Coupling between gamma-band power and cerebral blood volume during recurrent acute neocortical seizures

Characterization of neural and hemodynamic biomarkers of epileptic activity that can be measured using non-invasive techniques is fundamental to the accurate identification of the epileptogenic zone (EZ) in the clinical setting. Recently, oscillations at gamma-band frequencies and above (>30 Hz) have been suggested to provide valuable localizing information of the EZ and track cortical activation associated with epileptogenic processes. Although a tight coupling between gamma-band activity and hemodynamic-based signals has been consistently demonstrated in non-pathological conditions, very little is known about whether such a relationship is maintained in epilepsy and the laminar etiology of these signals. Confirmation of this relationship may elucidate the underpinnings of perfusion-based signals in epilepsy and the potential value of localizing the EZ using hemodynamic correlates of pathological rhythms. Here, we use concurrent multi-depth electrophysiology and 2-dimensional optical imaging spectroscopy to examine the coupling between multi-band neural activity and cerebral blood volume (CBV) during recurrent acute focal neocortical seizures in the urethane-anesthetized rat. We show a powerful correlation between gamma-band power (25-90 Hz) and CBV across cortical laminae, in particular layer 5, and a close association between gamma measures and multi-unit activity (MUA). Our findings provide insights into the laminar electrophysiological basis of perfusion-based imaging signals in the epileptic state and may have implications for further research using non-invasive multi-modal techniques to localize epileptogenic tissue

Symmetry-related transitions in the spectrum of nanosized Cubic Y2O3: Tb3+

Herein the preparation and cathodoluminescence of nanoparticles of cubic Y2O3:Tb3+ having Tb3+ concentration varying between 0.1 and 10 Mol% are described. The cathodoluminescence spectra were recorded with a high resolution spectrometer, which enabled the identification of Tb3+ lines with C2 and S6 symmetry: the lines at 542.8 nm and 544.4 nm were designated as 5D4→7F5 (C2) and 5D4→7F5 (S6) respectively. The critical distance for energy transfer from Tb3+ ions at S6 lattice sites to Tb3+ ions at C2 lattice sites was found to be >1.7 nm. At the greater distances which prevail at low Tb3+ concentration, this energy transfer virtually stops. From cathodoluminescence spectra recorded in a scanning transmission electron microscope it was concluded that this energy transfer also did not take place if the temperature was reduced below 102 K. The efficiency of the cathodoluminescence of 1% Y2O3:Tb3+ was 6 lm/w at a beam voltage of 15 kV. The decay time of the 5D4→7F5 (C2) transition was substantially shorter than that of the 5D4→7F5 (S6) transition at low Tb3+ concentrations. The decay behavior of the cathodoluminescence images in a field emission scanning electron microscope has been explained in terms of phosphor saturation.We are grateful to the EPSRC and the Technology Strategy Board (TSB) for funding the PURPOSE (TP11/MFE/6/I/AA129F; EPSRCTS/G000271/1) and CONVERTED (JeS no. TS/1003053/1) programs. We are also grateful to the TSB for funding the CONVERT program

Symmetry-related transitions in the photoluminescence and cathodoluminescence spectra of nanosized cubic Y2O3:Tb3+

Herein the photoluminescence spectra of nanosized cubic Y2O3:Tb3+ having Tb3+ concentrations varying between 0.1 and 10 Mol% are described. Low temperature cathodoluminescence spectra from these materials recorded in a scanning transmission electron microscope are presented and discussed. By studying the photoluminescence-spectra recorded at room temperature and focused on the 5D4→7F5 (C2) and 5D4→7F5 (C3i) transitions, at 542.8 and 544.4 nm respectively, it was found that the critical distance for energy transfer from Tb3+ ions at C3i lattice sites to Tb3+ ions at C2 lattice sites was 1.7 nm; at distances >1.7 nm, which prevail at low Tb3+ concentration, this energy transfer virtually stops. The gradual change of the excitation spectra upon increasing the Tb3+ concentration is also explained in terms of energy transfer from Tb3+ at C3i sites to Tb3+ at C2 sites. Cathodoluminescence spectra recorded at low temperatures with the scanning transmission electron microscope provided additional evidence for this radiationless energy transfer.We are grateful to the EPSRC and the Technology Strategy Board (TSB) for funding the PURPOSE (TP11/MFE/6/I/AA129F; EPSRCTS/G000271/1) and CONVERTED (JeS no. TS/1003053/1) programs. The TSB funded the CONVERT program

Graphene films printable on flexible substrates for sensor applications

Fifteen-layered graphene films have been successfully deposited onto flexible substrates using a commercial ink consisting of graphene particles dispersed in an acrylic polymer binder. A value of 74.9 × 105cm−2 was obtained for the density of defects, primarily located at the flake edges, from the ratio of the D and G Raman peaks located at 1345cm1 and 1575cm1 respectively. 0.5μm thick drop-cast films on interdigitated silver electrodes exhibited Ohmic conduction with a small activation energy of 12meV over the temperature range from 260K to 330K . The photo-thermoelectric effect is believed to be responsible for photoconduction through graphene films under illumination intensity of 10mWm-2 at 270 nm, corresponding to the UV absorption peak. The photo-transient decay at the bias of 1V involves two relaxation processes when the illumination is switched off and values of 8.9 × 103 and 4.3 × 104 are found for the relaxation time constant using the Kohlrauch stretched exponential function analysis.Dr. Indrani Banerjee is grateful to Commonwealth Association, UK for funding the present research work under the fellowship placement scheme (Grant reference INCF-2014-66). The studentship of Ms Faris is partially sponsored by the Air Force Office of Scientific Research, Air Force Material Command, USAF, under Grant No. FA9550-15-1-0123. We are also thankful to Miss V. M. Torrejon of Brunel University for support in computer graphics

Non-passive behavior of equivalent circuit components in AC powder electroluminescence (ACPEL) lamps

For the first time, the voltage and frequency characteristics of a single layer AC powder electroluminescent lamp have been examined in detail to reveal the individual contributions of the material components involved. Statistical modelling has been employed to refine the equivalent circuit description of the lamp. DC-blocked resistance-capacitance networks can be reduced to a single effective resistance and capacitance in series. The frequency dependence of these two quantities in the range 4–1600 Hz has been used to unravel the behavior of the different underlying resistance and capacitance components at different voltage amplitudes in the range 25–150 V. The resistive contribution, R, of the activated ZnS phosphor is shown to be non-passive, and obeys the form: R(V,f) = R0(V).f−1/3.e−T.f, where V is the applied voltage, f is the frequency and T is a time constant, at all voltages. For both ZnS and BaTiO3, other characteristics indicate the presence of a thinner, non-polarized region within each semiconducting particle located within the particle's crust. A marked change in the characteristics of the different component values occurs between 25 and 50 V, consistent with the onset of light emission, after which smooth changes in all values are observed up to 150 V.We are grateful to the Technology Strategy Board (TSB) (UK) for substantial financial funding in the form of TSB Technology programs for the PLACES, FAB3D, ACTIVEL, SHAPEL, and BEDS programs and to our many industrial collaborators on these programs

Ultraviolet and blue cathodoluminescence from cubic Y2O3 and Y2O3: Eu3+ generated in a transmission electron microscope

Herein we describe the investigation of transmission electron microscopeof non-doped Y2O3 and Y2O3 doped with Eu3+ in a transmission electron microscope (TEM) equipped with a spectrometer to detect cathodoluminescence from individual particles. Each submicron particle was made up of nanometre sized crystals. We found that these crystals showed a broad emission band at 353 nm upon bombardment with 200 keV or 80 keV electrons. Upon increasing the Eu3+ concentration from 0 to 2 mol% this UV/blue emission was gradually quenched: at Eu3+ concentrations >2 mol% no UV/blue emission was detected, only the well-known cathodoluminescence (CL) spectrum of Y2O3:Eu3+ could be recorded. This UV/blue emission has been attributed to the intrinsic luminescence of Y2O3 caused by self-trapped excitons. We found that the UV/blue luminescence was strongly temperature dependent and that the trap depth of the self-trapped excitons was 0.14 eV. The ratios of the spectral radiances of 5D1 → 7FJ and 5D0 → 7FJ (J = 0, 1...6) Eu3+ transitions in the CL-TEM spectra of Y2O3:Eu3+ at low Eu3+ concentrations was about a factor of 10 larger than those recorded at 15 keV. This phenomenon has been explained by absorption of the intrinsic luminescence of Y2O3 by Eu3+.The EPSRC and the Technology Strategy Board (TSB) funded the PURPOSE (TP11/MFE/6/I/AA129F; EPSRC TS/G000271/1), CONVERTED (JeS no. TS/1003053/1) and PRISM (EP/N508974/1) programs. The TSB for funding the CONVERT program.We are grateful to the EPSRC and the Technology Strategy Board (TSB) for funding the PURPOSE (TP11/MFE/6/I/AA129F; EPSRC TS/G000271/1), CONVERTED (JeS no. TS/1003053/1) and PRISM (EP/N508974/1) programs. We are also grateful to the TSB for funding the CONVERT program

Is telomere length socially patterned? Evidence from the West of Scotland Twenty-07 study

Lower socioeconomic status (SES) is strongly associated with an increased risk of morbidity and premature mortality, but it is not known if the same is true for telomere length, a marker often used to assess biological ageing. The West of Scotland Twenty-07 Study was used to investigate this and consists of three cohorts aged approximately 35 (N = 775), 55 (N = 866) and 75 years (N = 544) at the time of telomere length measurement. Four sets of measurements of SES were investigated: those collected contemporaneously with telomere length assessment, educational markers, SES in childhood and SES over the preceding twenty years. We found mixed evidence for an association between SES and telomere length. In 35-year-olds, many of the education and childhood SES measures were associated with telomere length, i.e. those in poorer circumstances had shorter telomeres, as was intergenerational social mobility, but not accumulated disadvantage. A crude estimate showed that, at the same chronological age, social renters, for example, were nine years (biologically) older than home owners. No consistent associations were apparent in those aged 55 or 75. There is evidence of an association between SES and telomere length, but only in younger adults and most strongly using education and childhood SES measures. These results may reflect that childhood is a sensitive period for telomere attrition. The cohort differences are possibly the result of survival bias suppressing the SES-telomere association; cohort effects with regard different experiences of SES; or telomere possibly being a less effective marker of biological ageing at older ages

CP Violation and Dark Matter

A brief review is given of the effects of CP violation on the direct detection of neutralinos in dark matter detectors. We first summarize the current developments using the cancellation mechanism which allows for the existence of large CP violating phases consistent with experimental limits on the electron and on the neutron electric dipole moments in a broad class of SUSY, string and D brane models. We then discuss their effects on the scattering of neutralinos from quarks and on the event rates. It is found that while CP effects on the event rates can be enormous such effects are reduced significantly with the imposition of the EDM constraints. However, even with the inclusion of the EDM constraints the effects are still very significant and should be included in a precision prediction of event rates in any SUSY, string or D brane model.Comment: Based on an invited talk at the conference "Sources and Detection of Dark Matter in the Universe", at Marina del Rey, CA, Feb. 23-25, 2000; 12 pages, Latex including 2 figure