The effect of transverse wavefront width on specular neutron reflection.

In the analysis of neutron scattering measurements of condensed matter structure, it normally suffices to treat the incident and scattered neutron beams as if composed of incoherent distributions of plane waves with wavevectors of different magnitudes and directions that are taken to define an instrumental resolution. However, despite the wide-ranging applicability of this conventional treatment, there are cases, such as specular neutron reflectometry, in which the structural length scales of the scattering object require that the wavefunction of an individual neutron in the beam be described by a spatially localized packet - in particular with respect to the transverse extent of its wavefronts (i.e. normal to the packet's mean direction of propagation). It is shown in the present work that neutron diffraction patterns observed for periodic transmission phase gratings, as well as specular reflection measurements from patterned thin films with repeat units of the order of micrometres, can be accurately described by associating an individual neutron with a wave packet and treating a beam as a collection of independent packets. In these cases, accurate analysis requires that the transverse spatial extent of a neutron packet wavefront be accounted for in addition to the angular divergence of the beam that is characterized by a distribution of packet mean wavevector directions. It is shown how a measure of the effective transverse spatial extent of the neutron packet - over which its wavefronts are of sufficient uniformity to produce coherent scattering - can be determined by employing reference diffraction gratings and patterned thin films of known structure and composition.

Wavefront shaping assisted design of spectral splitters and solar concentrators.

Spectral splitters, as well as solar concentrators, are commonly designed and optimized using numerical methods. Here, we present an experimental method to spectrally split and concentrate broadband light (420-875 nm) via wavefront shaping. We manage to spatially control white light using a phase-only spatial light modulator. As a result, we are able to split and concentrate three frequency bands, namely red (560-875 nm), green (425-620 nm), and blue (420-535 nm), to two target spots with a total enhancement factor of 715%. Despite the significant overlap between the color channels, we obtain spectral splitting ratios as 52%, 57%, and 66% for red, green, and blue channels, respectively. We show that a higher number of adjustable superpixels ensures higher spectral splitting and concentration. We provide the methods to convert an optimized phase pattern into a diffractive optical element that can be fabricated at large scale and low cost. The experimental method that we introduce, for the first time, enables the optimization and design of SpliCons, which is [Formula: see text] times faster compared to the computational methods.

Case report: laser-assisted rebonding of a central incisor tooth due to a severe trauma - 4 years of follow-up.

BACKGROUND: The success of reattaching fractured tooth crowns fragments, as a result of trauma, has improved as a result of the introduction of lasers in dental care. This case report documents a 4 year follow-up of a re-bonded tooth fragment on a maxilary first permanent incisor. CASE REPORT: An 8-year-old girl presented with a fractured maxillary might first permanent incisor (II) as a result of a severe trauma. The child's parents had preserved the tooth fragment in a glass of milk immediately after the injury. TREATMENT: An Er,Cr:YSGG Laser with a wavelength of 2,780 nm was used with 20Hz, 5 W (250 mJ), 90 % air, 80% water for etching of the enamel and 20 Hz, 3W (150 mJ), 65% air, 55% water for dentine etching with a G6 (600 micron, sapphire, 6mm long) tip. For conditioning the enamel and dentine no additional acid etching was used. Only a 2 step self-etched adhesive system Clearfil Protect® (Kuraray Medical, Japan) was applied. Then a flowable composite resin, Grandi Flow® (Voco, Cuxhaven, Germany) was applied in order to bind the broken fragment onto the tooth. FOLLOW-UP: The re-bonded tooth fragment has been retained in place and symptom free, as assessed by clinical examination, intraoral photographs and radiographs for a period of 4 years. CONCLUSION: Laser-assisted re-bonding of a tooth fragment was found to be successful.

Analysis of multibeam data for neutron reflectivity.

We offer mathematical proof that multiple-beam neutron reflectivity, corresponding to simultaneous collection of data at multiple angles (wavevector transfers) does not perform better, errorwise for counting noise, than single-beam data collection for the same total number of reflected neutrons-and may perform much worse, depending on the beam modulation strategy used. The basic idea is that the nominal statistical benefit of summing data at, say, N different wavevector transfers is undone by needing to collect N differently modulated (i.e., weighted) sums in order to extract the reflectivities. To our knowledge, a general proof of this behavior for arbitrary strategies has been lacking. The formal result can be summarized by saying that the best nondiagonal matrix modulation strategies are orthogonal (unitary) matrices, or constant multiples thereof, and that these can do no better than diagonal--i.e., single-beam--strategies.

Statistical analysis of phase-inversion neutron specular reflectivity.

The phase-inversion approach to neutron specular reflection is elucidated in a formal setting, in order to emphasize its conceptual coherence and to facilitate study of some of its statistical properties in the context of real data. An operational notion of data degradation is introduced and illustrated with the randomizing effects of shot noise ("counting" noise) and the systematic "bias" induced by data truncation. Some basic statistical effects of phase-inversion are worked out in the new formalism and illustrated by simulated examples. A principal is advanced that phase-inversion sets the limit of available information from specular reflection.

Progress in the development of phase-sensitive neutron reflectometry methods.

It has been a number of years since phase-sensitive specular neutron reflectometry (PSNR) methods employing reference layers were first introduced to help remove the ambiguity inherent in the reconstruction of scattering length density (SLD) depth profiles (Majkrzak, C. F.; Berk, N. F. Physica B 2003, 336, 27) from specular reflectivity measurements. Although a number of scientific applications of PSNR techniques have now been successfully realized (Majkrzak, C. F.; Berk, N. F.; Perez-Salas, U. A. Langmuir 2003, 19, 7796 and references therein), in certain cases practical difficulties remain. In this article, we describe possible solutions to two specific problems: (1) the need for explicit, detailed knowledge of the SLD profile of a given reference layer of finite thickness; and (2) for a reference layer of finite thickness in which only two density variations are possible, how to identify which of two mathematical solutions corresponds to the true physical structure.

Platelet-monocyte complexes support monocyte adhesion to endothelium by enhancing secondary tethering and cluster formation.

OBJECTIVE: Adhesion of monocytes to endothelium can be supported by monocyte-monocyte interactions resulting in the formation of cell aggregates at the vessel wall (clusters). Since platelets that are bound to the injured vessel wall support monocyte adhesion and platelet activation in the circulation leads to formation of platelet-monocyte complexes (PMCs), we examined whether adhesion of PMCs to the vessel wall enhances monocyte clustering. METHODS AND RESULTS: The effect of PMC formation in monocyte adhesion and clustering on human umbilical vein endothelial cells (HUVECs) was studied in vitro with a perfusion system. In the presence of 10% to 20% PMCs, monocyte adhesion and cluster formation to stimulated HUVECs increased 2-fold above levels obtained with pure monocytes. While the observed effects increased with higher PMC levels, blocking-monoclonal antibodies directed against platelet-associated P-selectin or monocyte P-selectin glycoprotein ligand-1 (PSGL-1) reversed adhesion and clustering to control values. In the presence of PMCs, blocking L-selectin decreased adhesion by 25%. When PMCs were present, clustering was only supported by L-selectin at higher shear. These data indicate that monocyte adhesion to the vessel wall is enhanced by PMC-mediated monocyte secondary tethering. These interactions are mainly mediated by P-selectin and PSGL-1. CONCLUSIONS: PMCs in the circulation might be proatherogenic, and prevention of their formation is a possible therapeutic goal.

Perception of orthodontic treatment need: opinion comparisons of orthodontists, pediatric dentists, and general practitioners.

AIM: To determine the relationship between treatment need assessment scores of orthodontists, general practitioners, and pediatric dentists. STUDY DESIGN: Observational. SAMPLE: Ten general dental practitioners, 18 orthodontists and 15 pediatric dentists reviewed 137 dental casts and recorded their opinion on whether orthodontic treatment was needed. RESULTS: We found a high level of agreement between pediatric dentists, orthodontists and general practitioners (Kappa range 0.86-0.95). Between the groups, the amount of agreement was lower. CONCLUSIONS: Orthodontists, general dental practitioners, and pediatric dentists in this sample exhibit high levels of agreement on orthodontic treatment need.

Teaching ethics in dental schools: trends, techniques, and targets.

The importance of promoting ethical behavior in dental students is reflected in the emphasis on formal ethics teaching within the curricula of most dental schools. Over the last three decades, dental educators have addressed the need for ethics training and examined varied teaching approaches. Today, state-of-the-art ethics education has moved from purely didactic instruction to more interactional teaching methods that promote student introspection and group problem-solving. This paper provides an overview of trends in ethics teaching in dental schools and the current teaching approaches advocated in health science schools. In addition, future needs in dental ethics education are explored including the importance of addressing the unique aspects of the dental education environment.

Social anxiety in Chinese adults with oral-facial clefts.

OBJECTIVE: This study examined social anxiety and measures of psychosocial adjustment in Chinese adults with oral-facial clefts, their unaffected siblings, and age-matched controls. DESIGN: This cross-sectional study utilized a matched case-control study design. PARTICIPANTS: Eighty-five adult cleft lip and cleft palate (CL/CP) subjects and 85 unaffected siblings (one adult sibling of each CL/CP subject) were recruited in Shanghai, China, from a larger CL/CP study. Eighty-five unaffected controls, gender- and age-matched to the CL/CP subjects, were recruited from Shanghai work units including factories, universities, and other institutions. OUTCOME MEASURES: Social Avoidance and Distress Scale, Fear of Negative Evaluation, Rosenberg Self-Esteem Scale, Interpersonal Support Evaluation List. RESULTS: Affected adults reported significantly more social anxiety than unaffected siblings and controls. Affected adults also scored significantly lower on measures of self-esteem and social support than unaffected siblings and controls. Unaffected siblings and controls were not found to differ on any of these measures. CONCLUSIONS: Findings suggest that individuals with oral-facial clefts may be more disadvantaged with respect to social affiliation and adaptation than unaffected adults. Cross-cultural research is essential in enabling us to determine whether similar trends exist across cultures.

Hydration state of single cytochrome c monolayers on soft interfaces via neutron interferometry.

Yeast cytochrome c (YCC) can be covalently tethered to, and thereby vectorially oriented on, the soft surface of a mixed endgroup (e.g., -CH3/-SH = 6:1, or -OH/-SH = 6:1) organic self-assembled monolayer (SAM) chemisorbed on the surface of a silicon substrate utilizing a disulfide linkage between its unique surface cysteine residue and a thiol endgroup. Neutron reflectivities from such monolayers of YCC on Fe/Si or Fe/Au/Si multilayer substrates with H2O versus D2O hydrating the protein monolayer at 88% relative humidity for the nonpolar SAM (-CH3/-SH = 6:1 mixed endgroups) surface and 81% for the uncharged-polar SAM (-OH/-SH = 6:1mixed endgroups) surface were collected on the NG1 reflectometer at NIST. These data were analyzed using a new interferometric phasing method employing the neutron scattering contrast between the Si and Fe layers in a single reference multilayer structure and a constrained refinement approach utilizing the finite extent of the gradient of the profile structures for the systems. This provided the water distribution profiles for the two tethered protein monolayers consistent with their electron density profile determined previously via x-ray interferometry (Chupa et al., 1994).

First-principles determination of hybrid bilayer membrane structure by phase-sensitive neutron reflectometry.

The application of a new, phase-sensitive neutron reflectometry method to reveal the compositional depth profiles of biomimetic membranes is reported. Determination of the complex reflection amplitude allows the related scattering length density (SLD) profile to be obtained by a first-principles inversion without the need for fitting or adjustable parameters. The SLD profile so obtained is unique for most membranes and can therefore be directly compared with the SLD profile corresponding to the chemical compositional profile of the film, as predicted, for example, by a molecular dynamics simulation. Knowledge of the real part of the reflection amplitude, in addition to enabling the inversion, makes it possible to assign a spatial resolution to the profile for a given range of wavevector transfer over which the reflectivity data are collected. Furthermore, the imaginary part of the reflection amplitude can be used as a sensitive diagnostic tool for recognizing the existence of certain in-plane inhomogeneities in the sample. Measurements demonstrating the practical realization of this phase-sensitive technique were performed on a hybrid bilayer membrane (self-assembled monolayer of thiahexa (ethylene oxide) alkane on gold and a phospholipid layer) in intimate contact with an aqueous reservoir. Analysis of the experimental results shows that accurate compositional depth profiles can now be obtained with a spatial resolution in the subnanometer range, primarily limited by the background originating from the reservoir and the roughness of the film's supporting substrate.

Medical genetics on the cleft palate-craniofacial team: understanding parental preference.

OBJECTIVE: This study examined health care professionals' perceptions of parental preferences and preferences of parents of affected children (cleft lip, cleft palate, both, or other craniofacial anomaly) for prenatal testing with respect to oral-facial clefts and craniofacial anomalies. DESIGN: This was a descriptive study assessing and comparing questionnaire responses of two independent groups. PARTICIPANTS: Healthcare professional participants comprised 570 U.S. members of the American Cleft Palate-Craniofacial Association. Parent participants comprised 97 parents of children seen at the University of Pittsburgh Cleft Palate-Craniofacial Center. MAIN OUTCOME MEASURES: A practitioner survey was developed to examine practitioner perception of parental desire for involvement, desire for knowledge, and reaction to learning of a birth defect. A parent survey was developed to correspond with the practitioner survey. RESULTS: Health professionals' perceptions of parental preferences often paralleled parental preference data. However, parental responses were found to be significantly different from practitioner perception of parental preferences on one question reflecting desire for involvement (chi2 = 33.35, df=1, p = .001) and on one question reflecting desire for knowledge (chi2 = 4.82, df = 1, p = .03). For both questions, higher percentages of parents responded that they would want this involvement or information. CONCLUSIONS: Findings are consistent with those reported in other studies of prenatal testing preferences and susceptibility. Results suggest that parents of affected children have a strong desire for information and involvement in prenatal testing and counseling decisions. Parents appear to value preparation in spite of acknowledging anxiety associated with prenatal information.

Use of alkaline comet assay (single cell gel electrophoresis technique) to detect DNA damages in lymphocytes of operating room personnel occupationally exposed to anaesthetic gases.

Here, we report the possible in vivo induction DNA damage by exposure to various waste anaesthetic gases such as halothane, nitrous oxide and isoflurane. The alkaline comet assay (single cell gel electrophoresis technique) was carried out on 66 operating room personnel (anaesthetists [doctors]; anaesthesia nurses and anaesthesia unit technicians) currently employed at the Ankara Hospital in Turkey. A significant increase in the number of lymphocytes with DNA migration was observed in operating room personnel as compared to controls. Also, the extent of damage in exposed smokers were significantly higher than exposed nonsmokers. This study supports the existence of an association between DNA damage and occupational exposure to inhalation anaesthetics.

Improving portable inhalation therapy through real-time assessment of patient pulmonary state.

Metered-dose inhalation therapy is the method of choice for a number of respiratory conditions including asthma and bronchitis. Correct use of the metered-dose inhaler (MDI) has been the subject of much research. Devices have been developed to assist with training in their proper use and to enhance the effectiveness of MDI therapy. However, all lack patient pulmonary state assessment. We have approached the development of an improved portable MDI device by focusing on the total system elements that contribute to a smart inhalation therapy device. Components of such a system should include assessment of the patient's therapeutic state, tracking of drug usage, and also include physician-modified alarm thresholds. Therapeutic state is best assessed with end-expiratory CO2 measurements augmented by inspiratory and expiratory flow efforts. Drug usage monitoring needs to include the time history of drug administration. Physician-modified alarms should allow configuration of the smart inhaler to account for patient condition so that appropriate alarm limits can be established; for example, raising the CO2 alarm threshold for patients with chronic lung disease.

Neutron reflectivity studies of single lipid bilayers supported on planar substrates.

Neutron reflectivity was used to probe the structure of single phosphatidylcholine (PC) lipid bilayers adsorbed onto a planar silicon surface in an aqueous environment. Fluctuations in the neutron scattering length density profiles perpendicular to the silicon/water interface were determined for different lipids as a function of the hydrocarbon chain length. The lipids were studied in both the gel and liquid crystalline phases by monitoring changes in the specularly-reflected neutron intensity as a function of temperature. Contrast variation of the neutron scattering length density was applied to both the lipid and the solvent. Scattering length density profiles were determined using both model-independent and model-dependent fitting methods. During the reflectivity measurements, a novel experimental set-up was implemented to decrease the incoherent background scattering due to the solvent. Thus, the reflectivity was measured to Q approximately 0.3 A-1, covering up to seven orders of magnitude in reflected intensity, for PC bilayers in D2O and silicon-matched (38% D2O/62% H2O) water. The kinetics of lipid adsorption at the silicon/water interface were also explored by observing changes in the reflectivity at low Q values under silicon-matched water conditions.

Outline of Neutron Scattering Formalism.

Neutron scattering formalism is briefly surveyed. Topics touched upon include coherent and incoherent scattering, bound and free cross-sections, the Van Hove formalism, magnetic scattering, elastic scattering, the static approximation, sum rules, small angle scattering, inelastic scattering, thermal diffuse scattering, quasielastic scattering, and neutron optics.

Microstructural Characterization of Ceramic Materials by Small Angle Neutron Scattering Techniques.

The use of small angle neutron scattering (SANS) techniques for ceramic materials is discussed. Two areas are emphasized: 1) diffraction for microstructural phenomena of less than 100 nm, and 2) beam broadening for microstructural phenomena greater than 90 nm.