Compact in-plane dual-axis spring-steel accelerometer

Presented in this paper is an improvement over a spring-steel dual-axis accelerometer that we had reported earlier.The fabrication process (which entails wire-cut electro discharge machining of easily accessible and inexpensive spring-steelfoil) and the sensing of the displacement (which is done using off-the-shelf Hall-effect sensors) remain the same. Theimprovements reported here are twofold: (i) the footprint of the packaged accelerometer is reduced from 80 mm square to 40mm square, and (ii) almost perfect de-coupling and symmetry are achieved between the two in-plane axes of the packageddevice as opposed to the previous embodiment where this was not the case. Good linearity with about 40 mV/g was measuredalong both the in-plane axes over a range of 0.1 to 1 g. The first two natural frequencies of the devices are at 30 Hz and 100Hz, respectively, as per the experiment. The highlights of this work are cost-effective processing, easy integration of the Hall-effect sensing capability on a customised printed circuit board, and inexpensive packaging without overly compromising eitherthe overall size or the sensitivity of the accelerometer. Through this work, we have reaffirmed the practicability of spring-steelaccelerometers towards the eventual goal of making it compete with micro machined silicon accelerometers in terms of sizeand performance. The cost is likely to be much lower for the spring-steel accelerometers than that of silicon accelerometers, especially when the volume of production is low and the sensor is to be used as a single packaged unit.

Vertical uplift resistance of two horizontal strip anchors with common vertical axis

With an application of the upper bound finite element limit analysis, the vertical pullout capacity of a group of two horizontal strip plate anchors, with the common vertical axis and placed in a cohesive-frictional soil, has been computed. The variation of the uplift factors Fc, Fq and Fy, due to the contributions of soil cohesion, surcharge pressure and unit weight, respectively, has been evaluated for different combinations of S/B and H/B. As compared to single isolated anchor, the group of two anchors generates significantly greater magnitude of Fc for Φ ≤ 20° especially with greater values of H/B and under fully bonded anchor-soil interface condition. The factor Fc attains almost the maximum value when the upper anchor plate is placed midway between ground surface and the lower anchor plate. The factors Fq and Fy, on the other hand, for a group of two anchors are found to remain almost equal to that of a single isolated anchor as long as the levels of the lower plate in the group and the single isolated anchor are kept the same.

A MICROMACHINED WIDE-BAND IN-PLANE SINGLE-AXIS CAPACITIVE ACCELEROMETER WITH A DISPLACEMENT-AMPLIFYING COMPLIANT MECHANISM

With the premise that electronic noise dominates mechanical noise in micromachined accelerometers, we present here a method to enhance the sensitivity and resolution at kHz bandwidth using mechanical amplification. This is achieved by means of a Displacement-amplifying Compliant Mechanism (DaCM) that is appended to the usual sensing element comprising a proof-mass and a suspension. Differential comb-drive arrangement is used for capacitive-sensing. The DaCM is designed to match the stiffness of the suspension so that there is substantial net amplification without compromising the bandwidth. A spring-mass-lever model is used to estimate the lumped parameters of the system. A DaCM-aided accelerometer and another without a DaCM-both occupying the same footprint-are compared to show that the former gives enhanced sensitivity: 8.7 nm/g vs. 1.4 nm/g displacement at the sensing-combs under static conditions. A prototype of the DaCM-aided micromachined acclerometer was fabricated using bulk-micromachining. It was tested at the die-level and then packaged on a printed circuit board with an off-the-shelf integrated chip for measuring change in capacitance. Under dynamic conditions, the measured amplification factor at the output of the DaCM was observed to be about 11 times larger than the displacement of the proof-mass and thus validating the concept of enhancing the sensitivity of accelerometers using mechanical amplifiers. The measured first in-plane natural frequency of the fabricated accelerometer was 6.25 kHz. The packaged accelerometer with the DaCM was measured to have 26.7 mV/g sensitivity at 40 Hz.

Design and Modeling of an Active Five-Axis Compliant Micromanipulator

This paper presents the design and modeling of an active five-axis compliant micromanipulator whose tip orientation can be independently controlled by large angles about two axes and the tip-position can be controlled in three dimensions. These features enable precise control of the contact point of the tip and the tip-sample interaction forces with three-dimensional nanoscale objects, including those features that are conventionally inaccessible. Control of the tip-motion is realized by means of electromagnetic actuation combined with a novel kinematic and structural design of the micromanipulator, which, in addition, also ensures compatibility with existing high-resolution motion-measurement systems. The design and analysis of the manipulator structure and those of the actuation system are first presented. Quasi-static and dynamic lumped-parameter (LP) models are then derived for the five-axis compliant micromanipulator. Finite element (FE) analysis is employed to validate these models, which are subsequently used to study the effects of tip orientation on the mechanical characteristics of the five-axis micromanipulator. Finally, a prototype of the designed five-axis manipulator is fabricated by means of focused ion-beam milling (FIB).

REPRESENTING A CUBIC GRAPH AS THE INTERSECTION GRAPH OF AXIS-PARALLEL BOXES IN THREE DIMENSIONS

We show that every graph of maximum degree 3 can be represented as the intersection graph of axis parallel boxes in three dimensions, that is, every vertex can be mapped to an axis parallel box such that two boxes intersect if and only if their corresponding vertices are adjacent. In fact, we construct a representation in which any two intersecting boxes touch just at their boundaries.

Identification of a novel AMPK-PEA15 axis in the anoikis-resistant growth of mammary cells

Introduction: Matrix detachment triggers anoikis, a form of apoptosis, in most normal epithelial cells, while acquisition of anoikis resistance is a prime requisite for solid tumor growth. Of note, recent studies have revealed that a small population of normal human mammary epithelial cells (HMECs) survive in suspension and generate multicellular spheroids termed `mammospheres'. Therefore, understanding how normal HMECs overcome anoikis may provide insights into breast cancer initiation and progression. Methods: Primary breast tissue-derived normal HMECs were grown as adherent monolayers or mammospheres. The status of AMP-activated protein kinase (AMPK) and PEA15 signaling was investigated by immunoblotting. Pharmacological agents and an RNA interference (RNAi) approach were employed to gauge their roles in mammosphere formation. Immunoprecipitation and in vitro kinase assays were undertaken to evaluate interactions between AMPK and PEA15. In vitro sphere formation and tumor xenograft assays were performed to understand their roles in tumorigenicity. Results: In this study, we show that mammosphere formation by normal HMECs is accompanied with an increase in AMPK activity. Inhibition or knockdown of AMPK impaired mammosphere formation. Concomitant with AMPK activation, we detected increased Ser(116) phosphorylation of PEA15, which promotes its anti-apoptotic functions. Inhibition or knockdown of AMPK impaired PEA15 Ser(116) phosphorylation and increased apoptosis. Knockdown of PEA15, or overexpression of the nonphosphorylatable S116A mutant of PEA15, also abrogated mammosphere formation. We further demonstrate that AMPK directly interacts with and phosphorylates PEA15 at Ser(116) residue, thus identifying PEA15 as a novel AMPK substrate. Together, these data revealed that AMPK activation facilitates mammosphere formation by inhibition of apoptosis, at least in part, through Ser(116) phosphorylation of PEA15. Since anoikis resistance plays a critical role in solid tumor growth, we investigated the relevance of these findings in the context of breast cancer. Significantly, we show that the AMPK-PEA15 axis plays an important role in the anchorage-independent growth of breast cancer cells both in vitro and in vivo. Conclusions: Our study identifies a novel AMPK-PEA15 signaling axis in the anchorage-independent growth of both normal and cancerous mammary epithelial cells, suggesting that breast cancer cells may employ mechanisms of anoikis resistance already inherent within a subset of normal HMECs. Thus, targeting the AMPK-PEA15 axis might prevent breast cancer dissemination and metastasis.

An insight to the low temperature conduction mechanism of c-axis grown Al-doped ZnO, a widely used transparent conducting oxide

Al-doped ZnO thin films were synthesized from oxygen reactive co-sputtering of Al and Zn targets. Explicit doping of Al in the highly c-axis oriented crystalline films of ZnO was manifested in terms of structural optical and electrical properties. Electrical conduction with different extent of Al doping into the crystal lattice of ZnO (AZnO) were characterized by frequency dependent (40 Hz-50 MHz) resistance. From the frequency dependent resistance, the ac conduction of them, and correlations of localized charge particles in the crystalline films were studied. The dc conduction at the low frequency region was found to increase from 8.623 mu A to 1.14 mA for the samples AZnO1 (1 wt% Al) and AZnO2 (2 wt% Al), respectively. For the sample AZnO10 (10 wt% Al) low frequency dc conduction was not found due to the electrode polarization effect. The measure of the correlation length by inverse of threshold frequency (omega(0)) showed that on application of a dc electric field such length decreases and the decrease in correlation parameter(s) indicates that the correlation between potentials wells of charge particles decreases for the unidirectional nature of dc bias. The comparison between the correlation length and the extent of correlation in the doped ZnO could not be made due to the observation of several threshold frequencies at the extent of higher doping. Such threshold frequencies were explained by the population possibility of correlated charge carriers that responded at different frequencies. For AZnO2 (2% Al), the temperature dependent (from 4.5 to 288 K) resistance study showed that the variable range hopping mechanism was the most dominating conduction mechanism at higher temperature whereas at low temperature region it was influenced by the small polaronic hopping conduction mechanism. There was no significant influence found in these mechanisms on applications of 1, 2 and 3 V as biases.

Comparison of performance of solar photovoltaics on dual axis tracker with fixed axis at 13 degrees N latitude

Tracking systems, that continually orient photovoltaic (PV) panels towards the Sun, are expected to increase the power output from the PV panels. Tremendous amount of research is being done and funds are being spent in order to increase the efficiency of PV cells to generate more power. We report the performance of two almost identical PV systems; one at a fixed latitude tilt and the other on a two-axis tracker. We observed that the fixed axis PV panels generated 336.3 kWh, and the dual-axis Sun-tracked PV panels generated 407.2 kWh during August 2012 March 2013. The tracked panels generated 21.2% more electricity than the optimum tilt angle fixed-axis panels. The cost payback calculations indicate that the additional cost of the tracker can be recovered in 450 days.

Differential expression of estrogen receptor alpha in the embryonic adrenal-kidney-gonadal complex of the oviparous lizard, Calotes versicolor (Daud.)

Estrogen signalling is critical for ovarian differentiation in reptiles with temperature-dependent sex determination (TSD). To elucidate the involvement of estrogen in this process, adrenal-kidney-gonadal (AKG) expression of estrogen receptor (ER alpha) was studied at female-producing temperature (FPT) in the developing embryos of the lizard, Calotes versicolor which exhibits a distinct pattern of TSD. The eggs of this lizard were incubated at 31.5 +/- 0.5 degrees C (100% FPT). The torso of embryos containing adrenal-kidney-gonadal complex (AKG) was collected during different stages of development and subjected to Western blotting and immunohistochemistry analysis. The ER alpha, antibody recognized two protein bands with apparent molecular weight similar to 55 and similar to 45 kDa in the total protein extracts of embryonic AKG complex of C. versicolor. The observed results suggest the occurrence of isoforms of ER alpha. The differential expression of two different protein isoforms may reveal their distinct role in cell proliferation during gonadal differentiation. This is the first report to reveal two isoforms of the ER alpha in a reptile during development. Immunohistochemical studies reveal a weak, but specific, cytoplasmic ER alpha immunostaining exclusively in the AKG during late thermo-sensitive period suggesting the responsiveness of AKG to estrogens before gonadal differentiation at FPT. Further, cytoplasmic as well as nuclear expression of ER alpha in the medulla and in oogonia of the cortex (faint activity) at gonadal differentiation stage suggests that the onset of gonadal estrogen activity coincides with sexual differentiation of gonad. Intensity and pattern of the immunoreactions of ER alpha in the medullary region at FPT suggest endogenous production of estrogen which may act in a paracrine fashion to induce neighboring cells into ovarian differentiation pathway. (C) 2014 Elsevier Inc. All rights reserved.

Organization dependent collective magnetic properties of secondary nanostructures with differential spatial ordering and magnetic easy axis orientation

Achieving control on the formation of different organization states of magnetic nanoparticles is crucial to harness their organization dependent physical properties in desired ways. In this study, three organization states of iron oxide nanoparticles (gamma-Fe2O3), defining as (i) assembly (ii) network aggregate and (iii) cluster, have been developed by simply changing the solvent evaporation conditions. All three systems have retained the same phase and polydispersity of primary particles. Magnetic measurements show that the partial alignment of the easy axes of the particles in the network system due to the stacking aggregation morphology can result in significant enhancement of the coercivity and remanence values, while the opposite is obtained for the cluster system due to the random orientation of easy axes. Partial alignment in the aggregate system also results in noticeable non -monotonic field dependence of ZFC peak temperature (TpeaB). The lowest value of the blocking temperature (TB) for the cluster system is related to the lowering of the effective anisotropy due to the strongest demagnetizing effect. FC (Field cooled) memory effect was observed to be decreasing with the increasing strength of dipolar interaction of organization states. Therefore, the stacking aggregation and the cluster formation are two interesting ways of magnetic nanoparticles organization for modulating collective magnetic properties significantly, which can have renewed application potentials from recording devices to biomedicine. (C) 2016 Elsevier B.V. All rights reserved.