New Empirical Equation for the Atomic Form Factor Function in the Momentum Transfer Range,q?=?0–50 ??1 for the Elements in the Range 1≤ Z ≤30

The importance of Atomic Form Factors (f) is well-known to the scientific community. Tabulated values for f are mostly used in calculating cross-sections and Monte Carlo sampling for the coherent scattering of photons. The uses of these values are subjected to different approximations and interpolation techniques because the available data points for f in the literature for specified momentum-transfer-grids are very limited. In order to make it easier to accurately use the tabulated data, a mathematical expression for f functions would be a great achievement. Therefore, the current study was designed to suggest an empirical expression for the f functions. In the results, an empirical equation for Hubbell''s tabulated data for f is created in the momentum transfer range, q = 0–50 Å⁻¹ for the elements in the range 1≤ Z ≤30. The number of applied parameters was seven. The fitting to f showed that the maximum deviation was within 3%, 4% and 5% for the element having, Z = 1–11, Z = 12–22 and Z = 23–30, respectively, while the average deviations were within 0.3–2.25% for all elements (i.e., Z = 1–30). The values generated by the analytical equation were used in the Monte Carlo code instead of Hubbell’s tabulated values. The statistical noise in the Probability Distribution Functions of coherently scattered photons was efficiently removed. Furthermore, it also reduced the dependence on different interpolation techniques and approximations, and on the use of large tabulated data for f with the specified elements.     

Nicotine Dependence and Cost-Effectiveness of Individualized Support for Smoking Cessation: Evidence from Practice at a Worksite in Japan

Given the lack of economic studies evaluating the outcomes of smoking cessation programs from the viewpoint of program sponsors, we conducted a case study to provide relevant information for worksites. The present study was carried out between 2006 and 2008 at a manufacturing factory in the Toyama Prefecture of Japan and included subjects who voluntarily entered a smoking cessation program. The program included face-to-face counselling followed by weekly contact to provide encouragement over six months using e-mail or inter-office mail. Nicotine patches were available if required. All 151 participants stopped smoking immediately. Over the 24-month study period, self-report showed 49.7% abstained continuously from smoking. The rate of 24-month consecutive abstinence was higher in participants with lower Fagerström Test scores for Nicotine Dependence at baseline than in those with higher scores (63.6% for 0–2 points vs. 46.5% for 3–6 points vs. 43.8% for 7–10 points; chi-square test p = 0.19). A logistic regression model showed a significant linear trend for the association between the score and abstinence status after adjustment for possible confounding factors (p = 0.03). The crude incremental cost for one individual to successfully quit smoking due to the support program was ¥46,379 (i.e., ¥100 = $1.28, £0.83, or €1.03 at foreign exchange rates). The corresponding costs for the three categories of the Fagerström Test score for Nicotine Dependence were ¥31,953, ¥47,450 and ¥64,956, respectively. When a sensitivity analysis was conducted based on the 95% confidence interval of the success rate, the variance in the corresponding costs was ¥25,514–45,034 for 0–2 points, ¥38,344–61,824 for 3–6 points, and ¥45,698–108,260 for 7–10 points. The degree of nicotine dependence may therefore be an important determinant of the cost-effectiveness of smoking cessation programs.     

Demand for human allograft tissue in Canada

There is relatively little known about the demand for allograft tissues in Canada. The Canadian Council for Donation and Transplantation (CCDT) is a national advisory body that undertook a comprehensive “market survey” to estimate surgical demand for human allograft tissues in Canada. The report “Demand for Human Allograft Tissue in Canada” reflects survey results sent to 5 prominent User Groups. User Groups were identified as orthopaedic surgeons; neurosurgeons; corneal transplant surgeons; plastic surgeons, specifically those at Canadian Burn Units; and cardiac surgeons (adult and paediatric surgery). The demand for allograft grafts was determined and then extrapolated across the total User Group and then increases in allograft tissue use over the next 1–2 years across User Groups were predicted. The overall response rate for the survey was 21.4%. It varied from a low of 19.6% for the orthopaedic survey to a high of 40.5% for the corneal survey. The estimated current demand for allograft tissue in Canada ranges from a low of 34,442 grafts per year to a high of 62,098 grafts per year. The predicted increase in use of allograft tissue over the next 1–2 year period would suggest that annual demand could rise to somewhere in the range of 42,589–72,210 grafts. The highest rated preferences (98% and 94%) were for accredited and Canadian tissue banks, respectively. This study represents a key step in addressing the paucity of information concerning the demand for allograft tissue in Canada.     

Plasmid Encoded AcrAB–TolC Tripartite Multidrug-Efflux System in Acidiphilium symbioticum H8

Acidophilic bacterium, Acidiphilium symbioticum H8, is resistant to high levels of several heavy metals, hydrophobic agents, and organic solvents. The ~9.6 kb plasmid pASH8, was purified, digested with HindIII, and sub-cloned in pUC19 at the respective site. Three different fragment size clones were achieved. The clones were completely sequenced and analyzed. The first clone encodes for a single putative open reading frame (ORF), which showed significant homology to several rusticyaninA1 proteins. The second clone encodes for a 43-kDa protein, which has conserved domain homology with several outer envelop TolC proteins. The clone with pASH8 tolC gene can functionally complement an Escherichia coli tolC mutant strain, making it resistant to several toxic hydrophobic agents, earlier for which it was sensitive. The tolC gene was found to be essential for imparting resistance to the clone toward these toxic hydrophobic agents. The third clone encodes for a putative 318-aa AcrA (acriflavine resistance protein A) protein and the clone was resistance to plasmid curing dye acriflavine. The clone also has a truncated ORF, which showed significant homology to cation-efflux pump AcrB. This study is the first to report a multi-drug efflux system to be encoded on a plasmid of any Acidiphilium strain.     

A study of nephron function in normal tropical residents using the creatinine and lithium clearances

 The kidney bears the brunt of the demands of a tropical climate for water and electrolyte homeostasis. We hypothesised that a tropical climate may cause adaptive changes in the entire organism leading to altered renal function in our subjects. Hence renal function data for residents of a temperate climate may not be applic- able to tropical residents. We therefore sought to elucidate renal function in subjects residing in a tropical climate. We used lithium clearance, C _Li, a non-invasive tool for assessing proximal tubular function in humans, and endogenous creatinine clearance, C _Cr, to estimate proximal tubular function and glomerular function, respectively, in our subjects. We did this in order to establish whether or not nephron function in our subjects differs from that for residents of a temperate climate. Nineteen male and 12 female Ghanaian subjects aged between 15 and 48 years were studied. The estimated G _Cr was 117.3±6.6 ml/min for male subjects and 97±6.4 ml/min for female subjects. C _Li was 20.3±1.6 ml/min for male and 19.1±0.4 ml/min for female subjects, respectively. The estimated absolute reabsorption rate of fluid of proximal tubules was 97.0±6.0 ml/min for males and 78.1±6.0 ml/min for females. The percentage proximal fluid reabsorption for male and female subjects was 81.2±1.4 and 79.5±1.6, respectively. The differences between male and female values (mean±SEM) were not statistically significant. The data suggest that the proximal tubule in residents of a tropical climate may reabsorb more fluid compared to that in residents of a temperate climate. Our values for proximal tubular reabsorption are higher than those reported for residents of a temperature climate. Our estimate of glomerular filtration, however, is similar to published data for Caucasians. The difference in proximal tubular function may reflect possible renal adaptation to a hot, humid climate. We conclude that renal function of tropical residents differs from that of residents of a temperate climate. This difference may be due to renal adaptation to the hot, tropical climate. Received: 1 July 1996 / Revised: 22 December 1996 / Accepted: 8 January 1997     

Three-dimensional modeling of the cochlea by use of an arc fitting approach

Purpose: A cochlea modeling approach is presented allowing for a user defined degree of geometry simplification which automatically adjusts to the patient specific anatomy. Model generation can be performed in a straightforward manner due to error estimation prior to the actual generation, thus minimizing modeling time. Therefore, the presented technique is well suited for a wide range of applications including finite element analyses where geometrical simplifications are often inevitable. Methods: The method is presented for n=5 cochleae which were segmented using a custom software for increased accuracy. The linear basilar membrane cross sections are expanded to areas while the scalae contours are reconstructed by a predefined number of arc segments. Prior to model generation, geometrical errors are evaluated locally for each cross section as well as globally for the resulting models and their basal turn profiles. The final combination of all reconditioned features to a 3D volume is performed in Autodesk Inventor using the loft feature. Results: Due to the volume generation based on cubic splines, low errors could be achieved even for low numbers of arc segments and provided cross sections, both of which correspond to a strong degree of model simplification. Model generation could be performed in a time efficient manner. Conclusion: The proposed simplification method was proven to be well suited for the helical cochlea geometry. The generated output data can be imported into commercial software tools for various analyses representing a time efficient way to create cochlea models optimally suited for the desired task.     

Standardization of food allergen extracts for skin prick test

The aim of the study was to standardize and evaluate technically optimized food allergen extracts for use in skin prick test (SPT). The standardization procedure comprised 36 allergic histories in 32 food allergic patients with 21 healthy, non-atopic individuals serving as controls. The patients had a history of allergic symptoms upon ingestion of either cow’s milk (n=3), hen’s egg (n=9), wheat (n=4), hazelnut (n=14) or cod (n=6). They also had specific IgE in serum to the food in question and a positive SPT with a fresh preparation of the food. The diagnosis had been confirmed by a double-blind, placebo-controlled food challenge, except for the hazelnut-allergic patients. The controls were subjected to an open food challenge with all the foods to ensure tolerance. The standardization was performed by means of titrated SPT in accordance with the guidelines on biological standardization from the Nordic Council on Medicine. Regression analysis of the skin wheal areas was performed for each patient and the median protein concentration of allergen preparation (median C_h10) eliciting a wheal area of the same size as histamine 10 mg/ml was calculated. The median C_h10 was 0.56 mg/ml for milk, 0.88 mg/ml for egg, 5.4 mg/ml for wheat, 2.1 mg/ml for hazelnut and 0.017 mg/ml for the cod extract. The sensitivity of the median C_h10 estimated from the SPT data was 1 for milk, 0.98 for egg, 1 for wheat, 1 for hazelnut and 0.87 for the cod extract. The allergenic activity of the hazelnut extract was further investigated by leukocyte histamine release (HR) and immunoblotting experiments using sera from 27 hazelnut allergic patients. The clinical sensitivity of the optimized hazelnut extract evaluated by HR was 0.78 compared to 0.30 for a commercially available hazelnut extract (Soluprick). Immunoblotting results showed a stronger IgE binding capacity and additional IgE-binding bands of the optimized hazelnut extract compared with the Soluprick extract.     

Efficacy of loop mediated isothermal amplification (LAMP) assay for the laboratory identification of Mycobacterium tuberculosis isolates in a resource limited setting

Current methods of TB diagnosis are time consuming and less suited for developing countries. The LAMP (loop mediated isothermal amplification) is a rapid method more suitable for diagnosis in resource limited settings and has been proposed as a viable test requiring further evaluation for use as a laboratory method as well. We evaluated two LAMP assays, using culture lysates of clinical sputum samples (from Southern India) and compared it to a proprietary multiplex PCR reverse-hybridization line probe assay (‘GenoType MTBC’ from HAIN Lifescience GmbH, Germany). The LAMP procedure was modified to suit the local conditions. The Mycobacterium tuberculosis specific LAMP assay (‘MTB LAMP’) showed sensitivity and specificity, of 44.7% and 94.4% respectively in a 60 min format, 85.7% and 93.9% respectively in a 90 min format and 91.7%, and 90.9% respectively in a 120 min format. The Mycobacteria universal LAMP assay (‘Muniv LAMP’) showed a sensitivity of 99.1%. The LAMP was shown to be a rapid and accessible assay for the laboratory identification of M. tuberculosis isolates. Initial denaturation of template was shown to be essential for amplification in unpurified/dilute samples and longer incubation was shown to increase the sensitivity. The need for modification of protocols to yield better efficacy in this scenario needs to be addressed in subsequent studies.     

Alternative approach to species identification of Actaea racemosa L. (syn. Cimicifuga racemosa (L.) Nutt., black cohosh) herbal starting material: UV spectroscopy coupled with LDA

The North American Actaea racemosa L. (syn. Cimicifuga racemosa (L.) Nutt., commonly known as black cohosh), considered to be a more “natural” alternative to conventional therapies, is used to relieve menopausal symptoms. The high demand for plant material has led to problems with substitution/adulteration of raw material of wholesale origin. The authenticity of the starting material is crucial for the herbal product’s efficacy and safety, and tests on identity and substitution are integral parts of cGMP guidelines. Consequently, there is a need for economical and easy-applicable test procedures. The aim of this study is to reveal the capability of the well-established UV spectroscopy coupled with a multivariate classification procedure to serve as a tool for the identification of A. racemosa. We built a classification model applying linear discriminant analysis (LDA) to distinguish between A. racemosa and its common substitutes. The model showed a high level of accuracy predicting 100% of the samples correctly. Our results indicate that UV spectroscopy shows potential for the development of possible additional authentication methods for this herbal starting material.     

Monitoring vegetation change caused by trampling: a study in the Cairngorms,Scotland

Summary

A study was made in the Cairngorms, Scotland to make recommendations for a monitoring scheme capable of detecting changes in the vegetation caused by recreational pressure following the development of a funicular railway. Four methods were used in field trials to assess percentage cover of plant species and gravel, rock and bare ground, where appropriate, in two vegetation types (open and closed). The methods used were visual estimates in 50 × 40 cm quadrats (Q), the mean of visual estimates in twenty 10 × 10 cm sub-quadrats of the 50 × 40 cm quadrats (Q₂₀), a modified point intercept method (RL) and photography. Variances between observers and between-quadrats were estimated for the different methods. The sampling design for detecting change was based on a model of variance, constructed from field trial data.

Between-observer and between-quadrat variances were related to mean percentage cover and approximated to a binomial distribution. The between-quadrat variance was larger than observer variance. The Q₂₀ method achieved appreciably better precision than the other methods. Analysis of half of the 10 × 10 cmsub-quadrats (1/2Q₂₀) selected in a checker board design achieved a relative efficiency of 78% compared with the Q₂₀. This result suggests that comparable precision to the Q₂₀ method could be achieved by choosing about 14 sub-quadrats in a larger quadrat, thus saving some time. Variation between quadrats also suggested that the Q₂₀ method was the one of choice for maximising precision. The precision of the photographic method was based on fewer data points, so is less accurate than other estimates.

Minimum sample sizes were estimated for detecting a 10% relative change of a species in open vegetation with 30% cover (i.e. a change from 30% to <27 or to >33% cover). With a 10 % Type II error rate and 5 % Type I error rate the minimum sample sizes were 47 quadrats for Q, 18 for Q ₂₀, 43 for RL, and 23 for the means of ten 10 × 10 cm sub-quadrats in open vegetation.

The most time-efficient field recording appeared to be the use of Q despite the required sample size being 2.6 times higher than that of Q₂₀. The far lower time requirement per quadrat, however, compensated for the higher numbers. The number of quadrats would depend on the specified change in percentage cover and on the statistical significance level used. For example, to detect a 10% absolute change in cover (i.e. from 30% to either <20 % or >40 % cover) at 95 % probability the net effective recording time is estimated at 5 h per vegetation type while to detect a 5 % change at 99 % probability would require c. 25 h. Larger samples may be required for other species or for species with a low initial cover.     

Electrogenerated chemiluminescence of novel TiO2/CdS nanocomposites for sensitive assays of cancer cells

A novel TiO₂/CdS nanocomposite was prepared and used to fabricate an electrochemiluminescence (ECL) biosensor for the detection of cancer cells for the first time. The nanocomposite exhibited a strong cathodic ECL signal. Folic acid for targeting cell membranes was bound to a TiO₂/CdS/3-aminopropyltriethoxysilane film, and specific recognition of folic acid to targeting cells was achieved, leading to a significant decrease in ECL intensity. The decrease in ECL signal was logarithmically related to the cell concentration in the range of 150–9600 cells mL^-1. The ECL biosensor could provide a sensitive, selective, and convenient approach for early and accurate detection of cancer cells.     

Application of Sequential Classification of Prey/Predator Ratio Test to Tetranychus urticae and Phytoseiulus persimilis System in Greenhouse Roses

A sequential sampling procedure for classifying the ratio of prey/predators developed by Nyrop (1988) was examined to implement for a biological control in the greenhouse roses. The procedure was combined with a sequential density classification procedure for use in monitoring a phytophagous mite, Tetranychus urticae Koch, and a phytoseiid predator, Phytoseiulus persimilis Athias-Henriot. This procedure was required four parameters: Means and variances for T. urticae and P. persimilis, correlation coefficient between densities of prey and predator and critical ratio of prey and predator. The parameter values used in this study were 0.725 for the correlation coefficient and 10 for the critical ratio. The variances for each species were estimated using a Taylor's power law model. The procedure is proven to be successfully applicable to T. urticae and P. persimilis system in greenhouse roses at two action threshold levels of 5 and 10 T. urticae per three-leaflet leave. The limitations and implementation of this procedure is also discussed.     

Agrobacterium -mediated transformation of embryogenic cell suspensions of the banana cultivar Rasthali (AAB)

 A protocol was developed for establishing embryogenic suspension cultures from in vitro-grown, thin shoot-tip sections of the banana cultivar Rasthali. The best medium for callus induction was an MS-based medium supplemented with 2 mg/l 2,4-D and 0.2 mg/l zeatin. The callus was transferred to liquid medium to establish embryogenic cell suspensions. These cultures were subsequently used for Agrobacterium-mediated transformation. The Agrobacterium tumefaciens strain EHA105 containing the binary vector pVGSUN with the als gene as a selectable marker and an intron-containing the gusA gene as a reporter gene was used for transformations. The herbicide Glean was used as a selection agent. Two hundred putative transformants were recovered, of which a set of 16 was tested by histochemical analysis for GUS expression and by Southern blot analysis with a probe for the gusA gene. The plants were positive for GUS expression and integration of the gusA gene. Two of the transformants were grown to maturity under greenhouse conditions. Bananas were harvested to test GUS expression by histochemical analysis. The fruit from both transgenics tested positive for GUS expression. Received: 22 February 2000 / Revision received: 2 October 2000 / Accepted: 5 October 2000     

Modeling of adaptations to physical training by using a recursive least squares algorithm

Busso, Thierry, Christian Denis, Régis Bonnefoy,André Geyssant, and Jean-René Lacour. Modeling ofadaptations to physical training by using a recursive least squaresalgorithm. J. Appl. Physiol. 82(5):1685-1693, 1997.The present study assesses the usefulnessof a systems model with time-varying parameters for describing theresponses of physical performance to training. Data for two subjectswho undertook a 14-wk training on a cycle ergometer were used to testthe proposed model, and the results were compared with a model withtime-invariant parameters. Two 4-wk periods of intensive training wereseparated by a 2-wk period of reduced training and followed by a 4-wkperiod of reduced training. The systems input ascribed to the trainingdoses was made up of interval exercises and computed in arbitraryunits. The systems output was evaluated one to five times per week byusing the endurance time at a constant workload. The time-invariantparameters were fitted from actual performances by using the leastsquares method. The time-varying parameters were fitted by using arecursive least squares algorithm. The coefficients of determinationr² were 0.875 and0.879 for the two subjects using the time-varying model, higher thanthe values of 0.682 and 0.666, respectively, obtained with thetime-invariant model. The variations over time in the model parametersresulting from the expected reduction in the residuals appearedgenerally to account for changes in responses to training. Such a modelwould be useful for investigating the underlying mechanisms ofadaptation and fatigue.

     

Characterization of the Minimal Replicon of a Cryptic Deinococcus radiodurans SARK Plasmid and Development of Versatile Escherichia coli-D. radiodurans Shuttle Vectors

The nucleotide sequence of a 12-kb fragment of the cryptic Deinococcus radiodurans SARK plasmid pUE10 was determined, in order to direct the development of small, versatile cloning systems for Deinococcus. Annotation of the sequence revealed 12 possible open reading frames. Among these are the repU and resU genes, the predicted products of which share similarity with replication proteins and site-specific resolvases, respectively. The products of both genes were demonstrated using an overexpression system in Escherichia coli. RepU was found to be required for replication, and ResU was found to be required for stable maintenance of pUE10 derivatives. Gel shift analysis using purified His-tagged RepU identified putative binding sites and suggested that RepU may be involved in both replication initiation and autoregulation of repU expression. In addition, a gene encoding a possible antirestriction protein was found, which was shown to be required for high transformation frequencies. The arrangement of the replication region and putative replication genes for this plasmid from D. radiodurans strain SARK is similar to that for plasmids found in Thermus but not to that for the 45.7-kb plasmid found in D. radiodurans strain R1. The minimal region required for autonomous replication in D. radiodurans was determined by sequential deletion of segments from the 12-kb fragment. The resulting minimal replicon, which consists of approximately 2.6 kb, was used for the construction of a shuttle vector for E. coli and D. radiodurans. This vector, pRAD1, is a convenient general-purpose cloning vector. In addition, pRAD1 was used to generate a promoter probe vector, and a plasmid containing lacZ and a Deinococcus promoter was shown to efficiently express LacZ.     

Characterization of a commercial scintillation detector for 2-D dosimetry in scanned proton and carbon ion beams

IntroductionPencil beam scanning technique used at CNAO requires beam characteristics to be carefully assessed and periodically checked to guarantee patient safety. This study aimed at characterizing the Lynx® detector (IBA Dosimetry) for commissioning and periodic quality assurance (QA) for proton and carbon ion beams, as compared to EBT3 films, currently used for QA checks.Methods and materialsThe Lynx® is a 2-D high-resolution dosimetry system consisting of a scintillating screen coupled with a CCD camera, in a compact light-tight box. The scintillator was preliminarily characterized in terms of short-term stability, linearity with number of particles, image quality and response dependence on iris setting and beam current; Lynx® was then systematically tested against EBT3 films. The detector response dependence on radiation LET was also assessed.ResultsPreliminary results have shown that Lynx is suitable to be used for commissioning and QA checks for proton and carbon ion scanning beams; the cross-check with EBT3 films showed a good agreement between the two detectors, for both single spot and scanned field measurements. The strong LET dependence of the scintillator due to quenching effect makes Lynx® suitable only for relative 2-D dosimetry measurements.ConclusionLynx® appears as a promising tool for commissioning and periodic QA checks for both protons and carbon ion beams. This detector can be used as an alternative of EBT3 films, allowing real-time measurements and analysis, with a significant time sparing.     

Surface Plasmon Dynamics of High-Aspect-Ratio Gold Nanorods

Ultrafast transient absorption studies are reported for high-aspect-ratio gold nanorods that were fabricated by electrochemical deposition in polycarbonate templates. The nanorods are 60 nm in diameter with distribution of lengths of up to 6 μm. The average aspect ratio was ∼50, resulting in a longitudinal surface plasmon resonance (SPR_L) band in the mid-IR, as well as a transverse (SPR_T) band in the visible. The rods were excited at 400 nm and probed at a range of wavelengths from the visible to the mid-IR to interrogate both SPR bands. The dynamics observed, including the electron–phonon coupling time and coherent acoustic breathing mode oscillations, closely resemble those previously reported for gold spherical nanoparticles and smaller-aspect-ratio nanorods. The electron–phonon coupling time was similarly determined to be 3.3 ± 0.2 ps for both of the SPR bands. Also, oscillations with a 32-ps period were observed for probing near the SPR_T band in the visible region due to impulsive coherent excitation of the acoustic breathing mode, which are consistent with the 60-nm diameter of the nanorods determined by scanning electron microscopy. The results demonstrate that the dynamics for long gold nanorods are similar to those for smaller nanoparticles. Gerald M. Sando is a NRL-ASEE Research Associate     

Uncertainty in positioning ion chamber at reference depth for various water phantoms

Background

Uncertainty in the calibration of high-energy radiation sources is dependent on user and equipment type.

Studies of the complex between transfer RNAs with complementary anticodons: I. Origins of enhanced affinity between complementary triplets

We used the temperature-jump method to study the complex between yeast t RNA^Pheand Escherichia coli tRNA^Glu, which have the complementary anticodons GmAA and s²UUC, respectively. The binding constant (3.6 × 10⁵m^?1 at 25 °C) is about six orders of magnitude larger than expected for two complementary trinucleotides. The association rate constant (3 × 10⁶m^?1 at 25 °C) is similar to typical values observed for oligonucleotides, so the enhanced affinity in the tRNA · tRNA complex is due entirely to a much slower dissociation than expected for a three base-pair helix. We found an association enthalpy of ?25 kcal/mol, nearly twice as large as expected for two stacking interactions in a three base-pair helix. The association entropy (?58 cal/deg per mol) is close to the expected value. The reaction occurs with a single relaxation, and therefore does not involve any slow reorganization of the tRNA molecule.We studied structural variations to investigate the origin of affinity enhancement. The following general factors are important. (1) The “loop constraint”, or closure of the two anticodon sequences into hairpin loops, accounts for about a factor 50 in the affinity. (2) “Dangling ends”, or non-complementary nucleotides at the end of the double helix contribute strongly to the affinity. (3) Modified nucleotides, like the Y base, in the dangling ends can contribute a special stabilization of up to a factor seven. These observations can be understood in terms of a model in which the short three base-pair helix is sandwiched between stacked bases and hence stabilized. The potential importance of loop-loop interactions and stacking effects for codon-anticodon bonding is emphasized. The results suggest a possible simple physical basis for the evolutionary choice of a triplet coding system.     

Enquête nationale en médecine nucléaire : radiopharmaceutiques et activités utilisés en 2007 dans le secteur public

The Institute for radiation protection and nuclear safety (IRSN) and the National institute for health surveillance (InVS) have been collaborating since 2003 to provide updated data on medical exposure of the French population related to medical diagnosis. In this framework, a survey was carried out by IRSN in 2009 within all the 127 departments of nuclear medicine belonging to public hospitals. The rate of participation was high (72% of the departments). The first objective of this survey was to estimate the activity of these nuclear medicine departments (numbers and types of examination, according to their code in the French common classification for medical care). The second objective was to collect data related to the dose delivered to the patient for each type of examination. This article details this second part of the survey and presents, for the 32 most frequent types of examination, the radionuclide used and its chemical form, the average administered activity per examination and the activity range for the responding departments. When a French dose reference level exists, this survey showed that the average administered activity is in agreement with it, excepted for the ^99mTc thyroid scintigraphy with an administered activity close to twice the dose reference level (DRL). The dispersion of administered activity between the departments for a same type of examination depends on the type of examination, and is comprised between 2 and 10 for a 70 kg patient.