Granular flow down an inclined plane: Bagnold scaling and rheology

We have performed a systematic, large-scale simulation study of granular media in two and three dimensions, investigating the rheology of cohesionless granular particles in inclined plane geometries, i.e., chute flows. We find that over a wide range of parameter space of interaction coefficients and inclination angles, a steady-state flow regime exists in which the energy input from gravity balances that dissipated from friction and inelastic collisions. In this regime, the bulk packing fraction (away from the top free surface and the bottom plate boundary) remains constant as a function of depth z, of the pile. The velocity profile in the direction of flow vx(z) scales with height of the pile H, according to vx(z) proportional to H(alpha), with alpha=1.52+/-0.05. However, the behavior of the normal stresses indicates that existing simple theories of granular flow do not capture all of the features evidenced in the simulations.

Association between blood pressure level and the risk of myocardial infarction, stroke, and total mortality: the cardiovascular health study

BACKGROUND

Recent reports have drawn attention to the importance of pulse pressure as a predictor of cardiovascular events. Pulse pressure is used neither by clinicians nor by guidelines to define treatable levels of blood pressure.

METHODS

In the Cardiovascular Health Study, 5888 adults 65 years and older were recruited from 4 US centers. At baseline in 1989-1990, participants underwent an extensive examination, and all subsequent cardiovascular events were ascertained and classified.

RESULTS

At baseline, 1961 men and 2941 women were at risk for an incident myocardial infarction or stroke. During follow-up that averaged 6.7 years, 572 subjects had a coronary event, 385 had a stroke, and 896 died. After adjustment for potential confounders, systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure were directly associated with the risk of incident myocardial infarction and stroke. Only SBP was associated with total mortality. Importantly, SBP was a better predictor of cardiovascular events than DBP or pulse pressure. In the adjusted model for myocardial infarction, a 1-SD change in SBP, DBP, and pulse pressure was associated with hazard ratios (95% confidence intervals) of 1.24 (1.15-1.35), 1.13 (1.04-1.22), and 1.21 (1.12-1.31), respectively; and adding pulse pressure or DBP to the model did not improve the fit. For stroke, the hazard ratios (95% confidence intervals) were 1.34 (1.21-1.47) with SBP, 1.29 (1.17-1.42) with DBP, and 1.21 (1.10-1.34) with pulse pressure. The association between blood pressure level and cardiovascular disease risk was generally linear; specifically, there was no evidence of a J-shaped relationship. In those with treated hypertension, the hazard ratios for the association of SBP with the risks for myocardial infarction and stroke were less pronounced than in those without treated hypertension.

CONCLUSION

In this population-based study of older adults, although all measures of blood pressure were strongly and directly related to the risk of coronary and cerebrovascular events, SBP was the best single predictor of cardiovascular events.

Emotion processing in borderline personality disorders

The aim of this study was to examine the ways in which adults with borderline personality disorder (BPD) experience and manage their feelings. Responses of 30 subjects who met the criteria for BPD on the Structured Clinical Interview for DSM-III-R were compared with 40 non-BPD controls on the following measures of emotion processing and affect regulation: 1) level of emotional awareness, 2) capacity to coordinate mixed valence feelings, 3) accuracy at identifying facial expressions of emotion, and 4) intensity of response to negative emotions. The results showed significant differences between the two groups on all measures. The borderlines showed significantly lower levels of emotional awareness, less capacity to coordinate mixed valence feelings, lower accuracy at recognizing facial expressions of emotion, and more intense responses to negative emotions than the nonborderline controls. The findings corroborate clinical observations of borderline patients' difficulties in regulating emotions. The implications of the results for the therapeutic management of BPD patients are discussed.

Placenta accreta: evaluation with color Doppler US, power Doppler US, and MR imaging

PURPOSE

To determine the value of transabdominal ultrasound (US), transvaginal US, color Doppler US, power Doppler US, and magnetic resonance (MR) imaging in the diagnosis of placenta accreta.

MATERIALS AND METHODS

Nineteen patients in the third trimester of pregnancy who were at risk for placenta accreta underwent color Doppler and power Doppler US; 18 patients also underwent MR imaging. Images were interpreted prospectively for signs of accreta by two reviewers. The reviewers' confidence in their diagnosis was graded on a five-point scale.

RESULTS

Outcomes at delivery were as follows: normal placenta (n = 11), hysterectomy owing to uncontrollable bleeding (n = 1), and placenta accreta (n = 7). Five cases of lower-uterine-segment placenta accreta were diagnosed with a high level of confidence with vaginal and power Doppler US. In one patient with a posterior placenta who had previously undergone myomectomy, MR imaging enabled the diagnosis of placenta accreta, which was not well depicted at US.

CONCLUSION

In patients with a history of uterine scars, vaginal US with power Doppler US performed well in the evaluation of lower-uterine-segment placenta accreta. MR imaging depicts posterior placenta accreta.

Cortical maturation in normal and abnormal fetuses as assessed with prenatal MR imaging

PURPOSE

To establish the appearance of normal fetal cortical development in utero and compare it with the appearance of abnormal cortical development.

MATERIALS AND METHODS

Magnetic resonance (MR) images of the brain in 53 normal and 40 abnormal fetuses at 14-38 weeks gestational age (GA) were reviewed. The GAs at the time of MR imaging visualization of the fissures or sulci were compared with the GA guidelines based on neuroanatomic studies.

RESULTS

In normal fetuses, the sulcation landmarks appeared on MR images in the order predicted by using anatomic studies, with a 0-8-week lag in the MR imaging visualization of the sulci compared with the reported time of visualization of the sulci in anatomic specimens. When landmarks were grouped by range of GAs, the expected MR imaging sulcation landmarks in the group with younger GAs than the actual GA were seen in 50 of 53 (94%) normal fetuses, in five of nine fetuses (56%, P < .05) with isolated mild ventriculomegaly, and in 24 of 31 fetuses (77%, P < .05) with other CNS anomalies.

CONCLUSION

Normal fetal cortical maturation at MR imaging follows a predictable course that is slightly delayed compared with that described in neuroanatomic specimens. This maturation is often further delayed in fetuses with CNS abnormalities.

Obstetric MR imaging

The surge in the development of fast magnetic resonance (MR) techniques has revolutionized our ability to image the pregnant patient and the fetus. Fast MR imaging techniques provide excellent resolution for imaging the maternal and fetal anatomies without the need for sedation. This article addresses the use of fast MR imaging techniques in the evaluation of the pregnant patient for adnexal masses, pelvimetry, hydroureteronephrosis of pregnancy, and placenta accreta. In addition, fetal anomalies for which MR imaging has proved useful, such as ventriculomegaly, arachnoid cysts, and abdominal masses, are described.

Fetal fast MR imaging: reproducibility, technical quality, and conspicuity of anatomy

PURPOSE

To evaluate the normal appearance of fetal anatomy, the conspicuity of fetal organs, the reproducibility of images, and the limitations to image quality with the use of half-Fourier, single-shot rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Fifty-four fetuses of 49 pregnancies underwent MR imaging with the half-Fourier, single-shot RARE technique. Two reviewers attempted to identify 47 organs and anatomic regions in each fetus. Organ or region conspicuity, image quality, and the limitations of image quality were graded.

RESULTS

Fetal anatomy was well depicted in fetuses over 20 weeks in gestational age. Fetal imaging was limited by gestational age of 20 weeks or less usually owing to the small size of the organ or region being evaluated and, less frequently, by motion.

CONCLUSION

Half-Fourier, single-shot RARE MR imaging provided a detailed and reproducible evaluation of normal fetal anatomy, which can be used as a standard of reference in MR imaging of fetal anomalies.

Factors related to sleep disturbance in older adults experiencing knee pain or knee pain with radiographic evidence of knee osteoarthritis

OBJECTIVES

To describe the types and frequencies of sleep complaints and the biopsychosocial factors associated with sleep disturbance in a large community sample of older adults experiencing knee pain or knee pain with radiographic evidence of knee osteoarthritis (OA).

DESIGN

Baseline analyses of an observational prospective study.

SETTING AND PARTICIPANTS

Participants were 429 men and women aged 65 years and older experiencing knee pain or knee pain with radiographic evidence of OA enrolled in the Observational Arthritis Study in Seniors (OASIS).

MEASUREMENTS

Demographic variables (age, gender, ethnicity, education), health (X-rays of knee rated for OA severity, medical conditions, medication use, smoking status, body mass index, self-rated health), physical functioning (self-rated physical functioning, physical performance), knee pain, and psychosocial functioning (social support, depression) were measured.

RESULTS

Problems with sleep onset, sleep maintenance, and early morning awakenings occurred at least weekly among 31%, 81%, and 51% of participants, respectively. Bivariate correlates of greater sleep disturbance in those with OA were less education, cardiovascular disease, more arthritic joints, poorer self-rated health, poorer physical functioning, poorer physical performance, knee pain, depression, and less social support. In regression analyses, each set of variables representing the domains of health, physical functioning, pain, and psychosocial functioning contributed to the prediction of sleep disturbance beyond the demographic set. Finally, in a simultaneous model, white race (trend, P = .06), poorer self-rated health, poorer physical functioning, and depressive symptoms were predictive of sleep disturbance.

CONCLUSIONS

Sleep disturbance is common in older adults experiencing knee pain or knee pain with radiographic evidence of OA and is best understood through the consideration of demographic, physical health, physical functioning, pain, and psychosocial variables. Interventions that take into account the multidetermined nature of sleep disturbance in knee pain or knee OA are most likely to be successful.

Fetal central nervous system anomalies: MR imaging augments sonographic diagnosis

PURPOSE

To evaluate fetuses with sonographically suspected central nervous system anomalies to determine the frequency with which obstetric magnetic resonance (MR) imaging adds clinically useful information to that provided by ultrasonography (US).

MATERIALS AND METHODS

US and MR images and diagnoses in 18 pregnant women were reviewed and compared by two radiologists. Postnatal physical examination and imaging findings and fetal autopsy results were standards. Referring physicians were questioned as to how the additional information provided by MR imaging changed patient counseling.

RESULTS

In 10 (55%) patients, MR imaging demonstrated 11 additional findings. These findings were agenesis of the corpus callosum (n = 4), cerebellar hypoplasia (n = 2), cortical cleft (n = 2), polymicrogyria (n = 1), porencephaly (n = 1), and partial agenesis of the septi pellucidi (n = 1). In seven (39%) patients, additional information provided by MR imaging altered counseling. In one case of suspected agenesis of the corpus callosum, diagnosis at MR imaging was at least partially incorrect.

CONCLUSION

US and MR imaging are complementary imaging methods in the evaluation of high-risk pregnancy. When a central nervous system anomaly is suspected at US, MR imaging may demonstrate additional findings that can alter patient counseling.

Thyroid abnormalities following the use of cytotoxic T-lymphocyte antigen-4 and programmed death receptor protein-1 inhibitors in the treatment of melanoma

CONTEXT

Checkpoint inhibitors are emerging as important cancer therapies but are associated with a high rate of immune side effects, including endocrinopathy.

OBJECTIVE

To determine the burden of thyroid dysfunction in patients with melanoma treated with immune checkpoint inhibitors and describe the clinical course.

DESIGN AND PATIENTS

Consecutive patients with melanoma treated with either ipilimumab, nivolumab, pembrolizumab or the combination of ipilimumab and nivolumab were identified. Baseline thyroid function tests were used to exclude those with pre-existing thyroid abnormalities, and thyroid function tests during treatment used to identify those with thyroid dysfunction.

RESULTS

Rates of overt thyroid dysfunction were in keeping with the published phase 3 trials. Hypothyroidism occurred in 13·0% treated with a programmed death receptor-1 (PD-1) inhibitor and 22·2% with a combination of PD-1 inhibitor and ipilimumab. Transient subclinical hyperthyroidism was observed in 13·0% treated with a PD-1 inhibitor, 15·9% following a PD-1 inhibitor, and 22·2% following combination treatment with investigations suggesting a thyroiditic mechanism rather than Graves' disease, and a high frequency of subsequent hypothyroidism. Any thyroid abnormality occurred in 23·0% following ipilimumab, 39·1% following a PD-1 inhibitor and 50% following combination treatment. Abnormal thyroid function was more common in female patients.

CONCLUSION

Thyroid dysfunction occurs commonly in patients with melanoma treated with immune checkpoint inhibitors, with rates, including subclinical dysfunction, occurring in up to 50%.

Candida infective endocarditis

Candida infective endocarditis (IE) is uncommon but often fatal. Most epidemiologic data are derived from small case series or case reports. This study was conducted to explore the epidemiology, treatment patterns, and outcomes of patients with Candida IE. We compared 33 Candida IE cases to 2,716 patients with non-fungal IE in the International Collaboration on Endocarditis-Prospective Cohort Study (ICE-PCS). Patients were enrolled and the data collected from June 2000 until August 2005. We noted that patients with Candida IE were more likely to have prosthetic valves (p < 0.001), short-term indwelling catheters (p < 0.0001), and have healthcare-associated infections (p < 0.001). The reasons for surgery differed between the two groups: myocardial abscess (46.7% vs. 22.2%, p = 0.026) and persistent positive blood cultures (33.3% vs. 9.9%, p = 0.003) were more common among those with Candida IE. Mortality at discharge was higher in patients with Candida IE (30.3%) when compared to non-fungal cases (17%, p = 0.046). Among Candida patients, mortality was similar in patients who received combination surgical and antifungal therapy versus antifungal therapy alone (33.3% vs. 27.8%, p = 0.26). New antifungal drugs, particularly echinocandins, were used frequently. These multi-center data suggest distinct epidemiologic features of Candida IE when compared to non-fungal cases. Indications for surgical intervention are different and mortality is increased. Newer antifungal treatment options are increasingly used. Large, multi-center studies are needed to help better define Candida IE.

Pravastatin therapy in hyperlipidemia: effects on thrombus formation and the systemic hemostatic profile

OBJECTIVES

The study sought to determine the effects of lipid-lowering with pravastatin on the systemic fibrinolytic profile and on thrombus formation under dynamic flow conditions.

BACKGROUND

Lowering cholesterol (C) decreases clinical events in coronary artery disease (CAD) patients, but an analysis of the effects of lipid-lowering on the entire hemostatic and thrombotic profile has not been conducted.

METHODS

We prospectively studied 93 stable patients with untreated low-density lipoprotein cholesterol (LDL-C) >145 mg/dl. The CAD patients received pravastatin, and non-CAD patients were randomized to pravastatin versus placebo (double-blind). Thrombus formation upon an injured vascular surface was assessed in a substudy of 40 patients with a previously validated ex vivo perfusion chamber system. Systemic hemostatic markers and thrombus formation were evaluated at baseline, three and six months.

RESULTS

Placebo produced no changes in either the lipid profile, any of the hemostatic markers, or the ex vivo thrombus formation. Both pravastatin groups (CAD and non-CAD) showed decreased LDL-C by 30% within 6 weeks (188 to 126 mg/dl, p < 0.001 vs. baseline), and decreased plasminogen activator inhibitor-1 at 3- and 6-month follow-up compared to baseline (15% to 18% decrease at 3 months and 21% to 23% at 6 months). For the tissue plasminogen activator antigen, CAD and non-CAD groups showed significant decreases at 6 months compared to baseline (10% and 13%, respectively). No significant changes were observed with treatment in d-dimer, fibrinopeptide A, prothrombin fragment F1.2, factor VIIa, von Willebrand factor, or C-reactive protein. Fibrinogen levels were significantly increased at 6 months compared to baseline, though still below the upper normal limit. In the perfusion chamber substudy, there was a decrease in thrombus area in non-CAD patients treated with pravastatin at both 3 and 6 months compared to baseline (by 21% and 34%, respectively). The CAD patients showed decreases in thrombus formation by 13% at 3 months, and by 16% at 6 months. The change in LDL-C- correlated modestly with the change in thrombus formation (r = 0.49; p < 0.01).

CONCLUSIONS

Pravastatin therapy significantly decreased thrombus formation and improved the fibrinolytic profile in patients with and without CAD. These early effects may, in part, explain the benefit rendered in primary and secondary prevention of CAD.

Mood, vegetative disturbance, and dexamethasone suppression test after stroke

Assessments of mood disturbance and "vegetative" (appetite or sleep) disturbance as well as a single-dose dexamethasone suppression test (DST) were carried out in 25 randomly selected stroke patients and in 13 nonstroke control patients hospitalized in a rehabilitation center. Prevalence rates of moderate-to-serve depression of mood and vegetative disturbance were significantly higher in stroke patients than controls (48% and 52% versus 0% and 8%, respectively), as was the prevalence of abnormal DST results (52% versus 8%). Abnormal DST results were associated with the occurrence of moderate to severe mood, appetite, and sleep disturbances among all patients. in 2 stroke patients, repeated DST results paralleled the clinical course. The DST may be useful as an adjunct to the diagnosis and in monitoring the progress of the common and potentially reversible mood and vegetative disturbances occurring after stroke.

The effects of pelvic movement on lumbar lordosis in the standing position

The purpose of this study was to investigate whether the maneuver of altering the angle of pelvic tilt when standing is effective in changing the angle of lumbar lordosis. The importance of the study was to establish a scientific basis for a common clinical assumption. Pelvic tilt and lumbar lordosis were measured during three conditions: with subjects in a normal standing posture, with subjects assuming a maximal anterior pelvic tilt posture, and with subject assuming a maximal posterior pelvic tilt posture. Measurements of pelvic tilt and lumbar lordosis were obtained using a television/computer system that obtained the three-dimensional coordinates of markers on the pelvis and spine at 20-msec intervals. Each measurement was made three times, and all were found to be reliable, with intraclass correlation coefficients (3,1) ranging from 0.78 to 0.95 (p < 0.001). Adopting a maximal anterior pelvic tilt changed the pelvic attitude relative to the horizontal by an average fo 11.4 degrees (p < 0.001) and increased the lumbar lordosis by an average of 10.8 degrees (p < 0.001). Adopting a maximal posterior pelvic tilt changed the pelvic attitude by an average of 8.7 degrees (p < 0.001) and decreased the lumbar lordosis by an average of 9.0 degrees (p < 0.001). The results of this study demonstrate that altering the pelvic tilt significantly changes the angle of lumbar lordosis. This lends support to the use of pelvic tilting exercises to increase or decrease the degree of lumbar lordosis, at least for the duration of the exercise.

Comparison of long-term numerical and experimental total knee replacement wear during simulated gait loading

Pre-clinical experimental wear testing of total knee replacement (TKR) components is an invaluable tool for evaluating new implant designs and materials. However, wear testing can be a lengthy and expensive process, and hence parametric studies evaluating the effects of geometric, loading, or alignment perturbations may at times be cost-prohibitive. The objectives of this study were to develop an adaptive FE method capable of simulating wear of a polyethylene tibial insert and to compare predicted kinematics, weight loss due to wear, and wear depth contours to results from a force-controlled experimental knee simulator. Finite element-based computational wear predictions were performed to 5 million gait cycles using both force- and displacement-controlled inputs. The displacement-controlled inputs, by accurately matching the experimental tibiofemoral motion, provided an evaluation of the simple wear theory. The force-controlled inputs provided an evaluation of the overall numerical method by simultaneously predicting both kinematics and wear. Analysis of the predicted wear convergence behavior indicated that 10 iterations, each representing 500,000 gait cycles, were required to achieve numerical accuracy. Using a wear factor estimated from the literature, the predicted kinematics, polyethylene wear contours, and weight loss were in reasonable agreement with the experimental data, particularly for the stance phase of gait. Although further development of the simplified wear theory is important, the initial predictions are encouraging for future use in design phase implant evaluation. In contrast to the experimental testing which occurred over approximately 2 months, computational wear predictions required only 2h.

Minimally invasive plate osteosynthesis of distal fractures of the tibia

Minimally invasive plate osteosynthesis of distal tibial fractures is technically feasible and may be advantageous in that it minimizes soft tissue compromise and devascularization of the fracture fragments. The technique involves open reduction and internal fixation of the associated fibular fracture when present, followed by temporary external fixation of the tibia until swelling has resolved. Subsequent limited, but open reduction and internal fixation of the articular fragments when displaced followed by minimally invasive plate osteosynthesis of the tibia utilizing precontoured tubular plates and percutaneously placed cortical screws is performed. The semitubular plate was chosen because it adapts more easily to the bone contours than the stiffer small fragment LC-DCP does. Twenty patients (age 25-59 years) with unstable intraarticular or open extraarticular fractures have been treated including 12 A-type, 1 B-type and 7 C-type fractures according to the AO classification. Two fractures were open (both Gustilo Type I). Closed soft tissue injury was graded according to Tscherne with 3 type C0, 7 type C1, 7 type C2 and 1 type C3. All fractures healed without the need for a second operation. Time to full weight-bearing averaged 10.7 weeks (range 8-16 weeks). Two fractures healed with > 5 degrees varus alignment and 2 fractures healed with > 10 degrees recurvatum. No patient had a deep infection. The average range of motion in the ankle for dorsiflexion was 14 degrees (range 0-30 degrees) and plantar flexion averaged 42 degrees (range 20-50 degrees). With longer follow-up and a larger number of patients, the authors feel confident that the minimally invasive technique for plate osteosynthesis for the treatment of distal tibial fractures will prove to be a feasible and worthwhile method of stabilization while avoiding the severe complications associated with the more standard methods of internal or external fixation of those fractures.

Fetal anatomy revealed with fast MR sequences

Although all the imaging studies in this pictorial essay were done for maternal rather than fetal indications, fetal anatomy was well visualized. However, when scans are undertaken for fetal indications, fetal motion in between scout views and imaging sequences may make specific image planes difficult to obtain. Of the different techniques described in this review, we preferred the HASTE technique and use it almost exclusively for scanning pregnant patients. The T2-weighting is ideal for delineating fetal organs. Also, the HASTE technique allows images to be obtained in 430 msec, limiting artifacts arising from maternal and fetal motion. MR imaging should play a more important role in evaluating equivocal sonographic cases as fast scanning techniques are more widely used. Obstetric MR imaging no longer will be limited by fetal motion artifacts. When complex anatomy requires definition in a complicated pregnant patient, MR imaging should be considered as a useful adjunct to sonography.

Central nervous system abnormalities assessed with prenatal magnetic resonance imaging

OBJECTIVE

To determine the frequency at which magnetic resonance imaging (MRI) provides additional information in fetuses with suspected central nervous system (CNS) abnormalities on ultrasound.

METHODS

Between May 1, 1996, and March 26, 1999, 83 women with 90 fetuses (including seven sets of live twins) had 91 ultrasonographic and MRI examinations of the fetal CNS. Eight women were studied twice, one for two different indications. If referrals came from outside our institution, a confirmatory sonogram was obtained. Indications for examination were ventriculomegaly (n = 25), suspected neural tube defect (n = 16), arachnoid cyst (n = 12), large cisterna magna (n = 11), and miscellaneous indications (n = 20).

RESULTS

Magnetic resonance imaging findings led to changed diagnoses in 26 (40%) of 66 fetuses with abnormal confirmatory sonograms. Magnetic resonance imaging findings not found by ultrasound included partial or complete agenesis of the corpus callosum (n = 11), porencephaly (n = 6), hemorrhage (n = 5), tethered cord (n = 3), cortical gyral abnormality (n = 2), cortical cleft (n = 2), midbrain abnormality (n = 2), and partial or complete agenesis of the septi pellucidi (n = 3), as well as holoprosencephaly, cerebellar hypoplasia, subependymal and cortical tubers, vascular malformation, and vermian cysts (one case each). Abnormalities better delineated by MRI than ultrasound included three cephaloceles, a dural arteriovenous malformation, one distal sacral neural tube defect, and the mass effect of three arachnoid cysts. That information was used to alter patient counseling and at times management.

CONCLUSION

When a CNS anomaly is detected by sonography or suspected on ultrasound, MRI findings might lead to altered diagnosis and patient counseling.