Dynamic modulation of modal coupling in microelectromechanical gyroscopic ring resonators

Abstract: Understanding and controlling modal coupling in micro/nanomechanical devices is integral to the design of high-accuracy timing references and inertial sensors. However, insight into specific physical mechanisms underlying modal coupling, and the ability to tune such interactions is limited. Here, we demonstrate that tuneable mode coupling can be achieved in capacitive microelectromechanical devices with dynamic electrostatic fields enabling strong coupling between otherwise uncoupled modes. A vacuum-sealed microelectromechanical silicon ring resonator is employed in this work, with relevance to the gyroscopic lateral modes of vibration. It is shown that a parametric pumping scheme can be implemented through capacitive electrodes surrounding the device that allows for the mode coupling strength to be dynamically tuned, as well as allowing greater flexibility in the control of the coupling stiffness. Electrostatic pump based sideband coupling is demonstrated, and compared to conventional strain-mediated sideband operations. Electrostatic coupling is shown to be very efficient, enabling strong, tunable dynamical coupling

Farmers’ attitudes about farming and the environment: A survey of conventional and organic farmers

Farmers have been characterized as people whose ties to the land have given them a deep awareness of natural cycles, appreciation for natural beauty and sense of responsibility as stewards. At the same time, their relationship to the land has been characterized as more utilitarian than that of others who are less directly dependent on its bounty. This paper explores this tension by comparing the attitudes and beliefs of a group of conventional farmers to those of a group of organic farmers. It was found that while both groups reject the idea that a farmer’s role is to conquer nature, organic farmers were significantly more supportive of the notion that humans should live in harmony with nature. Organic farmers also reported a greater awareness of and appreciation for nature in their relationship with the land. Both groups view independence as a main benefit of farming and a lack of financial reward as its main drawback. Overall, conventional farmers report more stress in their lives although they also view themselves in a caretaker role for the land more than do the organic farmers. In contrast, organic farmers report more satisfaction with their lives, a greater concern for living ethically, and a stronger perception of community. Finally, both groups are willing to have their rights limited (organic farmers somewhat more so) but they do not trust the government to do so.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83671/1/Sullivan,_S.,_E._McCann,_R._De_Young_&_D._Erickson_(1996)._Farmers_attitudes_about_farming_and_the_environment,_JAEE,_9,_123-143.pd

Ligand binding by antibody IgE Lb4: assessment of binding site preferences using microcalorimetry, docking, and free energy simulations.

Antibody IgE Lb4 interacts favorably with a large number of different compounds. To improve the current understanding of the structural basis of this vast cross-reactivity, the binding of three dinitrophenyl (DNP) amino acids (DNP-alanine, DNP-glycine, and DNP-serine) is investigated in detail by means of docking and molecular dynamics free energy simulations. Experimental binding energies obtained by isothermal titration microcalorimetry are used to judge the results of the computational studies. For all three ligands, the docking procedure proposes two plausible subsites within the binding region formed by the antibody CDR loops. By subsequent molecular dynamics simulations and calculations of relative free energies of binding, one of these subsites, a tyrosine-surrounded pocket, is revealed as the preferred point of complexation. For this subsite, results consistent with experimental observations are obtained; DNP-glycine is found to bind better than DNP-serine, and this, in turn, is found to bind better than DNP-alanine. The suggested binding mode makes it possible to explain both the moderate binding affinity and the differences in binding energy among the three ligands

Papillary Thyroid Carcinoma in a Boy with Familial Tuberous Sclerosis Complex Attributable to a TSC2 Deletion—A Case Report

Tuberous sclerosis complex (TSC), a phacomatosis, is a rare genetic disease (autosomal dominant; incidence: 1 in 6,800–17,300) associated with mutations in the TSC1 and TSC2 genes, 70% of which are sporadic. The disease causes benign tumours in the brain, kidneys, heart, lungs, skin, and eyes; thyroid lesions are extremely rare. A 13-year-old euthyroid boy with a hereditary form of TSC (del 4730G in TSC2, also seen in 2 sisters and the father) was admitted to hospital with a thyroid nodule. Physical examination revealed a nodular left lobe with increased consistency. Thyroid ultrasonography revealed a heterogeneous left lobe, predominantly hypoechoic with multiple microcalcifications and the presence of suspicious cervical lymph nodes on the left side. A macrocalcification was observed on the right lobe. Fine-needle biopsy results showed a few groups of cells with discrete atypical characteristics, including abundant cytoplasm, nuclei with conspicuous nucleoli, intra-nuclear inclusions, and nuclear grooves. The patient underwent total thyroidectomy with lymphadenectomy. Histopathology examination confirmed papillary thyroid carcinoma. The coincidence of endocrine neoplasia including thyroid cancer and TSC is rare, and TSC with papillary thyroid carcinoma has never been described in a child. Studies of mutations in the tumour suppressor genes TSC1, TSC2, and STK11, activating the mtor (mammalian target of rapamycin) pathway, might support their role in the pathogenesis of thyroid cancer

Effective quality factor tuning mechanisms in micromechanical resonators

Quality factor (Q) is an important property of micro- and nano-electromechanical (MEM/NEM) resonators that underlie timing references, frequency sources, atomic force microscopes, gyroscopes, and mass sensors. Various methods have been utilized to tune the effective quality factor of MEM/NEM resonators, including external proportional feedback control, optical pumping, mechanical pumping, thermal-piezoresistive pumping, and parametric pumping. This work reviews these mechanisms and compares the effective Q tuning using a position-proportional and a velocity-proportional force expression. We further clarify the relationship between the mechanical Q, the effective Q, and the thermomechanical noise of a resonator. We finally show that parametric pumping and thermal-piezoresistive pumping enhance the effective Q of a micromechanical resonator by experimentally studying the thermomechanical noise spectrum of a device subjected to both techniques. (C) 2018 Author(s)