Expecting the uncertain: The applicability of the intolerance of uncertainty model on fear of childbirth.

A considerable number of pregnant women experience fear of childbirth (FOC), characterized by worries and fear of the unpredictable. Despite this, the psychological processes in FOC have received notably little attention. The aim of this study was to advance the understanding by exploring the applicability of the Intolerance of Uncertainty (IU) model on FOC. Anonymous data was collected in a sample of pregnant women (N = 357) with varying levels of FOC. Analyses supported the associations between FOC and all proposed psychological processes: IU, negative problem orientation, positive beliefs about worry and avoidance of inner experiences. The exploration of potential mediators of the relation between IU and FOC revealed that, of the three processes from the model, only positive beliefs about worry were a mediator, and more specifically, a partial mediator between IU and FOC. These findings add to the theoretical understanding of FOC, by indicating that the role of IU may be similar to other conditions inflicted by worry and anxiety, which may inform treatment development.

Nanoparticle rearrangement under stress in networks of cellulose nanofibrils using in situ SAXS during tensile testing.

This study aims to describe and evaluate the mechanism for increased strain-at-break of composites made of cellulose nanofibrils (CNFs) reinforced with nanoscopic latex particles (<200 nm) stabilized by a cationic polyelectrolyte as corona. The applied latex nanoparticles (NPs), synthesized by polymerization-induced self-assembly (PISA), are composed of a neutral core polymer, either poly(butyl methacrylate) (PBMA) or poly(methyl methacrylate) (PMMA). At room temperature, PBMA is close to its glass transition (Tg), while PMMA is below its Tg. Nanocomposites with 75 wt% CNFs and 25 wt% NPs were analyzed using in situ small angle X-ray scattering during tensile testing, monitoring the structural evolution of the NPs under strain. The scattering of the spherical PMMA NPs, which do not coalesce like the PBMA NPs, shows changes to the organization of the NPs in the CNF-network. The observations are corroborated by cross-sectional transmission and scanning electron microscopy. No distinct change from spherical to ellipsoidal shape is evidenced for the PMMA NP cores during tensile strain. Changes in anisotropic scattering produced by the three-dimensional NP structure appear to be very different between nanocomposites loaded with PMMA or PBMA NPs, contrasting commonly described two-dimensional CNF networks. The discrete PMMA NPs can reorganize within the CNF-NP double network under strain, resulting in maintained strength and increased strain-at-break. Increasing the humidity (20, 50 and 80% RH) during in situ measurements further emphasizes this effect in the PMMA composite, relative to the PBMA composite and CNF reference films. The onset of deformation occurs at strain values beyond the fracture of the more brittle films, indicating the effect of secondary nanoscale interaction available only for the PMMA composite, extending the plastic deformation and increasing the ductility. These results provide key insights into the deformation mechanism occurring during tensile testing in the CNF composites loaded with PMMA NPs.

Outcome After Fenestrated and Branched Repair of Aortic Aneurysms-Device Failures Predict Reintervention Rates.

BACKGROUND: Previous reports have indicated endovascular repair to be safe and effective in the treatment of complex aortic aneurysms. The endovascular technology evolves rapidly, and continuous evaluation of F/B-EVAR results is critical to detect failing techniques. Our aim was to analyze the outcome after endovascular repair of complex abdominal aortic and thoracoabdominal aneurysms. METHODS: Single-center, retrospective cohort study, of all F/B-EVAR from August 2009 to December 2018. Primary outcomes were branch instability and freedom from reinterventions at 2 years. Secondary outcomes were major adverse events and all-cause mortality at 30 and 90 days. RESULTS: A total of 72 consecutive patients were included, 55 with a complex abdominal aortic aneurysm (AAA) and 17 with a thoracoabdominal aortic aneurysm (TAAA). Two patients were operated on for rupture. A total of 219 vessels were stented through fenestrations (n = 163) or branches (n = 56). Median follow-up was 24 months (IQR 4-24). Fractured bridging stent graft was the most common cause for reintervention, n = 6. All fractures were in vessels stented with first generation BeGrafts, (6/41 BeGraft vs 0/61 other stents, P < 0.01). Freedom from reinterventions at 2 years was 75% and 35%, in the complex AAA and TAAA groups, respectively (P = 0.04) and excluding BeGrafts 79% (cAAA) and 66% (TAAA). The most common major adverse event was spinal cord ischemia (SCI), in total 8.3% with either transient (2.8%) or permanent (5.6%) deficit. Elective mortality at 30 days was 1.4% (1/70) and at 90 days was 2.9% (2/70). CONCLUSIONS: The rate of branch instability and reintervention was high, with a clear relation to fractured first-generation BeGrafts. Mortality and major adverse event rates were low. Long-term close surveillance of bridging stent graft performance is crucial, and the endovascular community should strive to find ways to report failing materials at an early stage to avoid potentially serious complications.

Tailoring adhesion of anionic surfaces using cationic PISA-latexes - towards tough nanocellulose materials in the wet state.

Cationic latexes with Tgs ranging between -40 °C and 120 °C were synthesised using n-butyl acrylate (BA) and/or methyl methacrylate (MMA) as the core polymers. Reversible addition-fragmentation chain transfer (RAFT) combined with polymerisation-induced self-assembly (PISA) allowed for in situ chain-extension of a cationic macromolecular RAFT agent (macroRAFT) of poly(N-[3-(dimethylamino)propyl] methacrylamide) (PDMAPMA), used as stabiliser in so-called surfactant-free emulsion polymerisation. The resulting narrowly distributed nanosized latexes adsorbed readily onto silica surfaces and to model surfaces of cellulose nanofibrils, as demonstrated by quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. Adsorption to anionic surfaces increased when increasing ionic strength to 10 mM, indicating the influence of the polyelectrolyte effect exerted by the corona. The polyelectrolyte corona affected the interactions in the wet state, the stability of the latex and re-dispersibility after drying. The QCM-D measurements showed that a lower Tg of the core results in a more strongly interacting adsorbed layer at the solid-liquid interface, despite a comparable adsorbed mass, indicating structural differences of the investigated latexes in the wet state. The two latexes with Tg below room temperature (i.e. PBATg-40 and P(BA-co-MMA)Tg3) exhibited film formation in the wet state, as shown by AFM colloidal probe measurements. It was observed that P(BA-co-MMA)Tg3 latex resulted in the largest pull-off force, above 200 m Nm-1 after 120 s in contact. The strongest wet adhesion was achieved with PDMAPMA-stabilized latexes soft enough to allow for interparticle diffusion of polymer chains, and stiff enough to create a strong adhesive joint. Fundamental understanding of interfacial properties of latexes and cellulose enables controlled and predictive strategies to produce strong and tough materials with high nanocellulose content, both in the wet and dry state.

The relationship between the Driver Behavior Questionnaire, Sensation Seeking Scale, and recorded crashes: A brief comment on Martinussen et al. (2017) and new data from SHRP2.

We provide a brief comment on the work of Martinussen et al. (2017), who studied the relationships between self-reported driving behavior, registered traffic offences, and registered crash involvement. It is argued that if the number of crashes is small, then the correlation with crashes is also small. Our analysis of the SHRP2 naturalistic driving study shows that the violations score of the Driver Behavior Questionnaire and the Sensation Seeking Scale exhibit small correlations with recorded crashes, and small-to-moderate correlations with recorded near-crashes and measures of driving style.

Who's on first? Tracking in real time the growth of multiple crystalline phases of an organic semiconductor: Tetracene on SiO2.

We have examined the effect of growth rate on the evolution of two polymorphs of thin films of tetracene on SiO2 using synchrotron X-ray radiation and molecular beam techniques. Ex situ X-ray reflectivity shows that tetracene forms two phases on SiO2: a thin-film phase and a bulk phase. We have used in situ, real-time grazing incidence diffraction during growth to reveal the nature of growth concerning these two phases. We observe that there is initially growth of only the thin-film phase, up to a thickness of several monolayers. This is followed by the nucleation of the bulk phase, growth of both phases, and finally growth of only the bulk phase. We find that the deposited thickness when the bulk phase nucleates increases with increasing growth rate. Similarly, we find that the deposited thickness at which the thin-film phase saturates also increases with increasing growth rate. These apparent dependencies on growth rate are actually a consequence of the local coverage, which depends on growth rate, particularly for the former effect. At low growth rates, there is 3D growth resulting from the upward transport of tetracene at island edges, resulting in tall features where molecules escape the influence of the substrate and form into the bulk phase. Increasing the growth rate leads to growth that is more 2D and uniform in coverage, delaying the formation of the bulk phase.

Physiological changes associated with routine nursing procedures in critically ill are common: an observational pilot study.

BACKGROUND: Nursing procedures that are routinely performed in the intensive care unit (ICU) are assumed to have minimal side effects. However, these procedures may sometimes cause physiological changes that negatively affect the patient. We hypothesized that physiological changes associated with routine nursing procedures in the ICU are common. METHODS: A clinical observational study of 16 critically ill patients in a nine-bed mixed university hospital ICU. All nursing procedures were observed, and physiological data were collected and subsequently analyzed. Minor physiological changes were defined as minimal changes in respiratory or circulatory variables, and major physiological changes were marked as hyper/hypotension, bradycardia/tachycardia, bradypnea/tachypnea, ventilatory distress, and peripheral blood oxygen desaturation. RESULTS: In the 16 patients, 668 procedures generated 158 major and 692 minor physiological changes during 187 observational hours. The most common procedure was patient position change, which also generated the majority of the physiological changes. The most common major physiological changes were blood oxygen desaturation, ventilatory distress, and hypotension, and the most common minor changes were arterial pressure alteration, coughing, and increase in respiratory rate. CONCLUSION: In this pilot study, we examined physiological changes in connection with all regular routine nursing procedures in the ICU. We found that physiological changes were common and sometimes severe.

Which breast pump for which mother: an evidence-based approach to individualizing breast pump technology.

The majority of new mothers in the United States use breast pumps in the first 4 months postbirth in order to achieve their personal human milk feeding goals. Although these mothers seek guidance from health-care professionals with respect to the type and use of breast pumps, there are few evidence-based guidelines to guide this professional advice. This paper reviews the evidence to facilitate professional individualization of breast pump recommendations using three categories of literature: the infant as the gold standard to which the pump is compared; the degree of maternal breast pump dependency (for example, the extent to which the breast pump replaces the infant for milk removal and mammary gland stimulation); and the stage of lactation for which the pump replaces the infant. This review can also serve to inform public and private payers with respect to individualizing breast pump type to mother-infant dyad characteristics.

Endovascular treatment of true and false aneurysms in hemodialysis access.

Formation of true and false aneurysms in vascular access for hemodialysis is a complication associated with an immediate or chronic threat to the patient, which jeopardizes access function for further dialysis. Although open surgical repair remains the established treatment of choice, during the last decade, endovascular procedures, largely utilizing stent grafts, have emerged as a viable option for treatment in emergencies as well as for elective cases. Here, basic concepts in vascular access aneurysm management are recapitulated and strategies for endovascular treatment of these complications discussed.

Quality indicators for human milk use in very low-birthweight infants: are we measuring what we should be measuring?

OBJECTIVE: The objective of this study was to compare the currently used human milk (HM) quality indicators that measure whether very low-birthweight (VLBW; <1500 g birthweight) infants 'ever' received HM and whether they were still receiving HM at discharge from the neonatal intensive care unit (NICU) to the actual amount and timing of HM received. STUDY DESIGN: This study used data from a large NIH-funded cohort study and calculated whether VLBW infants ever received HM (HM-Ever) and of these infants, the percentage who were still receiving HM at NICU discharge (HM-DC). Then, the HM-DC indicator (exclusive, partial and none) was compared with the amount and timing of HM feedings received by these same infants. RESULT: Of the 291 VLBW infants who met inclusion criteria, 285 received some HM (HM-Ever=98%). At NICU discharge (HM-DC), 24.2, 15.1 and 60.7% were receiving exclusive, partial and no HM, respectively. Of the 60.7% infants with no HM-DC, some had received higher amounts of HM during the NICU hospitalization than infants categorized as exclusive and partial for HM-DC. Of the infants with no HM-DC, 76.8 and 59.7% had received exclusive HM during the days 1-14 and days 1-28 exposure periods, respectively. CONCLUSION: The average daily dose (HM-DD; in ml kg(-1) d(-1)) and cumulative percentage (HM-PCT; as % of cumulative enteral intake) of HM feedings were sufficient to significantly reduce the risk of multiple morbidities, including late-onset sepsis, necrotizing enterocolitis, neurocognitive delay and rehospitalization, in the majority of the VLBW infants who were discharged with no HM-DC. Quality indicators that focus on the amount and timing of HM feedings in the NICU should be added to the HM-Ever and HM-DC measures.

Impact of early human milk on sepsis and health-care costs in very low birth weight infants.

OBJECTIVE: To study the incidence of sepsis and neonatal intensive care unit (NICU) costs as a function of the human milk (HM) dose received during the first 28 days post birth for very low birth weight (VLBW) infants. STUDY DESIGN: Prospective cohort study of 175 VLBW infants. The average daily dose of HM (ADDHM) was calculated from daily nutritional data for the first 28 days post birth (ADDHM-Days 1-28). Other covariates associated with sepsis were used to create a propensity score, combining multiple risk factors into a single metric. RESULT: The mean gestational age and birth weight were 28.1 ± 2.4 weeks and 1087 ± 252 g, respectively. The mean ADDHM-Days 1-28 was 54 ± 39 ml kg(-1) day(-1) (range 0-135). Binary logistic regression analysis controlling for propensity score revealed that increasing ADDHM-Days 1-28 was associated with lower odds of sepsis (odds ratio 0.981, 95% confidence interval 0.967-0.995, P=0.008). Increasing ADDHM-Days 1-28 was associated with significantly lower NICU costs. CONCLUSION: A dose-response relationship was demonstrated between ADDHM-Days 1-28 and a reduction in the odds of sepsis and associated NICU costs after controlling for propensity score. For every HM dose increase of 10 ml kg(-1) day(-1), the odds of sepsis decreased by 19%. NICU costs were lowest in the VLBW infants who received the highest ADDHM-Days 1-28.

Intensive buffering can keep pH above 7.2 for over 4 h during apnea: an experimental porcine study.

BACKGROUND: Ventilation with low tidal volumes reduces mortality in acute respiratory distress syndrome. A further reduction of tidal volumes might be beneficial, and it is known that apneic oxygenation (no tidal volumes) with arteriovenous CO(2) removal can keep acid-base balance and oxygenation normal for at least 7 h in an acute lung injury model. We hypothesized that adequate buffering might be another approach and tested whether tris-hydroxymethyl aminomethane (THAM) alone could keep pH at a physiological level during apneic oxygenation for 4 h. METHODS: Six pigs were anesthetized, muscle relaxed, and normoventilated. The lungs were recruited, and apneic oxygenation as well as administration of THAM, 20 mmol/kg/h, was initiated. The experiment ended after 270 min, except one that was studied for 6 h. RESULTS: Two animals died before the end of the experiment. Arterial pH and arterial carbon dioxide tension (PaCO(2) ) changed from 7.5 (7.5, 7.5) to 7.3 (7.2, 7.3) kPa, P < 0.001 at 270 min, and from 4.5 (4.3, 4.7) to 25 (22, 28) kPa, P < 0.001, respectively. Base excess increased from 5 (3, 6) to 54 (51, 57) mM, P < 0.001. Cardiac output and arterial pressure were well maintained. The pig, which was studied for 6 h, had pH 7.27 and PaCO(2) 27 kPa at that time. CONCLUSION: With intensive buffering using THAM, pH can be kept in a physiologically acceptable range for 4 h during apnea.

Breast pump suction patterns that mimic the human infant during breastfeeding: greater milk output in less time spent pumping for breast pump-dependent mothers with premature infants.

OBJECTIVE: The objective of this study was to compare the effectiveness, efficiency, comfort and convenience of newly designed breast pump suction patterns (BPSPs) that mimic sucking patterns of the breastfeeding human infant during the initiation and maintenance of lactation. STUDY DESIGN: In total, 105 mothers of premature infants ≤34 weeks of gestation were randomly assigned to 1 of 3 groups within 24 h post-birth. Each group tested two BPSPs; an initiation BPSP was used until the onset of lactogenesis II (OOL-II) and a maintenance BPSP was used thereafter. RESULT: Mothers who used the experimental initiation and the standard 2.0 maintenance BPSPs (EXP-STD group) demonstrated significantly greater daily and cumulative milk output, and greater milk output per minute spent pumping. CONCLUSION: BPSPs that mimic the unique sucking patterns used by healthy-term breastfeeding infants during the initiation and maintenance of lactation are more effective, efficient, comfortable and convenient than other BPSPs.

Non-toxic alveolar oxygen concentration without hypoxemia during apnoeic oxygenation: an experimental study.

BACKGROUND: Oxygenation without tidal breathing, i.e. apnoeic oxygenation in combination with extracorporeal carbon dioxide removal, might be an option in the treatment of acute respiratory failure. However, ventilation with 100% O2, which is potentially toxic, is considered a prerequisite to ensure acceptable oxygenation. We hypothesized that trapping nitrogen (N2) in the lungs before the start of apnoeic oxygenation would keep the alveolar O2 at a non-toxic level and still maintain normoxaemia. The aim was to test whether a predicted N2 concentration would agree with a measured concentration at the end of an apnoeic period. METHODS: Seven anaesthetized, muscle relaxed, endotracheally intubated pigs (22-27 kg) were ventilated in a randomized order with an inspired fraction of O2 0.6 and 0.8 at two positive end-expiratory pressure levels (5 cm and 10 cm H2O) before being connected to continuous positive airway pressure using 100% O2 for apnoeic oxygenation. N2 was measured before the start of and at the end of the 10-min apnoeic period. The predicted N2 concentration was calculated from the initial N2 concentration, the end-expiratory lung volume, and the anatomical dead space. RESULTS: The mean difference and standard deviation between measured and predicted N2 concentration was -0.5 ± 2%, P = 0.587. No significant difference in the agreement between measured and predicted N2 concentrations was seen in the four settings. CONCLUSIONS: This study indicates that it is possible to predict and keep alveolar N2 concentration at a desired level and, thus, alveolar O2 concentration at a non-toxic level during apnoeic oxygenation.

Hyperthermal organic thin film growth on surfaces terminated with self-assembled monolayers. I. The dynamics of trapping.

We have examined the initial stages of growth of a crystalline small molecule organic thin film, diindenoperylene (DIP), on SiO(2) surfaces terminated with a series of self-assembled monolayers (SAMs). In this study we make use of supersonic molecular beam techniques to vary the incident kinetic energy of the DIP molecules, and we use in situ, real time synchrotron x-ray scattering to monitor the buildup of each molecular layer in the growing thin film. We find that the effects of the SAMs are most apparent concerning growth in the sub-monolayer regime, before the substrate is entirely covered by the DIP thin film. In this coverage regime on bare SiO(2), and SiO(2) terminated with either hexamethyldisilazane or perflurooctyltrichlorosilane the adsorption dynamics are consistent with trapping-mediated adsorption as observed in more simple systems, where the probability of adsorption decreases significantly with increasing kinetic energy. Once these surfaces are covered with DIP, however, the adsorption probability increases, particularly at the highest incident kinetic energy, and the probability of adsorption exhibits only a weak dependence on the incident kinetic energy. In contrast, on surfaces terminated by octyl- (OTS) and octadecyltrichlorosilane (ODTS) the trapping probability is high and exhibits little dependence on the incident kinetic energy, essentially the same as what is observed on these same surfaces covered by DIP. We postulate, which is backed by the results of molecular dynamics simulations, that direct molecular insertion into the OTS and ODTS layers is a primary explanation for efficient trapping on these surfaces.

Neurologic abnormalities in HTLV-I- and HTLV-II-infected individuals without overt myelopathy.

BACKGROUND: Human T-lymphotropic virus (HTLV) type I is the causative agent of HTLV-associated myelopathy (HAM)/tropical spastic paraparesis, and a number of HAM cases with HTLV-II infection have also been reported. However, despite some reports, it is unclear whether HTLV-I or -II infection is associated with other neurologic manifestations. METHODS: An analysis of medical histories and screening neurologic examinations from a prospective cohort of 153 HTLV-I, 388 HTLV-II, and 810 HTLV-seronegative individuals followed up for means of 11.5, 12.0, and 12.2 years was performed. Participants diagnosed with HAM were excluded. We calculated odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for age, sex, race or ethnicity, income, educational attainment, body mass index, alcohol and cigarette consumption, injection drug use, diabetes, and hepatitis C virus status, using generalized estimating equations for repeated measures. RESULTS: HTLV-I and -II participants were more likely than seronegative participants to have leg weakness (ORs 1.67 [95% CI 1.28-2.18] and 1.44 [1.16-1.78]), impaired tandem gait (ORs 1.25 [95% CI 1.07-1.47] and 1.45 [1.27-1.64]), Babinski sign (ORs 1.54 [95% CI 1.13-2.08] and 1.51 [1.18-1.93]), impaired vibration sense (ORs 1.16 [95% CI 1.01-1.33] and 1.27 [1.14-1.42]), and urinary incontinence (ORs 1.45 [95% CI 1.23-1.72] and 1.70 [1.50-1.93]). For both HTLV-I and -II participants, higher odds of sensory neuropathy by monofilament examination were no longer significant after adjustment for confounding. CONCLUSIONS: These results provide strong evidence that human T-lymphotropic virus (HTLV)-I and -II are associated with a spectrum of predominantly motor abnormalities in patients without overt HTLV-associated myelopathy. Further investigation of the clinical course and etiology of these abnormalities is warranted.

Calculating postnatal growth velocity in very low birth weight (VLBW) premature infants.

OBJECTIVE: Currently, there is no standardized approach to the calculation of growth velocity (GV; g kg (-1) day(-1)) in hospitalized very low birth weight (VLBW) infants. Thus, differing methods are used to estimate GV, resulting in different medical centers and studies reporting growth results that are difficult to compare. The objective of this study was to compare actual GV calculated from infant daily weights during hospitalization in a Neonatal Intensive Care Unit (NICU) with estimated GV using two mathematical models that have been shown earlier to provide good estimated GVs in extremely low birth weight (ELBW) infants: an exponential model (EM) and a 2-Point model (2-PM). STUDY DESIGN: Daily weights from 81 infants with birth weights (BWs) of 1000 to 1499 g were used to calculate actual GV in daily increments from two starting points: (1) birth and (2) day of life (DOL) of regaining BW. These daily GV values were then averaged over the NICU stay to yield overall NICU GV from the two starting points. We compared these actual GV with estimated GV calculated using the EM and 2-PM methods. RESULTS: The mean absolute difference between actual and EM estimates of GV showed <1% error for 100% of infants from both starting points. The mean absolute difference between actual and 2-PM estimates showed <1% error for only 38 and 44% of infants from birth and regaining BW, respectively. The EM was unaffected by decreasing BW and increasing length of NICU stay, whereas the accuracy of the 2-PM was diminished significantly (P<0.001) by both factors. CONCLUSION: In contrast to the 2-PM, the EM provides an extremely accurate estimate of GV in larger VLBW infants, and its accuracy is unaffected by common infant factors. The EM has now been validated for use in all VLBW infants to assess growth and provides a simple-to-use and consistent approach.

Coverage dependent adsorption dynamics in hyperthermal organic thin film growth.

We have examined the dynamics of adsorption of diindenoperylene (DIP) on SiO(2) and SiO(2) modified with an interfacial organic layer using in situ real time synchrotron x-ray scattering, focusing on the effects of coverage. On both surfaces we observe a substantial increase in the probability of adsorption with increasing coverage, which is most dramatic at the highest incident kinetic energies. On the initially uncovered surfaces, we observe a smooth decrease in the probability of adsorption with increasing incident kinetic energy, indicative of trapping-mediated adsorption. Once both surfaces are covered by DIP, the effects of incident kinetic energy are greatly reduced, and trapping is very efficient over the range of kinetic energies examined. Possible reasons for efficient trapping at high coverage and at high incident kinetic energy include more efficient momentum transfer due to mass matching, and possibly direct molecular insertion. Comparison to results on another small-molecule, pentacene, suggests that this behavior should be common to hyperthermal growth of a variety of other small-molecule thin films.

Magnetic resonance neurography in extraspinal sciatica.

BACKGROUND: Sciatica without evidence of lumbosacral root compression is often attributed to piriformis syndrome. However, specific diagnostic tools have not been available to demonstrate sciatic nerve entrapment by the piriformis muscle. OBJECTIVE: To evaluate the use of magnetic resonance (MR) neurography in identifying abnormalities of the sciatic nerve in patients with unexplained sciatica. DESIGN: Case series from a retrospective medical record review. PATIENTS: Fourteen patients with sciatic distribution pain and normal results on MR imaging for lumbosacral radiculopathy were referred for MR neurography of the lumbosacral plexus and sciatic nerves. RESULTS: In 12 patients, MR neurography demonstrated increased fluid-attenuated inversion recovery signal in the ipsilateral sciatic nerve. In most patients, this abnormal signal was seen at the sciatic notch, at or just inferior to the level of the piriformis muscle. To date, 4 patients have undergone surgical decompression, with excellent relief of symptoms in 3 of them. CONCLUSION: Magnetic resonance neurography often identifies an abnormal increased signal in the proximal sciatic nerve in patients with extraspinal sciatica and allows more accurate diagnosis of sciatic nerve entrapment in suspected cases.

A supersonic molecular beam study of the reaction of tetrakis(dimethylamido)titanium with self-assembled alkyltrichlorosilane monolayers.

The reaction of a transition metal coordination complex, Ti[N(CH(3))(2)](4), with self-assembled monolayers (SAMs) possessing-OH, -NH(2), and -CH(3) terminations has been examined using supersonic molecular beam techniques. The emphasis here is on how the reaction probability varies with incident kinetic energy (E(i)=0.4-2.07 eV) and angle of incidence (theta(i)=0 degrees -60 degrees ). The most reactive surface is the substrate underlying the SAMs-SiO(2) with a high density of -OH(a) (>5 x 10(14) cm(-2)), "chemical oxide." On chemical oxide, the dynamics of adsorption are well described by trapping, precursor-mediated adsorption, and the initial probability of adsorption depends only weakly on E(i) and theta(i). The dependence of the reaction probability on substrate temperature is well described by a model involving an intrinsic precursor state, where the barrier for dissociation is approximately 0.2-0.5 eV below the vacuum level. Reaction with the SAMs is more complicated. On the SAM with the unreactive, -CH(3), termination, reactivity decreases continuously with increasing E(i) while increasing with increasing theta(i). The data are best interpreted by a model where the Ti[N(CH(3))(2)](4) must first be trapped on the surface, followed by diffusion through the SAM and reaction at the SAMSiO(2) interface with residual -OH(a). This process is not activated by E(i) and most likely occurs in defective areas of the SAM. On the SAMs with reactive end groups, the situation is quite different. On both the-OH and -NH(2) SAMs, the reaction with the Ti[N(CH(3))(2)](4) as a function of E(i) passes through a minimum near E(i) approximately 1.0 eV. Two explanations for this intriguing finding are made-one involves the participation of a direct dissociation channel at sufficiently high E(i). A second explanation involves a new mechanism for trapping, which could be termed penetration facilitated trapping, where the Ti[N(CH(3))(2)](4) penetrates the near surface layers, a process that is activated as the molecules in the SAM must be displaced from their equilibrium positions.