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Synthetic biology—the redesign of biological molecules, structures and organisms—is potentially one of the most powerful emerging technologies today. The modification of biological structures has already been pursued for a variety of nanotechnological objectives; but synthetic biology could provide the tools and understanding needed both to develop 'nanobiotechnology' in a more systematic manner and to expand the scope of what it might achieve. In this article I shall review what has been attained so far in this field, and look at some of the nanoscale possibilities that an engineering approach to cell biology might herald.

Recently, semiconducting nanoparticles have been successfully applied in live mammalian cell cultures, as alternative biological labels for multicolour imaging, by verifying known physiological processes. Here, we report the application of semiconducting nanoparticles to live plant cells in culture. Utilizing this technique, we have uncovered new knowledge regarding the localization of a plant pollen tube adhesion protein, stigma/stylar cysteine-rich adhesin (SCA). The potential of these nanoparticles is evident when the results were compared with conventional immunolocalization methods using fluorescently labelled antibodies.

We present an atomistic self-consistent study of the electronic and transport properties of semiconducting carbon nanotubes in contact with metal electrodes of different work functions, which shows simultaneous electron and hole doping inside the nanotube junction through contact-induced charge transfer. We find that the band lineup in the nanotube bulk region is determined by the effective work function difference between the nanotube channel and source/drain electrodes, while electron transmission through the SWNT junction is affected by the local band structure modulation at the two metal–nanotube interfaces, leading to an effective decoupling of interface and bulk effects in electron transport through nanotube junction devices.

An economic method is presented to grow undoped/doped tungsten oxide nanowires with high purity and erect orientation, simply by heating a tungsten filament in a vacuum chamber with some room air leakage. Tungsten oxide nanowires were studied using scanning electron microscopy (SEM), energy dispersion x-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Wires are found standing straight and clean on the filament,  nm in diameter and up to a few tens of micrometres long. The composition along the wire is uniform for all elements including dopants.

This paper discusses the mechanical effect of water on the deformation of silicon monocrystals under nano-indentation with the aid of molecular dynamics analysis. The rigid TIP4P model was used to simulate the interactions between water molecules while the long-ranged non-bonded Lennard-Jones potential was applied for the pairs of unlike molecules. It was found that upon loading water molecules are lodged into the cavities of the silicon substrate, causing subsurface damage. The diamond cubic structure in the indentation zone transforms into an amorphous state with a body-centred tetragonal form (β-silicon) below the indentor. The presence of water significantly reduces the indentor–silicon adhesion that alters the structure of the residual deformation zone after complete unloading.

We have successfully synthesized multiwall carbon nanotubes by a low temperature solvothermal approach at 310 °C, in which ethoxylated alcohol polyoxyethylene (4) ether was used as carbon source. Transmission electron microscopy observations indicated that the multiwall carbon nanotubes have outer diameters between 5 and 20 nm, and inner diameters between 2 and 8 nm. The length of the multiwall carbon nanotubes is of several micrometres. A possible growth mechanism has been proposed.

Ferromagnetic-film-coated carbon nanotube (CNT) probes were employed in a magnetic force microscope (MFM) observation. We succeeded in making a uniform ferromagnetic film on the CNT probes by improving the coating process and selecting materials. The performance of the CoFe-coated CNT probe was evaluated in ultra-high-density perpendicular magnetic storage media with densities from 600 to 1100 k flux changes per inch (FCI). The magnetic domain structure of the magnetic storage media was clearly observed up to 1100 kFCI. The ultimate lateral resolution of the newly developed MFM probes is down to about 10 nm, which exceeds the bit length of a magnetic recording with a density of Tbit inch⁻².

Atomic force microscopy (AFM) lithography has been performed in La_0.8Ba_0.2MnO₃ (LBMO) films. Unexpectedly, controllable nano-sized patterns can be obtained with an excellent reproducibility under a negative sample bias rather than a positive one, which is completely different from doped SrTiO₃ and high T_C superconductors, though they are of similar perovskite structure. The size of AFM lithography patterns can be controlled well by the sample bias and the selection of tips. Compared to the non-patterned region, AFM lithography patterns exhibit different mechanical, electrical, even possible magnetic properties. Moreover, a simple wet etching can transfer AFM lithography patterns into nano-grooves with a high etching selectivity and without destroying the physical properties of LBMO thin films. It is expected that various spintronic nano-devices will be fabricated with perovskite manganites by AFM lithography and etching techniques.

Silicon nanocrystals (Si-nc) were produced by the implantation of Si⁺ in excess into amorphous quartz and a 1 µm SiO₂ film thermally grown on an Si substrate. In the latter, the photoluminescence (PL) spectra from the Si-nc, induced by Ar⁺ laser excitation, are modulated by Fabry–Perot type interference fringes due to the interference of the emitted light reflected at the Si/SiO₂ interface with that propagating directly towards the surface. In this paper, we investigate the spectral modulation and the PL as a function of the incidence angle of the pump laser and the Si⁺ dose implantation. The modulation of the PL spectra is influenced by the distribution in depth of the pump laser intensity in the SiO₂ layer, the depth distribution of the Si-nc and the refractive index distribution of the layered structures. One goal of our work is to modulate the emission spectra by acting on the thickness of the SiO₂ layer. Simulations have been undertaken to establish a relation between the modulation of the PL spectrum and the depth distribution of both the pump laser intensity and the Si-nc. This study required the precise measurements of the depth distribution of both the complex refractive index (n,k) by ellipsometry and the Si-nc by transmission electron microscopy (TEM).

Nickel oxide nanoparticles with an average diameter of about 9 nm were synthesized via thermal decomposition of NiC₂O₄ precursor at 450 °C. The nanoparticles were investigated using XRD, TEM, TGA, and UV–vis spectrophotometry. The optical absorption spectrum indicates that the NiO nanoparticles have a direct band gap of 3.56 eV. The electrochemical tests show that the ultrafine NiO nanoparticles, as a promising electrode material, can deliver a large reversible discharge capacity of about 610 mA h g⁻¹.

The aim of this study was to develop a viable technology to realize arbitrary shaped and sized patterns embedded in three-dimensional microstructures. In this paper, we present a new fabrication process based on a binary resist process scheme with the combined use of electron-beam lithography and multi-tilted x-ray lithography. We demonstrate the fabrication of three-dimensional photonic crystal structures with embedded waveguides and the fabrication of a flyover micro-fluidic channel.

A nanoscaled Ba_0.5Sr_0.5TiO₃ (BST) powder was successfully synthesized using a modified hydrothermal process at a low temperature (). By dissolving Ba(OH)₂·8H₂O and Sr(OH)₂·8H₂O in deionized water as a base solution, nanocrystalline BST powder can be obtained by mixing an ethanol solution of tetrabutyl titanate with a hot base solution by stirring. The grain size of BST is close to 17–20 nm, as calculated by XRD patterns and confirmed by TEM and SEM measurements. A perovskite structure core material of the nanoscaled BST was successfully self-wrapped by a non-ferroelectric oxide MgO derived from a magnesium nitrate (Mg(NO₃)₂·6H₂O) solution under ultrasonic dispersion. A small amount of ammonia solution was added to this mixture to adjust it to a proper level of acidity in order to form a homogeneous core-shell structure. Straightforward experimental results revealed the formation of a core-shell structure. High-resolution transmission electron microscopy (HRTEM) combined with EDX was used to confirm the composition and its variation. TEM, SEM, and XRD results showed that the average particle size of a core-shell structure was less than 150 nm up to sintering at 1100 °C, depending on the core BST powder and its dispersion.

The ultrafast phase dynamics of carriers in Ge quantum dots (QDs) is studied by using photocurrent correlation phase spectroscopy (PCPS) at room temperature. For better understanding the ultrafast phase dynamics of carriers on the sublevels of Ge QDs, the sublevels in Ge QDs are first investigated by Fourier transform infrared photocurrent spectroscopy, and the result shows that there are two sublevels (0.76 and 0.84 eV) in Ge QDs. The ultrafast phase dynamics signals measured by PCPS are well behaved with a smooth wave line and oscillating trailing edge. The dephasing time has been obtained by numerically simulating the PCPS data in terms of optical Bloch equations. The dephasing time () originating in the transition from the sublevel of the Ge QDs to the conduction band is slightly longer than that () originating in the Si band-to-band transition.

A simple synthetic route for the preparation of luminescent and rodlike CdS nanocrystals embedded in poly(BA -co-GMA -co-GMA-IDA) (PBGM) copolymer templates, by soap-free emulsion copolymerization, is presented. In this study, GMA-IDA chelating groups within the copolymer were the coordination sites for chelating Cd²⁺, at which nanosized CdS nanocrystals were grown by the dry method (H₂S) and the wet method (Na₂S). The particle size and morphology of CdS nanocrystals were observed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). TEM observations demonstrate that the mean diameters of CdS nanoparticles can be prepared between 1 and 2 nm inside the matrix of PBGM membranes by the dry method and between 3 and 6 nm by the wet method. AFM images reveal that CdS nanocrystals on the surfaces of PBGM membranes formed by the dry method have rodlike morphology. The optical absorption spectra indicate a clear blue-shift in the absorption edge for the PBGM-CdS membranes, such that the bandgaps calculated from the absorption spectra are higher than those calculated for the bulk CdS. The particle sizes, estimated from the bandgaps, are in the nanometre range, suggesting that both the particle size and the bandgap can be adjusted via the mole fraction of GMA-IDA in the PBGM membranes. Luminescence spectrophotometry of the samples also indicates a blue-shift in the emission spectra.

We have extended the chemical bath deposition technique modified by microwave irradiation to rapidly deposit ternary oxide Eu:YVO₄ thin films. The obtained films are dense, adherent, and mirror-like. Structure (XRD), morphological (TEM), and optical (UV–vis–NIR and PL) characterizations of the films are presented. The results indicate that the deposited Eu:YVO₄ films with (002) preferential orientation consisted of nano-size grains and had strong emission under UV excitation. The kinetic mechanism of this novel solution processing has been investigated.

A zinc oxide (ZnO) whisker network array with sixfold symmetry was fabricated on ZnO-buffered (0001) sapphire substrate by the vapour-phase transport method using a mixture of zinc oxide and graphite powders as source materials and patterned gold as catalyst. From the ZnO buffer layer, hexagonal ZnO nanorods with identical in-plane structure grew epitaxially along the [0001] orientation to form vertical stems. The branches grew horizontally from six side-surfaces of the vertical stem along and other equivalent directions. Most whiskers were confined along the six preferential orientations and interconnected with each other to form a regular network structure. The growth mechanism is discussed.

Solid-state systems such as P donors in Si have considerable potential for the realization of scalable quantum computation. Recent experimental work in this area has focused on implanted Si:P double quantum dots (DQDs) that represent a preliminary step towards the realization of single donor charge-based qubits. This paper focuses on the techniques involved in analysing the charge transfer within such DQD devices and understanding the impact of fabrication parameters on this process. We show that misalignment between the buried dots and surface gates affects the charge transfer behaviour, and identify some of the challenges posed by reducing the size of the metallic dot to the few donor regime.

Hydroxyapatite (HAp) nanorods, bowknot-like nanostructures and flower-like architectures have been directly synthesized and assembled under microwave irradiation without the help of any templates. The uniform nanorods present an average diameter of about 40 nm and a length of up to about 400 nm. The as-prepared bowknot-like nanostructures consist of sword-like HAp nanorods with a typical width of 150 nm and lengths up to 1–2 µm. The flower-like architectures are composed of leaf-like flakes with typical diameters of 150–200 nm and lengths up to 1–2 µm. The SAED and HRTEM experiments imply that the sword-like HAp nanorods and leaf-like flakes are single crystalline in nature and preferentially grow along the [001] direction. It is found that the pH value and the complex reagent EDTA play important roles in synthesis of the final HAp nanostructures. The possible mechanism is discussed for the formation of the HAp nanostructures in the presence of EDTA under microwave irradiation.

Using a simple method of direct heating of bulk copper plates in air, oriented CuO nanowire films were synthesized on a large scale. The length and density of nanowires could be controlled by growth temperature and growth time. Field emission (FE) measurements of CuO nanowire films show that they have a low turn-on field of 3.5–4.5 V µm⁻¹ and a large current density of 0.45 mA cm⁻² under an applied field of about 7 V µm⁻¹. By comparing the FE properties of two types of samples with different average lengths and densities (30 µm, 10⁸ cm⁻² and 4 µm, 4 × 10⁷ cm⁻², respectively), we found that the large length–radius ratio of CuO nanowires effectively improved the local field, which was beneficial to field emission. Verified with finite element calculation, the work function of oriented CuO nanowire films was estimated to be 2.5–2.8 eV.

In this paper, we report on a direct observation of the morphological evolution of one dimensional (1D) nanocrystals via a systematic metal–organic chemical vapour deposition (MOCVD) study. Several IrO₂ 1D nanostructures have emerged as a result of a decrease in the degree of interface instability. The morphological evolution occurs from triangular/wedged nanorods via incomplete/scrolled nanotubes to square nanotubes and square nanorods according to the morphological stability. The results show that the polycrystalline films composed of continuous 3D grains belong to the most stable form as compared to the 1D nanocrystals. The shape evolution has been found to highly correlate to a morphological phase diagram based on the growth kinetics.

A resonator system has been fabricated directly on a pre-processed CMOS chip. The system is to be used for high sensitivity mass sensing applications in air and vacuum. The resonator system, corresponding of a cantilever and structures for electrostatic actuation and capacitive read-out, have been defined by electron beam lithography on top of a charge and radiation sensitive CMOS layer in predefined areas as a post-process step. This has been accomplished without affecting the electronic properties of the pre-processed CMOS circuits. The subsequent etching steps to fully release the cantilevers have been obtained without stiction of the cantilevers to the substrate. Cantilevers are driven at their mechanical resonance in a lateral mode, and the frequency is monitored by capacitive read-out on the chip. CMOS integration enables signal detection directly on the chip, which radically decreases the parasitic capacitances. Consequently, low-noise electrical measurements with a very high mass sensitivity are obtained. Fabricated resonator systems were characterized to have resonance frequencies of approximately 1.49 MHz, which is in good agreement with a theoretical estimation of 1.41 MHz. The theoretical mass resolution, , is approximately 17 ag Hz⁻¹, using a Young modulus value of 160 GPa.

Ultra-thin alumina films with self-ordered cylindrical vertical pores were fabricated on a p-type silicon substrate by anodization of Al films with thickness in the range of 30–500 nm in sulfuric or oxalic acid aqueous solutions. In both cases the pores were arranged in hexagonal cells in a close-packed structure and their diameter and density depended on the electrochemical solution used. In the case of sulfuric acid both 30 and 500 nm Al films resulted in a similar uniform porous structure using exactly the same anodization conditions for both thicknesses, the pore diameter being in the range of 10–30 nm and their density of the order of 6–8 × 10¹⁰ pores cm⁻². In the case of oxalic acid the 500 nm thick films resulted in a uniform porous structure with larger pores than in sulfuric acid, of diameter in the range of 20–40 nm and a density of the order of . On the other hand, with oxalic acid it was impossible to form a uniform porous structure from the 30 nm thick Al film at the same conditions as used for the 500 nm thick film. Plan-view and cross-sectional transmission electron microscopy was used to investigate systematically the structure and morphology of the alumina films. Cross-sectional TEM images showed that the alumina/Si interface was sharp, but a void was observed beneath each pore, separated from the pore by a thin alumina layer. The same structure was obtained with both electrolytes. The effect of pre-annealing of the Al films on the anodic alumina layers was also investigated in detail.

Transparent polycrystalline ZnS nanobelts have been grown by chemical bath deposition within the pores of polyvinyl alcohol on glass and Si substrates. Zinc acetate and sodium sulphide, dissolved in an alkaline medium, were taken as the source of zinc and sulfur respectively. X-ray diffraction and transmission electron microscopy studies confirmed the cubic nanocrystalline ZnS phase formation. TEM micrographs of the films revealed the formation of ZnS nanobelts of width 5–20 nm and length of a few microns. UV–vis spectrophotometric measurement showed high transparency (around 80% in the wavelength range 350–800 nm) of the film with a direct allowed band gap in the range 4.03–3.90 eV; the band gap decreases with the increase of deposition temperature. Studies of the dielectric properties showed high dielectric constant (in the range 70–130) compared to only PVA and bulk ZnS thin film.

Polyaniline (PANI) composite microwires containing CdS nanoparticles were synthesized guided by poly(acrylic acid) (PAA). It was found that the morphology of the composite microwires was affected by the concentration of PAA. When the concentration of PAA was lower than 0.1 mg ml⁻¹, the PANI/CdS composite was wires. However, no wire-like structures of PANI/CdS composites were formed when the concentration of PAA was higher than 1.0 mg ml⁻¹. The complex of CdS nanoparticles with PANI matrix was affected by the molar ratio of CdS to aniline. When the molar ratio was 1:75, CdS nanoparticles were well combined with PANI matrix. However, when the molar ratio was 1:150, no CdS nanoparticles were combined with PANI wires. SEM, TEM, FTIR and XRD characterized the PANI/CdS composite microwires and proved that the CdS nanoparticles are combined with the PANI matrix in some conditions, and TEM proved that some of the microwires are in fact of helical shape. The photoluminescence of CdS is slightly affected by its combination with the PANI matrix.

The synthesis, and thermophysical and mechanical properties of anhydride-cured biobased epoxy containing diglycidyl ether of bisphenol F (DGEBF) epoxy and epoxidized linseed oil (ELO) reinforced with fluorinated single-wall carbon nanotubes (FSWCNT) are reported. Sonication was used to disperse FSWCNT in the biobased glassy epoxy network, resulting in great improvement of the modulus of nanocomposites containing extremely small amounts of FSWCNT. The glass transition temperature of the obtained nanocomposites decreased by approximately 30 °C after the addition of 0.20 wt% (0.16 vol%) FSWCNT, without adjusting the amount of the anhydride curing agent. This was because of the non-stoichiometry of the epoxy matrix, caused by the fluorine on the single wall carbon nanotubes. The adequate amount of the anhydride curing agent needed to achieve stoichiometry was experimentally determined by dynamic mechanical analysis (DMA). The storage modulus of the epoxy at room temperature, which is below the glass transition temperature of the nanocomposites, increased up to 0.44 GPa with the addition of only 0.24 wt% (0.20 vol%) of FSWCNT, representing an up to 14% improvement from the modulus of the biobased ELO neat epoxies. The fracture toughness of the neat biobased ELO epoxies was also improved by approximately 43% upon addition of FSWCNT. The excellent improvement of the modulus was achieved without sacrificing the fracture toughness.

Using a first-principles method, we study field emission properties of double-wall carbon nanotubes with various end geometries and combinations of inner and outer walls. The open double-wall nanotubes exhibit substantial contribution to the emission current from the extended π states. These states are insensitive to the detailed tip structure or the presence of foreign adsorbed molecules and the resulting emission current is expected to be stable under moderate vacuum environment. The mechanical stiffness also increases significantly compared to the single-wall nanotube, ensuring prolonged device lifetime under high-field operating conditions of the field emission display.

We found a novel morphology variation of carbon deposition derived from CH₄ decomposition over Ni-based catalysts. By altering the chemical composition and particle size of Ni-based catalysts, carbon filaments, nanofibres and nanotubes were observed over conventional Ni /γ-Al₂O₃, Ni–Co /γ-Al₂O₃ and nanoscale Ni–Co /γ-Al₂O₃ catalysts, respectively. The simple introduction of Co into a conventional Ni /γ-Al₂O₃ catalyst can vary the carbon deposition from amorphous filamentous carbon to ordered carbon fibres. Moreover, carbon nanotubes with uniform diameter distribution can be obtained over nanosized Ni–Co /γ-Al₂O₃ catalyst particles. In addition, the oxidation behaviour of the different deposited carbon was studied by using a temperature-programmed oxidation technique. This work provides a simple strategy to control over the size and morphology of the carbon deposition from catalytic decomposition of CH₄.

Suspended nanotubes or nanowires can be used in line-of-sight depositions to produce nanometre-scale lines. Reported here is the experimental quantification of line-of-sight shadow widths for multiwalled carbon nanotubes that are suspended (400 nm) over a silicon nitride (Si₃N₄) membrane (transmission electron microscopy) TEM grid by a lithographically defined resist line array. Aluminium evaporation was performed at incident angles of 0.7°–2.0° by use of the slit (0.81 mm diameter). Shadow widths and carbon nanotube diameters were directly observed by scanning transmission electron microscopy (STEM). Observed gaps were less (0–7 nm) than that predicted from simple line-of-sight geometry. Thus, surface migration assisted by the momentum of incident metal evaporant may be an important mechanism in nanoscale shadow lithography processes.

We have calculated the minimum chip area overhead, and hence the bit density reduction, that may be achieved by memory array reconfiguration (bad bit exclusion), combined with error correction code techniques, in prospective terabit-scale hybrid semiconductor/nanodevice memories, as a function of the nanodevice fabrication yield and the micro-to-nano pitch ratio. The results show that by using the best (but hardly practicable) reconfiguration and block size optimization, hybrid memories with a pitch ratio of 10 may overcome purely semiconductor memories in useful bit density if the fraction of bad nanodevices is below , while in order to get an order-of-magnitude advantage in density, the number of bad devices has to be decreased to . For the simple 'Repair Most' technique of bad bit exclusion, complemented with the Hamming-code error correction, these numbers are close to 2% and 0.1%, respectively. When applied to purely semiconductor memories, the same technique allows us to reduce the chip area 'swelling' to just 40% at as many as 0.1% of bad devices. We have also estimated the power and speed of the hybrid memories and have found that, at a reasonable choice of nanodevice resistance, both the additional power and speed loss due to the nanodevice subsystem may be negligible.

The mechanochemical processing properties of silicon are evaluated by diamond-tip sliding using atomic force microscopy (AFM) in the atmosphere. Sharp-diamond-tip sliding produces grooves on the silicon surface. In contrast, large-radius-diamond-tip sliding produces protuberances on the silicon surface. Potassium hydroxide (KOH) solution etching is performed on the mechanochemically processed areas. Processed protuberance areas are hardly etched with KOH solution. In particular, the processed area, in which plastic deformation is observed, also acts as an etching mask for KOH solution. By application of this mechanochemical local oxidation area as a KOH solution etching mask, three-dimensional nanoprofiles such as three 1000 nm × 1000 nm squares, lines and spaces with a 200 nm period and a two-step table were fabricated on a silicon surface. By using thick oxidized mechanochemically processed masks with a high load and removal of the natural oxide layer by mechanical action with a low load, nanometre-scale three-dimensional profiles were processed by additional KOH solution etching.

The measurement of optical extinction is used to determine the size of nearly spherical gold nanoparticles suspended in solution, produced by a 'reverse micelles' process. The contrast between the maximum and the minimum in the extinction spectra around 450 and 520 nm shows a linear dependence with the mean radius of the gold particles less than 3 nm; however, the method can be used to size particles up to 7 nm. Experimental results for extinction spectra can be fitted by Mie's theory if the optical constants from bulk material values are modified by introducing the limitation of the mean free path due to collisions of conduction electrons with the boundary of the nanoparticles.

Water-soluble Prussian-blue (PB) analogue transition metal hexacyanoferrate (HCF) nanoparticles FeHCF, CoHCF, NiHCF and CuHCF have been synthesized by using poly(N-vinyl-2-pyrrolidone) as a protective matrix. Transmission electron microscopy (TEM) images of the synthesized PB analogues showed stable and well dispersed nanoparticles with fairly narrow size distributions. Depending on transition metal ions, the PB analogue nanoparticles exhibited various novel shapes but with similar average sizes within the range of 45–60 nm. Spherical NiHCF, cubic CoHCF and CuHCF, and frustum-of-pyramid-like FeHCF nanoparticles, have been characterized from the TEM images. X-ray diffraction (XRD) analysis further identified a face-centred cubic structure of the nanoparticles. The FTIR and UV–vis spectroscopy were employed to investigate the optical properties of the nanoparticle–PVP composites, showing distinguished optical and electronic transitions from conventionally synthesized nanoparticles. The effect of feed ratio of PVP to transition metal ions on the size and optical properties of the nanoparticles was also discussed.

We present a model describing the temperature dependence of the resistivity of the Al₉₂Sm₈ system during formation of fcc-Al nanocrystals. We take into consideration changes in resistivity of the amorphous phase due to the changing content of Al, the varying density of the crystallization nuclei, the creation of the Sm layer on the grain surface and decomposition appearing during annealing of the amorphous phase.

Our calculations exhibit a better agreement with experimental electrical resistivity data for the nanocrystallization model considering previous decomposition of amorphous structure and formation of a monatomic Sm layer on grain boundaries than for a model of nanocrystallization on quenched-in nuclei with growth controlled by diffusion with a diffusion field impingement.