Filtros de búsqueda

Lista de obras de Humberto Terrones Maldonado

3D Nanocomposites of Covalently Interconnected Multiwalled Carbon Nanotubes with SiC with Enhanced Thermal and Electrical Properties

A Simple Route to Silicon-Based Nanostructures

article by Yan Qiu Zhu et al published July 1999 in Advanced Materials

A novel route to aligned nanotubes and nanofibres using laser-patterned catalytic substrates

A theoretical and experimental study on manipulating the structure and properties of carbon nanotubes using substitutional dopants

Acid modified bamboo-type carbon nanotubes and cup-stacked-type carbon nanofibres as adsorbent materials: cadmium removal from aqueous solution

Aligned CN[sub x] nanotubes by pyrolysis of ferrocene/C[sub 60] under NH[sub 3] atmosphere

Alloy nanowires: Invar inside carbon nanotubes

An Alternative Route to Molybdenum Disulfide Nanotubes

scholarly article by Wen Kuang Hsu et al published October 2000 in Journal of the American Chemical Society

An Atomistic Branching Mechanism for Carbon Nanotubes: Sulfur as the Triggering Agent

artículo científico publicado en 2008

Analysis of the molecular structure of human enamel with fluorosis using micro-Raman spectroscopy

artículo científico publicado en 2012

Anchorage of γ-Al 2 O 3 nanoparticles on nitrogen-doped multiwalled carbon nanotubes

Anomalous Paramagnetism in Doped Carbon Nanostructures

scientific article published on 01 January 2007

Architectures from Aligned Nanotubes Using Controlled Micropatterning of Silicon Substrates and Electrochemical Methods

artículo científico publicado en 2007

Assessment of isobaric-isothermal (NPT) simulations for finite systems

Atomic nanotube welders: boron interstitials triggering connections in double-walled carbon nanotubes

artículo científico publicado en 2005

Atypical Exciton-Phonon Interactions in WS2 and WSe2 Monolayers Revealed by Resonance Raman Spectroscopy

artículo científico publicado en 2016

BNC NanoShells a Novel Structure for Atomic Storage

artículo científico publicado en 2017

Band gap engineering and layer-by-layer mapping of selenium-doped molybdenum disulfide.

artículo científico publicado en 2013

Beryllium doping graphene, graphene-nanoribbons, C60-fullerene, and carbon nanotubes

scholarly article in Carbon, vol. 84, April 2015

Beyond C60: graphite structures for the future

Beyond Carbon Nanopeapods ⬇️

artículo científico publicado el 4 de mayo de 2012

Beyond Graphene: Progress in Novel Two-Dimensional Materials and van der Waals Solids

article published in 2015

Bilayers of transition metal dichalcogenides: Different stackings and heterostructures

article published in 2013

Biocompatibility and Toxicological Studies of Carbon Nanotubes Doped with Nitrogen

artículo científico publicado en 2006

Biotin molecules on nitrogen-doped carbon nanotubes enhance the uniform anchoring and formation of Ag nanoparticles

scholarly article in Carbon, vol. 88, July 2015

Bonding titanium on multi-walled carbon nanotubes for hydrogen storage: An electrochemical approach

Boron Nitride Nanoribbons Become Metallic ⬇️

artículo científico publicado el 20 de julio de 2011

Boron, nitrogen and phosphorous substitutionally doped single-wall carbon nanotubes studied by resonance Raman spectroscopy

Boron-Mediated Growth of Long Helicity-Selected Carbon Nanotubes

Boron-doping effects in carbon nanotubes

Bulk Production of a New Form of sp2Carbon: Crystalline Graphene Nanoribbons

scientific article published on 14 August 2008

CVD-grown monolayered MoS2 as an effective photosensor operating at low-voltage

Cables of BN-insulated B–C–N nanotubes

Carbon Nitride Nanocomposites: Formation of Aligned CxNy Nanofibers

Carrier lifetime enhancement in halide perovskite via remote epitaxy

artículo científico publicado en 2019

Chemical vapor deposition synthesis of N-, P-, and Si-doped single-walled carbon nanotubes

artículo científico publicado en 2010

Coalescence of Double-Walled Carbon Nanotubes: Formation of Novel Carbon Bicables

Coalescence of Single-Walled Carbon Nanotubes

artículo científico publicado en 2000

Collapsing carbon nanotubes and diamond formation under shock waves

article published in 1998

Comparison study of semi-crystalline and highly crystalline multiwalled carbon nanotubes

Controlled production of aligned-nanotube bundles

scientific article published in Nature

Controlled synthesis and transfer of large-area WS2 sheets: from single layer to few layers

artículo científico publicado en 2013

Controlling Edge Morphology in Graphene Layers Using Electron Irradiation: From Sharp Atomic Edges to Coalesced Layers Forming Loops

artículo científico publicado en 2010

Controlling the Optical, Electrical and Chemical Properties of Carbon Inverse Opal by Nitrogen Doping

Controlling the dimensions, reactivity and crystallinity of multiwalled carbon nanotubes using low ethanol concentrations

Controlling the velocity of jumping nanodroplets via their initial shape and temperature

artículo científico publicado en 2011

Correction to Boron Nitride Nanoribbons Become Metallic

scholarly article published in Nano Letters

Correction to “Structures, Energetics, and Electronic Properties of Layered Materials and Nanotubes of Cadmium Chalcogenides”

scholarly article published in Journal of Physical Chemistry C

Covalent 2D and 3D Networks from 1D Nanostructures: Designing New Materials

artículo científico publicado en 2007

Covalently bonded three-dimensional carbon nanotube solids via boron induced nanojunctions

artículo científico publicado en 2012

Curved nanostructured materials

Decorating carbon nanotubes with nanostructured nickel particles via chemical methods

Defect engineering of two-dimensional transition metal dichalcogenides

article published in 2016

Defect-induced photoluminescence in monolayer semiconducting transition metal dichalcogenides

artículo científico publicado en 2015

Determination of chiralities of single-walled carbon nanotubes by neutron powder diffraction technique

Differential Response of Doped/Defective Graphene and Dopamine to Electric Fields: A Density Functional Theory Study

Direct observation of the structure of gold nanoparticles by total scattering powder neutron diffraction

Doping (10, 0)-Semiconductor Nanotubes with Nitrogen and Vacancy Defects

Doping and connecting carbon nanotubes

Edge-edge interactions in stacked graphene nanoplatelets

artículo científico publicado en 2013

Effect of impurities on the electronic and magnetic properties of zinc oxide nanostructures

Effects of 45-nm silver nanoparticles on coronary endothelial cells and isolated rat aortic rings

artículo científico publicado en 2009

Efficient Anchoring of Silver Nanoparticles on N-Doped Carbon Nanotubes

artículo científico publicado en 2006

Efficient encapsulation of gaseous nitrogen inside carbon nanotubes with bamboo-like structure using aerosol thermolysis

Efficient route to large arrays of CNx nanofibers by pyrolysis of ferrocene/melamine mixtures

Efficient vapor sensors using foils of dispersed nitrogen-doped and pure carbon multiwalled nanotubes

artículo científico publicado en 2010

Electric-Field-Assisted Directed Assembly of Transition Metal Dichalcogenide Monolayer Sheets

artículo científico publicado en 2016

Electrochemical formation of novel nanowires and their dynamic effects

Electrochemical production of low-melting metal nanowires

article

Electrolytic Formation of Carbon-Sheathed Mixed Sn−Pb Nanowires

Electrolytic formation of carbon nanostructures

Electron and phonon renormalization near charged defects in carbon nanotubes

artículo científico publicado en 2008

Electron transport properties of ordered networks using carbon nanotubes

scientific article published on 24 June 2008

Electron transport study on functionalized armchair graphene nanoribbons: DFT calculations

scholarly article in RSC Advances, vol. 6 no. 26, 2016

Electronic Control over Attachment and Self-Assembly of Alkyne Groups on Gold

artículo científico publicado en 2012

Electronic Transport and Mechanical Properties of Phosphorus- and Phosphorus−Nitrogen-Doped Carbon Nanotubes

scientific article published on 02 July 2009

Electronic and optical properties of strained graphene and other strained 2D materials: a review

artículo científico publicado en 2017

Electronic and vibrational properties of defective transition metal dichalcogenide Haeckelites: new 2D semi-metallic systems

article

Electronic properties of giant fullerenes and complex graphitic nanostructures with novel morphologies

Electronic, magnetic, optical, and edge-reactivity properties of semiconducting and metallic WS2nanoribbons

Enhanced Electron Field Emission in B-doped Carbon Nanotubes

artículo científico publicado en 2002

Enhanced ferromagnetism in ZnO nanoribbons and clusters passivated with sulfur

Enhanced magnetic coercivities in Fe nanowires

Excited excitonic states in 1L, 2L, 3L, and bulk WSe2 observed by resonant Raman spectroscopy

artículo científico publicado en 2014

Excitonic Complexes and Emerging Interlayer Electron-Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS0.6Se1.4.

artículo científico publicado en 2018

Experimental and Theoretical Studies Suggesting the Possibility of Metallic Boron Nitride Edges in Porous Nanourchins

artículo científico publicado en 2008

Experimental observation and quantum modeling of electron irradiation on single-wall carbon nanotubes

Experimental observation and quantum modeling of electron irradiation on single-wall carbon nanotubes

Exploring the carbon nanocosmos: doped nanotubes, networks, and other novel forms of carbon

Extraordinary room-temperature photoluminescence in triangular WS2 monolayers

artículo científico publicado en 2013

Extrapolating Dynamic Leidenfrost Principles to Metallic Nanodroplets on Asymmetrically Textured Surfaces

artículo científico publicado en 2015

Fabrication of vapor and gas sensors using films of aligned CNx nanotubes

article published in 2004

Facile synthesis of MoS2 and MoxW1-xS2 triangular monolayers

article published in 2014

Femtosecond laser nanosurgery of defects in carbon nanotubes

artículo científico publicado en 2005

Field-effect transistors based on few-layered α-MoTe(2).

artículo científico

Fullerene Coalescence in Nanopeapods: A Path to Novel Tubular Carbon

Fullerene and nanotube growth: new insights using first principles and molecular dynamics

artículo científico publicado en 2016

Fullerene growth and the role of nonclassical isomers

scholarly article in Physical Review B, vol. 63 no. 19, April 2001

Fullerenes and nanotubes with non-positive Gaussian curvature

Fullerenes with Non-Positive Gaussian Curvature: Holey-Balls and Holey-Tubes

Generation of hollow crystalline tungsten oxide fibres

scholarly article by W.B. Hu et al published 1 February 2000 in Applied Physics A

Geometry and stability of graphitic onion-like structures

Graphene and graphite nanoribbons: Morphology, properties, synthesis, defects and applications

scientific article published in 2010

Graphitic cones in palladium catalysed carbon nanofibres

Ground-state electronic structure of nanoscale carbon cones

scholarly article in Physical Review B, vol. 72 no. 23, December 2005

Guiding Electrical Current in Nanotube Circuits Using Structural Defects: A Step Forward in Nanoelectronics

artículo científico publicado en 2008

Harold Walter Kroto

Heterodoped nanotubes: theory, synthesis, and characterization of phosphorus-nitrogen doped multiwalled carbon nanotubes

artículo científico publicado en 2008

Heterojunctions between metals and carbon nanotubes as ultimate nanocontacts

artículo científico publicado en 2009

How to Identify Haeckelite Structures: A Theoretical Study of Their Electronic and Vibrational Properties

Hydrogen storage in nanoporous carbon materials: myth and facts

scientific article published on 23 March 2007

Hydrogen storage in spherical nanoporous carbons

Hydroxyl-functionalized and N-doped multiwalled carbon nanotubes decorated with silver nanoparticles preserve cellular function

artículo científico publicado en 2011

Identification of Electron Donor States in N-Doped Carbon Nanotubes

article published in 2001

Identification of individual and few layers of WS2 using Raman Spectroscopy

artículo científico publicado en 2013

In situ nucleation of carbon nanotubes by the injection of carbon atoms into metal particles

artículo científico publicado en 2007

Infrared and Raman spectra, conformational stability, ab initio calculations of structure, and vibrational assignment of α and β glucose

article

Iron Particle Nanodrilling of Few Layer Graphene at Low Electron Beam Accelerating Voltages

KCl crystallization within the space between carbon nanotube walls

Large second harmonic generation in alloyed TMDs and boron nitride nanostructures.

artículo científico publicado en 2018

Large-area Si-doped graphene: controllable synthesis and enhanced molecular sensing

artículo científico publicado en 2014

Longitudinal Cutting of Pure and Doped Carbon Nanotubes to Form Graphitic Nanoribbons Using Metal Clusters as Nanoscalpels

scientific article published on 01 February 2010

Magnetic Behavior in Zinc Oxide Zigzag Nanoribbons

scientific article published on 05 January 2008

Magnetic properties of individual carbon clusters, clusters inside fullerenes and graphitic nanoribbons

Magnetic response in finite carbon graphene sheets and nanotubes

Mechanical properties of hypothetical graphene foams: Giant Schwarzites

scholarly article in Carbon, vol. 96, January 2016

Metal particle catalysed production of nanoscale BN structures

Metal to Insulator Quantum-Phase Transition in Few-Layered ReS₂.

artículo científico publicado en 2015

Metallic and ferromagnetic edges in molybdenum disulfide nanoribbons

scientific article published on 21 July 2009

Metallic behaviour of boron-containing carbon nanotubes

Metallic edges in zinc oxide nanoribbons

Microscopy Study of the Growth Process and Structural Features of Silicon Oxide Nanoflowers

Microstructural changes induced in “stacked cup” carbon nanofibers by heat treatment

Microstructural evolution of the system Ni–ZrO2–SiO2 synthesized by the sol–gel process

Millimeter-long carbon nanotubes: outstanding electron-emitting sources.

artículo científico publicado en 2011

Mixed-Phase WxMoyCzS2Nanotubes

Model for icosahedral aperiodic graphite structures

scientific article published on 01 September 1993

Molecular Junctions by Joining Single-Walled Carbon Nanotubes

artículo científico publicado en 2002

Molecular dynamics study of the dewetting of copper on graphite and graphene: implications for nanoscale self-assembly.

artículo científico publicado en 2011

Morphology, structure and growth of WS2 nanotubes

Multivalency-Induced Band Gap Opening at MoS2 Edges

N-doping and coalescence of carbon nanotubes: synthesis and electronic properties

Nanocages of layered BN: Super-high-pressure nanocells for formation of solid nitrogen

Nanocomposites: synthesis and elemental mapping of aligned B–C–N nanotubes

Nanotube brushes: polystyrene grafted covalently on CNx nanotubes by nitroxide-mediated radical polymerization

artículo científico publicado en 2005

New Metallic Allotropes of Planar and Tubular Carbon

artículo científico publicado en 2000

New first order Raman-active modes in few layered transition metal dichalcogenides

artículo científico publicado en 2014

Nitrogen-Doped Graphitic Nanoribbons: Synthesis, Characterization, and Transport

article published in 2013

Nitrogen-Mediated Carbon Nanotube Growth: Diameter Reduction, Metallicity, Bundle Dispersability, and Bamboo-like Structure Formation

artículo científico publicado en 2007

Nitrogen-doped graphene: beyond single substitution and enhanced molecular sensing

artículo científico publicado en 2012

Nitrogen–Silicon Heterodoping of Carbon Nanotubes

Nonlinear Behavior in the Thermopower of Doped Carbon Nanotubes Due to Strong, Localized States

Novel Carbon Adsorbents; Contributors

contributor list of a book

Novel NbS2 metallic nanotubes

artículo científico publicado en 2000

Novel hetero-layered materials with tunable direct band gaps by sandwiching different metal disulfides and diselenides ⬇️

artículo científico publicado el 1 de enero de 2013

Novel nanotubes and encapsulated nanowires

On the electronic structure of WS2 nanotubes

artículo científico publicado en 2000

One-dimensional extended lines of divacancy defects in graphene

artículo científico publicado en 2011

Pentagonal rings and nitrogen excess in fullerene-based BN cages and nanotube caps

Phase Modulators Based on High Mobility Ambipolar ReSe Field-Effect Transistors

artículo científico publicado en 2018

Philosophical transactions. Introduction

artículo científico publicado en 2004

Phosphorus and phosphorus–nitrogen doped carbon nanotubes for ultrasensitive and selective molecular detection

artículo científico publicado en 2010

Preparation of aligned carbon nanotubes catalysed by laser-etched cobalt thin films

scholarly article by Mauricio Terrones et al published March 1998 in Chemical Physics Letters

Preparation of aligned multi-walled BN and B/C/N nanotubular arrays and their characterization using HRTEM, EELS and energy-filtered TEM

Pressure Tuning of Bromine Ionic States in Double-Walled Carbon Nanotubes

scholarly article by A. L. Aguiar et al published 8 May 2017 in Journal of Physical Chemistry C

Pressure-Induced Selectivity for Probing Inner Tubes in Double- and Triple-Walled Carbon Nanotubes: A Resonance Raman Study

Probing the interlayer coupling of twisted bilayer MoS2 using photoluminescence spectroscopy.

artículo científico publicado en 2014

Production and Characterization of Single-Crystal FeCo Nanowires Inside Carbon Nanotubes

article

Production and State-of-the-Art Characterization of Aligned Nanotubes with Homogeneous BCxN (1 ≤ x ≤ 5) Compositions

article

Production and detailed characterization of bean husk-based carbon: Efficient cadmium (II) removal from aqueous solutions

artículo científico publicado en 2008

Production of WS2Nanotubes

article

Properties of One-Dimensional Molybdenum Nanowires in a Confined Environment

artículo científico publicado en 2009

Publisher Correction: Carrier lifetime enhancement in halide perovskite via remote epitaxy

scientific article published on 16 October 2019

Pure and doped boron nitride nanotubes

Pyrolytically grown BxCyNz nanomaterials: nanofibres and nanotubes

Quantitative density-functional study of nested fullerenes

scholarly article in Physical Review B, vol. 57 no. 21, June 1998

Quantum Transport in Graphene Nanonetworks

artículo científico publicado en 2011

Recent Advances in Two-Dimensional Materials beyond Graphene

artículo científico publicado en 2015

Resonance Raman study of linear carbon chains formed by the heat treatment of double-wall carbon nanotubes

scholarly article in Physical Review B, vol. 73 no. 19, May 2006

Resonant Raman and Exciton Coupling in High-Quality Single Crystals of Atomically Thin Molybdenum Diselenide Grown by Vapor-Phase Chalcogenization.

artículo científico publicado en 2017

Resonant Raman study on bulk and isolated graphitic nanoribbons

scientific article published on 01 December 2009

Selective Attachment of Gold Nanoparticles to Nitrogen-Doped Carbon Nanotubes

Self-Assembly Synthesis of Decorated Nitrogen-Doped Carbon Nanotubes with ZnO Nanoparticles: Anchoring Mechanism and the Effects of Sulfur

Self-assembly of Si nanostructures

Shape and complexity at the atomic scale: the case of layered nanomaterials

artículo científico publicado en 2004

SiC–SiOx heterojunctions in nanowires

Single-atom doping of MoS2 with manganese enables ultrasensitive detection of dopamine: Experimental and computational approach

artículo científico publicado en 2020

Soft purification of N-doped and undoped multi-wall carbon nanotubes

artículo científico publicado en 2008

Solid-phase production of carbon nanotubes

Spectroscopic characterization of N-doped single-walled carbon nanotube strands: an X-ray photoelectron spectroscopy and Raman study.

artículo científico publicado en 2010

Spectroscopic signatures for interlayer coupling in MoS2-WSe2 van der Waals stacking.

artículo científico publicado en 2014

Spin Polarized Conductance in Hybrid Graphene Nanoribbons Using 5−7 Defects

artículo científico publicado en 2009

Spin Transport of Polyacetylene Chains Bridging Zigzag Graphene Nanoribbon Electrodes: A Nonequilibrium Treatment of Structural Control and Spin Filtering

article published in 2013

Spin dependent transport in hybrid one dimensional BNC systems

Stable BC2N nanostructures: low-temperature production of segregated C/BN layered materials

Stable and solid pellets of functionalized multi-walled carbon nanotubes produced under high pressure and temperature

Strain and the optoelectronic properties of nonplanar phosphorene monolayers ⬇️

artículo científico publicado en 2015

Structural and morphological characteristics of polycrystalline BaTiO3:Er3+, Yb3+ ceramics synthesized by the sol–gel route: influence of chelating agents

Structural, energetic, and electronic properties of gyroidal graphene nanostructures

scholarly article in Carbon, vol. 96, January 2016

Structure and Electronic Properties of Edge-Functionalized Armchair Boron Nitride Nanoribbons

Structure and Electronic Properties ofMoS2Nanotubes

artículo científico publicado en 2000

Structure, Chirality, and Formation of Giant Icosahedral Fullerenes and Spherical Graphitic Onions

scientific article published in 2002

Structure, transport and field-emission properties of compound nanotubes: CN x vs. BNC x ( x <0.1)

Synthesis and characterization of long strands of nitrogen-doped single-walled carbon nanotubes

article published in 2006

Synthesis and electronic properties of coalesced graphitic nanocones

Synthesis and state of art characterization of BN bamboo-like nanotubes: Evidence of a root growth mechanism catalyzed by Fe

Synthesis of SWCNT rings made by two Y junctions and possible applications in electron interferometry

artículo científico publicado en 2007

Synthesis, Characterization and Magnetic Properties of Defective Nitrogen-Doped Multiwall Carbon Nanotubes Encapsulating Ferromagnetic Nanoparticles

Synthesis, Electronic Structure, and Raman Scattering of Phosphorus-Doped Single-Wall Carbon Nanotubes

artículo científico publicado en 2009

Synthetic routes to nanoscale BxCyNz architectures

article by Mauricio Terrones et al published August 2002 in Carbon

Tellurium-Assisted Low-Temperature Synthesis of MoS2 and WS2 Monolayers

artículo científico publicado en 2015

Temperature Dependence of Sensors Based on Silver-Decorated Nitrogen-Doped Multiwalled Carbon Nanotubes

Temperature- and power-dependent phonon properties of suspended continuous WS 2 monolayer films

The Role Of Defects In Graphitic Structures

The Role of Sulfur in the Synthesis of Novel Carbon Morphologies: From Covalent Y-Junctions to Sea-Urchin-Like Structures

The carbon nanocosmos: novel materials for the twenty-first century

artículo científico publicado en 2003

The characterisation of coordination polyhedra by invariants

The flipping of corannulene C20H10through surface transformations and the stability of C20isomers

The formation of ReS(2) inorganic fullerene-like structures containing Re(4) parallelogram units and metal-metal bonds.

artículo científico publicado en 2002

The geometry of hypothetical curved graphite structures

The importance of defects for carbon nanoribbon based electronics

The role of defects and doping in 2D graphene sheets and 1D nanoribbons

artículo científico publicado en 2012

The two peaks G′ band in carbon nanotubes

Theoretical Predictions of Freestanding Honeycomb Sheets of Cadmium Chalcogenides

Theoretical characterization of several models of nanoporous carbon

Thermal stability studies of CVD-grown graphene nanoribbons: Defect annealing and loop formation

Thermolysis of C 60 thin films yields Ni-filled tapered nanotubes

Third order nonlinear optical response exhibited by mono- and few-layers of WS2

Three-dimensional massless Dirac fermions in carbon schwarzites

scholarly article in Physical Review B, vol. 90 no. 12, September 2014

Three-dimensionally bonded spongy graphene material with super compressive elasticity and near-zero Poisson's ratio

artículo científico publicado en 2015

Transparent Foamlike 2D Networks of Nitrogen-Doped Multiwalled Carbon Nanotubes Obtained by Self-Assembly

Tungsten oxide tree-like structures

scholarly article by Yan Qiu Zhu et al published August 1999 in Chemical Physics Letters

Two-dimensional transition metal dichalcogenides: Clusters, ribbons, sheets and more

scholarly article by Ruitao Lv et al published October 2015 in Nano Today

Ultrafast structural evolution and formation of linear carbon chains in single-walled carbon nanotube networks by femtosecond laser irradiation

artículo científico publicado en 2017

Universal In Situ Substitutional Doping of Transition Metal Dichalcogenides by Liquid-Phase Precursor-Assisted Synthesis

artículo científico publicado en 2020

Vertical and in-plane heterostructures from WS2/MoS2 monolayers

artículo científico publicado en 2014

Viability studies of pure carbon- and nitrogen-doped nanotubes with Entamoeba histolytica: from amoebicidal to biocompatible structures

scientific article published on 01 October 2007

WxMoyCzS2 nanotubes

scholarly article in Carbon, vol. 39 no. 7, June 2001

Zipper Mechanism of Nanotube Fusion: Theory and Experiment

artículo científico publicado en 2004

Dominio Público Uruguay está sostenido por:

Acerca de Dominio Público Uruguay

Ayuda