The Successful Operation of Hole-type Gaseous Detectors at Cryogenic Temperatures

We have demonstrated that hole-type gaseous detectors, GEMs and capillary plates, can operate up to 77 K. For example, a single capillary plate can operate at gains of above 10E3 in the entire temperature interval between 300 until 77 K. The same capillary plate combined with CsI photocathodes could operate perfectly well at gains (depending on gas mixtures) of 100-1000. Obtained results may open new fields of applications for capillary plates as detectors of UV light and charge particles at cryogenic temperatures: noble liquid TPCs, WIMP detectors or LXe scintillating calorimeters and cryogenic PETs.Comment: Presented at the IEEE Nuclear Science Symposium, Roma, 200

Novel Single Photon Detectors for UV Imaging

There are several applications which require high position resolution UV imaging. For these applications we have developed and successfully tested a new version of a 2D UV single photon imaging detector based on a microgap RPC. The main features of such a detectors is the high position resolution - 30 micron in digital form and the high quantum efficiency (1-8% in the spectral interval of 220-140 nm). Additionally, they are spark- protected and can operate without any feedback problems at high gains, close to a streamer mode. In attempts to extend the sensitivity of RPCs to longer wavelengths we have successfully tested the operation of the first sealed parallel-plate gaseous detectors with CsTe photocathodes. Finally, the comparison with other types of photosensitive detectors is given and possible fields of applications are identified.Comment: Presented at the 5th International Workshop on RICH detectors Playa del Carmen, Mexico, November 200

A Novel UV Photon Detector with Resistive Electrodes

In this study we present first results from a new detector of UV photons: a thick gaseous electron multiplier (GEM) with resistive electrodes, combined with CsI or CsTe/CsI photocathodes. The hole type structure considerably suppresses the photon and ion feedback, whereas the resistive electrodes protect the detector and the readout electronics from damage by any eventual discharges. This device reaches higher gains than a previously developed photosensitive RPC and could be used not only for the imaging of UV sources, flames or Cherenkov light, for example, but also for the detection of X-rays and charged particles.Comment: Presented at the International Workshop on Resistive Plate Chambers, Korea, October 200

The Development and Study of High-Position Resolution (50 micron) RPCs for Imaging X-rays and UV photons

Nowadays, commonly used Resistive Plate Chambers (RPCs) have counting rate capabilities of ~10E4Hz/cm2 and position resolutions of ~1cm. We have developed small prototypes of RPCs (5x5 and 10x10cm2) having rate capabilities of up to 10E7Hz/cm2 and position resolutions of 50 micron("on line" without application of any treatment method like "center of gravity"). The breakthrough in achieving extraordinary rate and position resolutions was only possible after solving several serious problems: RPC cleaning and assembling technology, aging, spurious pulses and afterpulses, discharges in the amplification gap and along the spacers. High-rate, high-position resolution RPCs can find a wide range of applications in many different fields, for example in medical imaging. RPCs with the cathodes coated by CsI photosensitive layer can detect ultraviolet photons with a position resolution that is better than ~30 micron. Such detectors can also be used in many applications, for example in the focal plane of high resolution vacuum spectrographs or as image scanners.Comment: 6 pages, 5 figures, other comment

Cerebrospinal fluid anti-myelin antibodies are related to magnetic resonance measures of disease activity in multiple sclerosis

0.001), together constituting 85% of all positive CSF samples. In contrast, elevated anti-myelin IgG antibody reactivity was present in a minority of IND patients (21%), marginally present in controls (5%) and absent in OND patients (0%). Most strikingly, anti-myelin IgG antibody reactivity was related to the number of T2 lesions (r = 0.31, p = 0.041) and gadolinium enhancing T1 lesions (r = 0.37, p = 0.016) on brain MRI in CIS and relapse onset MS patients. Conclusion: CSF anti-myelin IgG antibodies are promising specific biomarkers in CIS and relapse onset MS and correlate with MR measures of disease activit

Dynamic Changes in Brain Mesenchymal Perivascular Cells Associate with Multiple Sclerosis Disease Duration, Active Inflammation, and Demyelination

Vascular changes, including blood brain barrier destabilization, are common pathological features in multiple sclerosis (MS) lesions. Blood vessels within adult organs are reported to harbor mesenchymal stromal cells (MSCs) with phenotypical and functional characteristics similar to pericytes. We performed an immunohistochemical study of MSCs/pericytes in brain tissue from MS and healthy persons. Post-mortem brain tissue from patients with early progressive MS (EPMS), late stage progressive MS (LPMS), and healthy persons were analyzed for the MSC and pericyte markers CD146, platelet-derived growth factor receptor beta (PDGFRβ), CD73, CD271, alpha-smooth muscle actin, and Ki67. The MS samples included active, chronic active, chronic inactive lesions, and normal-appearing white matter. MSC and pericyte marker localization were detected in association with blood vessels, including subendothelial CD146+PDGFRβ+Ki67+ cells and CD73+CD271+PDGFRβ+Ki67– cells within the adventitia and perivascular areas. Both immunostained cell subpopulations were termed mesenchymal perivascular cells (MPCs). Quantitative analyses of immunostainings showed active lesions containing increased regions of CD146+PDGFRβ+Ki67+ and CD73+CD271+PDGFRβ+Ki67– MPC subpopulations compared to inactive lesions. Chronic lesions presented with decreased levels of CD146+PDGFRβ+Ki67+ MPC cells compared to control tissue. Furthermore, LPMS lesions displayed increased numbers of blood vessels harboring greatly enlarged CD73+CD271+ adventitial and perivascular areas compared to control and EPMS tissue. In conclusion, we demonstrate the presence of MPC subgroups in control human brain vasculature, and their phenotypic changes in MS brain, which correlated with inflammation, demyelination and MS disease duration. Our findings demonstrate that brain-derived MPCs respond to pathologic mechanisms involved in MS disease progression and suggest that vessel-targeted therapeutics may benefit patients with progressive MS

Cardiovascular function in normal pregnancy and fetal growth

Background: Pregnancy is a challenge to a woman’s cardiovascular system, and extensive haemodynamic changes are required for optimal utero-placental circulation and fetal growth. The aim of this thesis was firstly to examine different aspects of vascular function in the same women longitudinally during normal pregnancy, and secondly to explore whether there is an association between maternal cardiovascular function, placental function, and fetal growth. Methods and Main Results: Study I and II were prospective cohort studies investigating cardiovascular structure and function in 52 healthy women longitudinally at 14, 24 and 34 weeks gestation, and nine months postpartum. In Study I, brachial and central blood pressure, pulse-wave velocity, augmentation index, common carotid artery structure and endothelial function in the brachial artery (FMD) and in the forearm skin microcirculation was assessed. The study found that brachial and central blood pressure initially decreased and then increased. FMD and endothelium dependent microvascular reactivity increased during pregnancy. Pulse wave velocity and augmentation index decreased, reaching a nadir in the second trimester. In Study II, cardiac function, myocardial mechano-energetic efficiency (MEE), and ventricular-arterial coupling (VAC) were measured. Left ventricular (LV) mass and cardiac output (CO) increased during pregnancy. LV diastolic function decreased but MEE and VAC maintained during pregnancy. There was a positive correlation between first and second trimester heart rate, and birth weight centile. Study III was a cross-sectional study (n=56) investigating the association between first trimester vascular function and birth weight centile. Maternal first trimester vascular reactivity in the brachial artery, and in the forearm skin microcirculation, related positively to birth weight centile. Study IV was a cross-sectional study (n=53) investigating the association between levels of circulating maternal pregnancy-associated plasma protein A (PAPP-A), and first trimester maternal vascular function. PAPP-A correlated positively to first trimester maternal skin microvascular endothelial function index. Conclusions: During normal pregnancy, there were profound structural and functional changes throughout the cardiovascular tree. These changes are probably necessary for sufficient fetal growth, which is supported by the observed relation between maternal heart rate, vascular vasodilator capacity, and fetal growth. Given that first trimester PAPP-A levels relate to placental function, our results suggest that placental function can be reflected by first trimester endothelium dependent skin microvascular reactivity

A Study of the Operation of Especially Designed Photosensitive Gaseous Detectors at Cryogenic Temperatures

In some experiments and applications there is need for large-area photosensitive detectors to operate at cryogenic temperatures. Nowadays, vacuum PMs are usually used for this purpose. We have developed special designs of planar photosensitive gaseous detectors able to operate at cryogenic temperatures. Such detectors are much cheaper PMs and are almost insensitive to magnetic fields. Results of systematic measurements of their quantum efficiencies, the maximum achievable gains and long-term stabilities will be presented. The successful operation of these detectors open realistic possibilities in replacing PMs by photosensitive gaseous detectors in some applications dealing with cryogenic liquids; for example in experiments using noble liquid TPCs or noble liquid scintillating calorimeters.Comment: Submitted to the Nuclear Instruments and Method

Assessment of arterial function in pregnancy: recommendations of the International Working Group on Maternal Haemodynamics.

There is strong evidence supporting a role of maternal arterial dysfunction in pregnancy-specific disorders such as pre-eclampsia and intra-uterine growth restriction. As more work is focused towards this field, it is important that methods and interpretation of arterial function assessment are utilised appropriately. Here, we summarise techniques and devices commonly used in maternal health studies, with considerations of technical application within pregnant cohorts