Effect of postweld heat treatment on the microstructure and cyclic deformation behavior of laser-welded NiTi-shape memory wires

NiTi wires of 0.5 mm diameter were laser welded using a CW 100-W fiber laser in an argon shielding environment with or without postweld heat-treatment (PWHT). The microstructure and the phases present were studied by scanning-electron microscopy (SEM), transmission-electron microscopy (TEM), and X-ray diffractometry (XRD). The phase transformation behavior and the cyclic stress–strain behavior of the NiTi weldments were studied using differential scanning calorimetry (DSC) and cyclic tensile testing. TEM and XRD analyses reveal the presence of Ni4Ti3 particles after PWHT at or above 623 K (350 °C). In the cyclic tensile test, PWHT at 623 K (350 °C) improves the cyclic deformation behavior of the weldment by reducing the accumulated residual strain, whereas PWHT at 723 K (450 °C) provides no benefit to the cyclic deformation behavior. Welding also reduces the tensile strength and fracture elongation of NiTi wires, but the deterioration could be alleviated by PWHT.

Effects of process parameters upon the shape memory and pseudo-elastic behaviors of laser-welded NiTi thin foil

This article discusses the effects of laser welding parameters such as power, welding speed, and focus position on the weld bead profile, microstructure, pseudo-elasticity (PE), and shape memory effect (SME) of NiTi foil with thickness of 250 um using 100W CW fiber laser. The parameter settings to produce the NiTi welds for analysis in this article were chosen from a fractional factorial design to ensure the welds produced were free of any apparent defect. The welds obtained were mainly of cellular dendrites with grain sizes ranging from 2.5 to 4.8 um at the weld centerline. A small amount of Ni3Ti was found in the welds. The onset of transformation temperatures (As and Ms) of the NiTi welds shifted to the negative side as compared to the as-received NiTi alloy. Ultimate tensile stress of the NiTi welds was comparable to the as received NiTi alloy, but a little reduction in the pseudo-elastic property was noted. Full penetration welds with desirable weld bead profiles and mechanical properties were successfully obtained in this study.

Development and validation of the first high performance-lateral flow immunoassay (HP-LFIA) for the rapid screening of domoic acid from shellfish extracts

A lateral flow immunoassay (LFIA) has been developed and fully validated to detect the primary amnesic shellfish poisoning (ASP) toxin, domoic acid (DA). The performance characteristics of two versions of the test were investigated using spiked and naturally contaminated shellfish (mussels, scallops, oysters, clams, and cockles). The tests provide a qualitative result, to indicate the absence or presence of DA in extracts of shellfish tissues, at concentrations that are relevant to regulatory limits. The new rapid assay (LFIA version 2) was designed to overcome the performance limitations identified in the first version of the assay. The improved test uses an electronic reader to remove the subjective nature of the generated results, and the positive cut-off for screening of DA in shellfish was increased from 10 ppm (version 1) to 17.5 ppm (version 2). A simple extraction and test procedure was employed, which required minimal equipment and materials; results were available 15 min after sample preparation. Stability of the aqueous extracts at room temperature (22 C) at four time points (up to 245 min after extraction) and across a range of DA concentrations was 100.3±1.3% and 98.8±2.4% for pre- and post-buffered extracts, respectively. The assay can be used both within laboratory settings and in remote locations. The accuracy of the new assay, to indicate negative results at or below 10 ppm DA, and positive results at or above 17.5 ppm, was 99.5% (n=216 tests). Validation data were obtained from a 2-day, randomised, blind study consisting of multiple LFIA lots (n=3), readers (n=3) and operators (n=3), carrying out multiple extractions of mussel tissue (n=3) at each concentration (0, 10, 17.5, and 20 ppm). No matrix effects were observed on the performance of the assay with different species (mussels, scallops, oysters, clams, and cockles). There was no impact on accuracy or interference from other phycotoxins, glutamic acid or glutamine with various strip incubations (8, 10, and 12 min). The accuracy of the assay, using naturally contaminated samples to indicate negative results at or below 12.5 ppm and positive results at or above 17.5 ppm, was 100%. Variability between three LFIA lots across a range of DA concentrations, expressed as coefficient of variation (% CV), was 1.1±0.4% (n=2 days) based on quantitative readings from the electronic reader. During an 8 week stability study, accuracy of the method with test strips stored at various temperatures (6, 22, 37 and 50 C) was 100%. Validation for both versions included comparisons with results obtained using reference LC-UV methods. © 2013 Elsevier B.V.

Improvement in clinical step and shoot intensity modulated radiation therapy delivery accuracy on an integrated linear accelerator control system

Purpose: The dose delivery accuracy of 30 clinical step and shoot intensity modulated radiation therapy plans was investigated using the single integrated multileaf collimator controller of the Varian Truebeam linear accelerator (linac) (Varian Medical Systems, Palo Alto, CA) and compared with the dose delivery accuracy on a previous generation Varian 2100CD C-Series linac.

Methods and Materials: Ten prostate, 10 prostate and pelvic node, and 10 head-and-neck cases were investigated in this study. Dose delivery accuracy on each linac was assessed using Farmer ionization chamber point dose measurements, 2-dimensional planar ionization chamber array measurements, and the corresponding Varian dynamic log files. Absolute point dose measurements, fluence delivery accuracy, leaf position accuracy, and the overshoot effect were assessed for each plan.

Results: Absolute point dose delivery accuracy increased by 1.5% on the Truebeam compared with the 2100CD linac. No improvement in fluence delivery accuracy between the linacs, at a gamma criterion of 3%/3 mm was measured using the 2-dimensional ionization chamber array, with median (interquartile range) gamma passing rates of 98.99% (97.70%-99.72%) and 99.28% (98.26%-99.75%) for the Truebeam and 2100CD linacs, respectively. Varian log files also showed no improvement in fluence delivery between the linacs at 3%/3 mm, with median gamma passing rates of 99.97% (99.93%-99.99%) and 99.98% (99.94%-100%) for the Truebeam and 2100CD linacs, respectively. However, log files revealed improved leaf position accuracy and fluence delivery at 1%/1 mm criterion on the Truebeam (99.87%; 99.78%-99.94%) compared with the 2100CD linac (97.87%; 91.93%-99.49%). The overshoot effect, characterized on the 2100CD linac, was not observed on the Truebeam.

Conclusions: The integrated multileaf collimator controller on the Varian Truebeam improves clinical treatment delivery accuracy of step and shoot intensity modulated radiation therapy fields compared with delivery on a Varian C-series linac. © 2014.

Lymphatic mapping and sentinel node biopsy in breast cancer

Background Sentinel lymph node biopsy is a recently developed, minimally invasive technique for staging the axilla in patients with breast cancer. It has been suggested that this technique will avoid the morbidity associated with more extensive axillary dissection. A wide range of different methods and materials has been employed for lymphatic mapping, but there has been little consensus on the most reliable and reproducible technique.

Methods This is a comprehensive review of all published literature on sentinel node biopsy in breast cancer, using the Medline and Embase databases and cross-referencing of major articles on the subject.

Results and conclusion Sentinel node biopsy is a valid technique in breast cancer management, providing valuable axillary staging information. The optimal technique of lymphatic mapping utilizes a combination of vital blue dye and radiolabelled colloid. However, there remain controversial issues which require to be resolved before sentinel node biopsy becomes a widely accepted part of breast cancer care.

Self-assembly using dendritic building blocks - towards controllable nanomaterials

Dendritic molecules have well defined, three-dimensional branched architectures, and constitute a unique nanoscale toolkit. This review focuses on examples in which individual dendritic molecules are assembled into more complex arrays via non-covalent interactions. In particular, it illustrates how the structural information programmed into the dendritic architecture controls the assembly process, and as a consequence, the properties of the supramolecular structures which are generated. Furthermore, the review emphasises how the use of non-covalent (supramolecular) interactions, provides the assembly process with reversibility, and hence a high degree of control. The review also illustrates how self-assembly offers an ideal approach for amplifying the branching of small, synthetically accessible, relatively inexpensive dendritic systems (e.g. dendrons), into highly branched complex nanoscale assemblies.

The review begins by considering the assembly of dendritic molecules to generate discrete, well-defined supramolecular assemblies. The variety of possible assembled structures is illustrated, and the ability of an assembled structure to encapsulate a templating unit is described. The ability of both organic and inorganic building blocks to direct the assembly process is discussed. The review then describes larger discrete assemblies of dendritic molecules, which do not exist as a single well-defined species, but instead exist as statistical distributions. For example, assembly around nanoparticles, the assembly of amphiphilic dendrons and the assembly of dendritic systems in the presence of DNA will all be discussed. Finally, the review examines dendritic molecules, which assemble or order themselves into extended arrays. Such systems extend beyond the nanoscale into the microscale or even the macroscale domain, exhibiting a wide range of different architectures. The ability of these assemblies to act as gel-phase or liquid crystalline materials will be considered.

Taken as a whole, this review emphasises the control and tunability that underpins the assembly of nanomaterials using dendritic building blocks, and furthermore highlights the potential future applications of these assemblies at the interfaces between chemistry, biology and materials science. 

Dublin’s ephemeral and imaginary architectures

In 1989, the Irish architectural practice O’Donnell and Tuomey were commissioned to build a temporary pavilion to represent Ireland at the 11 Cities/11 Nations exhibition at Leeuwarden in the Netherlands. Citing Peter Smithson, John Tuomey suggested the pavilion, which drew inspirations from the forms and materials of the modern Irish barn, embodied an intention ‘not just to build but to communicate’. Its subsequent reassembly for the inauguration of the Irish Museum of Modern Art in the courtyard of the seventeenth-century Royal Hospital Kilmainham in Dublin in 1991, drew comparisons between the urban sophistication of this colonial building, its svelte new refit, and the rural expression of O’Donnell + Tuomey’s barn. It was, one critic recently noted, as if ‘a wedding had been crashed by a country cousin who had forgotten to clean his boots’.
It has been argued that temporary or ephemeral pieces of architecture, unburdened by the traditional constraints of firmitas or utilitas, have the ability to offer a concise distillation of meaning and intention. Approaching the qualities of rhetoric, such architectures share similarities with the monument and yet differ in fundamental ways. Their rapid construction in lightweight materials can allow for an almost instantaneous negotiation of zeitgeist. And, unlike the monument, from the outset the space and form of these installations is designed to disappear.
This paper analyses the ephemeral architectures of Dublin in the modern period contextualising their qualities and intentions as they manifest themselves across colonial, post-colonial and contemporary epochs. It finds origins in the theatrical sets of the late eighteenth century and traces their movements into the semi-public sphere of the pleasure garden and finally into the theatre of the streets. It is here that temporary architecture in the city has been at its most potent, allowing the amplification or subversion of the meanings of much larger spaces. Historically, much of Dublin’s most conspicuous instances of ephemeral architecture have been realised as a means of articulating mass spectacle in political, religious or nationalistic events. And while much of this has sought to confirm dominant ideologies, it has also been possible to discern moments of opposition.
The contemporary period, however, has arguably witnessed a shift in ephemeral architectures from explicitly representing ‘positive ideologies’ towards something more oblique or nebulous. This turn towards abstraction in form and space has rendered an especially communicative form of architecture particularly elusive. By examining continuities within the apparent disjuncture between historical and contemporary examples, this paper begins to unpick the language of recent ephemeral architecture in Dublin and situate it within wider global trends where political and economic imperatives are often simultaneously obscured and expressed in public space by a vocabulary of universality. As Jurgen Habermas has suggested, the contemporary value given to the transitory and the ephemeral ‘discloses a longing for an undefiled, immaculate and stable present’.

LC- HRMS based metabolomics in food safety and doping control – DeTECH21

Issues surrounding the misuse of prohibited and licensed substances in animals destined for food production and performance sport competition continue to be an enormous challenge to regulatory authorities charged with enforcing their control. Efficient analytical strategies are implemented to screen and confirm the presence of a wide range of exogenous substances in various biological matrices. However, such methods rely on the direct measurement of drugs and/or their metabolites in a targeted mode, allowing the detection of restricted number of compounds. As a consequence, emerging practices, in particular the use of natural hormones, designer drugs and low-dose cocktails, remain difficult to handle from a control point of view. A new SME-led FP7 funded project, DeTECH21, aims to overcome current limitations by applying an untargeted metabolomics approach based on liquid chromatography coupled to high resolution mass spectrometry and bioinformatic data analysis to identify bovine and equine animals which have been exposed to exogenous substances and assist in the identification of administered compounds. Markerbased strategies, dealing with the comprehensive analysis of metabolites present in a biological sample (urine/plasma/tissue), offer a reliable solution in the areas of food safety and animal sport doping control by effective, high-throughput and sensitive detection of exogenously administered agents. Therefore, the development of the first commercially available forensic test service based on metabolomics profiling will meet 21st century demands in animal forensics.

Microstructure and Mechanical Propertiesof a Nitride-Strengthened Reduced ActivationFerritic/Martensitic Steel

Nitride-strengthened reduced activation ferritic/martensitic (RAFM) steels are developed taking advantage of the high thermal stability of nitrides. In the current study, the microstructure and mechanical properties of a nitride-strengthened RAFM steel with improved composition were investigated. Fully martensitic microstructure with fine nitrides dispersion was achieved in the steel. In all, 1.4 pct Mn is sufficient to suppress delta ferrite and assure the steel of the full martensitic microstructure. Compared to Eurofer97, the steel showed similar strength at room temperature but higher strength at 873 K (600 °C). The steel exhibited very high impact toughness and a low ductile-to-brittle transition temperature (DBTT) of 243 K (–30 °C), which could be further reduced by purification.

Microstructural evolution and mechanical properties of short-term thermally exposed 9/12Cr heat-resistant steels

The microstructural evolution during short-term (up to 3000 hours) thermal exposure of three 9/12Cr heat-resistant steels was studied, as well as the mechanical properties after exposure. The tempered martensitic lath structure, as well as the precipitation of carbide and MX type carbonitrides in the steel matrix, was stable after 3000 hours of exposure at 873 K (600 °C). A microstructure observation showed that during the short-term thermal exposure process, the change of mechanical properties was caused mainly by the formation and growth of Laves-phase precipitates in the steels. On thermal exposure, with an increase of cobalt and tungsten contents, cobalt could promote the segregation of tungsten along the martensite lath to form Laves phase, and a large size and high density of Laves-phase precipitates along the grain boundaries could lead to the brittle intergranular fracture of the steels.

Inter- and Intrafraction Target Motion in Highly Focused Single Vocal Cord Irradiation of T1a Larynx Cancer Patients

PURPOSE: The purpose of this study was to verify clinical target volume-planning target volume (CTV-PTV) margins in single vocal cord irradiation (SVCI) of T1a larynx tumors and characterize inter- and intrafraction target motion.

METHODS AND MATERIALS: For 42 patients, a single vocal cord was irradiated using intensity modulated radiation therapy at a total dose of 58.1 Gy (16 fractions × 3.63 Gy). A daily cone beam computed tomography (CBCT) scan was performed to online correct the setup of the thyroid cartilage after patient positioning with in-room lasers (interfraction motion correction). To monitor intrafraction motion, CBCT scans were also acquired just after patient repositioning and after dose delivery. A mixed online-offline setup correction protocol ("O2 protocol") was designed to compensate for both inter- and intrafraction motion.

RESULTS: Observed interfraction, systematic (Σ), and random (σ) setup errors in left-right (LR), craniocaudal (CC), and anteroposterior (AP) directions were 0.9, 2.0, and 1.1 mm and 1.0, 1.6, and 1.0 mm, respectively. After correction of these errors, the following intrafraction movements derived from the CBCT acquired after dose delivery were: Σ = 0.4, 1.3, and 0.7 mm, and σ = 0.8, 1.4, and 0.8 mm. More than half of the patients showed a systematic non-zero intrafraction shift in target position, (ie, the mean intrafraction displacement over the treatment fractions was statistically significantly different from zero; P<.05). With the applied CTV-PTV margins (for most patients 3, 5, and 3 mm in LR, CC, and AP directions, respectively), the minimum CTV dose, estimated from the target displacements observed in the last CBCT, was at least 94% of the prescribed dose for all patients and more than 98% for most patients (37 of 42). The proposed O2 protocol could effectively reduce the systematic intrafraction errors observed after dose delivery to almost zero (Σ = 0.1, 0.2, 0.2 mm).

CONCLUSIONS: With adequate image guidance and CTV-PTV margins in LR, CC, and AP directions of 3, 5, and 3 mm, respectively, excellent target coverage in SVCI could be ensured.

Arsenic-glutathione complexes - Their stability in solution and during separation by different HPLC modes

Complexes of arsenic compounds and glutathione are believed to play an essential part in the metabolism and transport of inorganic arsenic and its methylated species. Up to now, the evidence of their presence is mostly indirect. We studied the stability and Chromatographic behaviour of glutathione complexes with trivalent arsenic: i.e. As^III(GS)₃, MA ^III(GS)₂ and DMA^III(GS) under different conditions. Standard ion chromatography using PRP X-100 and carbonate or formic acid buffer disintegrated the complexes, while all three complexes are stable and separable by reversed phase chromatography (0.1% formic acid/acetonitrile gradient). As^III(GS)₃ and MA^III(GS)₂ were more stable than DMA^III(GS), which even under optimal conditions tended to degrade on the column at 25 °C. Chromatography at 6 °C can retain the integrity of the samples. These results shed more light on the interpretation of a vast number of previously published arsenic speciation studies, which have used Chromatographic separation techniques with the assumption that the integrity of the arsenic species is guaranteed. © The Royal Society of Chemistry 2004.

Hydrogel-Forming Microneedle Arrays Allow Detection of Drugs and Glucose In Vivo: Potential for Use in Diagnosis and Therapeutic Drug Monitoring

We describe, for the first time the use of hydrogel-forming microneedle (MN) arrays for minimally-invasive extraction and quantification of drug substances and glucose from skin in vitro and in vivo. MN prepared from aqueous blends of hydrolysed poly(methyl-vinylether-co-maleic anhydride) (11.1% w/w) and poly(ethyleneglycol) 10,000 daltons (5.6% w/w) and crosslinked by esterification swelled upon skin insertion by uptake of fluid. Post-removal, theophylline and caffeine were extracted from MN and determined using HPLC, with glucose quantified using a proprietary kit. In vitro studies using excised neonatal porcine skin bathed on the underside by physiologically-relevant analyte concentrations showed rapid (5 min) analyte uptake. For example, mean concentrations of 0.16 μg/mL and 0.85 μg/mL, respectively, were detected for the lowest (5 μg/mL) and highest (35 μg/mL) Franz cell concentrations of theophylline after 5 min insertion. A mean concentration of 0.10 μg/mL was obtained by extraction of MN inserted for 5 min into skin bathed with 5 μg/mL caffeine, while the mean concentration obtained by extraction of MN inserted into skin bathed with 15 μg/mL caffeine was 0.33 μg/mL. The mean detected glucose concentration after 5 min insertion into skin bathed with 4 mmol/L was 19.46 nmol/L. The highest theophylline concentration detected following extraction from a hydrogel-forming MN inserted for 1 h into the skin of a rat dosed orally with 10 mg/kg was of 0.363 μg/mL, whilst a maximum concentration of 0.063 μg/mL was detected following extraction from a MN inserted for 1 h into the skin of a rat dosed with 5 mg/kg theophylline. In human volunteers, the highest mean concentration of caffeine detected using MN was 91.31 μg/mL over the period from 1 to 2 h post-consumption of 100 mg Proplus® tablets. The highest mean blood glucose level was 7.89 nmol/L detected 1 h following ingestion of 75 g of glucose, while the highest mean glucose concentration extracted from MN was 4.29 nmol/L, detected after 3 hours skin insertion in human volunteers. Whilst not directly correlated, concentrations extracted from MN were clearly indicative of trends in blood in both rats and human volunteers. This work strongly illustrates the potential of hydrogel-forming MN in minimally-invasive patient monitoring and diagnosis. Further studies are now ongoing to reduce clinical insertion times and develop mathematical algorithms enabling determination of blood levels directly from MN measurements.