The Effect of Coating Patterns with Spinel-Based Investment on the Castability and Porosity of Titanium Cast into Three Phosphate-Bonded Investments

Purpose: This study evaluated the effect of pattern coating with spinel-based investment Rematitan Ultra (RU) on the castability and internal porosity of commercially pure (CP) titanium invested into phosphate-bonded investments. The apparent porosity of the investment was also measured. Materials and Methods: Square patterns (15 x 15 x 0.3 mm(3)) were either coated with RU, or not and invested into the phosphate-bonded investments: Rematitan Plus (RP), Rema Exakt (RE), Castorit Super C (CA), and RU (control group). The castings were made in an Ar-arc vacuum-pressure machine. The castability area (mm(2)) was measured by an image-analysis system (n = 10). For internal porosity, the casting (12 x 12 x 2 mm(3)) was studied by the X-ray method, and the projected porous area percentage was measured by an image-analysis system (n = 10). The apparent porosity of the investment (n = 10) was measured in accordance with the ASTM C373-88 standard. Results: Analysis of variance (One-way ANOVA) of castability was significant, and the Tukey test indicated that RU had the highest mean but the investing technique with coating increased the castability for all phosphate-bonded investments. The analysis of the internal porosity of the cast by the nonparametric test demonstrated that the RP, RE, and CA with coating and RP without coating did not differ from the control group (RU), while the CA and RE casts without coating were more porous. The one-way ANOVA of apparent porosity of the investment was significant, and the Tukey test showed that the means of RU (36.10%) and CA (37.22%) were higher than those of RP (25.91%) and RE (26.02%). Conclusion: Pattern coating with spinel-based material prior to phosphate-bonded investments can influence the castability and the internal porosity of CP Ti.

The relationship of a clonal outbreak of Enterococcus faecium vanA to methicillin-resistant Staphylococcus aureus incidence in an Australian hospital

Australian isolates of vancomycin-resistant enterococci (VRE) have been widely scattered geographically, predominantly polyclonal and of the VanB phenotype. Forty-nine VRE were isolated from 47 patients in our hospital from October 1996 to December 1999. Forty-four of these VRE were Enterococcus faecium with a vanA glycopeptide resistance genotype. Four isolates were pathogenic. Thirty-five VRE were from an outbreak in the Renal and Infectious Diseases Units over a four-month period. Pulsed-field gel electrophoresis (PFGE) demonstrated that 41 of the 49 VRE were indistinguishable or closely related. Enhanced environmental cleaning, strict contact isolation of colonized patients and reducing inpatient admissions terminated the epidemic. Cohorting of methicillin-resistant Staphylococcus aureus (MRSA)-positive patients was restricted because VPE patients occupied the isolation facilities. This resulted in a statistically significant increase in MRSA infections across the hospital. VRE epidemics have the ability to influence the epidemiology of other nosocomial pathogens when infection control resources are exhausted. (C) 2001 The Hospital Infection Society.

Metastatic lesions in the joint associated with acute inflammatory arthritis after dendritic cell immunotherapy for metastatic melanoma

A 47 year old man undergoing immunotherapy for metastatic melanoma with autologous dendritic cells pulsed with autologous tumour peptide and hepatitis a surface antigen developed acute left ankle arthritis. Gout and acute infection were excluded, and an autoimmune aetiology or occult metastasis were considered. The arthritis initially subsided with indomethacin, but the symptoms recurred 2 months later, and magnetic resonance imaging demonstrated metastatic melanoma of the left talus. Immunohistochemical staining of a cerebral metastatic deposit biopsied 1 week after the onset of arthritis demonstrated T-cell and macrophage infiltration of the tumour. In addition, the patient developed melanoma-specific delayed type hypersensitivity and cytotoxic T-cell responses after vaccination. Thus, the monoarthritis represented an 'appropriate' inflammatory response directed against metastatic melanoma. (C) 2001 Lippincott Williams & Wilkins.

Recent advances in the preparation and utilization of carbon nanotubes for hydrogen storage

Recent progress in the production, purification, and experimental and theoretical investigations of carbon nanotubes for hydrogen storage are reviewed. From the industrial point of view, the chemical vapor deposition process has shown advantages over laser ablation and electric-arc-discharge methods. The ultimate goal in nanotube synthesis should be to gain control over geometrical aspects of nanotubes, such as location and orientation, and the atomic structure of nanotubes, including helicity and diameter. There is currently no effective and simple purification procedure that fulfills all requirements for processing carbon nanotubes. Purification is still the bottleneck for technical applications, especially where large amounts of material are required. Although the alkali-metal-doped carbon nanotubes showed high H-2 Weight uptake, further investigations indicated that some of this uptake was due to water rather than hydrogen. This discovery indicates a potential source of error in evaluation of the storage capacity of doped carbon nanotubes. Nevertheless, currently available single-wall nanotubes yield a hydrogen uptake value near 4 wt% under moderate pressure and room temperature. A further 50% increase is needed to meet U.S. Department of Energy targets for commercial exploitation. Meeting this target will require combining experimental and theoretical efforts to achieve a full understanding of the adsorption process, so that the uptake can be rationally optimized to commercially attractive levels. Large-scale production and purification of carbon nanotubes and remarkable improvement of H-2 storage capacity in carbon nanotubes represent significant technological and theoretical challenges in the years to come.

Articulatory dysfunction in multiple sclerosis: An electropalatographic study

Dysfunction of the articulatory subsystem (i.c.. the lips, tongue, and jaw) has bccn identified as a major contributor to the reduction in speech intelligibility experienced by a high proportion of people with multiple sclerosis (MS). In particular. consonant imprecision has been reported to be the articulatory deficit that contributes most to variations in overall intelligibility of MS speakers. Electropalatography(EPG) IS an instrurncntal technique that visually documents the location and timing of tongue-topalatc contacts during speech. Although such a technique would be valuablc in objectively assessing the articulatory disturbances exhibited by individuals with dysarthria ia motor speech disorder) associated with MS, to-date no such study ha< been reported. The aim of the present study was to use EPG to assess tongue-to-palate contact patterns and articulatory timing in patients with dysarthria associated with MS. A dysarthric participant with a diagnosis of definite MS was fitted with an acrylic EPG palate (Reading EPG.?) and asked to read aloud a list of single syllable words which contained lingual consonants in the word-initial position and in consonant clusters. Each mord was repeated five times. The EPG palate was specifically moulded to tit the participant's hard palate and contained 62 electrodes that detected the tongue contacts. A non-neurologically impaired participant matched for age and sex servcd as a control. The results of the study revealed that the tongue-to-palate contacts produced by the participant with MS varied from those produced by the control in a number of ways in regard to spatial configurations and timing characteristics exhibited. The rcsults arc discussed in relation to the neuropathophysiological effects of MS on speech production. The potcntial use of EPG in programs for treating speech disorders associated with MS will be highlightcd.

Dendritic cells rapidly undergo apoptosis in vitro following culture with activated CD4(+) V alpha 24 natural killer T cells expressing CD40L

Human V alpha 24 natural killer T (V alpha 24NKT) cells are activated by -glycosylceramide-pulsed dendritic cells (DCs) in a CDld-dependent and T-cell receptor-mediated manner. There are two major subpopulations of V alpha 24NKT cells, CD4(-) CD8(-) V alpha 24NKT and CD4(+) V alpha 24NKT cells. We have recently shown that activated CD4(-) CD8 V alpha 24NKT cells have cytotoxic activity against DCs, but knowledge of the molecules responsible for cytotoxicity of V alpha 24NKT cells is currently limited. We aimed to investigate whether CD4(+) V alpha 24NKT cells also have cytotoxic activity against DCs and to determine the mechanisms underlying any observed cytotoxic activity. We demonstrated that activated CD4(+) V alpha 24NKT cells [CD40 ligand (CD40L) -positive] have cytotoxic activity against DCs (strongly CD40-positive), but not against monocytes (weakly CD40-positive) or phytohaemagglutinin blast T cells (CD40-negative), and that apoptosis of DCs significantly contributes to the observed cytotoxicity. The apoptosis of DCs following culture with activated CD4(+) V alpha 24NKT cells, but not with resting CD4(+) V alpha 24NKT cells (CD40L-negative), was partially inhibited by anti-CD40L mAb, Direct ligation of CD40 on the DCs by the anti-CD40 antibody also induced apoptosis of DCs. Our results suggest that CD40-CD40L interaction plays an important role in the induction of apoptosis of DCs following culture with activated CD4+ Va24NKT cells. The apoptosis of DCs from normal donors. triggered by the CD40-CD40L interaction, may contribute to the homeostatic regulation of the normal human immune system, preventing the interminable activation of activated CD4(+) V alpha 24NKT cells by virtue of apoptosis of DCs.

TRAIL expression by activated human CD4(+)V alpha 24NKT cells induces in vitro and in vivo apoptosis of human acute myeloid leukema cells

Human V alpha 24NKT cells are activated by alpha -galactosylceramide (alpha -GalCer)-pulsed dendritic cells in a CD1d-dependent and a T-cell receptor-mediated manner. Here, we demonstrate that CD4(+)V alpha 24NKT cells derived from a patient with acute myeloid leukemia (AML) M4 are phenotypically similar to those of healthy donors and, in common with those derived from healthy donors, express tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) when the cells are activated by alpha -GalCer-pulsed dendritic cells but not prior to activation. We also show that myeloid that human activated CD4(+)V alpha 24NKT cells induced apoptosis of human leukemia cells in vivo. This is the first evidence that activated V alpha 24NKT cells express TRAIL and that TRAIL causes apoptosis of monocytic leukemia cells from patients with AML M4 in vitro and in vivo. Adoptive immune therapy with activated V alpha 24NKT cells, or other strategies to increase activated V alpha 24NKT cells in vivo, may be of benefit to patients with AML M4.

A cluster of melioidosis cases from an endemic region is clonal and is linked to the water supply using molecular typing of Burkholderia pseudomallei isolates

Nine cases of melioidosis with four deaths occurred over a 28-month period in members of a small remote Aboriginal community in the top end of the Northern Territory of Australia. Typing by pulsed-field gel electrophoresis showed isolates of Burkholderia pseudomallei from six of the cases to be clonal and also identical to an isolate from the community water supply, but not to soil isolates. The clonality of the isolates found in this cluster contrasts with the marked genetic diversity of human and environmental isolates found in this region which is hyperendemic for B. pseudomallei. It is possible that the clonal bacteria persisted and were propagated in biofilm in the water supply system. While the exact mode of transmission to humans and the reasons for cessation of the outbreak remain uncertain, contamination of the unchlorinated community water supply is a likely explanation.

Limitations of HLA-transgenic mice in presentation of HLA-restricted cytotoxic T-cell epitopes from endogenously processed human papillomavirus type 16 E7 protein

We investigated the use of mice transgenic for human leucocyte antigen (HLA) A*0201 antigen-binding domains to test vaccines composed of defined HLA A*0201-restricted cytotoxic T-lymphocyte (CTL) epitopes of human papillomavirus (HPV) type 16 E7 oncoprotein. HPV is detected in >90% of cervical carcinomas. HPV16 E7 oncoprotein transforms cells of the uterine cervix and functions as a tumour-associated antigen to which immunotherapeutic strategies may be directed. We report that although the HLA A*0201 E7 epitope peptides function both to prime for E7 CTL responses, and to sensitize target cells for E7-directed CTL killing in situations where antigen processing is not required, the epitopes are not processed out of either endogenously expressed or immunization-introduced E7, by the mouse antigen-processing and presentation machinery. Thus (1) CTL induced by HLA A*0201 peptide immunization killed E7 peptide-pulsed target cells, but did not kill target cells expressing whole E7; (2) immunization with whole E7 protein did not elicit CTL directed to HLA A*0201-restricted E7 CTL epitopes; (3) HLA A*0201-restricted CTL epitopes expressed in the context of a DNA polytope vaccine did not activate E7-specific T cells either in 'conventional' HLA A*0201 transgenic (A2.1K(b) ) mice, or in HHD transgenic mice in which expression of endogenous H-2 class 1 is precluded; and (4) HLA A*0201 E7 peptide epitope immunization was incapable of preventing the growth of an HLA A*0201- and E7-expressing tumour. There are generic implications for the universal applicability of HLA-class 1 transgenic mice for studies of human CTL epitope presentation in murine models of human infectious disease where recognition of endogenously processed antigen is necessary. There are also specific implications for the use of HLA A2 transgenic mice for the development of E7-based therapeutic vaccines for cervical cancer.

Pulpal heat changes with newly developed resin photopolymerisation systems

Composite resin is a widely-used direct tooth coloured restorative material. Photoactivation of the polymerisation reaction can be achieved by visible blue light from a range of light sources, including halogen lamps, metal halide lamps, plasma arc lamps, and Light Emitting Diode (LED) lights. Concerns have been raised that curing lights may induce a temperature rise that could be detrimental to the vitality of the dental pulp during the act of photoactivation. The present study examined heat changes associated with standardised class V restorations on the buccal surface of extracted premolar teeth, using a curing time of 40 seconds. The independent effects of type of light source, resin shade and remaining tooth thickness were assessed using a matrix experimental design. When a conventional halogen lamp, a metal halide lamp and two different LED lights were compared, it was found that both LED lamps elicited minimal thermal changes at the level of the dental pulp, whereas the halogen lamp induced greater changes and the metal halide lamp caused the greatest thermal insult of all the light sources. These thermal changes were influenced by resin shade, with different patterns for LED versus halogen or halide sources. Thermal stress reduced as the remaining thickness of tooth structure between the pulp and the cavity floor increased. From these results, it is concluded that LED lights produce the least thermal insult during photopolymerisation of composite resins.

Different mineralization styles in a volcanic-hosted ore deposit: the fluid and isotopic signatures of the Mt Morgan Au-Cu deposit, Australia

Quantitative laser ablation (LA)-ICP-MS analyses of fluid inclusions, trace element chemistry of sulfides, stable isotope (S), and Pb isotopes have been used to discriminate the formation of two contrasting mineralization styles and to evaluate the origin of the Cu and Au at Mt Morgan. The Mt Morgan Au-Cu deposit is hosted by Devonian felsic volcanic rocks that have been intruded by multiple phases of the Mt Morgan Tonalite, a low-K, low-Al2O3 tonalite-trondhjemite-dacite (TTD) complex. An early, barren massive sulfide mineralization with stringer veins is conforming to VHMS sub-seafloor replacement processes, whereas the high-grade Au-Cu. ore is associated with a later quartz-chalcopyrite-pyrite stock work mineralization that is related to intrusive phases of the Tonalite complex. LA-ICP-MS fluid inclusion analyses reveal high As (avg. 8850 ppm) and Sb (avg. 140 ppm) for the Au-Cu mineralization and 5 to 10 times higher Cu concentration than in the fluids associated with the massive pyrite mineralization. Overall, the hydrothermal system of Mt Morgan is characterized by low average fluid salinities in both mineralization styles (45-80% seawater salinity) and temperatures of 210 to 270 degreesC estimated from fluid inclusions. Laser Raman Spectroscopic analysis indicates a consistent and uniform array Of CO2-bearing fluids. Comparison with active submarine hydrothermal vents shows an enrichment of the Mt Morgan fluids in base metals. Therefore, a seawater-dominated fluid is assumed for the barren massive sulfide mineralization, whereas magmatic volatile contributions are implied for the intrusive related mineralization. Condensation of magmatic vapor into a seawater-dominated environment explains the CO2 occurrence, the low salinities, and the enriched base and precious metal fluid composition that is associated with the Au-Cu. mineralization. The sulfur isotope signature of pyrite and chalcopyrite is composed of fractionated Devonian seawater and oxidized magmatic fluids or remobilized sulfur from existing sulfides. Pb isotopes indicate that Au and Cu. originated from the Mt Morgan intrusions and a particular volcanic strata that shows elevated Cu background. (C) 2002 Elsevier Science B.V. All rights reserved.

Fluid-mobile trace element constraints on the role of slab melting and implications for Archaean crustal growth models

We use published and new trace element data to identify element ratios which discriminate between arc magmas from the supra-subduction zone mantle wedge and those formed by direct melting of subducted crust (i.e. adakites). The clearest distinction is obtained with those element ratios which are strongly fractionated during refertilisation of the depleted mantle wedge, ultimately reflecting slab dehydration. Hence, adakites have significantly lower Pb/Nd and B/Be but higher Nb/Ta than typical arc magmas and continental crust as a whole. Although Li and Be are also overenriched in continental crust, behaviour of Li/Yb and Be/Nd is more complex and these ratios do not provide unique signatures of slab melting. Archaean tonalite-trondhjemite-granodiorites (TTGs) strongly resemble ordinary mantle wedge-derived arc magmas in terms of fluid-mobile trace element content, implying that they-did not form by slab melting but that they originated from mantle which was hydrated and enriched in elements lost from slabs during prograde dehydration. We suggest that Archaean TTGs formed by extensive fractional crystallisation from a mafic precursor. It is widely claimed that the time between the creation and subduction of oceanic lithosphere was significantly shorter in the Archaean (i.e. 20 Ma) than it is today. This difference was seen as an attractive explanation for the presumed preponderance of adakitic magmas during the first half of Earth's history. However, when we consider the effects of a higher potential mantle temperature on the thickness of oceanic crust, it follows that the mean age of oceanic lithosphere has remained virtually constant. Formation of adakites has therefore always depended on local plate geometry and not on potential mantle temperature.

The martensitic transformation in ceramics - its role in transformation toughening

This paper reviews the current knowledge and understanding of martensitic transformations in ceramics - the tetragonal to monoclinic transformation in zirconia in particular. This martensitic transformation is the key to transformation toughening in zirconia ceramics. A very considerable body of experimental data on the characteristics of this transformation is now available. In addition, theoretical predictions can be made using the phenomenological theory of martensitic transformations. As the paper will illustrate, the phenomenological theory is capable of explaining all the reported microstructural and crystallographic features of the transformation in zirconia and in some other ceramic systems. Hence the theory, supported by experiment, can be used with considerable confidence to provide the quantitative data that is essential for developing a credible, comprehensive understanding of the transformation toughening process. A critical feature in transformation toughening is the shape strain that accompanies the transformation. This shape strain, or nucleation strain, determines whether or not the stress-induced martensitic transformation can occur at the tip of a potentially dangerous crack. If transformation does take place, then it is the net transformation strain left behind in the transformed region that provides toughening by hindering crack growth. The fracture mechanics based models for transformation toughening, therefore, depend on having a full understanding of the characteristics of the martensitic transformation and, in particular, on being able to specify both these strains. A review of the development of the models for transformation toughening shows that their refinement and improvement over the last couple of decades has been largely a result of the inclusion of more of the characteristics of the stress-induced martensitic transformation. The paper advances an improved model for the stress-induced martensitic transformation and the strains resulting from the transformation. This model, which separates the nucleation strain from the subsequent net transformation strain, is shown to be superior to any of the constitutive models currently available. (C) 2002 Elsevier Science Ltd. All rights reserved.

Alternative technologies for producing sterile low acid food products

Four emerging high-energy non-thermal technologies may replace or augment heating for producing sterile low-acid food products. High pressure, high-voltage pulsed electric field, high-energy ultrasound and high-intensity pulsed light are all capable of reducing bacterial spore counts under certain conditions. However, only non-continuous high pressure treatments, at temperatures higher than ambient, are currently capable of completely inactivating spores and producing sterile food products. The first three technologies also reduce the resistance of spores to inactivation by heat.

Finite difference time domain (FDTD) method for modeling the effect of switched gradients on the human body in MRI

Numerical modeling of the eddy currents induced in the human body by the pulsed field gradients in MRI presents a difficult computational problem. It requires an efficient and accurate computational method for high spatial resolution analyses with a relatively low input frequency. In this article, a new technique is described which allows the finite difference time domain (FDTD) method to be efficiently applied over a very large frequency range, including low frequencies. This is not the case in conventional FDTD-based methods. A method of implementing streamline gradients in FDTD is presented, as well as comparative analyses which show that the correct source injection in the FDTD simulation plays a crucial rule in obtaining accurate solutions. In particular, making use of the derivative of the input source waveform is shown to provide distinct benefits in accuracy over direct source injection. In the method, no alterations to the properties of either the source or the transmission media are required. The method is essentially frequency independent and the source injection method has been verified against examples with analytical solutions. Results are presented showing the spatial distribution of gradient-induced electric fields and eddy currents in a complete body model.