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Neutral Kaon Interferometry in Au+Au collisions at sqrt(s_NN) =200 GeV (open access)

Neutral Kaon Interferometry in Au+Au collisions at sqrt(s_NN) =200 GeV

We present the first statistically meaningful results fromtwo-K0s interferometry in heavy-ion collisions. A model that takes theeffect of the strong interaction into account has been used to fit themeasured correlation function. The effects of single and coupled channelwere explored. At the mean transverse mass m_T = 1.07 GeV, we obtain thevalues R = 4.09 +- 0.46 (stat.) +- 0.31 (sys) fm and lambda = 0.92 +-0.23 (stat) +- 0.13 (sys), where R and lambda are the invariant radiusand chaoticity parameters respectively. The results are qualitativelyconsistent with m_T systematics established with pions in a scenariocharacterized by a strong collective flow.
Date: August 5, 2006
Creator: Abelev, B. I.; Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D. et al.
System: The UNT Digital Library
Progress on the Europium Neutron-Capture Study using DANCE (open access)

Progress on the Europium Neutron-Capture Study using DANCE

The accurate measurement of neutron-capture cross sections of the Eu isotopes is important for many reasons including nuclear astrophysics and nuclear diagnostics. Neutron capture excitation functions of {sup 151,153}Eu targets were measured recently using a 4{pi} {gamma}-ray calorimeter array DANCE located at the Los Alamos Neutron Science Center for E{sub n} = 0.1-100 keV. The progress on the data analysis efforts is given in the present paper. The {gamma}-ray multiplicity distributions for the Eu targets and Be backing are significantly different. The {gamma}-ray multiplicity distribution is found to be the same for different neutron energies for both {sup 151}Eu and {sup 153}Eu. The statistical simulation to model the {gamma}-ray decay cascade is summarized.
Date: September 5, 2006
Creator: Agvaanluvsan, U.; Becker, J. A.; Macri, R. A.; Parker, W.; Wilk, P.; Wu, C. Y. et al.
System: The UNT Digital Library
An Integrated Hydrologic Bayesian Multi-Model Combination Framework: Confronting Input, parameter and model structural uncertainty in Hydrologic Prediction (open access)

An Integrated Hydrologic Bayesian Multi-Model Combination Framework: Confronting Input, parameter and model structural uncertainty in Hydrologic Prediction

This paper presents a new technique--Integrated Bayesian Uncertainty Estimator (IBUNE) to account for the major uncertainties of hydrologic rainfall-runoff predictions explicitly. The uncertainties from the input (forcing) data--mainly the precipitation observations and from the model parameters are reduced through a Monte Carlo Markov Chain (MCMC) scheme named Shuffled Complex Evolution Metropolis (SCEM) algorithm which has been extended to include a precipitation error model. Afterwards, the Bayesian Model Averaging (BMA) scheme is employed to further improve the prediction skill and uncertainty estimation using multiple model output. A series of case studies using three rainfall-runoff models to predict the streamflow in the Leaf River basin, Mississippi are used to examine the necessity and usefulness of this technique. The results suggests that ignoring either input forcings error or model structural uncertainty will lead to unrealistic model simulations and their associated uncertainty bounds which does not consistently capture and represent the real-world behavior of the watershed.
Date: May 5, 2006
Creator: Ajami, N. K.; Duan, Q. & Sorooshian, S.
System: The UNT Digital Library
Filtered cathodic arc deposition with ion-species-selectivebias (open access)

Filtered cathodic arc deposition with ion-species-selectivebias

A dual-cathode arc plasma source was combined with acomputer-controlled bias amplifier such as to synchronize substrate biaswith the pulsed production of plasma. In this way, bias can be applied ina material-selective way. The principle has been applied to the synthesismetal-doped diamond-like carbon films, where the bias was applied andadjusted when the carbon plasma was condensing, and the substrate was atground when the metal was incorporated. In doing so, excessive sputteringby too-energetic metal ions can be avoided while the sp3/sp2 ratio can beadjusted. It is shown that the resistivity of the film can be tuned bythis species-selective bias. The principle can be extended tomultiple-material plasma sources and complex materials
Date: October 5, 2006
Creator: Anders, Andre; Pasaja, Nitisak; Sansongsiri, Sakon & Lim, SunnieH.N.
System: The UNT Digital Library
Optical Properties in Non-equilibrium Phase Transitions (open access)

Optical Properties in Non-equilibrium Phase Transitions

An open question about the dynamical behavior of materials is how phase transition occurs in highly non-equilibrium systems. One important class of study is the excitation of a solid by an ultrafast, intense laser. The preferential heating of electrons by the laser field gives rise to initial states dominated by hot electrons in a cold lattice. Using a femtosecond laser pump-probe approach, we have followed the temporal evolution of the optical properties of such a system. The results show interesting correlation to non-thermal melting and lattice disordering processes. They also reveal a liquid-plasma transition when the lattice energy density reaches a critical value.
Date: January 5, 2006
Creator: Ao, T; Ping, Y; Widmann, K; Price, D F; Lee, E; Tam, H et al.
System: The UNT Digital Library
Developments in Realistic Design for Aperiodic Mo/Si Multilayermirrors (open access)

Developments in Realistic Design for Aperiodic Mo/Si Multilayermirrors

Aperiodic multilayers have been designed for various applications, using numeric algorithms and analytical solutions, for many years with varying levels of success. This work developed a more realistic model for simulating aperiodic Mo/Si multilayers to be used in these algorithms by including the formation of MoSi{sub 2}. Using a genetic computer code we were able to optimize a 45{sup o} multilayer for a large bandpass reflection multilayer that gave good agreement with the model.
Date: April 5, 2006
Creator: Aquila, A. L.; Salmassi, F.; Dollar, F.; Liu, Y. & Gullikson, E. M.
System: The UNT Digital Library
Towards the NNLL Precision in the Decay $\bar B \rightarrow X_s \gamma$ (open access)

Towards the NNLL Precision in the Decay $\bar B \rightarrow X_s \gamma$

The present NLL prediction for the decay rate of the rare inclusive process {bar B} {yields} X{sub s}{gamma} has a large uncertainty due to the charm mass renormalization scheme ambiguity. We estimate that this uncertainty will be reduced by a factor of 2 at the NNLL level. This is a strong motivation for the on-going NNLL calculation, which will thus significantly increase the sensitivity of the observable {bar B} {yields} X{sub s}{gamma} to possible new degrees of freedom beyond the SM. We also give a brief status report of the NNLL calculation.
Date: January 5, 2006
Creator: Asatrian, Hrachia M.; Hovhannisyan, Artyom; Poghosyan, Vahagn; Inst., /Yerevan Phys.; Greub, Christoph; U., /Bern et al.
System: The UNT Digital Library
Imaging at high spatial resolution: Soft x-ray microscopy to 15nm (open access)

Imaging at high spatial resolution: Soft x-ray microscopy to 15nm

Soft x-ray microscopy has now achieved 15 nm spatial resolution with new zone plates and bending magnet radiation. Combined with elemental sensitivity and flexible sample environment (applied magnetic or electric fields, wet samples, windows, overcoatings) this emerges as a valuable tool for nanoscience and nanotechnology, complimenting common electron and scanning tip microscopies. In this presentation we describe recent advances in spatial resolution, expectations for the near future, and applications to magnetic materials, bio-tomography, etc.
Date: April 5, 2006
Creator: Attwood, D.; Chao, W.; Anderson, E.; Liddle, J. A.; Harteneck, B.; Fischer, P. et al.
System: The UNT Digital Library
Measurement of the Pseudoscalar Decay Constantf_D_s Using Charm-Tagged Events in e+e- Collisions atsqrt{s}=10.58 GeV (open access)

Measurement of the Pseudoscalar Decay Constantf_D_s Using Charm-Tagged Events in e+e- Collisions atsqrt{s}=10.58 GeV

Using 230.2 fb{sup -1} of e{sup +}e{sup -} annihilation data collected with the BABAR detector at and near the peak of the {Upsilon}(4S) resonance, 489 {+-} 55 events containing the pure leptonic decay D{sub s}{sup +} {yields} {mu}{sup +}{nu}{sub {mu}} have been isolated in charm-tagged events. The ratio of partial widths {Lambda}(D{sub s}{sup +} {yields} {mu}{sup +}{nu}{sub {mu}})/{Lambda}(D{sub s}{sup +} {yields} {phi}{pi}{sup +}) is measured to be 0.143 {+-} 0.018 {+-} 0.006 allowing a determination of the pseudoscalar decay constant f{sub D{sub 2}} = (283 {+-} 17 {+-} 7 {+-} 14) MeV. The errors are statistical, systematic, and from the D{sub s}{sup +} {yields} {phi}{pi}{sup +} branching ratio, respectively.
Date: September 5, 2006
Creator: Aubert, B.
System: The UNT Digital Library
Measurement of the Spin of the Omega- Hyperon at Babar (open access)

Measurement of the Spin of the Omega- Hyperon at Babar

A measurement of the spin of the {Omega}{sup -} hyperon produced through the exclusive process {Xi}{sub c}{sup 0} {yields} {Omega}{sup -}K{sup +} is presented using a total integrated luminosity of 116 fb{sup -1} recorded with the BABAR detector at the e{sup +}e{sup -} asymmetric-energy B-Factory at SLAC. Under the assumption that the {Xi}{sub c}{sup 0} has spin 1/2, the angular distribution of the {Lambda} from {Omega}{sup -} {yields} {Lambda}K{sup -} decay is inconsistent with all half-integer {Omega}{sup -} spin values other than 3/2. Lower statistics data for the process {Omega}{sub c}{sup 0} {yields} {Omega}{sup -}{pi}{sup +} from a 230 fb{sup -1} sample are also found to be consistent with {Omega}{sup -} spin 3/2. If the {Xi}{sub c}{sup 0} spin were 3/2, an {Omega}{sup -} spin of 5/2 cannot be excluded.
Date: July 5, 2006
Creator: Aubert, B.
System: The UNT Digital Library
Measurements of the Branching Fractions and CP Asymmetries of B -> D0_CP K Decays (open access)

Measurements of the Branching Fractions and CP Asymmetries of B -> D0_CP K Decays

We present a study of the decay B{sup -} {yields} D{sub (CP)}{sup 0} K{sup -} and its charge conjugate, where D{sub (CP)}{sup 0} is reconstructed in CP-even, CP-odd, and non-CP flavor eigenstates, based on a sample of 232 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II e{sup +}e{sup -} storage ring. We measure the partial-rate charge asymmetries AC{sub CP{+-}} and the ratios R{sub CP{+-}} of the B {yields} D{sup 0} K decay branching fractions as measured in CP{+-} and non-CP D{sup 0} decays: A{sub CP+} = 0.35 {+-} 0.13(stat) {+-} 0.04(syst), A{sub CP-} = -0.06 {+-} 0.13(stat) {+-} 0.04(syst), R{sub CP+} = 0.90 {+-} 0.12(stat) {+-} 0.04(syst), R{sub CP-} = 0.86 {+-} 0.10(stat) {+-} 0.05(syst).
Date: January 5, 2006
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
System: The UNT Digital Library
DUAL ION EXPOSURE VS. SPLIT-DOSE EXPOSURES IN HUMAN CELL NEOPLASTIC TRANSFORMATION. (open access)

DUAL ION EXPOSURE VS. SPLIT-DOSE EXPOSURES IN HUMAN CELL NEOPLASTIC TRANSFORMATION.

Since radiation fields of space contain many-fold more protons than high atomic number, high energy (HZE) particles, cells in astronaut crews will experience on average several proton hits before an HZE hit. Thus radiation regimes of proton exposure before HZE particle exposure simulate space radiation exposure, and measurement of the frequency of neoplastic transformation of human primary cells to anchorage-independent growth simulates in initial step in cancer induction. Previously our group found that exposure to 20 cGy 1 GeV/n protons followed within about 1 hr by a HZE ion (20 cGy 1 GeV/n Fe or Ti ions) hit gave about a 3-fold increase in transformation frequency ([1]). To provide insight into the H-HZE induced increased transformation frequencies, we asked if split doses of the same ion gave similar increased transformation frequencies. However, the data show that the split dose of 20 cGy plus 20 cGy of either H or HZE ions gave about the same effect as the 40 cGy uninterrupted dose, quite different from the effect of the mixed ion H + HZE irradiation. We also asked if lower proton doses than 20 cGy followed 15 minutes later by 20 cGy of HZE ions gave greater than additive transformation …
Date: June 5, 2006
Creator: BENNETT, P.V.; CUTTER, N.C. & SUTHERLAND, B.M.
System: The UNT Digital Library
Determination of Dark Matter Properties at High-Energy Colliders (open access)

Determination of Dark Matter Properties at High-Energy Colliders

If the cosmic dark matter consists of weakly-interacting massive particles, these particles should be produced in reactions at the nextgeneration of high-energy accelerators. Measurements at these accelerators can then be used to determine the microscopic properties of the dark matter. From this, we can predict the cosmic density, the annihilation cross sections, and the cross sections relevant to direct detection. In this paper, we present studies in supersymmetry models with neutralino dark matter that give quantitative estimates of the accuracy that can be expected. We show that these are well matched to the requirements of anticipated astrophysical observations of dark matter. The capabilities of the proposed International Linear Collider (ILC) are expected to play a particularly important role in this study.
Date: November 5, 2006
Creator: Baltz, Edward A.; Battaglia, Marco; Peskin, Michael E. & Wizansky, Tommer
System: The UNT Digital Library
Use of Antineutrino Detectors for Nuclear Reactor Safeguards Effectiveness Assessment (open access)

Use of Antineutrino Detectors for Nuclear Reactor Safeguards Effectiveness Assessment

As described in an earlier article [1], important information regarding reactor power and the amount and type of fissile material in reactor cores can be determined by measuring the antineutrino rate and energy spectrum, using a cubic meter scale antineutrino detector at tens of meters standoff from the core. Current International Atomic Energy Agency (IAEA) safeguards techniques do not provide such real-time quantitative information regarding core power levels and isotopic composition. The possible benefits of this approach are several and have been discussed in the earlier article. One key advantage is that the method gives the inspecting agency completely independent access to real-time information on the operational status and fissile content of the core. Furthermore, the unattended and non-intrusive nature of the technology may reduce the monitoring burden on the plant operator, even though more information is being provided than is available within the current IAEA safeguards regime. Here we present a detailed analytical framework for measuring the impact that such a detector might have on IAEA safeguards, if implemented. To perform the analysis, we will use initial data from our operating detector and a standard analysis technique for safeguards regimes, developed at Lawrence Livermore National Laboratory. Because characterization of …
Date: June 5, 2006
Creator: Bernstein, A; Lambert, H E; Elayat, H A; O'Connell, W J; Rexroth, P; Baldwin, G et al.
System: The UNT Digital Library
A Photon Free Method to Solve Radiation Transport Equations (open access)

A Photon Free Method to Solve Radiation Transport Equations

The multi-group discrete-ordinate equations of radiation transfer is solved for the first time by Newton's method. It is a photon free method because the photon variables are eliminated from the radiation equations to yield a N{sub group}XN{sub direction} smaller but equivalent system of equations. The smaller set of equations can be solved more efficiently than the original set of equations. Newton's method is more stable than the Semi-implicit Linear method currently used by conventional radiation codes.
Date: September 5, 2006
Creator: Chang, B.
System: The UNT Digital Library
Is it Worth it? A Comparative Analysis of Cost-Benefit Projectionsfor State Renewables Portfolio Standards (open access)

Is it Worth it? A Comparative Analysis of Cost-Benefit Projectionsfor State Renewables Portfolio Standards

State renewables portfolio standards (RPS) have emerged as one of the most important policy drivers of renewable energy capacity expansion in the U.S. Collectively, these policies now apply to almost 40% of U.S. electricity load, and may have substantial impacts on electricity markets, ratepayers, and local economies. As RPS policies have been proposed or adopted in an increasing number of states, a growing number of studies have attempted to quantify the potential impacts of these policies, focusing primarily on projecting cost impacts, but sometimes also estimating macroeconomic and environmental effects. This report synthesizes and analyzes the results and methodologies of twenty-six distinct state or utility-level RPS cost impact analyses completed since 1998 (see Figure 1 and Appendix for a complete list of the studies). Together, these studies model proposed or adopted RPS policies in seventeen different states. We highlight the key findings of these studies on the costs and benefits of RPS policies, examine the sensitivity of projected costs to model assumptions, assess the attributes of different modeling approaches, and suggest possible areas of improvement for future RPS analysis.
Date: June 5, 2006
Creator: Chen, Cliff; Wiser, Ryan & Bolinger, Mark
System: The UNT Digital Library
Laboratory measurements of high-n iron L-shell x-ray lines (open access)

Laboratory measurements of high-n iron L-shell x-ray lines

We present a comprehensive wavelength survey of Fe L-shell X-ray lines between 7 and 11 {angstrom} measured using flat crystal spectrometers and the EBIT-I and EBIT-II electron beam ion traps at the Lawrence Livermore National Laboratory. This survey includes all significant emission lines produced by over 200 n {yields} 2 transitions in Fe XIX-XXIV, with n = 4-10. The identification and assignment of transitions are made with the help of detailed theoretical modeling using the Flexible Atomic Code (FAC).
Date: September 5, 2006
Creator: Chen, H; Gu, M F; Behar, E; Brown, G V; Kahn, S M & Beiersdorfer, P
System: The UNT Digital Library
Isochoric implosions for fast ignition (open access)

Isochoric implosions for fast ignition

Fast Ignition (FI) exploits the ignition of a dense, uniform fuel assembly by an external energy source to achieve high gain. In conventional ICF implosions, however, the fuel assembles as a dense shell surrounding a low density, high-pressure hotspot. Such configurations are far from optimal for FI. Here, it is shown that a self-similar spherical implosion of the type originally studied by Guderley [Luftfahrtforschung 19, 302 (1942).] may be employed to implode a dense, quasi-uniform fuel assembly with minimal energy wastage in forming a hotspot. A scheme for realizing these specialized implosions in a practical ICF target is also described.
Date: June 5, 2006
Creator: Clark, D S & Tabak, M
System: The UNT Digital Library
Charm Mixing at BaBar (open access)

Charm Mixing at BaBar

We report on searches for D{sup 0}-{bar D}{sup 0} mixing using decay-time distributions of D{sup 0} {yields} K{pi} and D{sup 0} {yields} K{sup (*)}e{nu} decays and a lifetime ratio analysis of D{sup 0} {yields} K{sup +}K{sup -}, {pi}{sup +}{pi}{sup -} decays using 91 fb{sup -1} of e{sup +}e{sup -} data taken at the PEP-II asymmetric-energy storage ring at energies near 10.6 GeV. Searches for CP-violation in D{sup 0} mixing and decay are also reported, as well as a measurement of R{sub D}, the ratio of the doubly Cabibbo-suppressed decay rate to the Cabibbo-allowed decay rate.
Date: July 5, 2006
Creator: Cowan, Ray F.
System: The UNT Digital Library
Reheating Metastable O'Raifeartaigh Models (open access)

Reheating Metastable O'Raifeartaigh Models

In theories with multiple vacua, reheating to a temperature greater than the height of a barrier can stimulate transitions from a desirable metastable vacuum to a lower energy state. We discuss the constraints this places on various theories and demonstrate that in a class of supersymmetric models this transition does not occur even for arbitrarily high reheating temperature.
Date: December 5, 2006
Creator: Craig, Nathaniel J.; Fox, Patrick J. & Wacker, Jay G.
System: The UNT Digital Library
Electrochemical Testing of Gas Tungsten Arc Welded and Reduced Pressure Electron Beam Welded Alloy 22 (open access)

Electrochemical Testing of Gas Tungsten Arc Welded and Reduced Pressure Electron Beam Welded Alloy 22

Alloy 22 (N06022) is the material selected for the fabrication of the outer shell of the nuclear waste containers for the Yucca Mountain high-level nuclear waste repository site. A key technical issue in the waste package program has been the integrity of the container weld joints. The currently selected welding process for fabricating and sealing the containers is the traditional gas tungsten arc welding (GTAW) or TIG method. An appealing faster alternative technique is reduced pressure electron beam (RPEB) welding. It was of interest to compare the corrosion properties of specimens prepared using both types of welding techniques. Standard electrochemical tests were carried on GTAW and RPEB welds as well as on base metal (non-welded) to determine their relative corrosion behavior in simulated concentrated water (SCW) at 90 C (alkaline), 1 M HCl at 60 C (acidic) and 1 M NaCl at 90 C (neutral) solutions. Results show that for all practical purposes, the three tested materials had the same electrochemical behavior in the three tested electrolytes.
Date: February 5, 2006
Creator: Day, S. D.; Wong, F. G.; Gordon, S. R.; Wong, L. L. & Rebak, R. B.
System: The UNT Digital Library
Sediment transport time measured with U-Series isotopes: Resultsfrom ODP North Atlantic Drill Site 984 (open access)

Sediment transport time measured with U-Series isotopes: Resultsfrom ODP North Atlantic Drill Site 984

High precision uranium isotope measurements of marineclastic sediments are used to measure the transport and storage time ofsediment from source to site of deposition. The approach is demonstratedon fine-grained, late Pleistocene deep-sea sediments from Ocean DrillingProgram Site 984A on the Bjorn Drift in the North Atlantic. The sedimentsare siliciclastic with up to 30 percent carbonate, and dated by sigma 18Oof benthic foraminifera. Nd and Sr isotopes indicate that provenance hasoscillated between a proximal source during the last three interglacialperiods volcanic rocks from Iceland and a distal continental sourceduring glacial periods. An unexpected finding is that the 234U/238Uratios of the silicate portion of the sediment, isolated by leaching withhydrochloric acid, are significantly less than the secular equilibriumvalue and show large and systematic variations that are correlated withglacial cycles and sediment provenance. The 234U depletions are inferredto be due to alpha-recoil loss of234Th, and are used to calculate"comminution ages" of the sediment -- the time elapsed between thegeneration of the small (<_ 50 mu-m) sediment grains in the sourceareas by comminution of bedrock, and the time of deposition on theseafloor. Transport times, the difference between comminution ages anddepositional ages, vary from less than 10 ky to about 300 to 400 ky forthe …
Date: June 5, 2006
Creator: DePaolo, Donald J.; Maher, Kate; Christensen, John N. & McManus,Jerry
System: The UNT Digital Library
Environmental application of stable xenon and radioxenonmonitoring (open access)

Environmental application of stable xenon and radioxenonmonitoring

Characterization of transuranic waste is needed to makedecisions about waste site remediation. Soil-gas sampling for xenonisotopes can be used to define the locations of spent fuel andtransuranic wastes. Radioxenon in the subsurface is characteristic oftransuranic waste and can be measured with extreme sensitivity usinglarge-volume soilgas samples. Measurements at the Hanford Site showed133Xe and 135Xe levels indicative of 240Pu spontaneous fission. Stablexenon isotopic ratios from fission are distinct from atmospheric xenonbackground. Neutron capture by 135Xe produces an excess of 136Xe inreactor-produced xenon providing a means of distinguishing spent fuelfrom separated transuranic materials.
Date: September 5, 2006
Creator: Dresel, P. Evan; Olsen, Khris B.; Hayes, James C.; McIntyre,Justin I.; Waichler, Scott R.; Milbrath, Brian D. et al.
System: The UNT Digital Library
ACCUMULATION OF RADIOCESIUM BY MUSHROOMS IN THE ENVIRONMENT: A LITERATURE REVIEW AND IMAGE GALLERY (open access)

ACCUMULATION OF RADIOCESIUM BY MUSHROOMS IN THE ENVIRONMENT: A LITERATURE REVIEW AND IMAGE GALLERY

During the last 50 years, a large amount of information on radionuclide accumulators or 'sentinel-type' organisms in the environment has been published. Much of this work focused on the risks of food-chain transfer of radionuclides to higher organisms such as reindeer and man. However, until the 1980's and 1990's, there has been little published data on the radiocesium ({sup 134}Cs and {sup 137}Cs) accumulation by mushrooms. This presentation will consist of a review of the published data for {sup 134,137}Cs accumulation by mushrooms in nature. The review will consider the time of sampling, sample location characteristics, the radiocesium source term and other aspects that promote {sup 134,137}Cs uptake by mushrooms. This review will focus on published data for mushrooms that demonstrate a large propensity for use in the environmental biomonitoring of radiocesium contamination. It will also provide photographs and descriptions of habitats for many of these mushrooms to facilitate their collection for biomonitoring.
Date: November 5, 2006
Creator: Duff, M & Mary Ramsey, M
System: The UNT Digital Library