Low-Coordinate Magnesium Sulfide and Selenide Complexes.

The reactions of [{(iPrDipNacNac)Mg}2] 1 (iPrDipnacnac = HC(iPrCNDip)2) with Ph3P═O at 100 °C afforded the phosphinate complex [(iPrDipNacNac)Mg(OPPh3)(OPPh2)] 3. Reactions of 1 with Ph3P═E (E = S, Se) proceeded rapidly at room temperature to low-coordinate chalcogenide complexes [{(iPrDipNacNac)Mg}2(µ-S)] 4 and [{(iPrDipNacNac)Mg}2(µ-Se)] 5, respectively. Similarly, reactions of RNHC═S ((MeCNR)2C═S with R = Me, Et, or iPr) with 1 afforded NHC adducts of magnesium sulfide complexes, [{(iPrDipNacNac)Mg(RNHC)}(µ-S){Mg(iPrDipNacNac)}] 6, that could alternatively be obtained by adding the appropriate RNHC to sulfide complex 4. Complex 4 reacted with 1-adamantylazide (AdN3) to give [{(iPrDipNacNac)Mg}2(µ-SN3Ad)] 7 and can form various simple donor adducts in solution, of which [(iPrDipNacNac)Mg(OAd)}2(µ-S)] 8a (OAd = 2-adamantanone) was structurally characterized. The nature of the ionic Mg-E-Mg unit is described by solution and solid-state studies of the complexes and by DFT computational investigations.

Umpolung of an Aliphatic Ketone to a Magnesium Ketone-1,2-diide Complex with Vicinal Dianionic Charge.

The new ß-diketimine iPrDip nacnacH, HC(iPrCNDip)2 H, Dip=2,6-iPr2 -C6 H3 , was converted to the magnesium(I) complex [{(iPrDip nacnac)Mg}2 ] and reaction with 2-adamantanone (OAd) afforded the ketone-1,2-diide complex [{(iPrDip nacnac)Mg}2 (µ-OAd)]. The complex contains the first stable dianion of an aliphatic ketone with an electropositive metal and shows an OAd2- unit with long C-O bond and pyramidal carbon centre. DFT studies reveal an anionic charge on both neighbouring C and O atoms. Reductions of aliphatic ketones with magnesium(I) complexes show that these likely proceed via highly reactive dianions and afforded a 1 : 1 mixture of an alkoxide and an enolate when an enolisable ketone was used, and rapid CH activations reactions, e.g., of stabilising ligand moieties, when non-enolisable ketones were employed.

Interviewing anorexia: How do individuals given a diagnosis of anorexia nervosa experience Voice Dialogue with their eating disorder voice? A qualitative analysis.

A proportion of individuals given an eating disorder diagnosis describe the experience of an eating disorder 'voice' (EDV). However, methods for working with this experience are currently lacking. Voice Dialogue (Stone & Stone, 1989) involves direct communication between a facilitator and parts of the self to increase awareness, understanding, and separation from inner voices. Adapted forms of this method have shown promise in working with voices in psychosis. This study aimed to explore the experience and acceptability of Voice Dialogue amongst individuals with anorexia nervosa who experience an EDV. Nine women participated in a semistructured interview following a single Voice Dialogue session. Interview transcripts were analysed using interpretative phenomenological analysis (IPA). Three overarching themes were identified as follows: (i) "separating from the EDV"; (ii) "better understanding of the EDV"; and (iii) "hopeful, motivated, and afraid of recovery". The majority of participants found Voice Dialogue acceptable and helpful for exploring their EDV. Whilst preliminary, the results suggest that Voice Dialogue has potential in terms of helping individuals establish a more constructive relationship with their EDV and motivating change. Further research is needed to build upon these findings. Implications for addressing the EDV using voice-focused interventions are explored.

Normal and abnormal NHC coordination in cationic hydride iodide complexes of aluminium.

The mixed N-heterocyclic carbene (NHC) complexes NHCAlHxI3-x, where NHC is IDip or IMes ((HCNAr)2C:, Ar = 2,6-iPr2C6H3 = Dip (IDip); or 2,4,6-Me3C6H2 = Mes (IMes)), x = 1 or 2, were either prepared from NHCAlH3 and NHCAlI3 or by halogenation of NHCAlH3 with MeI. Reaction of [(IDip)AlHxI3-x], with x = 0-3, with another equivalent of IDip afforded either fluxional equilibria in benzene solution for x = 0, no reaction for x = 3, or the new mixed normal-abnormal NHC-coordinated ionic complexes [(IDip)AlH2(aIDip)]I (9) and [(IDip)AlHI(aIDip)]I (10), where aIDip is the abnormal IDip carbene tautomer bonded through its 4-position. The molecular structures of 9 and 10 were determined and show slightly shorter Al-C(aIDip) than Al-C(IDip) distances. In addition, a complex containing [(IDip)AlI2(aIDip)]I (11) was structurally characterized though could not intentionally be synthesised. Possible formation mechanisms for 9-11 are discussed and the normal and abnormal IDip coordination to the aluminium(iii) centre is believed to occur for steric reasons.

A study of tumor motion management in the conformal radiotherapy of lung cancer.

PURPOSE: To assess the benefit derived from the reduction of planning target volumes (PTVs) afforded by tumor motion management in treatment planning for lung cancer. METHODS: We use a simple formula that combines measurements of tumor motion and set-up error for 7 patients to determine PTVs based on the following scenarios: standard uniform 15 mm margin, individualized PTVs (no gating), spirometry-based gating, and active breath-control (ABC). We compare the percent volumes of lung receiving at least 20 Gy (V20) for a standard prescription, and the maximum tolerated doses (MTDs) at fixed V20. In anticipation of improvements in set-up accuracy, we repeat the analysis assuming a reduced set-up margin of 3mm. RESULTS: Relative to the standard, the average percent reductions in V20 (+/- 1 standard deviation) for the ungated and gated scenarios are 17+/-5 and 21+/-8; the percent gains in MTD are 25+/-12 and 33+/-11, respectively. For the 3mm set-up margin, the corresponding results for V20 are 28+/-7 and 36+/-7, and for MTD are 57+/-23 and 79+/-31. CONCLUSIONS: Any form of motion management provides a benefit over the use of a standard margin. The benefit derived from gating compared to the use of ungated individualized PTVs increases with tumor mobility but is generally modest. While motion management may benefit patients with highly mobile tumors, we expect efforts to reduce set-up error to be of greater overall significance. The practical limit for lung PTV margins is likely around 4-5mm, provided set-up error can be reduced sufficiently.

A deformable-model approach to semi-automatic segmentation of CT images demonstrated by application to the spinal canal.

Because of the importance of accurately defining the target in radiation treatment planning, we have developed a deformable-template algorithm for the semi-automatic delineation of normal tissue structures on computed tomography (CT) images. We illustrate the method by applying it to the spinal canal. Segmentation is performed in three steps: (a) partial delineation of the anatomic structure is obtained by wavelet-based edge detection; (b) a deformable-model template is fitted to the edge set by chamfer matching; and (c) the template is relaxed away from its original shape into its final position. Appropriately chosen ranges for the model parameters limit the deformations of the template, accounting for interpatient variability. Our approach differs from those used in other deformable models in that it does not inherently require the modeling of forces. Instead, the spinal canal was modeled using Fourier descriptors derived from four sets of manually drawn contours. Segmentation was carried out, without manual intervention, on five CT data sets and the algorithm's performance was judged subjectively by two radiation oncologists. Two assessments were considered: in the first, segmentation on a random selection of 100 axial CT images was compared with the corresponding contours drawn manually by one of six dosimetrists, also chosen randomly; in the second assessment, the segmentation of each image in the five evaluable CT sets (a total of 557 axial images) was rated as either successful, unsuccessful, or requiring further editing. Contours generated by the algorithm were more likely than manually drawn contours to be considered acceptable by the oncologists. The mean proportions of acceptable contours were 93% (automatic) and 69% (manual). Automatic delineation of the spinal canal was deemed to be successful on 91% of the images, unsuccessful on 2% of the images, and requiring further editing on 7% of the images. Our deformable template algorithm thus gives a robust segmentation of the spinal canal on CT images. The method can be extended to other structures, although it remains to be shown that chamfer matching is sufficiently robust for the delineation of soft-tissue structures surrounded by soft tissue.

Assessment of consistency in contouring of normal-tissue anatomic structures.

The purpose of this work is to estimate the uncertainty in the manual contouring of normal anatomical structures. The heart, esophagus, and spinal cord were contoured manually on six sets of computed tomography images by six dosimetrists whose experience ranged from 1 year to over 15 years. To determine the differences between inter- and intraobserver variations, each data set was contoured by one of the dosimetrists five times and once each by the five other dosimetrists. The magnitude of the discrepancies in delineating the contours was assessed. Intradosimetrist contouring discrepancies were as follows: esophagus, average 0.3 cm and maximum 2.9 cm; heart, average 0.5 cm and maximum 7.6 cm; and spinal cord, average 0.1 cm and maximum 0.7 cm. Interdosimetrist contouring discrepancies were as follows: esophagus, average 0.4 cm and maximum 3.1 cm; heart, average 0.7 cm and maximum 8.1 cm; and spinal cord, average 0.2 cm and maximum 0.9 cm. Significant discrepancies can occur when normal anatomic structures are contoured manually. Interdosimetrist discrepancies are typically slightly greater than intradosimetrist discrepancies. The magnitude of the discrepancies does not appear to be correlated to the experience of the dosimetrist.

A Newtonian model of perceptual distortion in visuo-spatial neglect.

We propose a simple mathematical model that describes how unilateral brain damage distorts the representation of length in two-dimensional space. The model was tested on eighteen normal adults and six patients with left visuo-spatial neglect after right hemisphere lesion. The subjects bisected lines at eight orientations from vertical to horizontal and the displacement of their transections from true centre was expressed as a function of inclination. Although accuracy differed considerably from patient to patient, sinusoidal functions of the predicted form were found in all cases. The pattern of distortion is an exaggeration of one subtype of normal performance, and is fully consistent with the hypothesis that the cerebral hemispheres have antagonistic attentional biases.