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Summary Background Tracheostomy is a lifesaving procedure to secure the airway and provide respiratory support. The decision to decannulate has classically been an individual physician decision without consensus among experts. The objective of this retrospective study was to assess the safety and efficacy of a standard institutional protocol that utilizes the sleep laboratory to assist in the decannulation process. Methods Between 2006 and 2013, patients were identified using a clinical database of decannulation studies. A protocol, finalized in 2005, was implemented for each decannulation attempt. In brief, all patients eligible for decannulation based on physician's assessment undergoes bronchoscopy. Once bronchoscopy findings reveal that the patient's airway is free of significant obstruction, decannulation is conducted in the sleep laboratory. The stoma is covered by an occlusive dressing and respiratory parameters are measured awake and asleep during the day and overnight by polysomnogram (PSG). The patient undergoes re-cannulation if the study shows significant obstruction, hypoventilation, or prolonged desaturation. Results A total of 210 decannulation attempts were performed on 189 patients (16 patients had multiple attempts). One hundred sixty-seven (79.5%) decannulation attempts were successful. Of those successfully decannulated, four (2.4%) were recannulated within 6 months. PSG parameters, specifically the apnea-hypopnea index, percent of total sleep time with oxygen saturation levels less than 90%, and lowest oxygen saturation levels were significantly associated with successful decannulation. No deaths occurred. Conclusions We present a safe and successful decannulation protocol that includes bronchoscopy coupled with PSG evaluation of the patient with the stoma decannulated and covered by an occlusive dressing. Pediatr Pulmonol. © 2016 Wiley Periodicals, Inc.

Summary Introduction Bronchopulmonary dysplasia (BPD) is the primary respiratory complication of premature birth. Some preterm newborns develop chronic respiratory failure, requiring home ventilator support. While physiologic measures have been described for prematurely born children, little is known about spirometric indices in patients with severe BPD who were previously ventilator dependent at home. Methods We retrospectively reviewed medical charts of patients with severe BPD who were ventilator dependent at home. We excluded patients with other comorbidities that could contribute to the severity of BPD. Spirometry was performed when the patient was able to follow commands. Results Between 1984 and 2012, within our severe BPD cohort who previously required home ventilator support, 19 patients were able to perform reproducible spirometry meeting ATS/ERS acceptability criteria. Ten (52.6%) were females, 13 (68.4%) were Caucasians. Mean age at liberation from ventilation was 2.4 years (C.I. 2.0, 2.9) and at decannulation was 3.5 years (C.I. 2.9, 4.0); median age at first reproducible spirometry measurement was 6.6 years (IQR: 4.9, 8.3). Spirometry results revealed significant airway obstruction, as demonstrated by Z-scores values of −1.5 (C.I. −2.5, −0.4) for FVC, −2.7 (C.I. −3.3, −1.9) for FEV1, and −3.6 (C.I. −4.3, −2.9) for FEF25–75. More so, serial spirometric measurements' slopes revealed that the airway obstruction remained static over time (FEV1 slope: −0.07, P-value: 0.2624; FVC slope: −0.01, P-value: 0.9064; and FEF25–75: 0.0, P-value: 0.8532). Conclusions Extreme prematurity associated with severe BPD requiring home ventilator support carries significant risks of morbidity. These patients had substantially diminished respiratory function reflecting airflow abnormalities that remained static over time. Pediatr Pulmonol. 2015; 50:1113–1118. © 2014 Wiley Periodicals, Inc.

Purpose Decay due to diffusion in the internal field (DDIF) MRI allows for measurements of microstructures of porous materials at low spatial resolution and thus has potential for trabecular bone quality measurements. In trabecular bone, solid bone changes (osteoporosis) as well as changes in bone marrow composition occur. The influence of such changes on DDIF MRI was studied by simulations and in vivo measurements. Methods Monte Carlo simulations of DDIF in various trabecular bone models were conducted. Changes in solid bone and marrow composition were simulated with numerical bone erosion and marrow susceptibility variations. Additionally, in vivo measurements were performed in the lumbar spine of healthy volunteers aged 23–62 years. Results Simulations and in vivo results showed that 1) DDIF decay times decrease with increasing marrow fat and 2) the marrow fat percentage needs to be incorporated in the DDIF analysis to discriminate between healthy and osteoporotic solid bone structures. Conclusions Bone marrow composition plays an important role in DDIF MRI: incorporation of marrow fat percentage into DDIF MRI allowed for differentiation of young and old age groups (in vivo experiments). DDIF MRI may develop into a means of assessing osteoporosis and disorders that affect marrow composition. Magn Reson Med 72:1499–1508, 2014. © 2013 Wiley Periodicals, Inc.

Objective The objective of this study was to review the published literature on pregnancy termination following a prenatal diagnosis of Down syndrome in the United States. Method A systematic search of US English-language articles (1995–2011) was conducted to identify primary research studies that reported data for pregnancies with definitive prenatal diagnosis of Down syndrome with subsequent pregnancy termination. Studies that provided indirect estimates of pregnancy termination, such as mathematical models, were excluded. The weighted mean termination rate was calculated across studies. Results Twenty-four studies were accepted. The weighted mean termination rate was 67% (range: 61%–93%) among seven population-based studies, 85% (range: 60%–90%) among nine hospital-based studies, and 50% (range: 0%–100%) among eight anomaly-based studies. Evidence suggests that termination rates have decreased in recent years. Termination rates also varied with maternal age, gestational age, and maternal race/ethnicity. Conclusion This systematic review presents the largest synthesis of United States data on termination rates following a prenatal diagnosis of Down syndrome. Evidence suggests that termination rates are lower than noted in a previous review that was based on less contemporary studies and had an international focus. Heterogeneity across studies suggests that a summary termination rate may not be applicable to the entire US population. © 2012 John Wiley & Sons, Ltd.

Purpose To characterize the DDIF (Decay due to Diffusion in the Internal Field) method using intact animal trabecular bone specimens of varying trabecular structure and porosity, under ex vivo conditions closely resembling in vivo physiological conditions. The DDIF method provides a diffusion contrast which is related to the surface-to-volume ratio of the porous structure of bones. DDIF has previously been used successfully to study marrow-free trabecular bone, but the DDIF contrast hitherto had not been tested in intact specimens containing marrow and surrounded by soft tissue.

BACKGROUND. Although recent research has provided evidence for the predictive validity of personality traits in academic settings, the path to an improved understanding of the nature of personality influences on academic achievement involves a reconceptualization of both criterion and predictor construct spaces. AIMS. For the criterion space, one needs to consider student behaviours beyond grades and level of educational attainment, and include what the student does among other things outside of the classroom. For the predictor space, it is possible to bring some order to the myriad personality constructs that have been developed over the last century, by focusing on common variance among personality and other non-ability traits. METHODS. We review these conceptual issues and several empirical studies. CONCLUSIONS. We demonstrate the possible increments in understanding non-ability determinants of academic achievement that may be obtained by focusing on areas where there is a theoretical convergence between predictor and criterion spaces.

A battery of cognitive ability, knowledge, and non-ability measures were administered to 105 college students enrolled in a cooperative school-work program and used to predict academic and job performance. Composite scores for each domain were derived from factor analyses of 11 measures of verbal, numerical, and spatial abilities, four measures of domain knowledge, and 27 measures of personality and motivational traits, vocational interests, and self-assessments. Both ability and non-ability trait composites were significant predictors of academic performance, but only the non-ability trait composites predicted job performance. Implications for the integrative assessment of individual differences and their predictive validities for performance in different active work contexts, as well as the importance of trait composites across contexts, are discussed. Un ensemble de mesures relatives aux connaissances, aux aptitudes et autres dimensions furent obtenues aupres de 105 etudiants de 1° cycle impliques dans un programme de travail scolaire cooperatif, avec pour objectif de predire les resultats universitaires et la performance au travail. Des scores composites pour chacun de ces deux domaines ont ete constitues a partir d'analyses factorielles des onze mesures des aptitudes verbale, numerique et spatiale, des quatre mesures portant sur les connaissances et des 27 mesures relevant de traits de personnalite, de la motivation, des interets professionnels et de l'auto-evaluation. Les scores des aptitudes et des traits de personnalite furent des predicteurs significatifs du succes universitaire, mais seuls ces derniers ont predit la performance au travail. On reflechit aux consequences sur l'evaluation synthetique des differences individuelles et leur validite predictive de la performance dans differents contextes de travail productif, ainsi que sur l'importance des scores composites selon les situations.

Termites play important roles in organic matter decomposition, nutrient cycling, and soil structure in tropical rain forests. When forests are replaced by agriculture, termite species richness, abundance, and function often decline. We compared the termite assemblage of a primary forest site with that of a low plant diversity, palm-based agroforest (five plant species) and a high plant diversity, home-garden agroforest (10 plant species) using a rapid biodiversity assessment protocol. In comparing the primary forest termite species composition to previously published studies, we found soil feeders and the Apicotermitinae to be more dominant than previously reported in Amazonia. Thirty percent of the species belonged to the Apicotermitinae, and an unusually high percentage (57%) of species were soil feeders. Unexpectedly, the palm-based agroforest, despite its lower plant diversity, was closer to primary forest in termite species composition, rate of species accumulation, and proportions of species in taxonomic and functional classes than was the home-garden agroforest. This suggests that particular plant attributes may better determine the termite assemblage than plant diversity alone in these agroecosystems. Unlike other agroecosystems reported in the literature, Apicotermitinae and soil feeders were proportionally more abundant in these agroforests than in primary forest. The ability of agroforests to support populations of soil feeders has a potentially positive effect on soil fertility in these agroecosystems; insomuch as feeding guild is a proxy for function, these closed-canopy agroforests may be able to sustain the same termite-mediated functions as primary forest.

The density of the organic matrix of bone substance is a critical parameter necessary to clinically evaluate and distinguish structural and metabolic pathological conditions such as osteomalacia in adults and rickets in growing children. Water and fat suppressed proton projection MRI (WASPI) was developed as a noninvasive means to obtain this information. In this study, a density calibration phantom was developed to convert WASPI intensity to true bone matrix density. The phantom contained a specifically designed poly(ethylene oxide)/poly(methyl methacrylate) blend, whose MRI properties (T1, T2 and resonance linewidth) were similar to those of solid bone matrix (collagen, tightly bound water, other immobile molecules), minimizing the need to correct for differences in T1 and/or T2 relaxation between the phantom and the subject. Cortical and trabecular porcine bone specimens were imaged using WASPI with the calibration phantom in the field of view as a stable intensity reference. Gravimetric and amino acid analyses were carried out on the same specimens after WASPI and the chemical results were found to be highly correlated (r2 = 0.98 and 0.95 respectively) to the WASPI intensity. By this procedure the WASPI intensity can be used to obtain the true bone matrix mass density in g cm−3.

The 1998 global coral bleaching event was the largest recorded historical disturbance of coral reefs and resulted in extensive habitat loss. Annual censuses of reef fish community structure over a 12-year period spanning the bleaching event revealed a marked phase shift from a prebleach to postbleach assemblage. Surprisingly, we found that the bleaching event had no detectable effect on the abundance, diversity or species richness of a local cryptobenthic reef fish community. Furthermore, there is no evidence of regeneration even after 5–35 generations of these short-lived species. These results have significant implications for our understanding of the response of coral reef ecosystems to global warming and highlight the importance of selecting appropriate criteria for evaluating reef resilience.

Using the theory of planned behavior (TPB), individual reactions to a new technology and technology usage behavior were studied over a 12-month period among 552 employees being introduced to a new computer-based system in the workplace. When considering gender as a psychological construct by employing Bern's Sex Role Inventory (BSRI), important distinctions were revealed. Specifically, masculine gender-typed individuals exhibited the same pattern as did men in previous research; feminine gender-typed individuals were different from women in that they were influenced only by subjective norm and PBC. The balanced decision-making process was observed only in the case of individuals categorized as androgynous. The high percentage of women who tested to be androgynous explains the divergence in results from the previous work, and provides evidence of changing gender roles for women in today's organizations and society.

In order to improve the performance of magnetic resonance imaging and spectroscopy of atherosclerotic plaque the potential use of novel radiofrequency coil structures with sensitive detection volumes tailored to the geometry of the arterial wall was investigated. It was found that a cylindrical meanderline (zig-zag) coil design provides a sensitive volume that is restricted to a cylindrical shell, thereby maximizing the filling factor and signal-to-noise ratio for plaques while reducing the intense blood signal. The cylindrical meanderline coil has the added advantages of an open interior, which allows for unimpeded blood flow during scanning, and the potential to be expanded against the walls of the artery, thereby stabilizing the coil against the pulsatile blood flow and minimizing motion artifacts. The performance of cylindrical meanderline coils with theoretical simulations of the electromagnetic fields as well as with experimental images of test objects (phantoms) and human endarterectomy surgical specimens is demonstrated. This radically new RF coil geometry offers the potential to improve the efficiency of MR data acquisition in medical applications in which curved surfaces or slabs contain the material of interest.

Water- and fat-suppressed projection MR imaging (WASPI) utilizes the large difference between the proton Ts of the solid organic matrix and the fluid constituents of bone to suppress the fluid signals while preserving solid matrix signals. The solid constituents include collagen and some molecularly immobile water and exhibit very short T. The fluid constituents include mobile water and fat, with long T. In WASPI, chemical shift selective low-power π/2 pulses excite mobile water and fat magnetization which is subsequently dephased by gradient pulses, while the magnetization of collagen and immobile water remains mostly in the z-direction. Additional selective π pulses in alternate scans further cancel the residual water and fat magnetization. Following water and fat suppression, the matrix signal is excited by a short hard pulse and the free induction decay acquired in the presence of a gradient in a 3D projection method. WASPI was implemented on a 4.7 T MR imaging system and tested on phantoms and bone specimens, enabling excellent visualization of bone matrix. The bone matrix signal per unit volume of bovine trabecular specimens was measured by this MR technique and compared with that determined by chemical analysis. This method could be used in combination with bone mineral density measurement by solid state 31P projection MRI to determine the degree of bone mineralization. Magn Reson Med 50:59–68, 2003. © 2003 Wiley-Liss, Inc.

Objective We evaluated inpatient treatment of depression, prescribing patterns for antidepressants, and associated hospital charges. Methods We reviewed administrative data of the UCLA Neuropsychiatric Hospital between July 1994 and July 1997 for all 1698 hospitalizations for mood disorders. We evaluated drug utilization patterns and hospital charges by analysis of variance and multiple regression, and by stratifying on diagnosis, severity, age, and other factors. Results Length of stay was the major contributor to total charges, which included room charges and charges for services, procedures, supplies, and tests. The selective serotonin reuptake inhibitors (SSRIs) were prescribed most often (to 47% of patients), followed by the atypicals (heterocyclics, 12%), the tricyclics (TCAs, 7%), venlafaxine (7%) and the monoamine oxidase inhibitors (MAOIs

Studies of the apatitic crystals of bone and enamel by a variety of spectroscopic techniques have established clearly that their chemical composition, short-range order, and physical chemical reactivity are distinctly different from those of pure hydroxyapatite. Moreover, these characteristics change with aging and maturation of the bone and enamel crystals. Phosphorus-31 solid state nuclear magnetic resonance (NMR) spin-spin relaxation studies were carried out on bovine bone and dental enamel crystals of different ages and the data were compared with those obtained from pure and carbonated hydroxyapatites. By measuring the 31P Hahn spin echo amplitude as a function of echo time, Van Vleck second moments (expansion coefficients describing the homonuclear dipolar line shape) were obtained and analyzed in terms of the number density of phosphorus nuclei. 31P magnetization prepared by a 90 degree pulse or by proton-phosphorus cross-polarization (CP) yielded different second moments and experienced different degrees of proton spin-spin coupling, suggesting that these two preparation methods sample different regions, possibly the interior and the surface, respectively, of bone mineral crystals. Distinct differences were found between the biological apatites and the synthetic hydroxyapatites and as a function of the age and maturity of the biological apatites. The data provide evidence that a significant fraction of the protonated phosphates (HPO4(-2)) are located on the surfaces of the biological crystals, and the concentration of unprotonated phosphates (PO4(-3)) within the apatitic lattice is elevated with respect to the surface. The total concentration of the surface HPO4(-2) groups is higher in the younger, less mature biological crystals.

Purkinje cells of different molecular phenotypes subdivide the cortex of the cerebellum both rostrocaudally into parasagittal bands and mediolaterally into transverse zones. Superimposed on the Purkinje cell compartmentation, the cerebellar cortex is pleated into a reproducible array of lobes and lobules. During cerebellar development, Purkinje cell bands are formed through the rostrocaudal dispersal of embryonic clusters, triggered primarily by a Reelin-dependent signaling pathway. In the naturally occurring mouse mutant cerebellar deficient folia (cdf), there is a failure of Purkinje cell dispersion that results in widespread Purkinje cell ectopia in the adult. The ectopia is restricted primarily to that subset of Purkinje cells that does not express zebrin II/aldolase C and that forms ectopic clusters in among the cerebellar nuclei. Most Purkinje cells that express zebrin II are located normally in a monolayer. Thus, the cerebellum of cdf mutants has a failure of Purkinje cell dispersion that is confined primarily to a zebrin II-negative (zebrin II−) subpopulation. Despite the Purkinje cell ectopia, the parasagittal band organization of the cerebellum is still clear. The shortening of the cortex is distributed evenly over all lobules, with the result that transverse expression boundaries are relocated with respect to the lobules and fissures. The number of Purkinje cells in the cdf/cdf cerebellum is similar to the number in littermate controls. Therefore, it appears that the lesion in cdf results in the failure of a zebrin II− Purkinje cell subset to disperse either due to a cell intrinsic defect or due to an abnormal interaction between the Purkinje cells and either granule cells or afferent inputs. J. Comp. Neurol. 436:42–51, 2001. © 2001 Wiley-Liss, Inc.

Empirical evidence on the conceptual and construct validity of the motivational trait taxonomy proposed by Kanfer and Heggestad is presented. 228 adults completed a shortened form of the Motivational Trait Questionnaire (MTQ), along with a battery of personality and ability measures. Relationships of the MTQ with personality measures show evidence of convergent and discriminant validity for trait constructs of Personal Mastery, Competitive Excellence, and Motivation Related to Anxiety. In addition, MTQ scale scores were generally unrelated to composite measures of fluid and crystallised intelligence. Examination of age differences showed a pattern of developmental decline in the achievement trait complex, but not the anxiety complex.

Characterization of the very early calcium phosphate (CaP) crystals deposited in bone or in osteoblast cell cultures has been hampered by the overwhelming presence of organic matrix components and cells that obscure spectral analyses. We have overcome this problem using isolated protein-free crystals and have obtained new data including 31P nuclear magnetic resonance (NMR) spectra for the first time from mineral crystals deposited during osteoblast calcification in culture. Crystals were isolated from cultures at two time points: (a) at first calcium accumulation (day 8-10) and (b) after 60 days of culture, to assess maturational changes. The analyses show that the chemical composition overall and short range order of the early and mature crystals are characteristic of the apatite crystals found in young embryonic chick bone in vivo. No mineral phase other than apatite was detected by any of the methods used. 31P NMR spectroscopy identified the HPO4 groups as those present in bone apatite. Similar to bone apatites, no OH groups were detected by Fourier transform infrared (FTIR) spectroscopy. The temporal maturational changes in composition and structure of the mineral phase were difficult to assess because of the continuous deposition of crystals throughout culturing. The pathway of the maturational changes observed were similar to those occurring in chick bone in vivo and synthetic apatite crystals in vitro although to a much smaller extent.

It is shown that solid-state phosphorus-31 nuclear magnetic resonance imaging can be used to measure quantitatively the mass of hydroxyapatite (HA), a synthetic calcium phosphate used as an orthopedic implant material, in the presence of bone. A three-dimensional projection reconstruction tech-nique was used to produce solid-state images from 998 free induction decays sampled in the presence of a fixed amplitude field gradient whose direction was varied uniformly over the unit sphere. Chemical selection is achieved using T1 contrast, as the synthetic calcium phosphate has a shorter T1 (1.8 sec at 4.7 T) compared with the bone (approximately 15 sec at 4.7 T in vivo, 42 sec ex vivo). Experimental results demonstrating the linear relationship between image intensity and HA density in phantoms containing HA and silicon (IV) oxide, and HA and bone are shown. Chemically pure images of bone mineral and synthetic HA have been computed from images of New Zealand White rabbits acquired in vivo at two different recycle times. The technique can be used to follow non-invasively the resorption and remodeling of calcium phosphate implants in vivo. Magn Reson Med 41:1214–1220, 1999. © 1999 Wiley-Liss, Inc.

The initial phase of mammalian preimplantation development is directed by stored maternal mRNAs and their encoded proteins, yet most of the molecules controlling this process have not been described. We have used differential display analysis of cDNA libraries prepared from unfertilized eggs and preimplantation embryos to isolate three maternal cDNAs that represent novel genes exhibiting different patterns of expression during this developmental period. One of these, Melk, encodes a protein with a kinase catalytic domain and a leucine zipper motif, a new member of the Snf1/AMPK family of kinases. This gene product may play a role in the signal transduction events in the egg and early embryo.

In vivo 1H NMR chemical shift imaging (CSI), 1H NMR localized spectroscopy (STEAM) and multinuclear NMR spectroscopy (29Si, 13C, 1H) were used to characterize the aging process of silicone gel-filled implants in a rat model after long-term implantation. Although no significant changes could be observed in the implants or surrounding tissue by in vivo 1H chemical shift imaging, in vivo 1H localized spectroscopy of the livers from the longer term population revealed the presence of silicone. Ex vivo 29Si spectroscopy of the liver, spleen, and the capsule formed around the 9 and 12 month implants clearly demonstrated and confirmed for the first time that a significant amount of free silicone migrates from silicone gel-filled implants. Also, these results show that silicones are not metabolically inert, and their biodegradation in tissue and within the implant can be monitored after 9 and 12 months by changes in the 29Si chemical shifts seen in corresponding ex vivo spectra. The NMR findings are supported by those obtained by atomic absorption spectroscopy. Silicone aging changes not only the chemical composition of the gel, but also its proton T2 relaxation times, which increase with long implantation times. The three dimensional structure of the gel disintegrates (i.e., polymer chain rupture), increasing the molecular mobility of the polymer and, consequently, its protons T2 values. The relaxation data we obtained reflect this in vivo degradation, especially in the case of implant rupture. Additionally, small concentrations of fat in the silicone gel were found within the implants. The presence of these lipophilic substances also might increase the T2 values (plasticizer effect). These findings may assist in evaluating the implant integrity and disease symptoms related to their presence in humans.

Thirty-two infants with cystic fibrosis (CF) had pulmonary function testing and chest radiographs at the time of diagnosis and on average 1 year later, when they had no acute respiratory symptoms. At diagnosis, 14 of 32 infants had respiratory symptoms (RESP) and 18 did not have respiratory symptoms (NRESP). There were no significant differences in age, weight, or length between the RESP and NRESP groups. At diagnosis, the RESP group had significantly lower forced expiratory flows compared to the NRESP group (41±32% vs. 98±48 % predicted); however, there were no significant differences in functional residual capacity or chest radiographic scores. Between diagnosis and follow-up, the NRESP group had no significant change in pulmonary function but a decline in chest roentgenographic (CXR) scores (22±2 to 21±2). For infants in the RESP group, there were no significant changes in FRC or CXR score. Maximal expiratory flow at functional residual capacity (Max FRC) rose from diagnosis to 1 year follow-up (41±32 % to 74±27 % predicted; P < 0.002); however, at follow-up flows for the RESP group remained significantly lower than flows for the NRESP group (74 % vs. 113 % predicted; P < 0.0.005). For the 32 infants with CF, there was significant correlation between percent predicted Max FRC at follow-up and at diagnosis (r = 0.47; P

In order to study the aging process (i.e., silicone migration, fat infiltration) of silicone (polydimethylsiloxane, PDMS) based biomaterials in living subjects by NMR imaging, a hybrid 1H selective excitation and saturation chemical shift imaging technique (IR/CHESS-CSSE) has been developed. This sequence allows selective mapping of the distribution of silicone protons in vivo, while suppressing the contributions of fat and water. Our results indicate that a combined inversion recovery and CHESS pulse, followed by a spoiler gradient, must be applied to suppress all contributions of fat protons to the NMR signal. The sensitivity of our experiments allows the detection of a chemically unchanged silicone concentration of 5% in a voxel of 0.9 mm3 at a signal/noise ratio of 2.

Background. Malignant mixed mullerian tumor (MMT) of tubal origin is rare and optimal therapy is unknown. Methods. Five new cases of MMT of the fallopian tube are presented, and the previous literature is reviewed. Results. Eight of 10 patients disease-free at 36 months had long-term cancer-free survival. Surgery alone was inadequate therapy even for those with apparent Stage I disease. Five of six treated postoperatively with radiation and chemotherapy have lived disease-free for at least 45 months. Conclusions. Combination radiation and chemotherapy may offer improved outcome. Cancer 1993; 71:187-92.

One-dimensional 31P nuclear magnetic resonance images (projections) of synthetic calcium hydroxyapatite, Ca10(OH)2(PO4)6, have been obtained for samples on the order of 0.5 to 1.0 cm in linear extent at 7.4 T magnetic field strength. Because of the solid state nature of these samples, short 31P spin-spin relaxation times under 1 ms occur, necessitating echo times of 1 ms and phase-encoding magnetic field gradient pulses shorter than 500 microseconds. Optimal projection quality and shortest acquisition times result from pulsed gradient phase-encoding of the spatial dimension, using a compensating gradient pulse to cancel the distorting effects of gradient waveform transients. The exceedingly long 31P spin-lattice relaxation times could lead to potentially intolerable image acquisition times; these have been reduced with a flipback pulse technique. In addition to holding great potential as a novel research tool in the study of biomineralization of those organisms containing calcium phosphate solid phases, these methods should be of general utility in the multinuclear imaging of a wide variety of solids of interest in biophysics and materials science.

We calculate the effects of subvoxel variations in magnetic susceptibility on MR image intensity for spin-echo (SE) and gradient-echo (GE) experiments for a range of microscopic physical parameters. The model used neglects the overlap of gradients from one magnetic inclusion to the next, and so is valid for low volume fractions and weak perturbations of the magnetic field. Transverse relaxation is predicted to deviate significantly from linear exponential decay in both SE and GE at a particle radius of 2.5 microns. Calculated changes in transverse relaxation rates for SE and GE increase linearly with volume fraction of high-susceptibility regions of 5 microns diameter, but increase with about the 3/2 power of volume fraction of regions with 15 micron spacing between centers. This sensitivity to the actual size and spacing of magnetized regions may allow them to be measured on the basis of contrast. without being resolved in images. GE and SE decay rates are approximately twice as sensitive to long cylinders of 5 microns diameter than to spheres of the same size, for diffusion constants of 2.5 micron 2/ms. Calculated changes in transverse decay rates increase with approximately the square of field and susceptibility variation for 5-microns spheres and a diffusion constant of 2.5 microns 2/ms. This exponent is smaller for cylindrical magnetized regions of the same size, and also depends on the diffusion constant. We discuss possible applications of our theoretical results to the analysis of the effects of high-susceptibility contrast agents in brain. Experimental data from the literature are compared with calculated signal changes according to the model. The monotonic dependence of decay rates on the volume of distribution of the contrast agent suggests that cerebral blood volume and flow could be measured using MR contrast.

Crown characteristics have been the parameter most frequently utilized in studies of tooth morphology. Dental root structures have received relatively little attention. Examination of unusual molar roots in a kindred has enabled us to (1) establish a typology for classifying molar roots, (2) devise a methodology for evaluating the degree of taurodontism and (3) hypothesize about phylogenetic, ontogenetic and genetic aspects of root morphology. The roots of molar teeth were studied radiographically in 20 members of a family of English–German ancestry in which there was no consanguinity. Taurodont, pyramidal (single conical root) and fused molar roots were common. Other ectodermal and mesodermal anomalies (unusual upper lip, glaucoma, syndactyly and clinodactyly) were also present. This unique constellation of dental, cutaneous, ocular and bone abnormalities constitutes a previously undescribed syndrome. Unusual roots may be a genetic marker, and the finding of unusual roots, such as prismatic or wholly pyramidal, should prompt a search for other abnormalites. Dental trait analysis for genetic and microevolutionary studies should include root, as well as crown, characteristics.

In current magnetic resonance imaging (MRI), valuable information must often be discarded because the NMR signal has greater dynamic range than the analog-to-digital converter (ADC) hardware. Typically, a small set of high-intensity data points near the center of the spin echo is responsible for most of the MRI data dynamic range. We predict that it is possible to reduce the dynamic range of the MRI spin echo by incorporating an identical nonlinear gradient pulse into each repetition of the imaging pulse sequence, prior to data sampling. This pulse converts the phase distribution of the subject, ordinarily a linear function of image coordinates, into a nonlinear function. A nonlinear phase distribution can have a negligible impact on image magnitude and yet a profound impact on spin-echo magnitude. Given a nonlinear phase distribution, there will no longer be a single data point at which all of the protons have an identical phase (the echo center). Instead, the protons become phase coherent on a piecemeal basis, the echo peak is smoothed out, and its maximum amplitude and dynamic range are greatly diminished. Using gradient pulses of quadratic spatial variation, we estimate that maximum echo amplitude and dynamic range can be reduced in most cases by an order of magnitude.

The author discusses and clarifies the “Theory of Logical Types” which forms the cornerstone of the “Double Bind Hypothesis.” A clear distinction is made between single sentence double binds and double binds that evolve in an interaction over time. The crucial term “metacommunication” is redefined in a manner consistent with logical type theory. The locus of message-level confusion is shifted from the messages of the sender to the arena of the communicant's interaction. Analysis of the interactional arena reveals a phenomenon which the author labels “Relational Paradox.” Several examples are given which illustrate how paradoxes can arise even if neither interactant is sending messages which are intrinsically bewildering.

In the subambient thermal volatilization analysis (TVA) technique, degradation products initially at −196°C are allowed to warm up to ambient temperature in a controlled manner under vacuum conditions, and volatilization from the sample tube to a trap at −196°C is monitored by means of a Pirani gauge. The technique is discussed in relation to earlier TVA work in which volatilization from a heated polymer sample was followed. Design and operation of a subambient TVA system are described, and examples of the application of the technique to the study of the degradation products of seven polymers are considered.

Films of poly(methyl acrylate), poly(ethyl acrylate), and poly(n-butyl acrylate) were irradiated by means of a high-pressure mercury lamp in oxygen and nitrogen atmospheres, and the molecular weight changes accompanying degradation were studied as a function of radiation dose. Crosslinked material was formed in all cases though less crosslinking occurred in oxygen than in nitrogen atmospheres. Scission was the major reaction in the photo-oxidation of poly(ethyl acrylate), and this was explained in terms of acetal formation. In a nitrogen atmosphere, the proportion of units fractured to the proportion of units crosslinked per unit radiation dose was constant for the three polymers. Gel permeation chromatographic studies showed the accumulation of low molecular weight fragments on prolonged photolysis, and this was explained in terms of a chain reaction mechanism.

We have measured the diffusion of poly(dimethylsiloxane) (PDMS) chains in PDMS model networks by using a pulsed field gradient NMR technique. The model networks have been prepared by tetrafunctional endliking of linear PDMS chains having molecular weights Mn of 3,700 and 7,400 g mol−1. The diffusants have been incorporated in the networks by immersing pieces of them in PDMS linear chains with molecular weights Mn between 3,000 and 12,000 g mol−1 and molecular weight distributions Mw/Mn between 1.1 and 1.7. Although spin-echo attenuation results were fitted to a model which takes into account polydispersity of the diffusant, these results did not exhibit any dependency upon the molecular weight distribution. The self-diffusion coefficients of PDMS chains in the PDMS model networks were found to be smaller than in the melt, and the exponents for the diffusion coefficient dependence on Mn in the networks were found to be about-1.3. Free diffusion will give an exponent equal to-1, whereas free volume contributions or behavior intermediate between free and entangled diffusion will increase the magnitude of the exponent.

Nuclear magnetic resonance(NMR)imaging of perfluorocarbon (PFC) emulsions and neat liquids has shown potential for i n v i v o oxygen imaging in blood and organ tissue. PFC compounds exhibit complicated NMR spectra caused by chemical shifts and spin–spin couplings which can lead to artifacts and degraded spatial resolution of resulting NMRimages. To correct for the chemical shift artifacts, the technique of spectral deconvolution has been applied to NMR imaging of PFC compounds. The temporal filter for this process can be directly applied to raw free induction decay data in projection reconstruction or to spin‐echo data in two‐dimensional Fourier transform imaging techniques. The effect of chemical shift artifacts was demonstrated through the NMR imaging of two PFC compounds (F‐tributylamine and F‐decalin) in phantoms. Methods are presented and demonstrated which allow the chemical shift artifacts to be removed and true images of the spatial distribution of the PFC’s to be recovered.

England had a housing shortage and a vigorous constructive housing policy prior to the war; but under present economic conditions and a greatly intensified shortage the policy no longer works.—An entirely new technique is emerging.