First-principles study of lithium aluminosilicate glass scintillators

Radiation sensors are an important enabling technology in several fields, such as medicine, scientific research, energy, defence, meteorology, and homeland security. Glass-based scintillators have been in use for more than 50 years and offer many benefits, including their ability to respond to different types of radiation, and to be readily formed into various shapes. There is, however, the prospect to develop new and improved glass scintillators, with low self-absorption, low refractive indices, and high radiative recombination rates. To investigate the factors limiting the improvement of glass scintillator properties, this work provides insight from atomic scale simulations of the cerium-doped lithium aluminosilicate (SiO2-Al2O3-MgO-Li2O-Ce2O3) glass scintillator system. Three glass compositions were studied using molecular dynamics and density functional theory to investigate the effect of the ratio (with RAl/M = [0.1, 0.8 and 1.2]) on the structural and electronic properties. For a ratio RAl/M > 1, it has been shown that glasses with increased polymerization allow for more effective incorporation of Ce3+ cations. The structural analysis also showed that the bond order of Al-O can be affected in the presence of a lithium-rich environment. Electronic density of states and Bader charge analysis indicate a decline in the population of localized trapping states with increasing RAl/M. This suggests a higher probability of radiative recombination which can increase the photon yield of these scintillators. These findings provide valuable guidance for optimizing Li-glasses in neutron detection systems by highlighting the intricate challenges.

THE UK NATIONAL THERMAL-HYDRAULICS FACILITY: MOTIVATIONS, DESIGN AND PLANNING STATUS

A UK National Thermal-Hydraulics Facility (NTHF) dedicated to supporting new reactor and other relevant business is being developed, one of the purposes being to deliver on the government’s carbon emission reduction commitments. The facility site is foreseen to be at Menai Science Park on the isle of Anglesey in North Wales, a region expected to see significant low carbon energy deployment in coming years. The UK NTHF is envisioned to cater for the needs of emerging nuclear in the UK – but also to serve as a hardware platform for international thermal-hydraulics research collaboration. Plans are to construct a platform capable of maintaining several test loops including support for the UK’s on-going, conventional nuclear new build programme as well as Gen-IV systems and associated materials like molten salt and liquid metal coolant media. Motivations are given for NTHF expected capabilities and requirements, which form the basis for its current design and planning state.

Calcium silicate sorbent from secondary waste ash: heavy metals-removal from acidic solutions

The layer lattice, ion-exchange material, Al-substituted 11 A tobermorite, has been synthesised via an alkaline hydrothermal route from a secondary waste ash arising from newsprint recycling. The hydrogarnet, katoite (Ca3Al2SiO12H8), was also formed. Batch sorption analyses have confirmed that the Al-substituted 11 A tobermorite-bearing product is an effective sorbent for Co2+, Cd2+ and Zn2+ ions from acidified aqueous media. Kinetic sorption data were analysed in accordance with the pseudo-first- and pseudo-second-order models and steady state data were fitted to the Langmuir and Freundlich isotherms. The Langmuir and pseudo-second-order models provided the most appropriate descriptions of the sorption processes. The maximum uptake capacities for Co2+, Cd2+ and Zn2+ at 20 degrees C were found to be 10.47, 2.92 and 3.09 mg g(-1), respectively, and the respective apparent pseudo-second-order rate constants were estimated to be 5.08 x 10(-3), 1.10 x 10(-3) and 1.13 x 10(-3) g mg(-1) min(-1).

The protective role of trait anxiety: a longitudinal cohort study

BACKGROUND

Most research has indicated that neuroticism (or trait anxiety) is associated with only negative outcomes. Such a common, heritable and variable trait is expected to have beneficial as well as detrimental effects. We tested the hypothesis that trait anxiety in childhood reduces the risk of dying from accidental causes in early adult life.

METHOD

A longitudinal, population-based, birth cohort study of 4,070 men and women born in the UK in 1946. Trait anxiety as judged by teachers when the participants were 13 and 15 years old, and the neuroticism scale of a Maudsley Personality Inventory (MPI) when the participants were 16 years old. Outcomes were deaths, deaths from accidents, non-fatal accidents, and non-fatal accidents requiring medical intervention.

RESULTS

Adolescents with low trait anxiety had higher rates of accident mortality to age 25 [low anxiety at 13, hazard ratio (HR) 5.9, low anxiety at 15, HR 1.8]. Low trait anxiety in adolescence was associated with decreased non-accidental mortality after age 25 (low anxiety at 13, HR 0; low anxiety at 15, HR 0.7; low neuroticism at 16, HR 0.7).

CONCLUSIONS

High trait anxiety measured in adolescence is associated with reduced accidents and accidental death in early adulthood but higher rates of non-accidental mortality in later life.

Podiatric biomechanics. An historical appraisal and discussion of the Root model as a clinical system of approach in the present context of theoretical uncertainty

This article attempts to review comprehensively the development of the established Root Model and to appraise dispassionately its place and role in today's field of clinical podiatric biomechanics. It also discusses several important emergent models (the models of Dananberg, Kirby, Fuller, McPoil, Hunt, and Demp) that have gained increasing popularity among the podiatric and nonpodiatric clinical communities over the last 10 to 15 years. All of these models (the Root model and emergent models) have been analyses against the background of the Kuhnian concepts of "paradigm" and "preparadigm." Discussion has been provided as to whether the domain of podiatric biomechanics presently resides in a paradigm driven normal science phase, or whether it is still functioning within a preparadigm phase with its defining hallmark of community nonconsensus. Suggestions are then made as to possible ways for research to progress within the present ferment of debate and theoretic uncertainty.

Biomechanical effects of malposition of tuberosity fragments on the humeral prosthetic reconstruction for four-part proximal humerus fractures

Variable outcomes in the prosthetic reconstruction of 4-part humerus fractures often can be attributed to inconsistent and nonanatomic tuberosity placement. To compare the effects of anatomic (anterior fin) versus nonanatomic (lateral fin) tuberosity placement, we developed a dynamic cadaver model for shoulder motion. With the use of a robotically driven, computer-controlled articulator, we tested external rotation torque in 5 fresh human shoulders. After evaluation of the intact shoulders, we experimentally induced 4-part humerus fractures in the specimens. These were then repaired by hemiarthroplasty, with the use of standard techniques to secure the greater and lesser tuberosities in either anatomic or nonanatomic positions; order was randomized. Nonanatomic tuberosity reconstruction led to significant impairment in external rotation kinematics and an 8-fold increase in torque requirements (P =.001). In contrast, anatomic reconstruction produced results indistinguishable from normal shoulder controls. This study underscores the importance of rotational alignment of tuberosities during reconstruction. Failure to properly position tuberosity fragments in the horizontal plane may result in insurmountable postoperative motion restriction.

Development of a multichannel microfluidic analysis system employing affinity capillary electrophoresis for immunoassay

A six-channel microfluidic immunoassay device with a scanned fluorescence detection system is described. Six independent mixing, reaction, and separation manifolds are integrated within one microfluidic wafer, along with two optical alignment channels. The manifolds are operated simultaneously and data are acquired using a singlepoint fluorescence detector with a galvano-scanner to step between separation channels. A detection limit of 30 pM was obtained for fluorescein with the scanning detector, using a 7.1-Hz sampling rate for each of the reaction manifolds and alignment channels (57-Hz overall sampling rate). Simultaneous direct immunoassays for ovalbumin and for anti-estradiol were performed within the microfluidic device. Mixing, reaction, and separation could be performed within 60 s in all cases and within 30 s under optimized conditions. Simultaneous calibration and analysis could be performed with calibrant in several manifolds and sample in the other manifolds, allowing a complete immunoassay to be run within 30 s. Careful chip conditioning with methanol, water, and 0.1 M NaOH resulted in peak height RSD values of 3-8% (N = 5 or 6), allowing for cross-channel calibration. The limit of detection (LOD) for an anti-estradial assay obtained in any single channel was 4.3 nM. The LOD for the cross-channel calibration was 6.4 nM. Factors influencing chip and detection system design and performance are discussed in detail.

Red diode laser induced fluorescence detection with a confocal microscope on a microchip for capillary electrophoresis

A highly sensitive laser induced fluorescence (LIF) detection system based on a 635 nm laser diode and cyanine-5 (Cy-5) dye, is described for use with a planar, microfluidic, capillary electrophoresis (CE) chip. The CE-chip is able to determine a protein biological threat agent simulant, ovalbumin (Ov), by performing an immunoassay separation of Cy-5 labeled anti-ovalbumin from its complex with Ov, in under 30 s. A confocal, epiluminescent detection system utilizing a photomultiplier tube gave optimum results with a 400 microm pinhole, an Omega 682DF22 emission filter, a 645DRLP02 dichroic mirror, a 634.54 +/- 5 nm excitation filter, and a Power Technology ACMO8 635 nm laser operated at 11.2 mW. Using this detector, a microchip CE device with a separation efficiency of 42,000 plates and an etch depth of 20 microm, gave a concentration detection limit of 9 pM Cy-5. This limit corresponds to the determination of 4560 injected molecules and detection of 900 of these molecules, given a probe volume of 1.6 pl and a probing efficiency of 20%.

Rapid detection and identification of biological and chemical agents by immunoassay, gene probe assay and enzyme inhibition using a silicon-based biosensor

A rapid biosensor assay procedure that utilizes biotin streptavidin mediated filtration capture onto nitrocellulose membrane, in conjunction with a silicon-based light-addressable potentiometric sensor (LAPS) was developed for detection and identification of biological and chemical threat agents. Sandwich immunoassays, nucleic acid hybridization assays and enzyme inhibition assays are described. For immunoassays, the lower limits of detection (LOD) per 100-microl sample were approximately 5 pg/ml for protein (Staphylococcal enterotoxin B), 2 ng/ml for virus (Newcastle disease virus), and 20 ng/ml for vegetative bacteria (Brucella melitensis). In a dual gene probe assay format, the LOD was 0.30 fmol (1.8 x 10(8) copies per 60-microl) of single stranded target DNA. Enzyme inhibition assays on the LAPS using acetylcholinesterase were able to detect soman and sarin in aqueous samples at 2 and 8 pg (100 and 600 pM), respectively. The assays were easy to perform and required a total time equal to the reaction period plus about 15 min for filtering, washing and sensing. The assay format is suitable for detection of a wide range of infectious and toxic substances. New assays can be developed and optimized readily, often within 1 or 2 days.

In vitro expression of the diphtheria toxin A-chain gene under the control of human chorionic gonadotropin gene promoters as a means of directing toxicity to ovarian cancer cell lines

OBJECTIVE

Our goal was to determine whether toxicity of the diphtheria toxin A-chain gene regulated by the human chorionic gonadotropin promoter can be directed to malignant ovarian cell lines.

STUDY DESIGN

Plasmids containing diphtheria toxin A-chain gene linked to the regulatory elements of the metalloergothioneine and human chorionic gonadotropin promoters were transfected into the cell lines. Expression of diphtheria toxin A-chain gene was determined by the inhibition of a cotransfected luciferase reporter gene.

RESULTS

Cytotoxicity of the diphtheria toxin A-chain gene is shown in a dose-responsive manner. Transfection of a plasmid expressing the diphtheria toxin A-chain gene controlled by a constitutive promoter readily inhibits protein synthesis. Specific inhibition of luciferase protein synthesis occurs in ovarian cancer cells transfected with the diphtheria toxin A-chain gene under the control of the human chorionic gonadotropin promoters when compared with normal ovarian epithelial cells or fibroblasts.

CONCLUSIONS

These data demonstrate the preferential expression of the diphtheria toxin A-chain gene, regulated by the human chorionic gonadotropin promoter, to ovarian cancer cell lines. This provides an avenue for targeting such cells for suicide, toxin, or cytokine genes.

Intravenous insertion site protection: moisture accumulation in intravenous site protectors

Stabilizing the intravenous catheter after insertion is a significant part of intravenous therapy. Dislodgments of the cannula from its optimal position in the vein can lead to complications such as phlebitis, thrombophlebitis, infiltration, and infection. Intravenous site protector shields are designed to protect the catheter from impact and tissue trauma at the insertion site. Nurses have requested ventilation in these shields to avoid moisture build up that may increase the risk of infections. To address this issue, experimental laboratory testing was performed to determine if moisture accumulation as evidenced by increased weight of the shield and visible evidence of condensation occurred. No moisture condensation problems with the ventilated intravenous site protectors were found.

Rapid immunofiltration assay of Newcastle disease virus using a silicon sensor

A rapid nonradioactive sandwich immunoassay which utilizes biotin-streptavidin mediated filtration capture of immune complexes in conjunction with a silicon sensor was developed for the detection of virus. Using purified Newcastle disease virus as a model, the lower limits of detection (LOD) were determined for a number of immunoassay configurations employing both monoclonal and polyclonal antibodies. The LODs ranged from 1.3 ng/ml (sample volume of 100 microliter) for an incubation of 60 min to 400 ng/ml for a 1 min incubation. The sandwich immune complexes were formed from one-step incubation of antibody and antigen. No 'hook' effects were observed over a wide range of analyte concentrations. The assays were easy to perform and required a total time equal to the incubation period plus about 5 min. The assay format is suitable for virus, bacteria and protein antigens. New assays can be developed and optimized readily, often within 1 day.

Core temperature rhythms in normal and tumor-bearing mice

The core temperature temporal behavior of DBA/2 mice (11 normal and 13 with an ascites tumor) was studied using surgically implanted radio telemetry transmitters. Normal mice continuously displayed a stable 24 hour temperature rhythm. Tumor-bearers displayed a progressive deterioration of the temperature rhythm following inoculation with tumor cells. While such disruptions have been noted by others, details on the dynamics of the changes have been mostly qualitative, often due to time-averaging or steady-state analysis of the data. The present study attempts to quantify the dynamics of the disruption of temperature rhythm (when present) by continuously monitoring temperatures over periods up to a month. Analysis indicated that temperature regulation in tumor-bearers was adversely affected during the active period only. Furthermore, it appears that the malignancy may be influencing temperature regulation via pathways not directly attributable to the energy needs of the growing tumor.

'Determination' of sugar alcohol and Polydextrose absorption in humans by the breath hydrogen (H2) technique: the stoichiometry of hydrogen production and the interaction between carbohydrates assessed in vivo and in vitro

The production of hydrogen from substrates and substrate mixture of sugar alcohols and Polydextrose was determined, both in vivo using the breath hydrogen test, and in vitro, using human faecal microorganisms in anaerobic culture. One objective was to test a previous assumption that the stoichiometry of hydrogen production from different alternative carbohydrates is similar. Another objective was to discover whether hydrogen responses from mixtures of substrates were simply additive, or whether interactions occurred. The breath tests were performed in a 10 subject x 10 substrate factorial design with substrates and substrate mixtures (5-11 g) administered in 42 g chocolate confectionery. Incorporation of the alternative carbohydrates lactitol (L), Isomalt (I) and Polydextrose (P) into otherwise conventional confectionery increased breath hydrogen production by approximately 112, 73 and 11%/g respectively. There was no interaction between L and I or between P and I, but a combination of L and P approximately doubled the breath hydrogen anticipated from their individual contributions (P < 0.05). Anaerobic cultures showed a sixfold range in the efficiency of converting individual substrates and mixtures to hydrogen gas (0.003-0.018 kJ H2 per kJ carbohydrate). The positive interaction between L and P, and the lack of interaction between L and I, and between P and I, found in vivo were reproduced in vitro. The work showed that interpretation of the hydrogen breath test is confounded by differing stoichiometries for hydrogen production, by interaction between substrates and by an uncertain extent to which small intestinal hydrolysis yielding species with a fermentation stoichiometry that differs from the parent substrate.

Assessing patient pain during dental laser treatment

Patients reported little or no pain during or after treatment with a dental laser. With many people reporting fear of pain as their chief reason for not seeking dental care, lasers may offer a more acceptable treatment technique.

Enhancement of the thermal and storage stability of urease by covalent attachment to phospholipid-bound silica

Urease was immobilized directly on silanized silica surfaces carrying alkyl moieties with terminal carboxylic groups. The enzyme was also covalently attached to phospholipid-bound silanized silica surfaces through the terminal carboxyl moiety on the sn-2 acyl chain of the lipid. The surfaces were characterized by X-ray photoelectron spectroscopy and ellipsometry. The activity of the immobilized urease was determined by UV spectrophotometry using a urea/bromocresol purple substrate. The enzymic activity decreases exponentially upon storage under dry solid conditions for 1 week or upon heating to 100 degrees C in the case of the silane/enzyme surfaces. On the other hand, the enzyme immobilized on phospholipid-carrying silica surfaces retained its entire original activity under dry storage or heat treatment conditions. Such immobilized urease systems could find extensive applicability in the design of in vivo dialysis equipment or for on-line monitoring of urea.

Distance dependence of the tryptophan-disulfide interaction at the triplet level from pulsed phosphorescence studies on a model system

In the present study the distance dependence of tryptophan-disulfide interaction is examined with a view to both utilizing the interaction as a more quantitative indicator of subtle conformational changes in proteins as well as elucidating the interaction mechanism. To examine perturbations specifically at the indole triplet level 2-(3-indolyl)-ethyl phenyl ketone (IEPK) in which excitation is transferred with high efficiency to the triplet state of the indole moiety was employed. Phosphorescence decays of IEPK excited by a laser pulse in 70/30 (vol/vol) ethanolether at 77 K were measured in the presence of various concentrations of simple disulfides. The nonexponential phosphorescence decays arising from a distribution of fixed chromophoreperturber separations and the steady-state quenching of IEPK were accounted for with an exponential dependence of the quenching rate constant with distance. The small effective Bohr radius (0.8 A) that appears in the exponent emphasizes the localized nature of the interaction. Comparison of the triplet quenching rate constant obtained at quencher contact with IEPK to that estimated in proteins suggests a dependence on the triplet energy of the indole moiety and an endothermic nature for the quenching process. The study predicts that in proteins tryptophan-disulfide interactions are very localized in nature and should give rise to detectable anomalous decays only out to 2 A beyond van der Waals contact between the interacting partners.

Perturbations to the intersystem crossing of proflavin upon binding to DNA and poly d(A-IU) from triplet-delayed emission spectroscopy

The steady-state prompt fluorescence, phosphorescence and delayed fluorescence spectra and triplet lifetimes of free proflavin and proflavin bound to native DNA and alternating poly d(A-IU) were obtained as a function of temperature in a buffer-glycerol solvent. The intensity of the proflavin E-type delayed fluorescence (DF) relative to both the phosphorescence (Ph) and the prompt fluorescence (F) was observed to increase with temperature, and plots of both ln (DF/Ph) and ln (DF/(F.tau T] as a function of 1/T were linear over a wide range of temperatures. Although the activation energies for the thermal repopulation of the proflavin excited singlet state from the triplet obtained from the slopes of these plots were essentially unchanged on binding, perturbations to the S1----T1 intersystem crossing rate constants extracted from the intercepts at infinite temperature were observed. The marked enhancement of the intersystem crossing that occurs with binding to the iodinated polynucleotide reflects an external heavy atom perturbation upon the intercalated dye which also induces a shortening in the triplet lifetime. With proflavin bound to DNA an enhancement to the S1----T1 intersystem crossing, though lesser in magnitude than for poly d(A-IU), is observed but with no change to the triplet lifetime. The well-studied fluorescence quenching of DNA-bound proflavin is a result of this increase in the intersystem crossing. It is proposed that these non-heavy atom enhancements in the intersystem crossing are due to distortions of the molecular plane of the bound proflavin molecule. In total these analyses provide a complete description of the excited state processes of the proflavin molecule and their variations with temperature.

The utilization of BMR measurements as a routine diagnostic procedure in normal health maintenance

The hypothesis that BMR measurements should become part of the routine diagnostics utilized by physicians in long term health maintenance programs is developed. The hypothesis is supported from two viewpoints. First, a number of conditions are known to cause increases in BMR. The conditions include endocrine disorders, cardiovascular abnormalities, and cancer. Thus an observed substantial rise in BMR could indicate the onset of a medical problem if the higher level is maintained over an extended period of time. Second, available data from a longitudinal aging study suggests that sustained periods of increased BMR indicate "killing" stresses which can be detrimental or even fatal to individual subjects. The recent improvements in BMR measurements techniques reported here now make it possible to set up an inexpensive, reliable, and easy-to-use apparatus. Thus it would not be difficult to incorporate BMR measurement techniques as one of the routinely utilized diagnostic procedures.