Measuring the electrical impedance of mouse brain tissue

We report on an experimental method to measure conductivity of cortical tissue. We use a pair of 5mm diameter Ag/AgCl electrodes in a Perspex sandwich device that can be brought to a distance of 400 microns apart. The apparatus is brought to uniform temperature before use. Electrical impedance of a sample is measured across the frequency range 20 Hz-2.0 MHz with an Agilent 4980A four-point impedance monitor in a shielded room. The equipment has been used to measure the conductivity of mature mouse brain cortex in vitro. Slices 400 microns in thickness are prepared on a vibratome. Slices are bathed in artificial cerebrospinal fluid (ACSF) to keep them alive. Slices are removed from the ACSF and sections of cortical tissue approximately 2 mm times 2 mm are cut with a razor blade. The sections are photographed through a calibrated microscope to allow identification of their cross-sectional areas. Excess ACSF is removed from the sample and the sections places between the electrodes. The impedance is measured across the frequency range and electrical conductivity calculated. Results show two regions of dispersion. A low frequency region is evident below approximately 10 kHz, and a high frequency dispersion above this. Results at the higher frequencies show a good fit to the Cole-Cole model of impedance of biological tissue; this model consists of resistive and non-linear capacitive elements. Physically, these elements are likely to arise due to membrane polarization and migration of ions both intra- and extra-cellularly.http://www.iupab2014.org/assets/IUPAB/NewFolder/iupab-abstracts.pd

Single microwave-photon detector using an artificial Λ\Lambda-type three-level system

Single photon detection is a requisite technique in quantum-optics experiments in both the optical and the microwave domains. However, the energy of microwave quanta are four to five orders of magnitude less than their optical counterpart, making the efficient detection of single microwave photons extremely challenging. Here, we demonstrate the detection of a single microwave photon propagating through a waveguide. The detector is implemented with an "impedance-matched" artificial $\Lambda$ system comprising the dressed states of a driven superconducting qubit coupled to a microwave resonator. We attain a single-photon detection efficiency of $0.66 \pm 0.06$ with a reset time of $\sim 400$~ns. This detector can be exploited for various applications in quantum sensing, quantum communication and quantum information processing.Comment: 5 pages (4 figures) + 4 pages (5 figures

Magnetic suspension array technology: Controlled synthesis and screening in microfluidic networks

Information tagging and processing are vital in information‐intensive applications, e.g., telecommunication and high‐throughput drug screening. Magnetic suspension array technology may offer intrinsic advantages to screening applications by enabling high distinguishability, the ease of code generation, and the feasibility of fast code readout, though the practical applicability of magnetic suspension array technology remains hampered by the lack of quality administration of encoded microcarriers. Here, a logic‐controlled microfluidic system enabling controlled synthesis of magnetic suspension arrays in multiphase flow networks is realized. The smart and compact system offers a practical solution for the quality administration and screening of encoded magnetic microcarriers and addresses the universal need of process control for synthesis in microfluidic networks, i.e., on‐demand creation of droplet templates for high information capacity. The demonstration of magnetic suspension array technology enabled by magnetic in‐flow cytometry opens the avenue toward point‐of‐care multiplexed bead‐based assays, clinical diagnostics, and drug discovery

Detection of TMPRSS2 : ERG fusion gene in circulating prostate cancer cells

Creative Commons Attribution-NonCommercial-Share Alike 3.0 license (CC BY-NC SA)Aim: To investigate the existence of TMPRSS2:ERG fusion gene in circulating tumor cells (CTC) from prostate cancer patients and its potential in monitoring tumor metastasis. Methods: We analyzed the frequency of TMPRSS2: ERG and TMPRSS2:ETV1 transcripts in 27 prostate cancer biopsies from prostatectomies, and TMPRSS2:ERG transcripts in CTC isolated from 15 patients with advanced androgen independent disease using reverse transcription polymerase chain reaction (RT-PCR). Fluorescence in situ hybridization (FISH) was applied to analyze the genomic truncation of ERG, which is the result of TMPRSS2:ERG fusion in 10 of the 15 CTC samples. Results: TMPRSS2: ERG transcripts were found in 44% of our samples, but we did not detect expression of TMPRSS2:ETV1. Using FISH analysis we detected chromosomal rearrangements affecting the ERG gene in 6 of 10 CTC samples, including 1 case with associated TMPRSS2:ERG fusion at the primary site. However, TMPRSS2:ERG transcripts were not detected in any of the 15 CTC samples, including the 10 cases analyzed by FISH. Conclusion: Although further study is required to address the association between TMPRSS2:ERG fusion and prostate cancer metastasis, detection of genomic truncation of the ERG gene by FISH analysis could be useful for monitoring the appearance of CTC and the potential for prostate cancer metastasis.Peer reviewedFinal Published versio

Microwave Down-Conversion with an Impedance-Matched Λ\Lambda System in Driven Circuit QED

By driving a dispersively coupled qubit-resonator system, we realize an "impedance-matched" $\Lambda$ system that has two identical radiative decay rates from the top level and interacts with a semi-infinite waveguide. It has been predicted that a photon input from the waveguide deterministically induces a Raman transition in the system and switches its electronic state. We confirm this through microwave response to a continuous probe field, observing near-perfect ($99.7\%$) extinction of the reflection and highly efficient ($74\%$) frequency down-conversion. These proof-of-principle results lead to deterministic quantum gates between material qubits and microwave photons and open the possibility for scalable quantum networks interconnected with waveguide photons.Comment: 10 pages, 8 figure

Measuring the bulk impedance of brain tissue in vitro

Theoretical and numerical models of brain activity suggest a link between seizures and electrical connectivity. We have therefore been motivated to measure electrical conductivity in brain tissue. Such measurements in vitro are difficult; it is necessary to use a conductive inorganic salt solution, artificial cerebrospinal fluid (ACSF), to keep the tissue alive. We have attempted to provide a robust method to make such measurements. Mouse brain tissue was sliced (400 μm) using established methods. Half the slices were placed in standard ACSF; half were placed in ACSF devoid of magnesium ions. The latter case promotes seizure activity. Electrical activity was measured with a tungsten electrode at various places on the slices. Sixty-nine samples of cortex (2 mm × 2 mm) were cut with a razor. Their areas were measured with a calibrated microscope. Each sample was placed between two flat Ag/AgCl electrodes in a Perspex sandwich. Excess ACSF was removed with filter paper. The impedance was measured at 25°C from 20 Hz to 2 MHz with an Agilent E4980A four-point impedance meter in a shielded room, using a low current. Between 1 kHz and 100 kHz the conductivity was approximately 0.2 S m⁻¹; outside this range dispersion occurred. Samples prepared in the magnesium-free ACSF had a conductivity about 10% lower. The Cole-Cole model of conductivity was fitted. There were few significant differences between the parameters for the different groups measured

Inactivating hepatic follistatin alleviates hyperglycemia

Unsuppressed hepatic glucose production (HGP) contributes substantially to glucose intolerance and diabetes, which can be modeled by the genetic inactivation of hepatic insulin receptor substrate 1 (Irs1) and Irs2 (LDKO mice). We previously showed that glucose intolerance in LDKO mice is resolved by hepatic inactivation of the transcription factor FoxO1 (that is, LTKO mice)-even though the liver remains insensitive to insulin. Here, we report that insulin sensitivity in the white adipose tissue of LDKO mice is also impaired but is restored in LTKO mice in conjunction with normal suppression of HGP by insulin. To establish the mechanism by which white adipose tissue insulin signaling and HGP was regulated by hepatic FoxO1, we identified putative hepatokines-including excess follistatin (Fst)-that were dysregulated in LDKO mice but normalized in LTKO mice. Knockdown of hepatic Fst in the LDKO mouse liver restored glucose tolerance, white adipose tissue insulin signaling and the suppression of HGP by insulin; however, the expression of Fst in the liver of healthy LTKO mice had the opposite effect. Of potential clinical significance, knockdown of Fst also improved glucose tolerance in high-fat-fed obese mice, and the level of serum Fst was reduced in parallel with glycated hemoglobin in obese individuals with diabetes who underwent therapeutic gastric bypass surgery. We conclude that Fst is a pathological hepatokine that might be targeted for diabetes therapy during hepatic insulin resistance

Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei

UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting sporadic occultation of stellar light by circumstellar dust. GM\,Cephei is such a UXor in the young ($\sim4$~Myr) open cluster Trumpler\,37, showing prominent infrared excess, emission-line spectra, and flare activity. Our photometric monitoring (2008--2018) detects (1)~an $\sim$3.43~day period, likely arising from rotational modulation by surface starspots, (2)~sporadic brightening on time scales of days due to accretion, (3)~irregular minor flux drops due to circumstellar dust extinction, and (4)~major flux drops, each lasting for a couple of months with a recurrence time, though not exactly periodic, of about two years. The star experiences normal reddening by large grains, i.e., redder when dimmer, but exhibits an unusual "blueing" phenomenon in that the star turns blue near brightness minima. The maximum extinction during relatively short (lasting $\leq 50$~days) events, is proportional to the duration, a consequence of varying clump sizes. For longer events, the extinction is independent of duration, suggestive of a transverse string distribution of clumps. Polarization monitoring indicates an optical polarization varying $\sim3\%$--8$\%$, with the level anticorrelated with the slow brightness change. Temporal variation of the unpolarized and polarized light sets constraints on the size and orbital distance of the circumstellar clumps in the interplay with the young star and scattering envelope. These transiting clumps are edge-on manifestations of the ring- or spiral-like structures found recently in young stars with imaging in infrared of scattered light, or in submillimeter of thermalized dust emission.Comment: 20 pages, 9 figure

Open defecation and childhood stunting in India: an ecological analysis of new data from 112 districts.

Poor sanitation remains a major public health concern linked to several important health outcomes; emerging evidence indicates a link to childhood stunting. In India over half of the population defecates in the open; the prevalence of stunting remains very high. Recently published data on levels of stunting in 112 districts of India provide an opportunity to explore the relationship between levels of open defecation and stunting within this population. We conducted an ecological regression analysis to assess the association between the prevalence of open defecation and stunting after adjustment for potential confounding factors. Data from the 2011 HUNGaMA survey was used for the outcome of interest, stunting; data from the 2011 Indian Census for the same districts was used for the exposure of interest, open defecation. After adjustment for various potential confounding factors--including socio-economic status, maternal education and calorie availability--a 10 percent increase in open defecation was associated with a 0.7 percentage point increase in both stunting and severe stunting. Differences in open defecation can statistically account for 35 to 55 percent of the average difference in stunting between districts identified as low-performing and high-performing in the HUNGaMA data. In addition, using a Monte Carlo simulation, we explored the effect on statistical power of the common practice of dichotomizing continuous height data into binary stunting indicators. Our simulation showed that dichotomization of height sacrifices statistical power, suggesting that our estimate of the association between open defecation and stunting may be a lower bound. Whilst our analysis is ecological and therefore vulnerable to residual confounding, these findings use the most recently collected large-scale data from India to add to a growing body of suggestive evidence for an effect of poor sanitation on human growth. New intervention studies, currently underway, may shed more light on this important issue