Self-assembly controlled at the level of individual functional groups.

Molecular self-assembly is driven by intermolecular interactions between the functional groups on the component molecules. Small changes in molecular structure can make large differences in extended structure, and understanding this connection will lead to predictive power and control of the self-assembly process. Scanning tunneling microscopy is used to study self-assembly in two-dimensional clusters and monolayers, and the experimental approach is to study "families" of molecules where one or more functional groups is varied in a methodical way. Studied families include indole carboxylic acids, isatin derivatives (which have the indole backbone), quinaldic acid, thioethers, and fluorenone derivatives. In these systems, a variety of intermolecular interactions drive the assembly of the molecular monolayer, including hydrogen bonds, van der Waals forces, zwitterionic interactions, surface interactions, and halogen interactions.

A Prospective Study of Magnetic Resonance Imaging Assessment of Post-radiation Changes Following Stereotactic Body Radiation Therapy for Non-small Cell Lung Cancer.

AIMS: Follow-up computed tomography scans after lung stereotactic body radiation therapy (SBRT) are difficult to interpret due to the presence of benign fibrosis, which can make the detection of local recurrence difficult. The objective of this study was to determine the feasibility of a novel thoracic magnetic resonance imaging (MRI) protocol incorporating diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) imaging for the assessment of the treated lung parenchyma after SBRT. MATERIALS AND METHODS: On a prospective trial, post-treatment MR images were acquired in 30 patients treated with SBRT (divided into three different cohorts according to the likelihood of local recurrence as per an expert panel). These images were assessed by an expert thoracic radiologist blind to clinical data, who indicated local recurrence in a dichotomous manner. Local recurrence was confirmed by biopsy or subsequent growth on follow-up computed tomography scans. RESULTS: Thirty patients underwent MRI as part of this study; 27/30 patients were analysable for local recurrence. MRI was conducted at a median of 27.3 months (range 6.5-71 months) from SBRT. No side-effects resulted from either MRI or contrast administration. At a median follow-up time of 45 months after treatment, three local recurrence episodes have occurred. MRI assessment diagnosed seven patients as having a local recurrence, which was later confirmed in three and did not miss any of the true local recurrences. When comparing apparent diffusion coefficient (ADC) values according to local recurrence, the mean ADC value for the local recurrence-free group was 1770 × 10-3 mm/s2 (range 1038-3105 × 10-3 mm/s2) versus 981 × 10-3 mm/s2 (range 926.6-1065 × 10-3 mm/s2) for the local recurrence group (P = 0.0014). CONCLUSIONS: A novel 3.0 T MRI protocol incorporating DWI and DCE was feasible and confirmed the suspicion of local recurrence in patients with highly suspicious computed tomography scans. This imaging tool could potentially aid in selecting patients for salvage treatment after local SBRT failure. Future work should be pursued to validate these findings.

Prolonged QT dispersion in Subclinical Hypothyroid Females: A Study in University Teaching Hospital in Central Nepal.

Background QT dispersion is a simple index derived from 12 lead ECG; its prolongation has been shown to be associated with increased arrhythmia risk. Increased cardiovascular risks, particularly occurrence of the malignant arrhythmias are a common finding in patients with subclinical hypothyroidism. This increased arrhythmia risk is found to be higher mainly in patients with TSH level more than 10 milli international unit per liter. Objective To assess QT dispersion among subclinical hypothyroid and euthyroid Nepalese females aged 20-59 years attending general practice out patient department of centrally located University Teaching Hospital from November 2016 to April 2017. Method Forty-three newly detected subclinical hypothyroid females and forty-one euthyroid females were enrolled. Resting electrocardiogram (ECG) was performed. QT dispersion was analyzed from ECG and corrected for heart rate using Framingham correction formula. Independent sample t-test was applied to compare mean QT dispersion between two groups. Pearson correlation test was used to examine the association between QT dispersion and TSH level. Result Mean QT dispersion for sub-clinical hypothyroid group was 75.35 ± 43.82 whereas mean QT dispersion for euthyroid group was 59.51 ± 22.13, with p value 0.041. A weak association between QT dispersion and TSH level was seen with correlation factor of 0.23. Conclusion The result showed prolongation of QT dispersion in sub-clinical hypothyroid group and weak positive correlation between TSH level and QT dispersion suggesting arrhythmia risk in subclinical hypothyroid females.

4-Methylpyrazole protects against acetaminophen hepatotoxicity in mice and in primary human hepatocytes.

Liver injury due to acetaminophen (APAP) overdose is the major cause of acute liver failure in the United States. While treatment with N-acetylcysteine is the current standard of care for APAP overdose, anecdotal evidence suggests that administration of 4-methylpyrazole (4MP) may be beneficial in the clinic. The objective of the current study was to examine the protective effect of 4MP and its mechanism of action. Male C57BL/6J mice were co-treated with 300 mg/kg of APAP and 50 mg/kg of 4MP. The severe liver injury induced by APAP at 6 h as indicated by elevated plasma alanine aminotransferase activities, centrilobular necrosis, and nuclear DNA fragmentation was almost completely eliminated by 4MP. In addition, 4MP largely prevented APAP-induced activation of c-Jun N-terminal kinase (JNK), mitochondrial translocation of phospho-JNK and Bax, and the release of mitochondrial intermembrane proteins. Importantly, 4MP inhibited the generation of APAP protein adducts and formation of APAP-glutathione (GSH) conjugates and attenuated the depletion of the hepatic GSH content. These findings are relevant to humans because 4MP also prevented APAP-induced cell death in primary human hepatocytes. In conclusion, early treatment with 4MP can completely prevent liver injury after APAP overdose by inhibiting cytochrome P450 and preventing generation of the reactive metabolite.

Structural Polymorphism as the Result of Kinetically Controlled Self-Assembly.

Traditionally, the goal of self-assembly and supramolecular chemistry is to engineer an equilibrium structure with a desired geometry and functionality; this is achieved through careful choice of molecular monomers, growth conditions, and substrate. Supramolecular assemblies produced under nonequilibrium conditions, in contrast, can form metastable structures with conformations quite different from those accessible in equilibrium self-assembly. The study of nonequilibrium growth of clusters potentially impacts the study of nucleation in atmospheric aerosols, nucleation in organic crystallization, and mesoscale organization for systems ranging from biological molecules to molecular electronics. In our experiments, we prepare surface monolayers of small organic and organometallic molecules through direct injection of a solution onto a substrate in high vacuum. During this process, the rapid evaporation of small solution droplets in high vacuum can lead to nonequilibrium growth conditions. The resulting structures are then characterized by scanning tunneling microscopy. Among the features observed in these experiments are cyclic, hydrogen-bonded pentamers. For carboxylic acids, the two-molecule ring dimer is the common binding motif. Large, cyclic hydrogen-bonded systems are uncommon, especially so for rings with five members. Despite this, pentagonal clusters appear to be a general phenomenon for systems containing adjacent strong and weak hydrogen-bonding elements on five-member aromatic rings. Regular pentamers have been observed as metastable structures for ferrocenecarboxylic acid, indole-2-carboxylic acid, and isatin (1-H-indole-2,3-dione). Electronic structure calculations confirm the relative stability of these structures with respect to the dimer or catemer conformations which are observed in the solid-state crystal structures. For ferrocenecarboxylic acid, cyclic pentamers undergo further self-assembly, resulting in long-range order in conjunction with local 5-fold rotational symmetry. This system is the first reported self-assembled molecular quasicrystal, and it remains the only example of a hydrogen-bonded quasicrystal. This supramolecular structure forms as a result of the cocrystallization of hydrogen-bonded cyclic pentamers with intercalated molecular dimers. The shared bonding to a single dimer is responsible for locking the adjacent pentamers in specific distances and orientations, which produces the quasicrystal. Careful analysis of experimental data provides evidence that, in some cases, metastable clusters are formed in solution and then subsequently adsorb on the surface. This is a unusual mechanism for supramolecular assembly, and it has important implications for understanding questions in crystal growth, namely: what the initial stages of crystal growth are as molecules are first precipitating from solution; what role the solvent plays in determining crystal structure; and whether solvent-mediated clustering is important in the broader phenomenon of solid-state polymorphism.

Non-intuitive clustering of 9,10-phenanthrenequinone on Au(111).

The direct injection of a 9,10-phenanthrenequinone in tetrahydrofuran solution on a Au(111) substrate in high vacuum results in the formation of metastable clusters with a non-intuitive structure. Metastable, rectangular tetramers of this molecule form in which the net molecular dipoles all orient toward the center of the cluster. This structure does not allow for additional hydrogen bonding and thus the origin of its metastability is not clear. We compare this feature to other structures observed on this surface, as well as those formed during the deposition of 9-fluorenone, which does not exhibit this anomalous clustering behavior.

24-h personal monitoring of exposure to Power Frequency Magnetic Fields in adolescents - Results of a National Survey.

OBJECTIVES: The aim of this exposure assessment study was to gain information about the exposure levels of adolescents in Israel to power frequency (50Hz) magnetic fields (MF) through personal monitoring, and to provide reliable data for national policy development. METHODS: 84 adolescents, 6-10th grade students, carried an EMDEX II meter attached to their body for 24h. The meter recorded the MF every 1.5s. The students documented their activities and microenvironments, such as apartment (awake or asleep), school, transportation, open public areas and other indoor environments. RESULTS: The geometric mean (GM) of the daily time weighted average (TWA) of all the participants was 0.059 µT (STD = 1.83). This result is similar to those of personal exposure surveys conducted in the UK (GM 0.042-0.054µT), but lower than levels found in the US (GM 0.089 - 0.134µT). The arithmetic mean was 0.073µT, 23% higher than the GM. Fields were lowest at school (GM 0.033µT), and average outdoor exposures were higher than indoor ones. 3.6% of the participants were exposed to daily TWA above 0.2µT. The typical time spent above 0.2µT ranged from few minutes to few hours. The time spent above 0.4µT and 1µT were much shorter, around 1-15min and from few seconds to 2min, respectively. Momentary peaks ever recorded were in the range of 0.35-23.6µT CONCLUSIONS: Exposure of adolescents in Israel is similar to data reported in other countries, being below 0.1µT for the vast majority, with very few average exposures above 0.2µT. Analysis of the different microenvironments allows for a cost-effective and equitable policy development.

Flying under the radar: treatment of refractory hyperglycemia.

UNLABELLED: Clinicians are often presented with the scenario of what to do when one medication in a drug class has failed a therapeutic trial on a patient. We encountered a patient who developed profound resistance to glargine, aspart and regular insulin, but had a rapid and sustained response to detemir. The mechanism of the increased sensitivity to detemir is unclear, but may be related to an additional carbon chain on detemir shielding it from an antibody response. This case highlights the profound impact that subtle differences in molecular structure can have on biological activity and thus patient outcomes. LEARNING POINTS: Subtle differences in molecular structure can have a profound impact on biological activity, and thus patient outcomes.Poor outcomes with one medication in a drug class should not be used to rule out the efficacy of all related medications.Detemir has been shown to be less immunogenic than other insulins, and should be considered in patients with insulin resistance.

Yield of intensified tuberculosis case-finding activities using Xpert(®) MTB/RIF among risk groups in Nepal.

SETTING: Twenty-two districts of Nepal, where intensified case-finding (ICF) activities for tuberculosis (TB) were implemented among risk groups under the TB REACH initiative in collaboration with the National TB Programme from July 2013 to November 2015. OBJECTIVES: To assess the yield of TB screening using an algorithm with smear microscopy followed by Xpert(®) MTB/RIF. DESIGN: A descriptive study using routinely collected data. RESULTS: Of 145 679 individuals screened, 28 574 (19.6%) had presumptive TB; 1239 (4.3%) of these were diagnosed with TB and 1195 (96%) were initiated on anti-tuberculosis treatment. The yield of screening was highest among people living with the human immunodeficiency virus (PLHIV) (6.1%), followed by household contacts (3.5%) and urban slum dwellers (0.5%). Among other risk groups, such as prisoners, factory workers, refugees and individuals with diabetes, the yield was less than 0.5%. The number needed to screen to diagnose an active TB case was 17 for PLHIV, 29 for household contacts and 197 for urban slum dwellers. Of 11 525 patients from ICF and the routine programme, 112 (1%) were diagnosed with multidrug-resistant TB. CONCLUSION: There was a substantial yield of TB cases among risk groups such as PLHIV and household contacts. Although the yield in urban slum dwellers was found to be moderate, some intervention should nonetheless be targeted because of the large population and poor access to care in this group.

Contexte : Vingt-deux districts du Népal où des activités intensifiées de recherche des cas (ICF) de la tuberculose (TB) ont été mises en œuvre au sein de groupes à risque sous l'égide du projet TB REACH en collaboration avec le programme national TB entre juillet 2013 et novembre 2015.Objectifs : Evaluer le rendement du dépistage de la TB grâce à un algorithme basé sur la microscopie de frottis suivie d'un test Xpert® MTB/RIF.Schéma : Etude descriptive basée sur des données recueillies en routine.Résultats : Sur un total de 145 679 individus dépistés, 28 574 (19,6%) ont été présumés atteints de TB ; 1239 (4,3%) d'entre eux ont eu une confirmation du diagnostic de TB ; parmi ces derniers, 1195 (96%) ont mis en route un traitement anti-tuberculose. Le rendement a été le plus élevé parmi les personnes vivant avec le virus l'immunodéficience humaine (PVVIH) (6,1%) suivies par les contacts domiciliaires (3,5%) et les habitants des bidonvilles (0,5%). Dans d'autres groupes à risque comme les prisonniers, les travailleurs d'usine, les réfugiés et les diabétiques, le rendement a été inférieur à 0,5%. Le nombre de personnes à dépister (NNS) pour diagnostiquer un cas de TB active a été de 17 pour les PVVIH, de 29 pour les contacts domiciliaires et de 197 pour les habitants des bidonvilles urbains. Sur 11 525 patients émanant soit du programme ICF soit du dépistage de routine, 112 (1%) ont eu un diagnostic de TB multirésistante.Conclusion : Le rendement en termes de cas de TB dépistés parmi les groupes à risque comme les PVVIH et les contacts domiciliaires a été substantiel. Même si ce rendement a été modeste parmi les habitants des bidonvilles, ceux-ci justifient néanmoins une intervention en raison de leur nombre élevé et de leur médiocre accès aux soins.

Marco de referencia: Veintidós distritos de Nepal, en los cuales se ejecutaron actividades de búsqueda intensiva de casos (ICF) de tuberculosis (TB) en los grupos de riesgo, en el marco del proyecto TB REACH en colaboración con el programa nacional contra la TB de julio del 2013 a noviembre del 2015.Objetivos: Evaluar el rendimiento de la detección sistemática de la TB aplicando un algoritmo que comporta la baciloscopia, seguida de la prueba Xpert® MTB/RIF.Método: Fue este un estudio descriptivo a partir de los datos recogidos de manera sistemática.Resultados: De las 145 679 personas en quienes se practicó la detección, en 28 574 hubo una presunción diagnóstica de TB (19,6%); en 1239 de estos pacientes se estableció el diagnóstico de TB (4,3%); e iniciaron el tratamiento 1195 pacientes (96%). El rendimiento diagnóstico fue más alto en las personas viviendo con el virus de la inmunodeficiencia humana (PVVIH, 6,1%), seguidas de los contactos domiciliarios (3,5%) y los residentes en tugurios (0,5%). En otros grupos de riesgo de contraer la TB como los reclusos, los obreros de fábricas, los refugiados o los pacientes diabéticos el rendimiento diagnóstico fue inferior a 0,5%. El número de personas que se debieron examinar con el fin de detectar un caso de TB activa fue 17 en las PVVIH, 29 en los contactos domiciliarios y 197 en los habitantes de los tugurios. De las 11 525 personas examinadas en la ICF y el programa corriente, se diagnosticó TB multiresistente en 112 casos (1%).Conclusión: La detección sistemática de casos de TB exhibió un alto rendimiento en los grupos de riesgo como las PVVIH y los contactos domiciliarios. Aunque el desempeño en los tugurios urbanos fue moderado, es importante dirigir intervenciones a estos entornos, dado el tamaño de estas poblaciones y su acceso deficiente a la atención de salud.

Synthesis of a Neutral Mixed-Valence Diferrocenyl Carborane for Molecular Quantum-Dot Cellular Automata Applications.

The preparation of 7-Fc(+) -8-Fc-7,8-nido-[C2 B9 H10 ](-) (Fc(+) FcC2 B9 (-) ) demonstrates the successful incorporation of a carborane cage as an internal counteranion bridging between ferrocene and ferrocenium units. This neutral mixed-valence Fe(II) /Fe(III) complex overcomes the proximal electronic bias imposed by external counterions, a practical limitation in the use of molecular switches. A combination of UV/Vis-NIR spectroscopic and TD-DFT computational studies indicate that electron transfer within Fc(+) FcC2 B9 (-) is achieved through a bridge-mediated mechanism. This electronic framework therefore provides the possibility of an all-neutral null state, a key requirement for the implementation of quantum-dot cellular automata (QCA) molecular computing. The adhesion, ordering, and characterization of Fc(+) FcC2 B9 (-) on Au(111) has been observed by scanning tunneling microscopy.

Hydrogen-bonded clusters of 1, 1'-ferrocenedicarboxylic acid on Au(111) are initially formed in solution.

Low-temperature scanning tunneling microscopy is used to observe self-assembled structures of ferrocenedicarboxylic acid (Fc(COOH)2) on the Au(111) surface. The surface is prepared by pulse-deposition of Fc(COOH)2 dissolved in methanol, and the solvent is evaporated before imaging. While the rows of hydrogen-bonded dimers that are common for carboxylic acid species are observed, the majority of adsorbed Fc(COOH)2 is instead found in six-molecule clusters with a well-defined and chiral geometry. The coverage and distribution of these clusters are consistent with a random sequential adsorption model, showing that solution-phase species are determinative of adsorbate distribution for this system under these reaction conditions.

Hydrogen-bonded clusters of ferrocenecarboxylic acid on Au(111).

Self-assembled monolayers of ferrocenecarboxylic acid (FcCOOH) contain two fundamental units, both stabilized by intermolecular hydrogen bonding: dimers and cyclic five-membered catemers. At surface coverages below a full monolayer, however, there is a significantly more varied structure that includes double-row clusters containing two to twelve FcCOOH molecules. Statistical analysis shows a distribution of cluster sizes that is sharply peaked compared to a binomial distribution. This rules out simple nucleation-and-growth mechanisms of cluster formation, and strongly suggests that clusters are formed in solution and collapse into rows when deposited on the Au(111) surface.

Factors influencing parental consent for participation in clinical research involving their children in Egypt.

Factors affecting parents' decision to involve their children in clinical research have not been studied in all cultural backgrounds. We aimed to explore the attitudes and beliefs influencing parents' decision to involve their children in clinical research in Mansoura, Egypt. Of 523 families approached, 357 filled the questionnaire. Only 98 (27.5%) parents consented to involve their child in clinical research. The children of consenters were significantly older than refusers: 8.6 (SD 7.2) versus 2.6 (SD 1.2) years. Factors favouring consent were: research of benefit to child (84.7%), enough explanation about the benefits (40.8%) and to learn more about child's condition (29.6%). Factors favouring refusal were: use of new drugs or vaccines (89.6%) and invasive procedures (84.2%). Parents' rate of consent was positively correlated with the research being non-invasive and the belief that research was of benefit to their child and negatively correlated with belief that refusal may negatively affect the care provided to their child.

Self-assembly of hydrogen-bonded two-dimensional quasicrystals.

The process of molecular self-assembly on solid surfaces is essentially one of crystallization in two dimensions, and the structures that result depend on the interplay between intermolecular forces and the interaction between adsorbates and the underlying substrate. Because a single hydrogen bond typically has an energy between 15 and 35 kilojoules per mole, hydrogen bonding can be a strong driver of molecular assembly; this is apparent from the dominant role of hydrogen bonding in nucleic-acid base pairing, as well as in the secondary structure of proteins. Carboxylic acid functional groups, which provide two hydrogen bonds, are particularly promising and reliable in creating and maintaining surface order, and self-assembled monolayers of benzoic acids produce structure that depends on the number and relative placement of carboxylic acid groups. Here we use scanning tunnelling microscopy to study self-assembled monolayers of ferrocenecarboxylic acid (FcCOOH), and find that, rather than producing dimeric or linear structures typical of carboxylic acids, FcCOOH forms highly unusual cyclic hydrogen-bonded pentamers, which combine with simultaneously formed FcCOOH dimers to form two-dimensional quasicrystallites that exhibit local five-fold symmetry and maintain translational and rotational order (without periodicity) for distances of more than 400 ångströms.

Observation of Dirac monopoles in a synthetic magnetic field.

Magnetic monopoles--particles that behave as isolated north or south magnetic poles--have been the subject of speculation since the first detailed observations of magnetism several hundred years ago. Numerous theoretical investigations and hitherto unsuccessful experimental searches have followed Dirac's 1931 development of a theory of monopoles consistent with both quantum mechanics and the gauge invariance of the electromagnetic field. The existence of even a single Dirac magnetic monopole would have far-reaching physical consequences, most famously explaining the quantization of electric charge. Although analogues of magnetic monopoles have been found in exotic spin ices and other systems, there has been no direct experimental observation of Dirac monopoles within a medium described by a quantum field, such as superfluid helium-3 (refs 10-13). Here we demonstrate the controlled creation of Dirac monopoles in the synthetic magnetic field produced by a spinor Bose-Einstein condensate. Monopoles are identified, in both experiments and matching numerical simulations, at the termini of vortex lines within the condensate. By directly imaging such a vortex line, the presence of a monopole may be discerned from the experimental data alone. These real-space images provide conclusive and long-awaited experimental evidence of the existence of Dirac monopoles. Our result provides an unprecedented opportunity to observe and manipulate these quantum mechanical entities in a controlled environment.

Factors influencing parental consent for participation in clinical research involving their children in Egypt

Factors affecting parents' decision to involve their children in clinical research have not been studied in all cultural backgrounds.We aimed to explore the attitudes and beliefs influencing parents' decision to involve their children in clinical research in Mansoura, Egypt.Of 523 families approached, 357 filled the questionnaire.Only 98 [27.5%]parents consented to involve their child in clinical research.The children of consenters were significantly older than refusers:8.6 [SD 7.2]versus 2.6 [SD 1.2]years.Factors favouring consent were:research of benefit to child [84.7%], enough explanation about the benefits [40.8%]and to learn more about child's condition [29.6%]. Factors favouring refusal were:use of new drugs or vaccines [89.6%]and invasive procedures [84.2%]. Parents' rate of consent was positively correlated with the research being non-invasive and the belief that research was of benefit to their child and negatively correlated with belief that refusal may negatively affect the care provided to their child

لم تخضع العوامل التي تؤثر على موافقة الوالدين على إشراك أطفالهم في البحوث السريرية، للدراسة في جميع الخلفيات الثقافية. وهدف الباحثون إلى التعرف على المواقف والمعتقدات التي تؤثر على القرارات التي يتخذها الوالدان حول مشاركة أطفالهم في البحوث السريرية في المنصورة في مصر. وقد تواصل الباحثون مع 523 أسرة، استكملت الاستبيانات منها 357 أسرة، واتضح أن 98 من الوالدين [27.5%]، فقط قد وافقوا على مشاركة أطفالهم في البحوث السريرية، وأن متوسط أعمار الأطفال الذين وافق الوالدان على مشاركتهم بالبحوث وهو 8.6 عاما [7.2 +/- ] أكبر بمقدار يعتد به إحصائيا من متوسط أعمار الأطفال الذين رفض الوالدان مشاركتهم بها وهو 2.6 عاما [1.2 +/- ]، وأن العوامل التي ترجح الموافقة هي:البحوث التي تعود بالنفع على الطفل [84.7 %]والشرح الوافي عن المنافع [40.8%]والتعلم أكثر عن حالة الطفل [29.6 %]أما العوامل التي ترجح رفض الموافقة فهي: استخدام أدوية أو لقاحات جديدة [89.6%]، والإجراءات الباضعة [84.2 %]. وكان هناك ترابطا إيجابي بين معدل موافقة الوالدين مع كون البحوث غير باضعة وكذلك مع الاعتقاد بأن البحوث نافعة لطفلها، وكان هناك ترابط سلبي مع الاعتقاد بأن رفض المشاركة قد يؤثر سلبيا على الرعاية التي تقدم لطفلها

Les facteurs influant sur la décision des parents de laisser leur enfant participer à une étude de recherche clinique n'ont pas été étudiés dans tous les contextes culturels.L'objectif de 'étude était d'examiner les attitudes et les croyances influant sur la décision des parents de laisser participer leur enfant à une étude de recherche à Mansoura [Egypte]. Sur 523 familles contactées, 357 ont rempli le questionnaire.Seuls 98 parents [27, 5 %]consentaient à laisser participer leur enfant a une recherche clinique.Les enfants des parents qui avaient donné leur consentement étaient nettement plus âgés que ceux dont les parents avaient refusé:8, 6 ans [ET 7, 2]contre 2, 6 ans [ET 1, 2]. Les facteurs favorisant le consentement étaient les suivants:une recherche bénéfique pour l'enfant [84, 7 %], des explications suffisantes sur les avantages [40, 8 %]et l'occasion de mieux connaitre l'affection de leur enfant [29, 6%]. Les facteurs favorisant le refus étaient les suivants:l'utilisation de nouveaux médicaments ou vaccins [89, 6 %]et des actes invasifs [84, 2 %]. Le taux de consentement des parents était positivement corrélé à une recherche non invasive et à la croyance que la recherche serait bénéfique pour leur enfant, et négativement corrélé à la croyance selon laquelle un refus pourrait négativement influer sur les soins fournis à leur enfant

Communication: Site-dependent reactivity between chlorine atoms and mixed-chain-length alkanethiolate monolayers.

The chemical reaction of atomic chlorine with mixed monolayers of alkanethiolates having different chain lengths was investigated. In situ scanning tunneling microscopy was used to acquire time-lapsed series of images, allowing the measurement of the effect of monolayer structure and composition on reactivity. The rate of chemical reaction is strongly site-dependent. In particular, the boundary between two different-length alkanethiolates greatly promotes the reactivity of nearby molecules, much more so than any other native defect typical of single-component alkanethiolate monolayers.

Compact, single-tube scanning tunneling microscope with thermoelectric cooling.

We have designed and built a scanning tunneling microscope with a compact inertial-approach mechanism that fits inside the piezoelectric scanner tube. Rigid construction allows the microscope to be operated without the use of external vibration isolators or acoustic enclosures. Thermoelectric cooling and a water-ice bath are used to increase temperature stability when scanning under ambient conditions.

The role of defects in the reaction of chlorine atoms with alkanethiol self-assembled monolayers.

Scanning tunneling microscopy (STM) in ultra-high-vacuum is used to investigate the reaction of gas-phase atomic chlorine with octanethiolate self-assembled-monolayers on Au(111). Exposure to Cl atoms results in the formation of a variety of surface defects, and eventually leads to a complete loss of order within the alkanethiolate monolayer. X-ray photoelectron spectroscopy and thermal desorption mass spectrometry show that these morphological changes are accompanied by significant chlorination of the monolayer as well as a ~30% decrease in the amount of adsorbed sulfur. The rate of reaction is measured through the analysis of sequences of STM images, and coverage-vs.-exposure data shows that the average reactivity of any given molecule within the monolayer decreases as the reaction progresses. Working with the assumption that monolayer defects created by Cl-atom reaction will affect the reactivity of neighboring molecules, a kinetic Monte Carlo simulation shows the data are consistent with defect sites inhibiting reaction rate by a factor of 5 or more. This behavior is opposite to that found for hydrogen-atom reactions, where edge and defect sites were far more reactive. The dynamics of chlorine-atom reactivity are described primarily in terms of the formation and subsequent reaction of surface-adsorbed radicals, with surface defects providing sites where these radicals can be quenched.

Normothermic acellular ex vivo liver perfusion reduces liver and bile duct injury of pig livers retrieved after cardiac death.

We compared cold static with acellular normothermic ex vivo liver perfusion (NEVLP) as a novel preservation technique in a pig model of DCD liver injury. DCD livers (60 min warm ischemia) were cold stored for 4 h, or treated with 4 h cold storage plus 8 h NEVLP. First, the livers were reperfused with diluted blood as a model of transplantation. Liver injury was determined by ALT, oxygen extraction, histology, bile content analysis and hepatic artery (HA) angiography. Second, AST levels and bile production were assessed after DCD liver transplantation. Cold stored versus NEVLP grafts had higher ALT levels (350 ± 125 vs. 55 ± 35 U/L; p < 0.0001), decreased oxygen extraction (250 ± 65 mmHg vs. 410 ± 58 mmHg, p < 0.01) and increased hepatocyte necrosis (45% vs. 10%, p = 0.01). Levels of bilirubin, phospholipids and bile salts were fivefold decreased, while LDH was sixfold higher in cold stored versus NEVLP grafts. HA perfusion was decreased (twofold), and bile duct necrosis was increased (100% vs. 5%, p < 0.0001) in cold stored versus NEVLP livers. Following transplantation, mean serum AST level was higher in the cold stored versus NEVLP group (1809 ± 205 U/L vs. 524 ± 187 U/L, p < 0.05), with similar bile production (2.5 ± 1.2 cc/h vs. 2.8 ± 1.4 cc/h; p = 0.2). NEVLP improved HA perfusion and decreased markers of liver duct injury in DCD grafts.