257 research outputs found
The piezoelectric effect in II-VI semiconductors
This thesis explores the nature and application of the piezoelectric effect in ZnSe-based semiconductors, and also includes a chapter on microscope analysis techniques.
Photoelectrochemical etching of ZnSe is shown to reveal defect sites that are related to features observed by a technique of luminescence microscopy. The defect densities are related to the optical quality of the material. Defect annealing under intense optical excitation has been observed.
The piezoelectric effect produces an internal electric field that shifts inter-band transitions to lower energies by the quantum confined Stark effect. Previous experiments of photocurrent on the piezoelectric effect in ZnCdSe / ZnSe quantum wells are expanded and improved on and with similar results obtained by photoluminescence excitation, provide a method of measuring the internal field. Photoluminescence experiments reveal the effect of the internal field on the free and donor bound excitons, as well as the exciton localisation.
Finally the piezoelectric effect is utilised to find the critical thickness of the start of strain relaxation in ZnCdSe / ZnSe quantum wells, as the internal field is directly proportional to the strain in the well layer
The island of Kauai, Hawaii's progressive shoreline setback and coastal protection ordinance
Approximately two-thirds of coastal and Great Lakes states have some type of shoreline construction setback or
construction control line requiring development to be a certain distance from the shoreline or other coastal feature
(OCRM, 2008). Nineteen of 30 coastal states currently use erosion rates for new construction close to the shoreline.
Seven states established setback distances based on expected years from the shoreline: the remainder specify a fixed setback distance (Heinz Report, 2000).
Following public hearings by the County of Kauai Planning Commission and Kauai County Council, the âShoreline
Setback and Coastal Protection Ordinanceâ was signed by the Mayor of Kauai on January 25, 2008. After a year of
experience implementing this progressive, balanced shoreline setback ordinance several amendments were recently
incorporated into the Ordinance (#887; Bill #2319 Draft 3). The Kauai Planning Department is presently drafting
several more amendments to improve the effectiveness of the Ordinance.
The intent of shoreline setbacks is to establish a buffer zone to protect shorefront development from loss due to
coastal erosion - for a period of time; to provide protection from storm waves; to allow the natural dynamic cycles of erosion and accretion of beaches and dunes to occur; to maintain beach and dune habitat; and, to maintain lateral beach access and open space for the enjoyment of the natural shoreline environment. In addition, a primary goal of the Kauai setback ordinance is to avoid armoring or hardening of the shore which along eroding coasts has been
documented to ultimately eliminate the fronting beach. (PDF contains 4 pages
Gynecological cancers: an alternative approach to healing
Grief and hope are two conflicting emotions that a patient recently diagnosed with cancer has to master. The real challenge for gynecologic oncologists is how to reach out. Conventional wisdom states that offering patients focus and belief when combating cancer in their lives allows them to embrace hope with greater confidence, which minimizes their grief. Three pictorial models are presented: â4-cusp approachâ model used at the initial consultation; âtapestry of bereavement or landscape of griefâ model at the postsurgery consultation; and âVenn-diagramâ model at any time during patient management. We have applied these models in our practice and believe that they can act as a fulcrum for the patient, the family and healthcare team around which therapy should be centered., Grief and hope are two emotions that a patient faces if diagnosed with cancer. The real challenge for the doctor is how to reach out and help the patient through this process. A doctor's role may be to offer focus and belief to the patient which may allow her to embrace hope with greater confidence. This will hopefully lessen the grief. We present three models which we believe can play a crucial part: â4-cusp approachâ used at the initial consultation; âtapestry of bereavement or landscape of grief modelâ at the postsurgery consultation; and âVenn-diagram modelâ at any time during care
Preferential closed channel blockade of HERG potassium currents by chemically synthesised BeKmâ1 scorpion toxin
The scorpion toxin peptide BeKmâ1 was synthesised by fluorenylmethoxycarbonyl solid phase chemistry and folded by air oxidation. The peptide's effects on heterologous human etherâaâgoâgoârelated gene potassium current (I
HERG) in HEK293 cells were assessed using 'wholeâcell' patch clamp. Blockade of I
HERG by BeKmâ1 was concentrationâdependent, temperatureâdependent, and rapid in onset and reversibility. Blockade also exhibited inverse voltage dependence, inverse dependence on duration of depolarisation, and reverse useâ and frequencyâdependence. Blockade by BeKmâ1 and recombinant ergtoxin, another scorpion toxin known to block HERG, differed in their recovery from HERG current inactivation elicited by strong depolarisation and in their ability to block HERG when the channels were already activated. We conclude that synthetic BeKmâ1 toxin blocks HERG preferentially through a closed (resting) state channel blockade mechanism, although some open channel blockade also occurs
Inhibition of voltage-gated Na<sup>+</sup> currents by eleclazine in rat atrial and ventricular myocytes
Beam tests of a large-scale TORCH time-of-flight demonstrator
The TORCH time-of-flight detector is designed to provide particle
identification in the momentum range 2-10 GeV/c over large areas. The detector
exploits prompt Cherenkov light produced by charged particles traversing a 10
mm thick quartz plate. The photons propagate via total internal reflection and
are focused onto a detector plane comprising position-sensitive Micro-Channel
Plate Photo-Multiplier Tubes (MCP-PMT) detectors. The goal is to achieve a
single-photon timing resolution of 70 ps, giving a timing precision of 15 ps
per charged particle by combining the information from around 30 detected
photons. The MCP-PMT detectors have been developed with a commercial partner
(Photek Ltd, UK), leading to the delivery of a square tube of active area 53
53mm with a granularity of 8 128 pixels equivalent. A
large-scale demonstrator of TORCH, having a quartz plate of dimensions 660
1250 10 mm and read out by a pair of MCP-PMTs with custom
readout electronics, has been verified in a test beam campaign at the CERN PS.
Preliminary results indicate that the required performance is close to being
achieved. The anticipated performance of a full-scale TORCH detector at the
LHCb experiment is presented.Comment: 12 pages, 7 figures, Paper submitted to Nuclear Instruments & Methods
in Physics Research, Section A - Special Issue VCI 201
Wide-field time-correlated single photon counting-based fluorescence lifetime imaging microscopy
Wide-field time-correlated single photon counting detection techniques, where the position and the arrival time of the photons are recorded simultaneously using a camera, have made some advances recently. The technology and instrumentation used for this approach is employed in areas such as nuclear science, mass spectroscopy and positron emission tomography, but here, we discuss some of the wide-field TCSPC methods, for applications in fluorescence microscopy. We describe work by us and others as presented in the Ulitima fast imaging and tracking conference at the Argonne National Laboratory in September 2018, from phosphorescence lifetime imaging (PLIM) microscopy on the microsecond time scale to fluorescence lifetime imaging (FLIM) on the nanosecond time scale, and highlight some applications of these techniques
Age-related fertility decline: is there a role for elective ovarian tissue cryopreservation?
Age-related fertility decline (ARFD) is a prevalent concern amongst western cultures due to the increasing age of first-time motherhood. Elective oocyte and embryo cryopreservation remain the most established methods of fertility preservation, providing women the opportunity of reproductive autonomy to preserve their fertility and extend their childbearing years to prevent involuntary childlessness. Whilst ovarian cortex cryopreservation has been used to preserve reproductive potential in women for medical reasons, such as in pre- or peripubertal girls undergoing gonadotoxic chemotherapy, it has not yet been considered in the context of ARFD. As artificial reproductive technology (ART) and surgical methods of fertility preservation continue to evolve, it is a judicious time to review current evidence and consider alternative options for women wishing to delay their fertility. This article critically appraises elective oocyte cryopreservation as an option for women who use it to mitigate the risk of ARFD and introduces the prospect of elective ovarian cortex cryopreservation as an alternative
Atrial-like cardiomyocytes from human pluripotent stem cells are a robust preclinical model for assessing atrial-selective pharmacology
Drugs targeting atrial-specific ion channels, K(v)1.5 or K(ir)3.1/3.4, are being developed as new therapeutic strategies for atrial fibrillation. However, current preclinical studies carried out in non-cardiac cell lines or animal models may not accurately represent the physiology of a human cardiomyocyte (CM). In the current study, we tested whether human embryonic stem cell (hESC)-derived atrial CMs could predict atrial selectivity of pharmacological compounds. By modulating retinoic acid signaling during hESC differentiation, we generated atrial-like (hESC-atrial) and ventricular-like (hESC-ventricular) CMs. We found the expression of atrial-specific ion channel genes, KCNA5 (encoding Kv1.5) and KCNJ3 (encoding K-ir 3.1), in hESC-atrial CMs and further demonstrated that these ion channel genes are regulated by COUP-TF transcription factors. Moreover, in response to multiple ion channel blocker, vernakalant, and K(v)1.5 blocker, XEN-D0101, hESC-atrial but not hESC-ventricular CMs showed action potential (AP) prolongation due to a reduction in early repolarization. In hESC-atrial CMs, XEN-R0703, a novel K(ir)3.1/3.4 blocker restored the AP shortening caused by CCh. Neither CCh nor XEN-R0703 had an effect on hESC-ventricular CMs. In summary, we demonstrate that hESC-atrial CMs are a robust model for pre-clinical testing to assess atrial selectivity of novel antiarrhythmic drugs
Status of the TORCH time-of-flight project
TORCH is a time-of-flight detector, designed to provide charged pi/K particle
identification up to a momentum of 10 GeV/c for a 10 m flight path. To achieve
this level of performance, a time resolution of 15 ps per incident particle is
required. TORCH uses a plane of quartz of 1 cm thickness as a source of
Cherenkov photons, which are then focussed onto square Micro-Channel Plate
Photomultipliers (MCP-PMTs) of active area 53 x 53 mm^2, segmented into 8 x 128
pixels equivalent. A small-scale TORCH demonstrator with a customised MCP-PMT
and associated readout electronics has been successfully operated in a 5 GeV/c
mixed pion/proton beam at the CERN PS facility. Preliminary results indicate
that a single-photon resolution better than 100 ps can be achieved. The
expected performance of a full-scale TORCH detector for the Upgrade II of the
LHCb experiment is also discussed.Comment: 9 pages, 6 figures, Paper submitted to Nuclear and Methods A :
Proceedings of the 10th International Workshop on Ring Imaging Cherenkov
Detectors (RICH 2018), Moscow, Russia, July 29 to August 4 201
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