Conformal boundary conditions and three-dimensional topological field theory

We present a general construction of all correlation functions of a two-dimensional rational conformal field theory, for an arbitrary number of bulk and boundary fields and arbitrary topologies. The correlators are expressed in terms of Wilson graphs in a certain three-manifold, the connecting manifold. The amplitudes constructed this way can be shown to be modular invariant and to obey the correct factorization rules.

An annular compliance chamber for the Pennsylvania State University electric total artificial heart.

To eliminate the need for a separate parapleural compliance chamber, we are currently investigating the feasibility of an annular compliance chamber. This chamber wraps around the energy converter and fits between the blood pumps of the Pennsylvania State University electric total artificial heart. For the 100 cc total artificial heart, the compliance chamber volume is 76 ml and the tissue contacting surface area is approximately 85 cm2. The chamber is made of Dacron velour covered segmented polyether polyurethane urea. The annular compliance chamber was evaluated in vitro by comparing pump balance control performance against that obtained with an open vent. In the CVP range of 5-12 mmHg, LAP was maintained within 1 mmHg of the values obtained with a vent. Studies continue to determine the range of volumes over which the chamber is effective, differences in rates of diffusion, and performance during changes in barometric pressure.

Steady state hemodynamic and energetic characterization of the Penn State/3M Health Care Total Artificial Heart.

Total Artificial Heart (TAH) development at Penn State University and 3M Health Care has progressed from design improvements and manufacturing documentation to in vitro and in vivo testing to characterize the system's hemodynamic response and energetic performance. The TAH system is completely implantable and intended for use as an alternative to transplantation. It includes a dual pusher plate pump and rollerscrew actuator, welded electronics and battery assembly, transcutaneous energy transmission system, telemetry, and a compliance chamber. In vitro testing was conducted on a Penn State mock circulatory loop with glycerol/water solution at body temperature. Tests were performed to characterize the preload and afterload response, left atrial pressure control, and power consumption. A sensitive preload response was demonstrated with left atrial pressure safely maintained at less than 15 mm Hg for flow rates up to 7.5 L/min. Variations in aortic pressure and pulmonary vascular resistance were found to have minimal effects on the preload sensitivity and left atrial pressure control. In vivo testing of the completely implanted system in its final configuration was carried out in two acute studies using implanted temperature sensors mounted on the electronics, motor, and energy transmission coil in contact with adjacent tissue. The mean temperature at the device-tissue interface was less than 4 degrees C above core temperature.

In vivo and in vitro stability of modified poly(urethaneurea) blood sacs.

In the present study, we investigate the in vivo and in vitro stability of modified poly(urethaneurea) (BioSpan MS/0.4) blood sacs. Blood sacs were utilized primarily in left ventricular assist devices that were implanted in calves for times ranging from 5 to 160 days. Cyclic testing in vitro was also conducted on similar sacs. Various analytical methods were employed to characterize the sacs after in vivo or in vitro service and corresponding retained "control" sacs. These methods included ATR-FTIR spectroscopy, scanning electron microscopy and gel permeation chromatography. In general, the characteristics of implanted and in vitro cycled sacs were similar to their control sacs. Thermal and microtensile properties were unchanged after testing. The same was true for the ATR-FTIR spectra, indicating relative chemical stability for the time frames explored here. The only significant changes occurred in molecular weight and gross surface morphology. A modest increase in weight average molecular weight was observed for most implanted blood sacs, indicating some type of chain extension or branching reaction in vivo. Although the surface morphologies of implanted blood sacs were often similar to their control sacs, we sometimes observed limited pitting on the nonblood contacting surfaces in regions of the sac that experience maximum bending during service.

[Intestinal motility and continuous enteral nutrition: electromyographic study in dogs]. / Motricité intestinale et nutrition entérale continue: étude électromyographique chez le chien.

In fasting dogs, intestinal motility is characterized by the recurrence of a cyclic pattern, named the myoelectric complex; when inhibited by meals, the myoelectric complex is replaced by typical postprandial activity. Numerous studies have been performed concerning small intestinal motility but they all concerned acute food intakes. On the contrary, the aim of our work was to investigate the influence of continuous enteral nutrition in dogs for different caloric loads. The results showed that after a temporary inhibition caused by the onset of continuous enteral nutrition, the myoelectric complexes reappeared, first with long and irregular intervals of recurrence, later and finally with the same characteristics observed during the fasting state. We conclude that small intestinal motility can present the typical features of the fasting state, in spite of the presence of nutrients in the digestive tract. The factors inducing postprandial inhibition of myoelectric complexes loose their effectiveness after a period of time which depends on the caloric load in continuous enteral nutrition.

[Intestinal motility following jejunal resection: electromyography study in the rat]. / Motricité intestinale après résection jéjunale: étude électromyographique chez le rat.

The influences of massive resections on motility of the small intestine remain poorly known. The aim of our study was to determine the effects of jejunal resection on the pattern of occurrence of the migrating myoelectric complex and its postprandial inhibition. The experiments were performed over a period of 1 month after surgery. Transections were done on the jejunum or on the ileum in sham-operated animals. Ten days after resection, the motility of the anastomosed jejunal and ileal segments was dissociated. After one month, a functional continuity appeared through the anastomosis: the whole intestine worked synchronously at the same rhythm as the ileum. Food intake induced an increase in the frequency of the migrating myoelectric complexes measured 10 days after surgery. An adaptative phenomenon appeared after 30 days, the postprandial motor activity returning to its control level.

[Can an online risk assessment tool for identification of hereditary colorectal cancer reach the at-risk population and influence screening compliance?]. / Kann mit einem Online-Risikotest die Risikopopulation für familiären und erblichen Darmkrebs erreicht und ihr Vorsorgeverhalten positiv beeinflusst werden?

BACKGROUND AND AIM: Lynch syndrome is a frequent autosomal dominant cancer predisposition leading to an estimated incidence of 3000-4000 new cancer diagnoses of colorectal and endometrial cancer in Germany per year. The underlying hereditary condition is largely underestimated and underrecognized by physicians. The usually young at-risk population, feeling insecure about their personal risk assessment, seeks information online. The aim of this study was to evaluate whether this online risk assessment tool for identification of increased risk for hereditary cancer predisposition reaches the target population and whether it succeeds in positively influencing intensified screening compliance. METHODS: The underlying algorithm for the test is based on the Bethesda and Amsterdam criteria and recent literature on polyposis syndromes. In the context of interrogating family and personal history, a total of five risk categories were defined. In addition to the cancers as defined in the above mentioned criteria, precursor lesions (polyps) were integrated into the risk estimate. Prior to launching, the algorithm was validated in family pedigrees of 102 mutation carriers with identified MLH-1 or MSH-2 mutations. RESULTS: During the time interval analysed, which was between October 2008 and April 2011 a total of 656 participants were included. Among these 19.1 % (125/656) belonged to the target population at increased familial or hereditary risk. 72.8 % (91/125) were yet healthy with known cancer-affected relatives. Merely 34.4 % (11/32) of the high-risk population were currently participating in a risk adjusted screening program. After completion of the online test 62.5 % (20/32) felt motivated to reconsider and adjust accordingly with increased surveillance. The test received an overall "good" evaluation (83 %) based on handling, performance and information content. CONCLUSION: This online risk-assessment tool was mainly completed by healthy (not cancer-affected) individuals with an increased risk for familial or hereditary colorectal cancer predisposition. The family pedigrees were comparable to these of known mutation carriers. The at-risk population was positively motivated to intensify screening strategies and the test received an overall positive evaluation.

Electromyographic characteristics of small bowel motility in the rat.

Rats are widely used in intestinal motility studies, but no precise observation has yet been carried out on the organization of motility throughout the whole small bowel of the rat. The aim of this work was to investigate the characteristics of small intestinal motility of the rat using an electromyographic technique. The variables describing the pattern of occurrence of the migrating myoelectric complex (MMC) were studied as well as the relative distribution of the 3 phases within the MMC cycles. The mean duration of the MMC was 20 min on the jejunum, and it increased up to twofold along the ileum. The propagation of the MMCs was regular in the jejunum, but about half the MMCs disappeared along the ileum and did not reach the caecum. The electromyographic characteristics of the jejunum are greatly different from those of the ileum, and the motility of a segment is not representative of the whole small bowel motility. Considering these particularities of intestinal motility, rats differ in many details from other species.

Dynamics of symmetry breaking and tachyonic preheating.

We reconsider the old problem of the dynamics of spontaneous symmetry breaking (SSB) using 3D lattice simulations. We develop a theory of tachyonic preheating, which occurs due to the spinodal instability of the scalar field. Tachyonic preheating is so efficient that SSB typically completes within a single oscillation as the field rolls towards the minimum of its effective potential. We show that, contrary to previous expectations, preheating in hybrid inflation is typically tachyonic. Our results may also be relevant for the theory of the formation of topological defects and of disoriented chiral condensates in heavy ion collisions.

An investigation of the in vivo stability of poly(ether urethaneurea) blood sacs.

In this paper we investigate the biostability of a series of Biolon blood sacs that were utilized in electric total artificial hearts for time periods of up to 19 weeks. A battery of experimental probes, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were used to characterize the bulk and surface properties of explanted and control blood sacs. Gel permeation chromatography (GPC) experiments showed that generally there was a dramatic increase in average molecular weight at longer implantation times. However, SEM and GPC observations suggest significant deterioration of the flex regions of right blood sacs after 17 weeks of service. XPS experiments indicated appreciable silicon and hydrocarbon concentrations on blood-contacting surfaces both before and after implantation, and we speculate as to their origin.