Thin hard coatings fracture propagation during the impact test

One of the most significant applications of the impact test is to investigate thin hard coatings fatigue properties. Herein the test conditions and duration up to the film damage initiation, are considered in order to determine the critical stresses associated with the coating fatigue strength. Moreover, the subsequent film damage propagation is a significant mechanism as well, since it refers to the ability of the coating to withstand loads after its fatigue damage initiation. In order to describe the film fracture propagation the failed area ratio was introduced and an algorithm to determine this magnitude developed, based on the analysis of imprint scanning electron microscopy graphs. The application of the coating failed area ratio will be demonstrated in various impact test film cases, also with superficial thin layers. The top layers do not affect, in general, the failure initiation of the basic coating. However, according to the obtained results, the superficial films influence the basic coating failure propagation rate during the impact test.     

Effect of anatomic distribution of pulmonary emboli on interobserver agreement in the interpretation of pulmonary angiography

OBJECTIVE: This study examines the anatomic distribution of emboli on pulmonary angiography and attempts to determine the relationship of vessel size to interobserver agreement, two factors having important implications in comparing pulmonary angiography with cross-sectional imaging for pulmonary embolism. MATERIALS AND METHODS: One hundred twenty-five consecutive pulmonary angiograms were reviewed retrospectively by three interventional radiologists. Initial interpretations were recorded and compared to determine interobserver agreement on a per-patient and per-embolus basis. Discordant interpretations were reviewed by all radiologists for a consensus interpretation. RESULTS: Unanimous per-patient agreement occurred in 91% (114/125) of initial interpretations. The largest artery containing acute pulmonary embolism was segmental or larger in 24 patients (83% of patients with acute positive findings, 19% of all patients) and subsegmental in only five patients (17% and 4%, respectively). On a per-patient basis, initial interobserver agreement averaged 45% and unanimous consensus agreement was achieved for 79% of patients having isolated subsegmental pulmonary embolism. Consensus readings altered initial per-patient interpretations for 30% of patients having only subsegmental pulmonary embolism; per-embolus interpretations were altered for 37% of all subsegmental emboli. CONCLUSION: Subsegmental emboli occurring as isolated findings are relatively rare. Approximately one third of subsegmental emboli and one third of patients having isolated subsegmental emboli may be initially misdiagnosed on pulmonary angiography. Objections to cross-sectional imaging for pulmonary embolism based on the inability to detect subsegmental pulmonary embolism when compared with pulmonary angiography should be reexamined with this data in mind.     

On optical data-guided optimal control simulations of human motion

Multibody System Dynamics - This work addresses the synergistic fusion of optimal control simulations and marker-based optical measurements of human motion. The latter is a widespread capturing...     

Experimental studies on the positive feedback effect of progesterone, 17 alpha-hydroxyprogesterone and 20 alpha-dihydroprogesterone on the pituitary release of LH and FSH in the human female. The estrogen priming of the progesterone feedback on pituitary gonadotropins in the eugonadal woman

Administration of progesterone eugonadal women during the midfollicular phase of the menstrual cycle failed to induce a positive feedback effect on the serum concentrations of LH and FSH. The levels of estradiol in serum decreased following the injection of progesterone without a parallel change in LH and FSH concentrations indicating a direct ovarian effect of the exogenous progesterone. In the late follicular phase of the cycle, when preovulatory levels of estradiol were present in serum, or under a ethinyl estradiol treatment progesterone was able to induce an LH discharge indicating the requirement of an estradiol priming of the positive feedback of progesterone in eugonadal women. In order to establish the time required for a sufficient estrogen priming with preovulatory levels of estradiol in serum 3 mg of estradiol-benzoate were administered i.m. 1, 12 and 24 h prior to the administration of 30 mg of microcristalline progesterone in the midfollicular phase of the menstrual cycle, when progesterone alone did not cause an LH surge. Only when estradiol-benzoate was injected 24 h prior to the progesterone administration an LH surge reproducible in time course and magnitude occurred. Administration of estradiol-benzoate alone under these conditions did not cause an LH surge within the elapse of time after the injection when the progesterone induced LH surge occurred. Thus, these experiments demonstrate that a defined estrogen priming is required for the positive feedback effect of progesterone on the gonadotropin release in eugonadal women. Furthermore, progesterone levels in serum of about only 1--2 ng/ml were required for the induction of an LH surge indicating that under physiological conditions progesterone may have an supplementory effect on the primarily estradiol induced LH midcycle peak. 17-hydroxyprogesterone administered during the mid follicular phase of the menstrual cycle and under pretreatment with ethinyl estradiol failed to induce a positive feedback effect on the serum concentrations of LH and FSH, indicating that this steroid does not play a regulatory role on the midcycle LH release in women. 20alpha-dihydroprogesterone administered under the same experimental conditions as 17-hydroxyprogesterone seems to be able to induce an LH surge in serum provided there is an adequate estrogen priming.     

Discontinuous variational time integrators for complex multibody collisions

The objective of the present work is to formulate a new class of discontinuous variational time integrators that allow the system to adopt two possibly different configurations at each sampling time t_k, representing predictor and corrector configurations of the system. The resulting sequence of configuration pairs then represents a discontinuous—or non‐classical—trajectory. Continuous or classical trajectories are recovered simply by enforcing a continuity constraint at all times. In particular, in systems subject to one‐sided contact constraints simulated via discontinuous variational time integrators, the predictor configuration is not required to satisfy the one‐sided constraints, whereas the corrector configuration is obtained by a closest‐point projection (CPP) onto the admissible set. The resulting trajectories are generally discontinuous, or non‐classical, but are expected to converge to classical or continuous solutions for decreasing time steps. We account for dissipation, including friction, by means of a discrete Lagrange–d'Alembert principle, and make extensive use of the spacetime formalism in order to ensure exact energy conservation in conservative systems, and the right rate of energy decay in dissipative systems. The structure, range and scope of the discontinuous variational time integrators, and their accuracy characteristics are illustrated by means of examples of application concerned with rigid multibody dynamics. Copyright © 2014 John Wiley & Sons, Ltd.     

Time-of-flight MR arteriography of below-knee arteries with maximum-intensity-projection reconstruction: is interpretation of the axial source images helpful?

OBJECTIVE: We evaluated the extent to which detailed review of axial source images enhances the interpretation of projectional reconstructions of two-dimensional time-of-flight MR arteriograms of the tibial vessels. SUBJECTS AND METHODS: Thirty-one patients (34 limbs) with limb-threatening ischemia underwent two-dimensional time-of-flight imaging and contrast-enhanced angiography of the below-knee arteries. Maximum-intensity-projection (MIP) reconstructions of the MR arteriograms were independently interpreted by three observers. The studies were then reinterpreted after detailed review of the axial source images. A consensus reading of each study was performed as well. The observers commented on the patency of 816 vascular segments and graded the extent of disease for 272 vessels. Interobserver agreement and correlation with contrast-enhanced angiography were determined. RESULTS: On average, the addition of axial images altered the observers' interpretation of MR arteriograms in 13% of segments for patency and in 18% of vessels for grading of disease severity. For determining the patency of vascular segments, mean interobserver agreement was 0.79 without and 0.80 with axial image interpretation, and mean agreement with contrast-enhanced angiography improved from 0.69 to 0.72 with the addition of axial images. When evaluating the extent of disease, correlation between observers improved for all combinations of observers with the addition of axial images, and correlation with contrast-enhanced angiography improved for two of three observers. Based on the consensus interpretation of the MR arteriograms, review of axial images was found to improve agreement with contrast-enhanced angiography in 34 vascular segments. In addition, axial image review correctly altered the number of stenoses identified in 12 vessels. When consensus interpretation identified a vessel as patent without significant stenosis on the MIP images, the MIP-based interpretation was found to be correct in all cases. CONCLUSION: Review of axial source images provides limited benefit to interpretation of MR arteriograms of the distal lower extremity in patients with peripheral vascular disease. Although selective review of axial source images may be appropriate, axial images can improve interpretation when MIP images are complicated by the presence of patient motion, difficult anatomy, or artifacts. Axial image review may also be appropriate when a significant stenosis is identified on the MIP images.     

Culture and early infancy among central African foragers and farmers

A 27-residue stretch of amino acids encompassing two putative 13-residue amphiphilic helical segments is an important determinant of activity in the 47-residue antibacterial peptide bovine seminalplasmin. Synthetic peptides corresponding to the 27-residue stretch (P27) SLSRYAKLANRLANPKLLETFLSKWIG as well as the 13-residue segments PKLLETFLSKWIG (SPF),exhibit antimicrobial activity. An analog of SPF where E has been replaced by K(SPFK) showed improved antimicrobial properties as compared to SPF. The peptides have the ability to bind and permeabilize membranes. We have modeled helical bundles of P27 and the two 13-residue peptides SPF and SPFK using simulated annealing via molecular dynamics. Octameric but not hexameric aggregates of P27 can form channels which would allow the passage of ions. In the case of 13-residue peptides, aggregates formed by 6 monomers can conceivably form ion conducting channels. Since the ability to form channels which would allow the passage of ions across the membranes is an important determinant of the biological activities of these peptides, knowledge of the pore forming structures should help in the design of analogs with improved activities.