The push-pull principle: an electrostatic actuator concept for low distortion acoustic transducers.

Electrostatic actuators are of particular interest for microsystems (MEMS), and in particular for MEMS audio transducers for use in advanced true wireless applications. They are attractive because of their typically low electrical capacitance and because they can be fabricated from materials that are compatible with standard complementary metal-oxide semiconductor (CMOS) technology. For high audio performance and in particular low harmonic distortion (THD) the implementation of the push-pull principle provides strong benefits. With an arrangement of three electrodes in a conjunct moving configuration on a beam, we demonstrate here for the first time a balanced bending actuator incarnating the push-pull principle operating at low voltages. Our first design already exhibits a harmonic distortion as low as 1.2% at 79 dB using a signal voltage of only 6 Vp and a constant voltage of only ±10 Vdc in a standard acoustic measurement setup. Thus, exceeding our previously reported approach in all three key performance indications at the same time. We expect that our novel electrode configurations will stimulate innovative electrostatic actuator developments for a broad range of applications. In this paper we report the basic theory, the fabrication and the performance of our novel actuator design acting as an audio transducer.

Coulomb-actuated microbeams revisited: experimental and numerical modal decomposition of the saddle-node bifurcation.

Electrostatic micromechanical actuators have numerous applications in science and technology. In many applications, they are operated in a narrow frequency range close to resonance and at a drive voltage of low variation. Recently, new applications, such as microelectromechanical systems (MEMS) microspeakers (µSpeakers), have emerged that require operation over a wide frequency and dynamic range. Simulating the dynamic performance under such circumstances is still highly cumbersome. State-of-the-art finite element analysis struggles with pull-in instability and does not deliver the necessary information about unstable equilibrium states accordingly. Convincing lumped-parameter models amenable to direct physical interpretation are missing. This inhibits the indispensable in-depth analysis of the dynamic stability of such systems. In this paper, we take a major step towards mending the situation. By combining the finite element method (FEM) with an arc-length solver, we obtain the full bifurcation diagram for electrostatic actuators based on prismatic Euler-Bernoulli beams. A subsequent modal analysis then shows that within very narrow error margins, it is exclusively the lowest Euler-Bernoulli eigenmode that dominates the beam physics over the entire relevant drive voltage range. An experiment directly recording the deflection profile of a MEMS microbeam is performed and confirms the numerical findings with astonishing precision. This enables modeling the system using a single spatial degree of freedom.

One-way rotation of a chemically anchored single molecule-rotor.

We present the chemical anchoring of a DMBI-P molecule-rotor to the Au(111) surface after a dissociation reaction. At the temperature of 5 K, the anchored rotor shows a sequential unidirectional rotational motion through six defined stations induced by tunneling electrons. A typical voltage pulse of 400 mV applied on a specific location of the molecule causes a unidirectional rotation of 60° with a probability higher than 95%. When the temperature of the substrate increases above 20 K, the anchoring is maintained and the rotation stops being unidirectional and randomly explores the same six stations. Density functional theory simulations confirm the anchoring reaction. Experimentally, the rotation shows a clear threshold at the onset of the C-H stretch manifold, showing that the molecule is first vibrationally excited and later it decays into the rotational degrees of freedom.

Primary Gastrointestinal Kaposi's Sarcoma in a Patient with Human Immunodeficiency Virus.

Gastrointestinal bleeding in HIV patients secondary to coinfection by HHV8 and development of Kaposi's sarcoma (KS) is a rare complication even if no skin lesions are detected on physical examination. This article indicates which patients might develop this type of clinical sign and also tries to recall that absence of skin lesions never rules out the presence of KS, especially if gastrointestinal involvement is documented. Gastrointestinal bleeding in terms of hematemesis has rarely been reported in the literature. We review some important clinical findings, diagnosis, and treatment approach. We present the case of an HIV patient who presented to the emergency department with hematemesis and gastrointestinal signs of KS on upper gastrointestinal endoscopy without any dermatological involvement.

Fibroelastoma papilar incidental o sintomático ¿Debeintervenirse? / Incidental or symptomatic papillary fibroelastoma: Should it be treated?

Resumen El fibroelastoma papilar, también conocido como papiloma fibroelástico, es un tumor benigno poco común, que se puede observar en las válvulas cardíacas o, en algunas ocasiones, en el endocardio ventricular. Se describen dos casos; el primero corresponde a un paciente de 72 años con fibrilación auricular paroxística, asintomático por lo demás, en quien en estudio de su fibrilación auricular se evidenció masa pediculada de 1 y 1 cm dependiente de la válvula pulmonar y por riesgo de embolia se llevó a cirugía en la que se resecó masa, sin complicaciones. El reporte de histopatología fue positivo para fibroelastoma papilar. El segundo caso es una paciente de 67 años, sintomática, con angina de esfuerzo en quien, mediante ecocardiograma transtorácico, se documentó masa de 1,5 y 1,5 cm dependiente de la valva coronariana derecha, se consideraron síntomas secundarios a la masa. Se llevó a cirugía por técnica mínimamente invasiva y se resecó la masa. El reporte de histopatología fue positivo para fibroelastoma papilar. Conclusión: el fibroelastoma papilar es una causa poco frecuente pero cada vez más reconocida de fenómenos embólicos. Su identificación oportuna permite la extirpación de la lesión, que es aparentemente curativa, segura y bien tolerada.

Abstract The papillary fibroelastoma, also known as fibroelastic papilloma, is a fairly uncommon benign tumour that can be found in cardiac valves or, in some occasions in the ventricular endocardium. Two cases are presented, with the first corresponding to a 72 year-old patient with intermittent atrial fibrillation, with no other symptoms. During the study of the atrial fibrillation, a pedunculated mass of 1 × 1 cm was observed hanging from the pulmonary valve. Due to the risk of emboli, the patient was taken to surgery where the mass was resected with no complications. The histopathology reported positive for a papillary fibroelastoma. The second case was a 67 year-old patient with symptoms of with angina of effort, which on observing a mass of 1.5 × 1.5 cm hanging from the right coronary valve, they were considered as symptoms secondary induced by the mass. He was taken to surgery, and the mass was resected using a minimally invasive technique. The histopathology reported positive for a papillary fibroelastoma. Conclusion: Papillary fibroelastoma is a rare cause, but increasingly recognised due to its embolic phenomena. Their timely identification allows the lesion to be extirpated, which is apparently curative, safe and well tolerated.

Lupus eritematoso sistémico en el anciano: una presentación atípica de una enfermedad común / Systemic lupus erythematosus in the elderly: An atypical presentation of a common disease

El lupus eritematoso sistémico (LES) del anciano, también llamado lupus de aparición tardía,es una enfermedad autoinmune que aparece después de los 50-60 años, con un curso clínicoy manifestaciones clínicas que difieren del LES clásico, cuya prevalencia es en personas másjóvenes, predominantemente mujeres. Se presenta, en este artículo, el caso de un pacientemasculino de 72 años con cuadro clínico de un mes de evolución de dolor en hemitóraxderecho, tipo pleurítico asociado a disnea, además de la presencia de lesiones eritematosasy descamativas en región malar y zona de exposición solar en tórax. Se descartó origeninfeccioso y neoplásico mediante imágenes diagnósticas y laboratorios y, posteriormente,se realiza perfil inmunológico que reporta ANAS positivo, Anti-DNA positivo y complementoconsumido, con evidencia de derrame pleural derecho masivo recidivante hasta la fecha.

Systemic lupus erythematosus (SLE) in the elderly, also called late-onset lupus, is an autoimmune disease that appears after 50-60 years old, with a clinical course and clinical manifestations that differ from classic SLE, with a prevalence predominantly in younger women. In this article a case of a 72 year-old male patient who, for one month, had clinical symptoms of right chest pain, associated with dyspnea and the presence of erythematous and scaly lesions on the malar area and sun exposure in the thorax. The possibilities of infectious or neoplastic origin were dismissed using diagnostic images and laboratory tests. An immunological profile was subsequently performed, reporting positive ANAS and Anti-DNA, positive, and consumed complement, with evidence of recurrent massive right pleural effusion to date.