Signal-to-motion artifact ratio versus frequency for impedance pneumography

We measured transthoracic impedance between 12.5 and 185 kHz in nine adults. We used a system with two impedance channels, both simultaneously detecting the real part of impedance at two different frequencies. We used only two electrodes in the midaxillary line, connecting both channels in parallel. The amplitude relation between the two channels was measured for different maneuvers and frequencies. Results show for normal breathing an increase of the signal of 20% and a decrease in motion artifacts from 12.5 to 185 kHz. We conclude that, for the maneuvers studied, it is better to work at higher frequencies than the ones commonly used. Also, we suggest a method to further increase the signal-to-motion artifact ratio based on measurement at two frequencies.Peer Reviewe

Reduction of motion artifacts using a two-frequency impedance plethysmograph and adaptative filtering

We measured transthoracic impedance in nine presumed healthy adult subjects with a two-frequency plethysmograph at 57 kHz and 185 kHz. The measurement protocol included periods of normal breathing without motion and periods of motion without breathing. We analyzed the cross-correlation and the ratio between the signals at both frequencies for all the different maneuvers. The correlation coefficient was between 0.97 and 1 for breathing, the minimal cross-correlation (0.81) was for simulated obstructive apnea. We found that the amplitude ratio between the two-frequency signals was different for normal breathing and for motion. Based on these results, we designed and tested an adaptive filter to increase the signal-to-artifact ratio (SAR). The increase in SAR(mean ± standard deviation) compared with the signal at 57 Miz was: 183% ± 117% for arm movement, 133% ± 93% for leg movement, and 34% ± 62% for simulated obstructive apnea.Peer Reviewe

Antenna design for microwave hepatic ablation using an axisymmetric electromagnetic model

BACKGROUND: An axisymmetric finite element method (FEM) model was employed to demonstrate important techniques used in the design of antennas for hepatic microwave ablation (MWA). To effectively treat deep-seated hepatic tumors, these antennas should produce a highly localized specific absorption rate (SAR) pattern and be efficient radiators at approved generator frequencies. METHODS AND RESULTS: As an example, a double slot choked antenna for hepatic MWA was designed and implemented using FEMLAB™ 3.0. DISCUSSION: This paper emphasizes the importance of factors that can affect simulation accuracy, which include boundary conditions, the dielectric properties of liver tissue, and mesh resolution

Higher polymerase activity of a human influenza virus enhances activation of the hemagglutinin-induced Raf/MEK/ERK signal cascade

Influenza viruses replicate within the nucleus of infected cells. Viral genomic RNA, three polymerase subunits (PB2, PB1, and PA), and the nucleoprotein (NP) form ribonucleoprotein complexes (RNPs) that are exported from the nucleus late during the infectious cycle. The virus-induced Raf/MEK/ERK (MAPK) signal cascade is crucial for efficient virus replication. Blockade of this pathway retards RNP export and reduces virus titers. Hemagglutinin (HA) accumulation and its tight association with lipid rafts activate ERK and enhance localization of cytoplasmic RNPs. We studied the induction of MAPK signal cascade by two seasonal human influenza A viruses A/HK/218449/06 (H3N2) and A/HK/218847/06 (H1N1) that differed substantially in their replication efficiency in tissue culture. Infection with H3N2 virus, which replicates efficiently, resulted in higher HA expression and its accumulation on the cell membrane, leading to substantially increased activation of MAPK signaling compared to that caused by H1N1 subtype. More H3N2-HAs were expressed and accumulated on the cell membrane than did H1N1-HAs. Viral polymerase genes, particularly H3N2-PB1 and H3N2-PB2, were observed to contribute to increased viral polymerase activity. Applying plasmid-based reverse genetics to analyze the role of PB1 protein in activating HA-induced MAPK cascade showed that recombinant H1N1 virus possessing the H3N2-PB1 (rgH1N1/H3N2-PB1) induced greater ERK activation, resulting in increased nuclear export of the viral genome and higr virus titers. We conclude that enhanced viral polymerase activity promotes the replication and transcription of viral RNA leading to increased accumulation of HA on the cell surface and thereby resulting in an upregulation of the MAPK cascade and more efficient nuclear RNP-export as well as virus production

Systematics and Palynology of Picrodendron Further Evidence for Relationship with the Oldfieldioideae (Euphorbiaceae)

Although known to botanical science for 285 years, the genus Picrodendron Planchon has been poorly understood for most of this time. The most pervasive problem has been that of discerning familial relationships, and there have been additional difficulties in typifying the generic name (Hayden & Reveal, 1980) and in distinguishing its three nominate species. This paper provides a systematic treatment for Picrodendron and demonstrates its relationships with Euphorbiaceae subfam. Oldfieldioideae Kohler & Webster as evidenced by data on gross morphology, palynology, anatomy, and cytology

Analysis of Climate Policy Targets under Uncertainty

Abstract and PDF report are also available on the MIT Joint Program on the Science and Policy of Global Change website (http://globalchange.mit.edu/).Although policymaking in response to the climate change is essentially a challenge of risk management, most studies of the relation of emissions targets to desired climate outcomes are either deterministic or subject to a limited representation of the underlying uncertainties. Monte Carlo simulation, applied to the MIT Integrated Global System Model (an integrated economic and earth system model of intermediate complexity), is used to analyze the uncertain outcomes that flow from a set of century-scale emissions targets developed originally for a study by the U.S. Climate Change Science Program. Results are shown for atmospheric concentrations, radiative forcing, sea ice cover and temperature change, along with estimates of the odds of achieving particular target levels, and for the global costs of the associated mitigation policy. Comparison with other studies of climate targets are presented as evidence of the value, in understanding the climate challenge, of more complete analysis of uncertainties in human emissions and climate system response.This study received support from the MIT Joint Program on the Science and Policy of Global Change, which is funded by a consortium of government, industry and foundation sponsors

Role of aberrant PI3K pathway activation in gallbladder tumorigenesis

The PI3K/AKT pathway governs a plethora of cellular processes, including cell growth, proliferation, and metabolism, in response to growth factors and cytokines. By acting as a unique lipid phosphatase converting phosphatidylinositol-3,4,5,-trisphosphate (PIP3) to phosphatidylinositol-4,5,-bisphosphate (PIP2), phosphatase and tensin homolog (PTEN) acts as the major cellular suppressor of PI3K signaling and AKT activation. Recently, PI3K mutations and loss/mutation of PTEN have been characterized in human gallbladder tumors; whether aberrant PTEN/PI3K pathway plays a causal role in gallbladder carcinogenesis, however, remains unknown. Herein we show that in mice, deregulation of PI3K/AKT signaling is sufficient to transform gallbladder epithelial cells and trigger fully penetrant, highly proliferative gallbladder tumors characterized by high levels of phospho-AKT. Histopathologically, these mouse tumors faithfully resemble human adenomatous gallbladder lesions. The identification of PI3K pathway deregulation as both an early event in the neoplastic transformation of the gallbladder epithelium and a main mechanism of tumor growth in Pten heterozygous and Pten mutant mouse models provides a new framework for studying in vivo the efficacy of target therapies directed against the PI3K pathway, as advanced metastatic tumors are often addicted to “trunkular” mutations

Isolation of Highly Pathogenic Avian Influenza H5N1 Virus from Saker Falcons ( Falco cherrug

There is accumulating evidence that birds of prey are susceptible to fatal infection with highly pathogenic avian influenza (HPAI) virus. We studied the antigenic, molecular, phylogenetic, and pathogenic properties of 2 HPAI H5N1 viruses isolated from dead falcons in Saudi Arabia and Kuwait in 2005 and 2007, respectively. Phylogenetic and antigenic analyses grouped both isolates in clade 2.2 (Qinghai-like viruses). However, the viruses appeared to have spread westward via different flyways. It remains unknown how these viruses spread so rapidly from Qinghai after the 2005 outbreak and how they were introduced into falcons in these two countries. The H5N1 outbreaks in the Middle East are believed by some to be mediated by wild migratory birds. However, sporting falcons may be at additional risk from the illegal import of live quail to feed them

Skin impedance from 1 Hz to 1 MHz

We measured the impedance of skin coated with gel, but otherwise unprepared from 1 Hz to 1 MHz at ten sites on the thorax, leg, and forehead of ten subjects. For a 1 cm2 area, the 1 Hz impedance varied from 10 kΩ to 1 MΩ, which suggests that biopotential amplifier input impedance should be very high to avoid common mode to differential mode voltage conversion. 1 MHz impedance was tightly clustered about 120 Ω. 100 kHz impedance was about 220 Ω,which suggests that the variation in skin impedance may cause errors in two electrode electrical impedance tomographs.Peer Reviewe

Pyrotechnic Actuator for Retracting Tubes Between MSL Subsystems

An apparatus, denoted the "retractuator" (a contraction of "retracting actuator"), was designed to help ensure clean separation between the cruise stage and the entry-vehicle subsystem of the Mars Science Laboratory (MSL) mission. The retractuator or an equivalent mechanism is needed because of tubes that (1) transport a heat-transfer fluid between the stages during flight and (2) are cut immediately prior to separation of the stages retractuator. The role of the retractuator is to retract the tubes, after they are cut and before separation of the subsystem, so that cut ends of the tubes do not damage thermal-protection coats on the entry vehicle and do not contribute to uncertainty of drag and consequent uncertainty in separation velocity