bluuebunny/crossref_metadata_2025 huggingface dataset:
Bone loss after childhood acute lymphoblastic leukaemia: an observational study with and without GH therapy
Authors: Follin Cecilia , Link Katarina , Wiebe Thomas , Moëll Christian , Björk Jonas , Erfurth E M
Published: March 2011

Objective

Bone mineral density (BMD) in survivors of acute lymphoblastic leukaemia (ALL) seems to vary with time, type of treatments and GH status. We aimed to evaluate BMD in ALL patients with GH deficiency (GHD), with and without GH therapy.

Design

Case–control study.

Methods

We examined 44 (21 women) GHD patients (median 25 years) treated with cranial radiotherapy (18–24 Gy) and chemotherapy and matched population controls for BMD with dual-energy X-ray absorptiometry. For 5 and 8 years, two subgroups with (0.5 mg/day) (n=16) and without GH therapy (n=13) and matched controls were followed respectively.

Results

At baseline, no significant differences in BMD or Z-scores at femoral neck and L2–L4 were recorded (all P>0.3). After another 8 years with GHD, the Z-scores at femoral neck had significantly decreased compared with baseline (0.0 to −0.5; P<0.03) and became lower at the femoral neck (P=0.05), and at L2–L4 (P<0.03), compared with controls. After 5 years of GH therapy, only female ALL patients had a significantly lower femoral neck Z-scores (P=0.03). The female ALL patients reached an IGF1 level of −0.7 s.d. and male patients reached the level of +0.05 s.d.

Conclusions

On average, 25 years after diagnosis, GH-deficient ALL patients experienced a significant decrease in Z-scores at femoral neck, and if Z-scores continue to decrease, there could be a premature risk for osteoporosis. GH therapy was not shown to have a clear beneficial effect on BMD. Whether higher GH doses, particularly in women, will improve Z-scores needs further investigation.
Associations of IGF1 and IGFBPs 1 and 3 with all-cause and cardiovascular mortality in older men: the Health In Men Study
Authors: Yeap Bu B , Chubb S A Paul , McCaul Kieran A , Ho Ken K Y , Hankey Graeme J , Norman Paul E , Flicker Leon
Published: March 2011

Objective

Circulating IGF1 declines with age while ill-health increases. Controversy remains whether differences in the levels of IGF1 and its binding proteins 1 and 3 (IGFBP1 and IGFBP3) determine health outcomes during ageing. We examined associations of IGF1, IGFBP1 and IGFBP3 with all-cause and cardiovascular mortality in older men.

Design

We conducted a prospective cohort study of community-dwelling men aged ≥70 years.

Methods

Plasma collected at baseline (2001–2004) was assayed for total IGF1, IGFBP1 and IGFBP3. Incidence and causes of death from time of recruitment to 31 December 2008 were ascertained using the Western Australian Data Linkage System. Cox regression analyses were performed, adjusting for conventional cardiovascular risk factors.

Results

Among 3983 men followed for 5.2 years (median), 694 deaths occurred, 243 from cardiovascular disease (CVD). There was no difference in survival according to quintiles of IGF1. Increased IGFBP1 predicted increased all-cause mortality (highest versus lowest quintile: adjusted hazard ratio (HR)=1.98, 95% confidence interval (CI)=1.52–2.57, P<0.001 for trend) and increased cardiovascular mortality (HR=3.42 (2.03–5.77), P<0.001 for trend). Decreased IGFBP3 predicted increased all-cause mortality (lowest versus highest quintile: HR=1.57, 95% CI=1.23–2.01, P=0.007 for trend). Associations of IGFBP1 and IGFBP3 with all-cause mortality were not attenuated by adjustment for IGF1 levels.

Conclusions

In older men, higher IGFBP1 and lower IGFBP3 levels predict overall and CVD-related mortality, while IGF1 levels are not associated with mortality. Further studies are needed to clarify the underlying mechanisms by which IGFBP1 and IGFBP3 levels are associated with mortality risk, and whether this occurs independently of IGF1.
Probiotics and pregnancy
Authors: Wacha Judit , Szijártó Attila
Published: March 2011

Prenatal care is one of the great challenges in the medicine. Aims of therapies and protocols may influence the life of mothers and babies. Diseases occurring during pregnancy are dubious, because of their potential danger and difficulties in their treatment strategy. Prevention must be emphasized using safe and natural drugs. Pre- and probiotics are in focus of the medical science. Publications and studies suggest the importance of these drugs in evidence base medicine. Safe methods are essential in prenatal care. Authors review published data on the effect and potential use of pre- and probiotics during pregnancy. Orv. Hetil., 2011, 152, 420–426.
Composites for Electronic Substrate Applications
Authors: Gerhardt R.
Published: March 2011

The need for low dielectric constant, high thermal conductivity, matched thermal expansion and co-processability in electronic substrates is reviewed. Since no single phase material is able to satisfy all the requirements, a microscopic composite approach is proposed. Recent experimental evidence supporting the concept is also presented.
Advanced Materials for Printed Circuit Boards
Authors: Wang David Wei
Published: March 2011

The printed circuit board is an integral part of the electronic packaging hierarchy. Its use began more than 40 years ago, and the demand for printed circuit boards has increased in parallel with the growth of the electronics industry.[1] According to a recent forecast, the worldwide production of printed circuit boards will reach to over 19 billion U.S. dollars' worth by 1990.[2] With continuing demands for more interconnections, the multilayer circuit board industry is experiencing its fastest growth rate. Boards with more than 20 inner planes of circuitry are being manufactured with high reliability.

Based on dollar values, more than 90% of the circuit boards produced are in the rigid board category, where starting materials are based on thermosetting prepregs produced by a solution impregnation method. This article is a review of materials currently used in rigid composites.
High Performance Silicone Gel as IC Device Chip Protection
Authors: Wong C. P.
Published: March 2011

Recent advances in IC device encapsulants and polymeric materials have made high reliability VLSI plastic packaging a reality. High performance silicone gel possesses excellent electrical and physical properties for IC protection. With their intrinsic low modulus and soft gel-like nature, silicone gels have become very effective encapsulants for the delicate larger chip size and wire-bonded VLSI chips. Recent studies indicate that adequate IC chip surface protection with high performance silicone gels in plastic packaging could possibly replace conventional ceramic: hermetic packaging. This paper will review some potential IC encapsulants. Special focus will be placed on the high performance silicone gel, its chemistry, and its application as a VLSI device encapsulant.
Chemistry of Adhesion at the Polyimide-Metal Interface
Authors: Grunze M. , Unertl W. N. , Gnanarajan S. , French J.
Published: March 2011

This article describes recent studies of the chemistry of adhesion between thin (d ≥ 11 Å) polyimide films and silver and copper substrates, and the structural changes in the polymer when polyamic acid is imidized to polyimide. The thin polyamic acid films were formed by vapor phase deposition of 1,2,4,5-benzenetetracarboxylic anhydride (PMDA) and 4,4-oxydianiline (ODA) under high vacuum conditions and subsequent imidization by heating in vacuum. Both ODA and PMDA are at least partially dissociated upon adsorption onto clean copper and silver and with increasing film thicknesses react to form the polyimide precursor, polyamic acid. Heating to T ≥ 425 K leads to polymerization to form polyimide films which are thermally stable to about 700 K. Polyimide films with mean thicknesses as small as 1.1 nm have been fabricated in this way and their bonding to the substrate as determined by x-ray photoemission studies is su marized. Infrared reflection absorption data gives further evidence that the polyimide bonds to the substrate via fragmented PMDA. Changes in the surface topography and molecular structure of the films during imidization are demonstrated by scanning tunneling micrographs and infrared reflection absorption data.
Etching and Surface Modification of Polymers in CF4/O2 Plasma Discharges
Authors: Scott P. M. , Babu S. V. , Partch R. E. , Matienzo L. J.
Published: March 2011

Some results of simultaneous measurement of polyimide etch rates, temperature, and O− and F− atom emission intensities in CF4/O2 plasma discharges are described. Several process variables have been investigated both during steady and unsteady plasma reactor operation. Atomic compositions on the polymer surface have been determined as a function of time of exposure to the plasma using ESCA, and the C IS spectra apalyzed to identify the various C-O and C-F bonds.
Aluminum Nitride fibers from a Thermoplastic Organoaluminum Precursor
Authors: Bolt John D. , Tebbe Fred N.
Published: March 2011

A new organoaluminum polymer (EtAINH)n(Et2AlNH2)m·AlEt3 derived from triethylaluminum and ammonia, is thermoplastic at elevated temperatures and a glassy solid at ambient temperature. As a thermoplastic it can be processed in certain shapes, solidified, cured and transformed to dense aluminum nitride with retention of its shape. Aluminum nitride fibers are prepared by melt spinning the polymer, pyrolyzing in ammonia and at high temperature in nitrogen. The AlN microstructure forms as very fine particles at 400–600°C, coarsens at higher temperature, and densifies at 1600–1800 °C into polycrystalline AlN with submicron grains. Mechanical strength, thermal expansion and dielectric constant are consistent with bulk ceramic values. Initial thermal conductivity deduced from composite measurements is 82 W/m°K in fibers containing 0.5 to 1.0 percent oxygen.
Diffusional Processes in Metallurgical Interconnections
Authors: Kang S. K. , Woychik C. G.
Published: March 2011

Diffusional processes, either solid- or liquid-state, are essential in promoting reliable metallurgical interconnections used in many electronic
packaging applications. The same phenomena often degrade the integrity and reliability of the interconnections as well. In this talk, both examples
are presented to illustrate how the diffusional processes are important in many interconnection technologies. Thermocompression bonding, eutectic
bonding, soldering and liquid-phase bonding are chosen for this purpose. Several issues related to soldering, such as dissolution, intermetallic
formation and microstructure of solder joints, will also be discussed in terms of diffusional processes.
Identification of the Failure Mechanism of a Thin Film on a Thick Substrate by Means of Synchrotron X-Ray Topography Combined with Transmission Electron Microscopy
Authors: Goyal D. , Ng W. , King A. H. , Bilello J. C.
Published: March 2011

We have used synchrotron x-ray topographic techniques to study the stresses in thin films formed upon silicon substrates either by evaporation or sputtering. It is found that the film stress generally decreases with increasing film thickness for evaporated films, but film delamination occurs at a well defined film thickness. Transmission electron microscope studies have been performed on the same specimens in order to reveal what mechanisms are involved with the delamination of the films.
Reaction Diffusion in the Au-Cu-Pb-Sn System at Low Temperature
Authors: Roeder J. F. , Notis M. R. , Goldstein J. I.
Published: March 2011

The microstructure of a Cu3Au v. Pb-5wt%Sn diffusion couple was examined in the as-dipped and annealed conditions. The as-dipped couple showed no reaction between the solder and the base metal. The couple developed intermediate layers of two intermetallic phases upon annealing for 289 hours at 169°C. These phases were identified as phi and eta’ which are contained in the Au-Cu-Sn ternary system. No phases containing significant amounts of Pb formed, indicating that even at low concentrations in a Pb-Sn solder, Sn is the active chemical specie in the solder for the Au-Cu-Pb-Sn system. The microhardness of the eta’ phase was found to be equal to that of Cu3Sn, which forms in the absence of Au in the Cu base metal. However, the the phi phase was harder, and therefore the presence of Au in the base metal may adversely affect the thermal fatigue resistance of the solder joint.
Nb Contacts to GaAs: Thermal Stability and Phase Formation
Authors: Schulz Kevin J. , Zheng Xiang-Yun , Chang Y. Austin
Published: March 2011

The applicability of Nb as a Schottky barrier on GaAs depends to a large extent on the thermal stability of the contacts. In this study, bulk diffusion couple and phase diagram studies in addition to thin film studies were completed to understand the stability of and the reactions at the Nb/GaAs interface. Nb thin films were deposited onto GaAs substrates by dc magnetron sputtering and were annealed in the temperature range 300 to 1000°C. Analysis was done using plan-TEM and XTEM. The Nb/GaAs interface was found to break down into a series of binary compounds above 500°C. Bulk diffusion couples annealed at 600°C were analyzed using an electron microprobe. The stable sequence of phases formed in the couple, i.e., the diffusion path, was determined and was used to rationalize the observed compound formation in the thin film contact system.
Production Contact Via Etching for GaAs MMICs.
Authors: Astell-Burt P. J. , Ditmer G. A. , Kadakia V. B. , Cochran B. C. , Webb D-R
Published: March 2011

Research has been undertaken in several major research laboratories to achieve a commercially successful GaAs via hole etching process. This work presents the achievement of results with the desired characteristics for through-wafer GaAs interconnects or vias, for production of MMICs.

We report vias acceptable for use in the production of microwave GaAs field effect transistors fabricated by a reactive ion etching process. Using conventional resist masks and non toxic gases, aspect ratios of up to 10:1 have been achieved with via sizes as small as 40μm × 40μm. Typical wafer thicknesses were greater than 100μm and the process showed high selectivity to the frontside metallization. The etching conditions had to be varied as a function of overall substrate area and exposed GaAs. To determine optimum process parameters, the RF power and resultant DC bias; gas flow rates and ratios; and system pressure were systematically varied. The effects of changes in area of wafer to be etched and of the composition of the electrode material were also studied. Details are presented of the optimum etching parameters for use in 2″ and 3″ GaAs MMIC production.
Thermal Stability of Amorphous Ni-Nb Thin Films for Use as Diffusion Barriers
Authors: Farrens S. N. , Perepezko J. H. , Doyle B. L. , Lee S. R.
Published: March 2011

The interdiffusion and crystallization reactions between amorphous Ni-Nb alloy films and Si substrates and several overlayer metals have been monitored by x-ray diffraction and high resolution Rutherford backscattering spectroscopy. Free standing amorphous thin films of Ni-Nb alloys crystallize in one hour at temperatures between 600–625 °C and show little dependence of the crystallization temperature, Tx, on composition over the range from 30–80 at.% Ni. However, in films that are sputter deposited onto Si substrates Tx tends to increase with increasing Nb composition. Ni60Nb40 samples without overlayers crystallize at 650–700 °C. Enhancement of the thermal stability to 700–750 °C is achieved with a Nb overlayer. In contrast, a Ni overlayer can reduce Tx to 450 °C. At the film/substrate interface silicide formation reactions with Ni from the film contribute to a destabilization of the amorphous alloy. The modification of Tx with Ni, Nb, and other overlayers appears to be related to changes in the reaction kinetics associated with penetration of the overlayer into the film.
Recent Advances in Thin Film Multilayer Interconnect Technology for IC Packaging
Authors: Jensen Ronald J.
Published: March 2011

A high-performance packaging technology being developed at Honeywell and a number of other companies uses thin-film processes to pattern high-density interconnections in multiple layers of a high-conductivity conductor (e.g., copper) and a polymer dielectric, primarily polyimide. This paper describes the physical characteristics and unique advantages of this thin film multilayer (TFML) interconnect technology; it then summarizes the results of recent work done at Honeywell in processing TFML structures, assessing the stability and reliability of the materials system, and fabricating test vehicles and demonstration packages.
Burial Effects on Nuclear Waste Glass
Authors: Hench Larry L. , Werme Lars , Lodding Alexander
Published: March 2011

The purpose of this experiment was to evaluate the effects of various components of the SKBF/KBS nuclear waste storage system on the leaching of the vitreous waste form. Two cohfigurations of nuclear waste glasses, canisters, overpacks, and backfill mate-7ial were inserted into 5.6 cm x 3 m deep boreholes located at the 350 m level in the STRIPA mine. Some were maintained at 90°C. The others were allowed to equilibrate at the ambient temperature of the mine, approximately 8°C. Two borosilicate nuclear waste glass compositions (termed ABS 39 and ABS 41) compatible with the French AVM process containing 9 percent by weight of simulated fission products were compared. The two compositions ( Table 1) bracket the range of Si02/Na2O/B203 ratios likely to be selected for commercial vitrification operations at La Hague.
The Chemical Durability of Some Hlw Glasses: Effects of Hydrothermal Conditions and Ionising Radiation
Authors: Cousens D.R. , Lewis R.A. , Myhra S. , Segall R.L. , Smart R.St.C. , Turner P.S.
Published: March 2011

The time dependence of leaching and dissolution under hydrothermal conditions at 250°C has been investigated in an autoclave designed for continuous sampling; it is found that the rates are in accord with those obtained by the commonly used procedures. The effect of pressure by itself has been studied in an ultracentrifuge; ambient rates for Si and Na loss remain unchanged up to about 40 MPa followed by a monotonic increase to about 1.5 times the ambient rates at 160 MPa. The surface layers formed as a result of chemical attack have been examined (XRD, IR, XPS and PIXE). It is found that Zn present in the glass or in the solution is retained in the siliceous layer which in some circumstances contains a crystalline zinchydroxy- silicate phase. A method for enhancing rates of displacement damage by a factor of ∼106 has been developed. Powdered borosilicate glass and glass doped with UO2 have been neutron-irradiated in a high-flux reactor. Damage is thereby introduced in the bulk as a result of 10B(n,α)7Li and (n,fission) events and subsequent slowing-down of energetic charged ions. Irradiation doses equivalent to 106 years HLW storage have been achieved. The resultant stored energy of ∼102 kJ kg−1 is released over the range 300 to 800 K. The initial leaching/dissolution rates are found to be increased by a factor of about three by irradiation; the changes in longer-term rates are difficult to determine due to the effects of back-reactions and changing particle size geometry and size distribution, but significant enhancement is found. Rates for fission and activation products are similar to those for bulk species.
Chemical Stability of Simiulated HLW Forms in Contact With Clay Media
Authors: Van Iseghem P. , Timmerans W. , De Batist R.
Published: March 2011

The corrosion stability of six simulated HLW forms proposed by several European countries (five borosilicate glasses and one borosilicate glass ceramic) in contact with different media relating to the clay disposal has been investigated for periods up to 80 days and at a surface area to solution volume ratio of 1 cm−1 under non de-aerated conditions. In the reference medium distilled water the corrosion stabilities are largely determined by saturation effects for elements such as Si, Ca, Mg, Sr, Fe and U. Si saturation is found to be enhanced by a large Al2O3 concentration in the glass. In the clay-water mixture these saturation effects are much less predominant. Wet clay attacks the waste forms faster than the clay-water mixture, although the corrosion rates tend to decrease with time in both clay media. In general, no simple Arrhenius-type temnnerature dependence for the corrosion behaviour is found for the interval between 40 and 200°C.
The Mechanisms for Hydrothermal Leaching of Nuclear Waste Glasses: Properties and Evaluation of Surface Layers
Authors: Malow GÜnter
Published: March 2011

Remobilization of solidified high-level waste by corrosion and transport of radionuclides by groundwater are the only likely events for radioactivity to find its way back to the environment. The interaction of the waste form with aqueous solutions is the most important mechanism and must be known for safety and risk analysis. It has been shown that the activity release depends on a number of experimental and environmental parameters. The corrosion mechanisms of the waste forms control the leach rate of individual components. Of particular importance to the resistance against water attack of various glass compositions is the formation of layers on the glass surface. The results for leaching in deionized water reveafed that the mechanism was strongly influenced by the formation of a surface layer which determined the further attack on the glass. In this work the specific weight losses of the glass after leaching in rock salt and MgCl2–MgSO4-NaCl-KCl solutions were measured and surface layers investigated.
Investigation on the Oxidation State and The Behaviour of Molybdenum in Silicate Glass
Authors: Horneber Anette , Camara Boubacar , Lutze Werner
Published: March 2011

Knowledge about the oxidation state of molybdenum in glasses and glass ceramics which contain nuclear waste is important because of the danger of formation of water-soluble Cs-molybdate with Cs-137. In a previous paper , the behaviour of molybdenum in glasses with and without fission products was investigated with the aid of ESR and optical spectroscopy.
The Materials Balance-Scientific Fundamentals for the Quality Assurance of Vitrified Waste
Authors: Schiewer Edwin , Rabe Harald , Weisenburger Siegfried
Published: March 2011

In the vitrification of HLW the aim is to create a product, the stability (thermal, mechanical) of which is, to the greatest possible degree, independent of fluctuations in its composition. Process control during vitrification of HLLW is necessary in order to assure the quality of the final glass product. The chemical processes are controlled by quantitative analysis of all material streams entering and leaving the melting device. There are six material streams to consider: frit input, waste input, corrosion products (generated by the vitrification process), off-gas, recycled off-gas, glass output. Additionally, the capacity of the glass for buffering short-term fluctuations in the incoming streams must be known. Sufficient sampling during non-radioactive vitrification in addition to materials tests can provide the necessary data basis. The results are combined in a materials balance.
The Microstructure of Synroc
Authors: Cousens D.R. , Myhra S. , Penrose J. , Segall R.L. , Smart R.St.C. , Turner P.S.
Published: March 2011

The Synroc concept was introduced by Ringwood in 19781 and, as is well known, the material now proposed for the disposal of hiah-level civilian nuclear waste consists primarily of hollandite (BaAl2 Ti6016), perovskite (CaTiO3) and zirconolite (CaZrTi207).
Near-Surface Leaching Studies of Pb-Implanted Savannah River Waste Glass
Authors: Arnold G. W. , Northrup C. J. M. , Bibler N. E.
Published: March 2011

Ion implantation into simulated nuclear waste glasses is a rapid means of producing near-surface energy deposition similar to that produced by α-recoil nuclei after long storage times (typically 103 – 106 years). For example, Dran, Maurette, and Petit1 used 200 keV Pb-ion implantations in glass at a fluence of 5 × 1012/cm2 to produce surface damage. This fluence is equivalent to approximately 2 × 1018 alpha-decays/cm3 which corresponds to approximately 106 years storage for glass containing Savannah River Plant (SRP) defense high-level waste (DHLW). These authors1 found that this fluence value corresponded to a critical fluence (Φc) for enhanced etching (a factor of 20 increase as inferred by step-height changes) for several silicate glasses when etched in a NaCl solution at 100°C. This critical fluence value also corresponds very well with the fluence at which significant overlap of individual ion tracks occurs.
Stability and Alteration of Naturally Occurring Low-Silica Glasses: Implications for the Long term Stability of Waste Form Glasses
Authors: Allen Carlton C.
Published: March 2011

Volcanic glass of basaltic composition (approximately 50 wt.% SiO2) was studied as a natural analogue to proposed nuclear waste form glasses. Basaltic glass can resist devitrification and remain glassy for periods in excess of 10 m.y. Surface alteration of the glass occurs rapidly upon exposure to water or hydrothermal fluids, but is essentially absent if the glass remains dry. Alteration is restricted to a rind of clay-like, cryptocrystalline palagonite, generally less than 100 μm thick. Formation of this rind protects the underlying glass from further alteration. Similar rinds, or “gel layers”, have been produced in laboratory and field tests with borosilicate glasses. Major cations within the basaltic glass are selectively depleted or enriched relative to the glass in the alteration rind. Qualitatively-similar depletion and enrichment patterns characterize the short-term leaching behavior of candidate waste form glasses.
Investigation of Titanium in Metamict Nb-Ta-Ti Oxides Using the Extended X-Ray Absorption Fine Structure Technique
Authors: Greegor R. B. , Lytle F. W. , Ewing R. C. , Haaker R. F.
Published: March 2011

Recent proposals have suggested that radioactive wastes can be isolated 1 as dilute solid solutions in a crystalline, titanate assemblage. One titanate assemblage, SYNROC, consists of zirconolite (CaZrTi207), perovskite (CaTiO3) and "hollandite" (BaAl2Ti6016) with additional accessory phases. There are two major problems in the evaluation of the long term stability of any crystalline wasteform such as SYNROC: 1) it is difficult to assess the long term stability of materials from short term laboratory experiments that are not necessarily valid simulations of complex geochemical processes, and 2)the corresponding titanate minerals are uncommon, making it difficult to study long term alteration and radiation effects on a significant number of specimens from different localities and geologic environments. There has even been considerable controversy concerning the stability of the reasonably common and simple phase, perovskite (CaTiO3)
The Isolation Capability of a Salt Dome Utilized for High-Level Waste Disposal
Authors: Hamstra J.
Published: March 2011

The overall objective of disposal of high-level and alpha bearing wastes in deep geologic formations is to isolate these wastes from the biosphere for such a period of time that a subsequent future release of radionuclides from the buried wastes will not result in undue radiation exposures to man.
Dissolution Rate of Salt Domes on the Basis of Interpretation of Measured Salinity Profiles
Authors: Lindstrøm Jensen K.E.
Published: March 2011

When radioactive waste is disposed in a salt dome, it is important to evaluate the hydrologic stability of the dome. It depends on the dissolution rate of the dome, which again is determined by the transport and dispersion properties of the cap rock and the other formations surrounding the dome. The same properties are also required in safety assessment work for calculation of migration of radionuclides, which might be released from the dome to the surrounding strata.
Leach Rates of High Level Waste and Spent Fuel. - Limiting Rates as Determined By Backfill and Bedrock Conditions.
Authors: Neretnieks Ivars
Published: March 2011

The release rate of radionuclides from a degraded canister containing radioactive waste is controlled by diffusion through the backfill and by diffusion into the water flowing past the canister. In low porosity low permeability bedrock like the Swedish granites the amount of water which can be contaminated may be very small. Two sample cases are calculated. One uses the conditions for a repository for vitrified high level waste, the other applies to a repository for spent fuel. The small amount of water which can carry the waste in combination with the low solubilities for the major longlived actinides limit the release rate from the repositories to very small values.
Recent Advances in Repository Seal Materials
Authors: Roy D.M. , Burns F.L.
Published: March 2011

One long-term solution proposed for isolating radioactive waste from the biosphere is containment in underground geologic repositories. A requirement for this procedure is that most penetrations into the repository region be sealed following emplacement of the waste. The general requirements of repository seal materials and the seal system are that these potential pathways to the biosphere be sealed adequately to prevent a) excess fluid flow into the repository and b) radionuclides in the waste from reaching the biosphere in quantities in excess of acceptable levels. For boreholes, shafts and tunnels it is generally recommended that in the post-closure phase, the permeability of sealed boreholes and shafts be approximately the same as the host rock or the aquitards in the zones where aquitards are intersected.
Transport of Actinides Through a Bentonite Backfill
Authors: Torstenfelt B. , Kipatsi H. , Andersson K. , Allard B. , Olofsson U.
Published: March 2011

Compacted bentonite has been proposed as a suitable backfill material in the Swedish concept for underground storage of high-level waste. The backfill barrier will serve both as a physical barrier, preventing convective water flow and allowing radionuclide penetration only by diffusion, and as a chemical barrier capable of chemically interacting with the radionuclides.
The Effect of Microbial Activity on the Containment of Radioactive Waste in a Deep Geological Repository
Authors: West Julia M. , Mckinley Ian G. , Chapman Neil A.
Published: March 2011

Much effort is currently centred on the construction of elaborate computer programs to model the release to the biosphere of radionuclides from proposed high level radioactive waste repositories in deep geological formations. Although the lack or poor quality of background data is often emphasised, it is generally considered that by examining a wide range of possible values of the important parameters involved, likely processes are assessed or their omission and possible relevence is acknowledged.
Stability and Construction of Caverns for The Disposal Of Cemented Low-And Medium-Level Wastes
Authors: Raab W. , Frohn C. , Schmidt M.W.
Published: March 2011

The geomechanical and mining-technological aspects of the construction of salt caverns as disposal chambers have been investigated during project phase 2, completed by mid 1981. With a view towards the stability analysis of such a cavern, FEM-estimates have been carried out and evaluated. From these it can be derived that

- a rotational ellipsoid would be the most suitable shape

- its dimensions should be 82 m (vertical axis) and 42 m (horizontal axis)

- the distance (safety pillar) between the neighbouring caverns should be 170 m (vertical) and 180 m (horizontal).

For practical engineering purposes the rotational ellipsoid can be modified into a cylinder with conic bottom and top. The numerical model simulated the short term as well as the long term characteristics of the surrounding salt rocks. The short term characteristics were assessed by an elastic approach, the long term characteristics by a rheological model. The input parameters have been determined by means of laboratory tests on ASSE rock salt.

In a second step the characteristics of partially and completely filled caverns were simulated. It was shown clearly that deformation of the salt rock comes to a halt when counteracted by the filling.

Based upon the results of the stability analysis, investigations were made to find out a suitable mining technique for the construction of the cavern. Solution mining and conventional development by means of drilling and blasting have been studied alternatively. Since both methods have their advantages and disadvantages a decision in favour of the one or the other cannot be made until the actual site has been defined.
Research Priorities for Nuclear Waste Isolation
Authors: Pigford T.H.
Published: March 2011

Hr. Gordon's comments are specific to defense waste only. The research priorities center around:

1.

Improvements in the technology for immobilizing high-level waste. For waste vitrification, these improvements include lower corrosiveness, less crystal formation, lower volatility, reduction in glass cracking, increased life of glass-melter, nondestructive testing methods, and remote handling techniques.

2.

Better understanding of the performance of the waste package components in the repository environment. This requires additional research in the areas of repository characterization, the mechanisms of waste form corrosion, radionuclide migration in geologic media, predictive models for projecting waste system performance.. and synergistic effects of waste system components.

3.

Confirmation of waste disposal risk assessments and their establishment as the technical basis for regulatory criteria.

4.

Research priorities for transuranic (TRU) waste isolation are focused on the development of processing technologies for immobilization and of improved instrumentation for classification and nondestructive examination.
Fundamental Relationships in Acid Decomposition of Samples for Elemental Analysis using Microwave Energy
Authors: Kingston H. M. , Jassie L. B.
Published: March 2011

Appropriate sample preparation is essential to achieve both accuracy and precision in analysis of materials. This preliminary step is one of the most time-consuming parts of many analyses and has become the rate limiting step for such multi-element techniques as ICP, AA, GFAAS and ICPMS. Acid dissolution of biological and botanical samples can take from 4 to 48 hours using classical digestion techniques. Standard reflux methods used in EPA procedures may take from 24–96 hours. Many of these same samples require only 10 to 20 minutes with microwave digestions, dramatically reducing preparation time. Volatile elements such as selenium and phosphorus can be quantitatively retained in a sealed vessel using microwave decomposition prior to instrumental analysis (1). The technique has been tested on all the major sample types including biological, botanical, geological, alloy, and glassy samples and has demonstrated advantages for each of these sample groups. The development of microwave procedures for each of these sample types is currently an intense area of research.
Dielectric Measurements of Particulate Organic Polymers
Authors: Bruce Ralph W. , Mccurdy M. W.
Published: March 2011

The process of removing the entrained water within an organic polymer has been one focus of RF and microwave energy use in the plastics industry. This processing is critically dependent upon the absorption of the energy which in turn is dependent upon the frequency and the material's dielectric loss factor. Knowledge, therefore, of this value is of great importance and is the subject of this study. Measurements were made on several plastic samples as a function of both temperature and frequency.
Microwave Processing of Polymers
Authors: Lewis D. A. , Hedrick J. C. , Lyle G. D. , Ward T. C. , McGrath J. E.
Published: March 2011

Novel morphologies were produced in phase segmented, toughened epoxies via microwave processing. Novel and exciting chemistries have been demonstrated through the specificity of delivery of electromagnetic radiation in tuned cavities.
Microwave Processing of Polymers and Biomass Materials
Authors: George Clifford E. , Lightsey G. R. , Wehr A. G.
Published: March 2011

Dielectric heating techniques have been applied to plastics drying applications, polymer blending, wood flour drying, and to an existing biomass conversion process. While both radio frequency and microwave equipment is expensive per unit of capacity, certain advantages may be gained in terms of the speed of drying, quality control, and the overall capitalized cost which may make dielectric heating feasible.
Enhanced Thermal Shock Properties of Y2O3-2 WT.% ZrO2 Heated Using 2.45 Ghz Radiation
Authors: Holcombe C. E. , Meek T. T. , Dykes N. L.
Published: March 2011

Microwave sintering of Y2O3-2wt.% ZrO2 has produced microstructures which yield mechanical and thermal properties that differ from those observed in commercially sintered Y2O3-2wt.% ZrO2. This paper discusses mechanical and thermal property data obtained on samples of Y2O3-2wt.% ZrO2 heated using 2.45 GHz electromagnetic radiation.
Processing of Superconducting Ceramics Using Microwave Energy
Authors: Ahmad Iftikhar , Chandler G. T. , Clark D. E.
Published: March 2011

Superconducting ceramics have been successfully prepared employing a novel internal heating mechanism which uses microwave energy. Calcining with microwaves requires further investigation to improve the superconducting properties. Sintering and annealing in microwave energy shows refined microstructure and improved oxygen content in the YBa2Cu3O7-x phase. This is attributed to the coupling of CuO with microwave energy. The onset of the superconductive transition occurs at 93°K for the conventionally calcined/microwave annealed samples. The conventionally processed samples have an onset transition at 90°K and exhibit weaker diamagnetism when compared with the microwave annealed sample.
The Effects of Power Level on the Microwave Heating of Selected Chemicals and Minerals
Authors: McGill S. L. , Walkiewicz J. W. , Smyres G. A.
Published: March 2011

The effect of power level on the microwave heating characteristics of a variety of reagent-grade chemicals and minerals has been determined in a Bureau of Mines study. Heating rates of the powdered samples are presented for incident power ranging from 500 to 2,000 W at 2.45 GHz. The apparatus consisted of a WR 975 waveguide-applicator mounted to WR 284 waveguide sections and connected to a 3-kW power source. Tests were conducted in an alumina crucible enclosed in a fused-quartz beaker that was fitted with a Teflon lid to allow for a controlled inert atmosphere and thermocouple insertion. In general, heating rates increased as input power increased. Exceptions to this were some very high-lossy (microwave receptive) and very low-lossy materials that showed negligible changes with increased power. Microwave data collected should provide insight as to possible chemical and mineral processing applications as well as to assist in predictions of processing parameters.
Microwave Joining of Ceramics
Authors: Palaith David , Silberglitt Richard , Wu Carl C. M. , Kleiner Ricrjard , Libeld E. Laurence
Published: March 2011

This paper presents a process developed at Quest Research Corporation for using microwave energy to join ceramics. It begins with a brief overview of the concept and a recent history of microwave ceramic processing. A mathematical treatment of the microwave heating process then is presented followed by a description of the joining technique, and a summary of the experimental results and joint characterizations. For one set of ceramic samples used, electron microscopy and fracture toughness and hardness measurements were made at the Naval Research Laboratory. Another set of sample material was provided by Coors and photomicrographic evaluations of joints produced by Quest using these samples were performed by Coors.
Microwave Heating of Ceramics and its Application to Joining
Authors: Fukushima H. , Yamanaka T. , Matsui M.
Published: March 2011

A new butt joining method for ceramics by microwave heating was developed. Ceramics were heated in a rectangular cavity. A klystron of maximum 3 kW at 6 GHz was used as the power amplifier. The heating system can control the iris, plunger and microwave power to keep a power efficiency up to 90% and a accuracy within ±10°C at 1800°C. Microwave ceramic-ceramic joining was tried by using this system. A bending strength of the joined alumina rod (92% purity) was 420 MPa without adhesive. This value was equal to the original strength. Silicon nitride ceramics were joined with adhesive, which was a sintered ceramic sheet having lower purity and larger dielectric loss factor than the base ceramics. The microwave energy was concentrated on the sheet, so that only the joining area was heated. The strengths of joined specimens were in excess of 70% of original strengths. The joined boundary line was not detected in microscopic observation, and there was little difference in microstructure between before and after joining. These results suggest that sintering aids in grain boundary phases were preferentially heated and melted or diffused, resulting in sound joining of ceramics.
Improved Grindability of Iron Ores using Microwave Energy
Authors: Walkiewicz J. W. , McGill S. L. , Moyer L. A.
Published: March 2011

The Bureau of Mines, U.S. Department of the Interior, has conducted studies to utilize rapid microwave heating to stress fracture ore samples. Iron ores containing hematite, magnetite, and goethite were subjected to microwave energy in batch operations at 3 kW and heated to average temperatures between 840° and 940° C. Scanning electron microscope (SEM) photomicrographs verified fracturing along grain boundaries and throughout the gangue matrix. Standard Bond grindability tests showed that microwave heating reduced the work index of iron ores by 9.9 to 23.7 pct. Preliminary studies using a continuous feed belt in a microwave applicator indicated that samples heat more uniformly and with better temperature control than in batch operations.
Rapid Electromagnetic Induction Bonding of Composites, Plastics, & Metals
Authors: Buckley John D. , Fox Robert L.
Published: March 2011

A rapid electromagnetic induction bonding system has been developed that joins composites, plastics, metals, and combinations of these materials. The equipment is self-contained, low power (100–400 watts) and portable. Gangs of bonders have been used as a seem welder to rapidly join plastic reinforced composite and sheet metal. Structures can be bonded in a factory or in the field. Bonding times for laboratory specimens have been cut by a factor of 10 to 100 times compared to standard press or autoclave bonding. This type of equipment allows for applying heat directly to the bond lines and/or the adherends without heating the entire structure, supports, and fixtures of a bonding assembly.

The bonder's portability and low power requirements allow for its use on site in any type of climate with power supplied by a variety of portable sources.
A Research Program for Dielectric Heating and Drying of Industrial Materials
Authors: Pearce John A. , Yang S. I. , Schmidt P. S.
Published: March 2011

A comprehensive program of research into dielectricallyassisted heating and drying of industrial products includes studies of the heat and mass transport processes and the spatial distribution of microwave (MW) and radio frequency (RF) power deposition in the objects of interest. Such studies enable the design of product specific drying machinery.
Thermodiffusion - A New Approach To Plasma Self-Confinement
Authors: Forchel A. , Laurich B. , Mahler G.
Published: March 2011

From a model for the thermodiffusion of high density plasmas an electronic mechanism for plasma self-confinement is derived. Due to the increase of the confinement densities with the density of states masses this effect should be most important in laser annealing experiments in Si but much weaker in GaAs. A fast diffusion of the surface generated plasma is found to enhance the impact ionization rate.
Femtosecond Time Resolved Reflectivity of Optically Excited Silicon
Authors: Yen R. , Shank C. V. , Hirlimann C.
Published: March 2011

We report measurements of the time resolved reflectivity of Silicon following excitation with an intense 90 femtosecond optical pulse. These measurements clearly time resolve the process of energy transfer from the optically excited electron-hole plasma to the crystal lattice and subsequent melting within the first few picoseconds.
Charged Dangling Bonds and Crystallization in Group IV Semiconductors
Authors: Germain P.J. , Paesler M.A. , Sayers D.E. , Zellama K.
Published: March 2011

Crystallization of amorphous Ge (or Si) has been studied as a function of temperature and the flux of ionizing radiation (or doping). The crystallization growth rate Vg takes on the form Vg = vo exp(−E/kT) where vo is an increasing function of flux (or doping). We propose the following to explain these data: A concentration of mobile dangling bonds (DBs) exists in the bulk and near the amorphous-crystalline (a-c) interface. Ionization and doping induce transitions from the uncharged state Do to the charged states D+ and D−. The process controlling crystallization resulting in the above activation energy is discussed. Only certain sites on the a-side of the a-c interface are available for crystallization, and these sites are those which have captured DBs. The charged D+; and D− states have a larger capture cross section than the uncharged Do state. Increased concentrations of charged DBs results in an enhancement of the prefactor in the above equation.
Laser-Induced Solid Phase Crystallization in Amorphous Silicon Films
Authors: Olson G.L. , Kokorowski S.A. , Roth J.A. , Hess L.D.
Published: March 2011

We review recent work on the kinetics of laser-induced solid phase epitaxial crystallization of silicon as determined from time-resolved reflectivity measurements. Specific topics which are addressed include: the intrinsic kinetics of solid phase epitaxy (SPE) in ion-implanted and UHV-deposited films; SPE rate enhancement by implanted dopant atoms and the effects of electrical compensation on the SPE rate; and the temperature dependence of SPE and competing processes in samples containing impurity atoms at concentrations exceeding the solid solubility limit. The high temperature kinetics results are compared with predictions from transition state theory and are discussed with respect to a proposed depression in the amorphous Si melting temperature.
Explosive Crystallization in a-Ge and a-Si : A Review
Authors: Bensahel D. , Auvert G.
Published: March 2011

Self-sustained or explosive crystallization results on a-Si and a-Ge are reviewed and compared. cw laser experiments on a-Si allow to follow all the phenomena encountered, and to experimentally measure the crystallization front velocity. The published theories agree well with the experimental results on a-Si. Moreover, a-Ge presents the same behaviour as a-Si, but for a-Si, the high nucleation rate can induce a specific explosive growth.
Surface Electromagnetic Waves in Laser Material Interactions
Authors: Ehrlich D. J. , Brueck S. R. J. , Tsao J. Y.
Published: March 2011

Transient ripple formation in pulsed laser annealing of semiconductor materials is shown to arise from amplified surface polariton scattering. The permanent ripple patterns are frozen in after transverse thermal and material diffusion during the laser-annealing process. The model is in good agreement with time-resolved measurements of the ripple formation in 1.06−µm laser annealing of Ge. Dispersion of the ripple wavevector in the UV spectral region is discussed.