosecond X-ray Pulses Beyond the Atomic Unit of Time Using Laser Induced Microbunching in Electron Beams

Ever since the discovery of mode-locking, efforts have been devoted to reducing the duration of laser pulses since the ultrashort pulses are critical to explore the dynamics occurred on a ever-shorter timescale. In this paper we describe a scheme that's capable of generating intense attosecond x-ray pulses with duration beyond the atomic unit of time ({approx}24 attoseconds). The scheme combines the echo-enabled harmonic generation technique with the bunch compression which allows one to generate harmonic numbers of a few hundred in a microbunched beam through up-conversion of the frequency of a UV seed laser. A few-cycle intense IR laser is used to generate the required energy chirp in the beam for bunch compression and for selection of an attosecond x-ray pulse. Using a representative realistic set of parameters, we show that 1 nm x-ray pulse with peak power of a few hundred MW and duration as short as 20 attoseconds (FWHM) can be generated from a 200 nm UV seed laser. The proposed scheme may enable the study of electronic dynamics with a resolution beyond the atomic unit of time and may open a new regime of ultrafast sciences.
Date: December 11, 2009
Creator: Xiang, D.; Huang, Z. & Stupakov, G.
Object Type: Article
System: The UNT Digital Library
Improved Thermoelectric Devices: Advanced Semiconductor Materials for Thermoelectric Devices (open access)

Improved Thermoelectric Devices: Advanced Semiconductor Materials for Thermoelectric Devices

Broad Funding Opportunity Announcement Project: Phononic Devices is working to recapture waste heat and convert it into usable electric power. To do this, the company is using thermoelectric devices, which are made from advanced semiconductor materials that convert heat into electricity or actively remove heat for refrigeration and cooling purposes. Thermoelectric devices resemble computer chips, and they manage heat by manipulating the direction of electrons at the nanoscale. These devices aren’t new, but they are currently too inefficient and expensive for widespread use. Phononic Devices is using a high-performance, cost-effective thermoelectric design that will improve the device’s efficiency and enable electronics manufacturers to more easily integrate them into their products.
Date: December 11, 2009
Creator: unknown
Object Type: Text
System: The UNT Digital Library
Laser Assisted Emittance Exchange: Downsizing the X-ray Free Electron Laser (open access)

Laser Assisted Emittance Exchange: Downsizing the X-ray Free Electron Laser

A technique is proposed to generate electron beam with ultralow transverse emittance through laser assisted transverse-to-longitudinal emittance exchange. In the scheme a laser operating in the TEM10 mode is used to interact with the electron beam in a dispersive region and to initiate the emittance exchange. It is shown that with the proposed technique one can significantly downsize an x-ray free electron laser (FEL), which may greatly extend the availability of these light sources. A hard x-ray FEL operating at 1.5 {angstrom} with a saturation length within 30 meters using a 3.8 GeV electron beam is shown to be practically feasible.
Date: December 11, 2009
Creator: Xiang, Dao
Object Type: Article
System: The UNT Digital Library
Major Tax Issues in the 111th Congress (open access)

Major Tax Issues in the 111th Congress

None
Date: December 11, 2009
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Measurements of Time-Dependent CP Violation in Radiative B Decays at BaBar (open access)

Measurements of Time-Dependent CP Violation in Radiative B Decays at BaBar

The authors present measurements of the CP-violation parameters S and C for the radiative decays B{sup 0} {yields} {pi}{sup 0}K{sub S}{sup 0}{gamma} and B{sup 0} {yields} {eta}K{sub S}{sup 0}{gamma}; for B {yields} {eta}K{gamma} they also measure the branching fractions and for B{sup +} {yields} {eta}K{sup +}{gamma} the time-integrated charge asymmetry A{sub ch}. The data, collected with the BABAR detector at the SLAC National Accelerator Laboratory, represent 467 x 10{sup 6} B{bar B} pairs produced in e{sup +}e{sup -} annihilation at the PEP-II collider. In this summary they present an updated measurement of the time-dependent CP asymmetry in B{sup 0} {yields} {pi}{sup 0}K{sub S}{sup 0}{gamma} decay mode and the first measurement of the time-dependent CP asymmetry in B{sup 0} {yields} {eta}K{sub S}{sup 0}{gamma} decay mode. Hadronic corrections in B{sup 0} {yields} {pi}{sup 0}K{sub S}{sup 0}{gamma} decay mode might permit S to be as large as {+-} 0.1. Such corrections and NP effects could depend on m({pi}{sup 0}K{sub S}{sup 0}), so they split the data into two parts: the K*(892) region with 0.8 < m({pi}{sup 0}K{sub S}{sup 0}) < 1.0 GeV/c{sup 2} and the non-K*(892) region with 1.1 < m({pi}{sup 0}K{sub S}{sup 0}) < 1.8 GeV/c{sup 2}. They also report updated measurements …
Date: December 11, 2009
Creator: Lazzaro, A.
Object Type: Article
System: The UNT Digital Library
MSSM Dark Matter Without Prejudice (open access)

MSSM Dark Matter Without Prejudice

Recently we examined a large number of points in a 19-dimensional parameter subspace of the CP-conserving MSSM with Minimal Flavor Violation. We determined whether each of these points satisfied existing theoretical, experimental, and observational constraints. Here we discuss the properties of the parameter space points allowed by existing data that are relevant for dark matter searches.
Date: December 11, 2009
Creator: Gainer, James S.
Object Type: Article
System: The UNT Digital Library
A Multi-Chamber System for Analyzing the Outgassing, Deposition,and Associated Optical Degradation Properties of Materials in a Vacuum (open access)

A Multi-Chamber System for Analyzing the Outgassing, Deposition,and Associated Optical Degradation Properties of Materials in a Vacuum

We report on the Camera Materials Test Chamber, a multi-vessel apparatus which analyzes the outgassing consequences of candidate materials for use in the vacuum cryostat of a new telescope camera. The system measures the outgassing products and rates of samples of materials at different temperatures, and collects films of outgassing products to measure the effects on light transmission in six optical bands. The design of the apparatus minimizes potential measurement errors introduced by background contamination.
Date: December 11, 2009
Creator: Singal, Jack; Schindler, Rafe; Chang, Chihway; Czodrowski, Patrick; Kim, Peter & /KIPAC, Menlo Park /SLAC /Stanford U.
Object Type: Article
System: The UNT Digital Library
Near Edge X-Ray Absorption Fine Structure Spectroscopy with X-Ray Free-Electron Lasers (open access)

Near Edge X-Ray Absorption Fine Structure Spectroscopy with X-Ray Free-Electron Lasers

We demonstrate the feasibility of Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy on solids by means of femtosecond soft x-ray pulses from a free-electron laser (FEL). Our experiments, carried out at the Free-Electron Laser at Hamburg (FLASH), used a special sample geometry, spectrographic energy dispersion, single shot position-sensitive detection and a data normalization procedure that eliminates the severe fluctuations of the incident intensity in space and photon energy. As an example we recorded the {sup 3}D{sub 1} N{sub 4,5}-edge absorption resonance of La{sup 3+}-ions in LaMnO{sub 3}. Our study opens the door for x-ray absorption measurements on future x-ray FEL facilities.
Date: December 11, 2009
Creator: Bernstein, D.P.; Acremann, Y.; Scherz, A.; Burkhardt, M.; Stohr, J.; Beye, M. et al.
Object Type: Article
System: The UNT Digital Library
On Soft Sngularities at Three Loops and Beyond (open access)

On Soft Sngularities at Three Loops and Beyond

We report on further progress in understanding soft singularities of massless gauge theory scattering amplitudes. Recently, a set of equations was derived based on Sudakov factorization, constraining the soft anomalous dimension matrix of multi-leg scattering amplitudes to any loop order, and relating it to the cusp anomalous dimension. The minimal solution to these equations was shown to be a sum over color dipoles. Here we explore potential contributions to the soft anomalous dimension that go beyond the sum-over-dipoles formula. Such contributions are constrained by factorization and invariance under rescaling of parton momenta to be functions of conformally invariant cross ratios. Therefore, they must correlate the color and kinematic degrees of freedom of at least four hard partons, corresponding to gluon webs that connect four eikonal lines, which first appear at three loops. We analyze potential contributions, combining all available constraints, including Bose symmetry, the expected degree of transcendentality, and the singularity structure in the limit where two hard partons become collinear. We find that if the kinematic dependence is solely through products of logarithms of cross ratios, then at three loops there is a unique function that is consistent with all available constraints. If polylogarithms are allowed to appear as …
Date: December 11, 2009
Creator: Dixon, Lance J.; Gardi, Einan. & Magnea, Lorenzo.
Object Type: Article
System: The UNT Digital Library
Operational Radiation Protection in Synchrotron Light and Free Electron Laser Facilities (open access)

Operational Radiation Protection in Synchrotron Light and Free Electron Laser Facilities

The 3rd generation synchrotron radiation (SR) facilities are storage ring based facilities with many insertion devices and photon beamlines, and have low injection beam power (< few tens of watts), but extremely high stored beam power ({approx} 1 GW). The 4th generation x-ray free electron laser (FEL) facilities are based on an electron Linac with a long undulator and have high injection beam power (a few kW). Due to its electron and photon beam characteristics and modes of operation, storage ring and photon beamlines have unique safety aspects, which are the main subjects of this paper. The shielding design limits, operational modes, and beam losses are first reviewed. Shielding analysis (source terms and methodologies) and interlocked safety systems for storage ring and photon beamlines (including SR and gas bremsstrahlung) are described. Specific safety issues for storage ring top-off injection operation and FEL facilities are discussed. The operational safety program, e.g., operation authorization, commissioning, training, and radiation measurements, for SR facilities is also presented.
Date: December 11, 2009
Creator: Liu, James C.; Rokni, Sayed H. & Vylet, Vaclav
Object Type: Article
System: The UNT Digital Library
PEP Integrated Test D Run Report Caustic and Oxidative Leaching in UFP-VSL-T02A (open access)

PEP Integrated Test D Run Report Caustic and Oxidative Leaching in UFP-VSL-T02A

Pacific Northwest National Laboratory (PNNL) has been tasked by Bechtel National Inc. (BNI) on the River Protection Project-Hanford Tank Waste Treatment and Immobilization Plant (RPP-WTP) project to perform research and development activities to resolve technical issues identified for the Pretreatment Facility (PTF). The Pretreatment Engineering Platform (PEP) was designed, constructed and operated as part of a plan to respond to issue M12, "Undemonstrated Leaching Processes" of the External Flowsheet Review Team (EFRT) issue response plan. The PEP is a 1/4.5-scale test platform designed to simulate the WTP pretreatment caustic leaching, oxidative leaching, ultrafiltration solids concentration, and slurry washing processes. The PEP replicates the WTP leaching processes using prototypic equipment and control strategies. The PEP also includes non-prototypic ancillary equipment to support the core processing. Two operating scenarios are currently being evaluated for the ultrafiltration process (UFP) and leaching operations. The first scenario (Test B and D) has caustic leaching performed in the UFP-2 ultrafiltration feed vessels (i.e., vessel UFP-VSL-T02A in the PEP and vessels UFP-VSL-00002A and B in the WTP PTF). The second scenario (Test A) has caustic leaching conducted in the UFP-1 ultrafiltration feed preparation vessels (i.e., vessels UFP-VSL-T01A and B in the PEP and vessels UFP VSL-00001A and …
Date: December 11, 2009
Creator: Sevigny, Gary J.; Bredt, Ofelia P.; Burns, Carolyn A.; Kurath, Dean E.; Geeting, John GH; Golovich, Elizabeth C. et al.
Object Type: Report
System: The UNT Digital Library
Precision Electroweak Measurements and Constraints on the Standard Model (open access)

Precision Electroweak Measurements and Constraints on the Standard Model

This note presents constraints on Standard Model parameters using published and preliminary precision electroweak results measured at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and D0 at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the combined set of results obtained in high-Q{sup 2} interactions, and used to predict results in low-Q{sup 2} experiments, such as atomic parity violation, Moeller scattering, and neutrino-nucleon scattering. The main changes with respect to the experimental results presented in 2008 are new combinations of results on the W-boson mass and the mass of the top quark.
Date: December 11, 2009
Creator: The , ALEPH, CDF, D0, ...
Object Type: Report
System: The UNT Digital Library
Preserving Homeownership: Foreclosure Prevention Initiatives (open access)

Preserving Homeownership: Foreclosure Prevention Initiatives

None
Date: December 11, 2009
Creator: unknown
Object Type: Report
System: The UNT Digital Library