737 research outputs found
Inelastic scattering in a monolayer graphene sheet; a weak-localization study
Charge carriers in a graphene sheet, a single layer of graphite, exhibit much
distinctive characteristics to those in other two-dimensional electronic
systems because of their chiral nature. In this report, we focus on the
observation of weak localization in a graphene sheet exfoliated from a piece of
natural graphite and nano-patterned into a Hall-bar geometry. Much stronger
chiral-symmetry-breaking elastic intervalley scattering in our graphene sheet
restores the conventional weak localization. The resulting carrier-density and
temperature dependence of the phase coherence length reveal that the
electron-electron interaction including a direct Coulomb interaction is the
main inelastic scattering factor while electron-hole puddles enhance the
inelastic scattering near the Dirac point.Comment: 12 pages, 3 figures, submitted to PR
EFFECTIVE DOSE MEASUREMENT FOR CONE BEAM COMPUTED TOMOGRAPHY USING GLASS DOSIMETER
During image-guided radiation therapy, the patient is exposed to unwanted radiation from imaging devices built into the medical LINAC. In the present study, the effective dose delivered to a patient from a cone beam computed tomography (CBCT) machine was measured. Absorbed doses in specific organs listed in ICRP Publication 103 were measured with glass dosimeters calibrated with kilovolt (kV) X-rays using a whole body physical phantom for typical radiotherapy sites, including the head and neck, chest, and pelvis. The effective dose per scan for the head and neck, chest, and pelvis were 3.37Ā±0.29, 7.36Ā±0.33, and 4.09Ā±0.29 mSv, respectively. The results highlight the importance of the compensation of treatment dose by managing imaging dose
Characterization of single photon sources for radiometry applications at room temperature
A single photon source with high repeatability and low uncertainties is the
key element for few-photon metrology based on photon numbers. While low photon
number fluctuations and high repeatability are important figures for
qualification as a standard light source, these characteristics are limited in
single photon emitters by some malicious phenomena like blinking or internal
relaxations to varying degrees in different materials. This study seeks to
characterize photon number fluctuations and repeatability for radiometry
applications at room temperature. For generality in this study, we collected
photon statistics data with various single photon emitters of
at low excitation power and room temperature in three material platforms:
silicon vacancy in diamond, defects in GaN, and vacancy in hBN. We found common
factors related with the relaxation times of the internal states that
indirectly affect photon number stability. We observed a high stability of
photon number with defects in GaN due to faster relaxations compared with
vacancies in hBN, which on the other hand produced high rates () of
photons per second. Finally, we demonstrate repeatable radiant flux
measurements of a bright hBN single photon emitter for a wide radiant flux
range from a few tens of femtowatts to one picowatt.Comment: Submitted to: Materials for Quantum Technology (IOP
Correction: COUP-TFII Mediates Progesterone Regulation of Uterine Implantation by Controlling ER Activity
COUP-TFII Mediates Progesterone Regulation of Uterine Implantation by Controlling ER Activity
Progesterone and estrogen are critical regulators of uterine receptivity. To facilitate uterine remodeling for embryo attachment, estrogen activity in the uterine epithelia is attenuated by progesterone; however, the molecular mechanism by which this occurs is poorly defined. COUP-TFII (chicken ovalbumin upstream promoter transcription factor II; also known as NR2F2), a member of the nuclear receptor superfamily, is highly expressed in the uterine stroma and its expression is regulated by the progesteroneāIndian hedgehogāPatched signaling axis that emanates from the epithelium. To further assess COUP-TFII uterine function, a conditional COUP-TFII knockout mouse was generated. This mutant mouse is infertile due to implantation failure, in which both embryo attachment and uterine decidualization are impaired. Using this animal model, we have identified a novel genetic pathway in which BMP2 lies downstream of COUP-TFII. Epithelial progesterone-induced Indian hedgehog regulates stromal COUP-TFII, which in turn controls BMP2 to allow decidualization to manifest in vivo. Interestingly, enhanced epithelial estrogen activity, which impedes maturation of the receptive uterus, was clearly observed in the absence of stromal-derived COUP-TFII. This finding is consistent with the notion that progesterone exerts its control of implantation through uterine epithelial-stromal cross-talk and reveals that stromal-derived COUP-TFII is an essential mediator of this complex cross-communication pathway. This finding also provides a new signaling paradigm for steroid hormone regulation in female reproductive biology, with attendant implications for furthering our understanding of the molecular mechanisms that underlie dysregulation of hormonal signaling in such human reproductive disorders as endometriosis and endometrial cancer
Auto-Guiding System for CQUEAN (Camera for QUasars in EArly uNiverse)
To perform imaging observation of optically red objects such as high redshift
quasars and brown dwarfs, the Center for the Exploration of the Origin of the
Universe (CEOU) recently developed an optical CCD camera, Camera for QUasars in
EArly uNiverse(CQUEAN), which is sensitive at 0.7-1.1 um. To enable
observations with long exposures, we developed an auto-guiding system for
CQUEAN. This system consists of an off-axis mirror, a baffle, a CCD camera, a
motor and a differential decelerator. To increase the number of available
guiding stars, we designed a rotating mechanism for the off-axis guiding
camera. The guiding field can be scanned along the 10 acrmin ring offset from
the optical axis of the telescope. Combined with the auto-guiding software of
the McDonald Observatory, we confirmed that a stable image can be obtained with
an exposure time as long as 1200 seconds.Comment: Accepted for publication in Journal of Korean Astronomical Society
(JKAS
Compartment syndrome due to extravasation of peripheral parenteral nutrition: extravasation injury of parenteral nutrition
Compartment syndrome is a rare but devastating condition that can result in permanent neuromuscular or soft tissue injuries. Extravasation injuries, among the iatrogenic causes of compartment syndrome, occur under a wide variety of circumstances in the inpatient setting. Total parenteral nutrition via a peripheral route is an effective alternative for the management of critically ill children who do not obtain adequate nutrition via the oral route. However, there is an inherent risk of extravasation, which can cause compartment syndrome, especially when detected at a later stage. Herein, we report a rare case of compartment syndrome and skin necrosis due to extravasation, requiring emergency fasciotomy and skin graft in a 7-month-old boy who was treated with peripheral parenteral nutrition via a pressurized infusion pump. Although we cannot estimate the exact time at which extravasation occurred, the extent and degree of the wound suggest that the ischemic insult was prolonged, lasting for several hours. Pediatric clinicians and medical teams should carefully examine the site of insertion of the intravenous catheter, especially in patients receiving parenteral nutrition via a peripheral intravenous catheter with a pressurized infusion pump
Early Growth, Pigmentation, Protein Content, and Phenylalanine Ammonia-lyase Activity of Red Curled Lettuces Grown under Different Lighting Conditions
Early growth, pigmentation, protein content, and phenylalanine ammonia-lyase (PAL) activity of red curly lettuces (Lactuca sativa L.) grown under different lighting conditions were investigated. Fluorescent lamps (control), blue, red, and blue plus red light-emitting diodes (LEDs) were used as light sources for 10 days. An equal proportion (1:1) of blue and red LEDs was used in the mixed radiation condition. Compared with the control, monochromic red or blue lighting increased fresh and dry weights of 'Ttuksum' and 'Jaju' lettuces. Anthocyanin synthesis was also significantly promoted by the mixed radiation of blue and red LEDs. The mixed radiation also increased the protein content and PAL enzyme activity of 'Ttuksum' leaves by about 200% compared to other treatments. Anthocyanin content was the highest in lettuces subjected to the mixture radiation of blue and red light treatment, while anthocyanin synthesis was inhibited by monochromic red light. The results of the present study indicate that growth and pigment synthesis in lettuces are significantly enhanced by exposure to mixed radiation from blue and red LEDs.This study was carried out with the support of Research Program for Agricultural Science & Technology Development (Project No. PJ0076662011), National Academy of Agricultural Science, Rural Development Administration, Republic of Korea.OAIID:oai:osos.snu.ac.kr:snu2012-01/102/0000027607/2SEQ:2PERF_CD:SNU2012-01EVAL_ITEM_CD:102USER_ID:0000027607ADJUST_YN:YEMP_ID:A075898DEPT_CD:517CITE_RATE:.237FILENAME:2012-2-kjhst-ledģ ģ¹ė§ģģ¶-ķģ ģ±.pdfDEPT_NM:ģė¬¼ģģ°ź³¼ķė¶EMAIL:[email protected]_YN:NCONFIRM:
Establishment of a pheasant ( Phasianus colchicus ) spermatogonial stem cell line for the production of interspecies germ line chimeras
Background: Spermatogonial stem cells (SSCs) are important for the
production of interspecies germ line chimeras. The interspecies germ
cell transfer technique has been suggested as a way to conserve
endangered birds. Our objective was to develop a technique for
restoring endangered birds by developing interspecies germ line
chimeras between pheasant ( Phasianus colchicus ) and chicken ( Gallus
gallus ) with SSCs. Results: SSCs were isolated fromthe surgically
removed testis of a pheasant. Growth conditions for pheasant SSCs were
established by co-culturing STO (SIM mouse embryo-derived thioguanine
and ouabain resistant) cells and pheasant SSCs. The colony-forming
cells divided and proliferated stably to yield an established SSC line.
Pheasant SSCs showed strong reactivity for GDNF family receptor alpha1
(GFR\u3b11) marker. Finally, production of germline chimeras was
attempted by transferring pheasant SSCs into recipient embryos.
Although final embryo survival was 5.6% (20/354), the initial survival
rate was 88% (312/354). To measure the percent transfer of donor SSC to
gonads, the pheasant SSCs were labeled with PKH 26 fluorescent dye. We
observed 30% donor cells and 9.48% c-kit/CD117-positive cells in the
gonads of recipient chickens. Donor SSCs were thus stably engrafted in
the recipient gonads. Conclusions: This study showed that SSCs can be
used as a tool for the conservation of endangered birds and the
production of germline chimeras. Our findings yield insights into howwe
may use the pheasant spermatogonial stem cell line for efficient
production of interspecies germ line chimeras and ultimately, to the
restoration of endangered birds
- ā¦