Purcell magneto-elastic swimmer controlled by an external magnetic field

International audienceThis paper focuses on the mechanism of propulsion of a Purcell swimmer whose segments are magnetized and react to an external magnetic field applied into the fluid. By an asymptotic analysis, we prove that it is possible to steer the swimmer along a chosen direction when the control functions are prescribed as an oscillating field. Moreover, we discuss what are the main obstructions to overcome in order to get classical controllability result for this system

Uniaxial and biaxial soft deformations of nematic elastomers

We give a geometric interpretation of the soft elastic deformation modes of nematic elastomers, with explicit examples, for both uniaxial and biaxial nematic order. We show the importance of body rotations in this non-classical elasticity and how the invariance under rotations of the reference and target states gives soft elasticity (the Golubovic and Lubensky theorem). The role of rotations makes the Polar Decomposition Theorem vital for decomposing general deformations into body rotations and symmetric strains. The role of the square roots of tensors is discussed in this context and that of finding explicit forms for soft deformations (the approach of Olmsted).Comment: 10 pages, 10 figures, RevTex, AmsTe

Toward the PSTN/Internet Inter-Networking--Pre-PINT Implementations

This document contains the information relevant to the development of the inter-networking interfaces underway in the Public Switched Telephone Network (PSTN)/Internet Inter-Networking (PINT) Working Group. It addresses technologies, architectures, and several (but by no means all) existing pre-PINT implementations of the arrangements through which Internet applications can request and enrich PSTN telecommunications services. The common denominator of the enriched services (a.k.a. PINT services) is that they combine the Internet and PSTN services in such a way that the Internet is used for non-voice interactions, while the voice (and fax) are carried entirely over the PSTN. One key observation is that the pre-PINT implementations, being developed independently, do not inter-operate. It is a task of the PINT Working Group to define the inter-networking interfaces that will support inter-operation of the future implementations of PINT services

Domain structure of bulk ferromagnetic crystals in applied fields near saturation

We investigate the ground state of a uniaxial ferromagnetic plate with perpendicular easy axis and subject to an applied magnetic field normal to the plate. Our interest is the asymptotic behavior of the energy in macroscopically large samples near the saturation field. We establish the scaling of the critical value of the applied field strength below saturation at which the ground state changes from the uniform to a branched domain magnetization pattern and the leading order scaling behavior of the minimal energy. Furthermore, we derive a reduced sharp-interface energy giving the precise asymptotic behavior of the minimal energy in macroscopically large plates under a physically reasonable assumption of small deviations of the magnetization from the easy axis away from domain walls. On the basis of the reduced energy, and by a formal asymptotic analysis near the transition, we derive the precise asymptotic values of the critical field strength at which non-trivial minimizers (either local or global) emerge. The non-trivial minimal energy scaling is achieved by magnetization patterns consisting of long slender needle-like domains of magnetization opposing the applied fieldComment: 38 pages, 7 figures, submitted to J. Nonlin. Sci

Three-sphere low-Reynolds-number swimmer with a passive elastic arm

One of the simplest model swimmers at low Reynolds number is the three-sphere swimmer by Najafi and Golestanian. It consists of three spheres connected by two rods which change their lengths periodically in non-reciprocal fashion. Here we investigate a variant of this model in which one rod is periodically actuated while the other is replaced by an elastic spring. We show that the competition between the elastic restoring force and the hydrodynamic drag produces a delay in the response of the passive elastic arm with respect to the active one. This leads to non-reciprocal shape changes and self-propulsion. After formulating the equations of motion, we study their solutions qualitatively and numerically. The leading-order term of the solution is computed analytically. We then address questions of optimization with respect to both actuation frequency and swimmer\u2019s geometry. Our results can provide valuable conceptual guidance in the engineering of robotic microswimmers

A Case of Tumor Lysis Syndrome after Docetaxel Administration for Recurrent Ovarian Cancer

Abstract Tumor Lysis Syndrome is a rare complication of the treatment of solid malignancies. A 51 year old female developed this condition one week after undergoing docetaxel chemotherapy for progressive, recurrent ovarian cancer. She was diagnosed based on classic laboratory disturbances including increased creatinine, hyperphosphatemia, hypercalcemia, hyperkalemia, and hyperuricemia. The patient was successfully treated with aggressive intravenous hydration, allopurinol, and rasburicase. Although uncommon, clinicians should be aware of this condition so that proper identification occurs and treatment can be implemented promptly. as this patient had a BMI over 25 (BMI 27.4, BSA 1.78). Creatinine clearance was calculated using the Cockroft Gault equation with a minimum creatinine value of 0.7 mg/dL. The Calvert formula was used for Carboplatin dosing. She received 6 cycles of dose-dense paclitaxel and carboplatin, with an initial improvement in her CA125. However, CT imaging at completion of 6 cycles demonstrated residual disease involving the chest, abdomen and pelvis and her CA125 plateaued. She was diagnosed with platinum resistant disease and was switched to a 28 cycle day regimen of gemcitabine (800 mg/m 2 , cycle days 1 and 8) and bevacizumab (15 mg/kg, cycle day1) of which she received 2 cycles. Her CA 125 count continued to rise despite this treatment, thus she was changed to a 28 cycle day regimen of liposomal doxorubicin (40 mg/m 2 , cycle day 1) and bevacizumab (15 mg/kg, cycle day 1). After 3 cycles of therapy, her disease failed to respond as evidenced by a rising CA 125. As a result, she was changed to docetaxel at a dose of 75 mg/m 2 and received one cycle uneventfully. Seven days after her first docetaxel administration, the patient presented with fatigue and decreased oral intake. She was admitted for supportive therapy for suspected chemotherapy-associated malaise. On the evening of hospital day #1 the patient reported increased shortness of breath. She was noted to be pale, hypotensive, and hypoxic. An EKG revealed new onset right bundle branch block. She was transferred to the ICU for critical care monitoring given her worsening clinical picture. TLS was diagnosed after laboratory evaluation revealed acute renal insufficiency (2.4 mg/dL) and severe electrolyte abnormalities (phosphorus 5.7 mg/dL, calcium 9.7 mg/dL, potassium 7.0 mmol/L and uric acid 10.1 mg/dL). Treatment with allopurinol, rasburicase, and aggressive hydration was promptly initiated. She received a single dose of intravenous rasburicase and started on allopurinol 300 mg BID. Six hours following administration of rasburicase, her uric acid had decreased to 2.9 mg/dL. She was continued on allopurinol for 3 days as her uric acid level continued to decrease. As her electrolyte

Local invertibility in Sobolev spaces with applications to nematic elastomers and magnetoelasticity

We define a class of deformations in W^1,p(\u3a9,R^n), p>n 121, with positive Jacobian that do not exhibit cavitation. We characterize that class in terms of the non-negativity of the topological degree and the equality between the distributional determinant and the pointwise determinant of the gradient. Maps in this class are shown to satisfy a property of weak monotonicity, and, as a consequence, they enjoy an extra degree of regularity. We also prove that these deformations are locally invertible; moreover, the neighbourhood of invertibility is stable along a weak convergent sequence in W^1,p, and the sequence of local inverses converges to the local inverse. We use those features to show weak lower semicontinuity of functionals defined in the deformed configuration and functionals involving composition of maps. We apply those results to prove existence of minimizers in some models for nematic elastomers and magnetoelasticity

When Anomaly Mediation is UV Sensitive

Despite its successes---such as solving the supersymmetric flavor problem---anomaly mediated supersymmetry breaking is untenable because of its prediction of tachyonic sleptons. An appealing solution to this problem was proposed by Pomarol and Rattazzi where a threshold controlled by a light field deflects the anomaly mediated supersymmetry breaking trajectory, thus evading tachyonic sleptons. In this paper we examine an alternate class of deflection models where the non-supersymmetric threshold is accompanied by a heavy, instead of light, singlet. The low energy form of this model is the so-called extended anomaly mediation proposed by Nelson and Weiner, but with potential for a much higher deflection threshold. The existence of this high deflection threshold implies that the space of anomaly mediated supersymmetry breaking deflecting models is larger than previously thought.Comment: 14 pages, 1 figure (version to appear in JHEP

Three examples concerning the interaction of dry friction and oscillations

We discuss recent work concerning the interaction of dry friction, which is a rate independent effect, and temporal oscillations. First, we consider the temporal averaging of highly oscillatory friction coefficients. Here the effective dry friction is obtained as an infimal convolution. Second, we show that simple models with state-dependent friction may induce a Hopf bifurcation, where constant shear rates give rise to periodic behavior where sticking phases alternate with sliding motion. The essential feature here is the dependence of the friction coefficient on the internal state, which has an internal relaxation time. Finally, we present a simple model for rocking toy animal where walking is made possible by a periodic motion of the body that unloads the legs to be moved

core level spectroscopy of free titanium clusters in supersonic beams

Synchrotron radiation x-ray absorption spectroscopy (XAS) is one of the most powerful techniques to interrogate the local electronic structure and chemical status of bulk and nanostructured systems. The application of this technique to the study of size effects in free clusters of transition metal atoms would advance substantially fundamental knowledge of nano-objects and the tailoring of their magnetic and catalytic properties. To date core level spectroscopy of free transition metal clusters has been out of reach due to the lack of a cluster source able to produce clusters in the gas phase with a density suitable for synchrotron radiation sources. Here we demonstrate the XAS characterization of free titanium clusters in a supersonic molecular beam. We use a high-intensity cluster beam source coupled to a synchrotron beamline to investigate the size dependence of core level excitation of Tin clusters in the mass range 1