Single-Supply Pre-Biasing Circuit for Low-Amplitude Energy Harvesting Applications

Published versio

Increased Power Output from Piezoelectric Energy Harvesters by Pre-Biasing

This paper presents, for the first time, experimental results demonstrating a new approach to increasing the power output of piezoelectric energy harvesters by applying a bias charge at the beginning of each half cycle of motion. Ultimate power limits of inertial energy harvesters depend only on the device size and nature of the excitation, rather than on the transduction mechanism. However, practical devices generally perform well below the theoretical limit, often because a sufficiently high transducer damping force cannot be achieved. For such cases, we show that the generator effectiveness is improved by a pre-biasing technique, and present simulation results with experimental verification. These results show that the effectiveness of the piezoelectric generator is improved by more than 10 times compared to an optimised purely resistive load. In practice our gains were limited by the voltage breakdown of the components used.Published versio

A risk-adjusted performance history of public and private market real estate investment, 1978-1997

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1999.Includes bibliographical references (leaves 51-54).Since the inception of the Real Estate Investment Trust ("REIT"), the relative efficiency of the public and private real estate markets has been the subject of debate. Consequently, a determination of the more efficient real estate investment vehicle will probably have a significant effect on the future flow of capital into all real estate assets. This thesis proposes to identify which real estate investment medium, public or private, has provided greater efficiency to its investors as measured by risk adjusted total return over the 20 year period from 1978-1997. The initial objective of this thesis was to create a publicly traded real estate equity index(the "Thesis index") for comparison to the existing National Association of Real Estate Investment Trusts ("NAREIT") equity index in an effort to replicate the returns of the latter. This equity Thesis index is an annual weighted compilation of the total returns of each existing equity REIT, as identified by a query of the Compustat database, for each given year from 1978 through 1997. Returns were calculated as of the calendar year end commencing in 1978 and continuing through calendar year end 1997. The core objective of this thesis was to ultimately compare the de-levered Thesis index to the existing National Council of Real Estate Investment Fiduciaries ("NCREIF") index in order to determine which index has provided a greater risk adjusted return over the time series in question. Given the disparities in the risk profiles of the underlying indices and the need to ensure a homogeneous comparison, adjustments to the Thesis index have been made in order to compensate for leverage in the REIT capital structure, for the presence of development risk in the current REIT asset base, and for the respective weight of each real estate asset class within the NCREIF index.by Mark P. Moriarty and Pennock J. Yeatman, IV.S.M

Development of the visual white matter pathways mediates development of electrophysiological responses in visual cortex

The latency of neural responses in the visual cortex changes systematically across the lifespan. Here, we test the hypothesis that development of visual white matter pathways mediates maturational changes in the latency of visual signals. Thirty-eight children participated in a cross-sectional study including diffusion magnetic resonance imaging (MRI) and magnetoencephalography (MEG) sessions. During the MEG acquisition, participants performed a lexical decision and a fixation task on words presented at varying levels of contrast and noise. For all stimuli and tasks, early evoked fields were observed around 100 ms after stimulus onset (M100), with slower and lower amplitude responses for low as compared to high contrast stimuli. The optic radiations and optic tracts were identified in each individual's brain based on diffusion MRI tractography. The diffusion properties of the optic radiations predicted M100 responses, especially for high contrast stimuli. Higher optic radiation fractional anisotropy (FA) values were associated with faster and larger M100 responses. Over this developmental window, the M100 responses to high contrast stimuli became faster with age and the optic radiation FA mediated this effect. These findings suggest that the maturation of the optic radiations over childhood accounts for individual variations observed in the developmental trajectory of visual cortex responses

Growth and characterization of semiconductor nanoparticles in porous sol-gel films

Published versio

Plasmonic optical fiber for bacteria manipulation—characterization and visualization of accumulation behavior under plasmo-thermal trapping

In this article, we demonstrate a plasmo-thermal bacterial accumulation effect using a miniature plasmonic optical fiber. Combined action of far-field convection and a near-field trapping force (referred to as thermophoresis)—induced by highly localized plasmonic heating—enabled large-area accumulation of Escherichia coli. The estimated thermophoretic trapping force agreed with previous reports, and we applied speckle imaging analysis to map the in-plane bacterial velocities over large areas. This is the first time that spatial mapping of bacterial velocities has been achieved in this setting. Thus, this analysis technique provides opportunities to better understand this phenomenon and to drive it towards in vivo applications

Whole Genome Sequencing Analysis of a Stage IV Colon Cancer Patient with a 10-Year Disease-Free Survival following Systemic Chemotherapy/Bevacizumab

It is rare that stage IV colon cancer is cured with chemotherapy. Here we report the long-term survival of a patient who presented with highly advanced disease characterized by a papillary architecture as well as porta hepatis lymph nodes but responded extremely well to FOLFIRI/bevacizumab. His original tumor underwent comprehensive genomic testing that included whole genome DNA sequencing, targeted sequencing, and RNA sequencing. These genetic results suggest the patient’s tumor harbored mutations in APC, KRAS, and TP53 as well as in PIK3CB. Moreover, the RNA-seq data suggested that the tumor belonged to the consensus molecular subtype 4, the “inflamed, immune phenotype,” with increased angiogenesis. Deep sequencing of highly responsive cancers may yield molecular insights into mechanisms underpinning a remarkable response

A micro electromagnetic generator for vibration energy harvesting

Vibration energy harvesting is receiving a considerable amount of interest as a means for powering wireless sensor nodes. This paper presents a small (component volume 0.1 cm3, practical volume 0.15 cm3) electromagnetic generator utilizing discrete components and optimized for a low ambient vibration level based upon real application data. The generator uses four magnets arranged on an etched cantilever with a wound coil located within the moving magnetic field. Magnet size and coil properties were optimized, with the final device producing 46 µW in a resistive load of 4 k? from just 0.59 m s-2 acceleration levels at its resonant frequency of 52 Hz. A voltage of 428 mVrms was obtained from the generator with a 2300 turn coil which has proved sufficient for subsequent rectification and voltage step-up circuitry. The generator delivers 30% of the power supplied from the environment to useful electrical power in the load. This generator compares very favourably with other demonstrated examples in the literature, both in terms of normalized power density and efficiency

Systematic review of patient-specific predictors of pain improvement to endometriosis surgery

BACKGROUND: Up to 28% of endometriosis patients do not get pain relief from therapeutic laparoscopy but this subgroup is not defined. OBJECTIVES: To identify any prognostic patient-specific factors (such as but not limited to patients’ type or location of endometriosis, sociodemographics and lifestyle) associated with a clinically meaningful reduction in post-surgical pain response to operative laparoscopic surgery for endometriosis. SEARCH STRATEGY: PubMed, Cochrane and Embase databases were searched from inception to 19th May 2020 without language restrictions. Backward and forward citation tracking was used. SELECTION CRITERIA, DATA COLLECTION AND ANALYSIS: Cohort studies reporting prognostic factors, along with scores for domains of pain associated with endometriosis before and after surgery, were included. Studies that compared surgeries, or laboratory tests, or outcomes without stratification were excluded. Results were synthesised but variation in study designs and inconsistency of outcome reporting precluded us from doing a meta-analysis. MAIN RESULTS: Five studies were included. Quality assessment using the Newcastle Ottawa Scale graded three studies as high, one as moderate and one as having a low risk of bias. Four of five included studies separately reported that a relationship exists between more severe endometriosis and stronger pain relief from laparoscopic surgery CONCLUSION: Currently there are few studies of appropriate quality to answer the research question. We recommend future studies report core outcome sets to enable meta-analysis. FUNDING: NIHR PB-PG-0317-20018 PROSPERO: CRD4201810860

Fiber-Flux Diffusion Density for White Matter Tracts Analysis: Application to Mild Anomalies Localization in Contact Sports Players

We present the concept of fiber-flux density for locally quantifying white matter (WM) fiber bundles. By combining scalar diffusivity measures (e.g., fractional anisotropy) with fiber-flux measurements, we define new local descriptors called Fiber-Flux Diffusion Density (FFDD) vectors. Applying each descriptor throughout fiber bundles allows along-tract coupling of a specific diffusion measure with geometrical properties, such as fiber orientation and coherence. A key step in the proposed framework is the construction of an FFDD dissimilarity measure for sub-voxel alignment of fiber bundles, based on the fast marching method (FMM). The obtained aligned WM tract-profiles enable meaningful inter-subject comparisons and group-wise statistical analysis. We demonstrate our method using two different datasets of contact sports players. Along-tract pairwise comparison as well as group-wise analysis, with respect to non-player healthy controls, reveal significant and spatially-consistent FFDD anomalies. Comparing our method with along-tract FA analysis shows improved sensitivity to subtle structural anomalies in football players over standard FA measurements