625 research outputs found
Comparative Analysis of LASIK Flap Diameter and its Centration Using Two Different Femtosecond Lasers
The aim of this study was to compare the diameter, accuracy, variability, and centration with respect to the limbus of corneal flaps created by two femtosecond lasers, the VisuMax, and Wavelight FS200, for laser in situ keratomileusis (LASIK) and how these flaps affect visual outcomes. This is a retrospective chart review of flap morphology created during LASIK Surgery. Overall, 168 eyes underwent flap creation using the WaveLight FS200 laser, and on 189 eyes, the VisuMax laser was used. Of these total number, flap morphology was analyzed in a random sample of 158 eyes; 80 with the Visumax laser and 78 with the WaveLight FS200 laser. Intraoperative photos of the flaps taken by the Wavelight Allegretto EX500 were analyzed. Flap diameters and centration were measured using Adobe Acrobat Pro. All patients had visual acuity measurements including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent refraction (SE) and refractive astigmatism recorded three months postoperatively. Greater than 90% of patients in both groups achieved a UDVA of 20/20 postoperatively. The mean difference between targeted and achieved flap diameter was 0.50 +/- 0.15 mm in the VisuMax group and 0.35 +/- 0.15 millimeters (mm) in the FS200 group (P<0.01). The flap diameters of the VisuMax group were more precise with a variance of 0.024 mm compared to a variance of 0.038 mm in the FS200 group (P<0.05). VisuMax flaps were more nasally displaced (log(NA/TA) = -0.21 +/- 0.10 mm) compared to the FS200 flaps (log(NA/TA) = 0.03 +/- 0.10 mm), (P< 0.01). We concluded that both the VisuMax and FS200 created flaps larger than the preoperative targeted diameter. VisuMax created corneal flaps that had a greater degree of deviation from the targeted diameter when compared to flaps from the FS200. However, there was less variance in the VisuMax flap diameter. In addition, VisuMax flaps were more nasally displaced. There were no statistically significant differences in visual outcomes when comparing the two femtosecond lasers
Spatially Resolved Spitzer-IRS Spectral Maps of the Superwind in M82
We have mapped the superwind/halo region of the nearby starburst galaxy M82
in the mid-infrared with . The spectral regions covered include
the H, [NeII], [NeIII] emission lines and PAH features. We
estimate the total warm H mass and the kinetic energy of the outflowing
warm molecular gas to be between M and
erg. Using the ratios of the 6.2, 7.7 and 11.3
micron PAH features in the IRS spectra, we are able to estimate the average
size and ionization state of the small grains in the superwind. There are large
variations in the PAH flux ratios throughout the outflow. The 11.3/7.7 and the
6.2/7.7 PAH ratios both vary by more than a factor of five across the wind
region. The Northern part of the wind has a significant population of PAH's
with smaller 6.2/7.7 ratios than either the starburst disk or the Southern
wind, indicating that on average, PAH emitters are larger and more ionized. The
warm molecular gas to PAH flux ratios (H) are enhanced in the outflow
by factors of 10-100 as compared to the starburst disk. This enhancement in the
H ratio does not seem to follow the ionization of the atomic gas (as
measured with the [NeIII]/[NeII] line flux ratio) in the outflow. This suggests
that much of the warm H in the outflow is excited by shocks. The observed
H line intensities can be reproduced with low velocity shocks ( km
s) driven into moderately dense molecular gas (
cm) entrained in the outflow.Comment: 19 pages and 12 figures; accepted in MNRA
ATP Binding Cassette Sub-family Member 2 (ABCG2) and Xenobiotic Exposure During Early Mouse Embryonic Stem Cell Differentiation
Background: ATP binding cassette sub-family member 2 (ABCG2) is a welldefined efflux transporter found in a variety of tissues. The role of ABCG2 during early embryonic development, however, is not established. Previous work which compared data from the ToxCast screening program with that from in-house studies suggested an association exists between exposure to xenobiotics that regulate Abcg2 transcription and differentiation of mouse embryonic stem cells (mESC), a relationship potentially related to redox homeostasis.
Methods: mESC were grown for up to 9 days. Pharmacological inhibitors were used to assess transporter function with and without xenobiotic exposure. Proliferation and differentiation were evaluated using RedDot1 and quantiative reverse transcriptase-polymerase chain reaction, respectively. ABCG2 activity was assessed using a Pheophorbide a-based fluorescent assay. Protein expression was measured by capillary-based immunoassay.
Results: ABCG2 activity increased in differentiating mESC. Treatment with K0143, an inhibitor of ABCG2, had no effect on proliferation or differentiation. As expected, mitoxantrone and topotecan, two chemotherapeutics, displayed increased toxicity in the presence of K0143. Exposure to K0143 in combination with chemicals predicted by ToxCast to regulate ABCG2 expression did not alter xenobiotic-induced toxicity. Moreover, inhibition of ABCG2 did not shift the toxicity of either tert-Butyl hydroperoxide or paraquat, two oxidative stressors.
Conclusion: As previously reported, ABCG2 serves a protective role in mESC. The role of ABCG2 in regulating redox status, however, was unclear. The hypothesis that ABCG2 plays a fundamental role during mESC differentiation or that regulation of the receptor by xenobiotics may be associated with altered mESC differentiation could not be supported
Forum 2: The migrant climate: resilience, adaptation and the ontopolitics of mobility in the Anthropocene
While modernist or ‘top-down’, ‘command-and-control’ approaches to climate and migration worked at the surface or ontic level of the redistribution of entities in time and space, resilience approaches call for a different approach to mobility (for an extensive discussion of resilience as a distinctive governance regime see, for example, Grove, 2018; Chandler, 2014). These discourses construct mobilities that are more transformative, in fact, ones that question traditional liberal modernist notions of time and space and of entities with fixed essences. These mobilities do not concern moving entities in space but rethinking mobility in relation to space. Mobility then becomes more a matter of changing the understandings and practices relating to spaces and entities than of moving things from one place to another. Becoming ‘mobile’ thus would apply to the development of capabilities or ‘response-abilities’ (Haraway, 2016: 2) to sense, adapt, recompose, repurpose and reimagine problems and possibilities; taking responses to crises beyond the static and binary conceptions of mobility and space epitomised by The Clash lyrics in the epigraph
Special Care in Lichen Planus Patients Undergoing LASIK: A Review Article
Laser-Assisted in Situ Keratomileusis (LASIK) is a common surgery for the correction of refractive errors. The majority of patients who undergo this procedure often have excellent results. However, uncontrolled autoimmune disorders and dry eye have both been listed as contraindications to this surgery. Lichen planus (LP) is an autoimmune, inflammatory disorder that characteristically affects mucocutaneous membranes. The etiology is unknown, but it most commonly affects middle-aged adults and presents with bilateral, purple papules. Clinical presentation is used to diagnose the condition, and a punch biopsy is confirmatory. LP may present with multiple different symptoms depending on the type, with ocular manifestations being rare. Multiple viruses and autoimmune conditions have been associated with the disorder, and physicians should take care when gathering a full history of the patient. Exacerbation of symptoms may happen if mood disorders such as depression and anxiety are not well controlled. There are several additional factors physicians must carefully consider before recommending LASIK to patients with LP. These include lichenoid reactions, current medications, and past or present ocular lesions. LASIK may be carefully considered in patients with well-controlled LP in the absence of ocular manifestations. Patients with ocular LP are not candidates for LASIK
Stepwise bending of DNA by a single TATA-box Binding Protein
The TATA-box Binding Protein (TBP) is required by all three eukaryotic RNA
polymerases for the initiation of transcription from most promoters. TBP
recognizes, binds to, and bends promoter sequences called ``TATA-boxes'' in the
DNA. We present results from the study of individual Saccharomyces cerevisia
TBPs interacting with single DNA molecules containing a TATA-box. Using video
microscopy, we observed the Brownian motion of beads tethered by short
surface-bound DNA. When TBP binds to and bends the DNA, the conformation of the
DNA changes and the amplitude of Brownian motion of the tethered bead is
reduced compared to that of unbent DNA. We detected individual binding and
dissociation events and derived kinetic parameters for the process.
Dissociation was induced by increasing the salt concentration or by directly
pulling on the tethered bead using optical tweezers. In addition to the
well-defined free and bound classes of Brownian motion, we observed another two
classes of motion. These extra classes were identified with intermediate states
on a three-step, linear binding pathway. Biological implications of the
intermediate states are discussed.Comment: Accepted for publication in: Biophysical Journa
Comparative Analysis of LASIK Flap Diameter and its Centration Using Two Different Femtosecond Lasers
The aim of this study was to compare the diameter, accuracy, variability, and centration with respect to the limbus of corneal flaps created by two femtosecond lasers, the VisuMax, and Wavelight FS200, for laser in situ keratomileusis (LASIK) and how these flaps affect visual outcomes. This is a retrospective chart review of flap morphology created during LASIK Surgery. Overall, 168 eyes underwent flap creation using the WaveLight FS200 laser, and on 189 eyes, the VisuMax laser was used. Of these total number, flap morphology was analyzed in a random sample of 158 eyes; 80 with the Visumax laser and 78 with the WaveLight FS200 laser. Intraoperative photos of the flaps taken by the Wavelight Allegretto EX500 were analyzed. Flap diameters and centration were measured using Adobe Acrobat Pro. All patients had visual acuity measurements including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent refraction (SE) and refractive astigmatism recorded three months postoperatively. Greater than 90% of patients in both groups achieved a UDVA of 20/20 postoperatively. The mean difference between targeted and achieved flap diameter was 0.50 +/- 0.15 mm in the VisuMax group and 0.35 +/- 0.15 millimeters (mm) in the FS200 group (P<0.01). The flap diameters of the VisuMax group were more precise with a variance of 0.024 mm compared to a variance of 0.038 mm in the FS200 group (P<0.05). VisuMax flaps were more nasally displaced (log(NA/TA) = -0.21 +/- 0.10 mm) compared to the FS200 flaps (log(NA/TA) = 0.03 +/- 0.10 mm), (P< 0.01). We concluded that both the VisuMax and FS200 created flaps larger than the preoperative targeted diameter. VisuMax created corneal flaps that had a greater degree of deviation from the targeted diameter when compared to flaps from the FS200. However, there was less variance in the VisuMax flap diameter. In addition, VisuMax flaps were more nasally displaced. There were no statistically significant differences in visual outcomes when comparing the two femtosecond lasers
Discovery of a Nearby Low-Surface-Brightness Spiral Galaxy
During the course of a search for compact, isolated gas clouds moving with
anomalous velocities in or near our own Galaxy (Braun and Burton 1998 A&A, in
press), we have discovered, in the data of the Leiden/Dwingeloo survey
(Hartmann and Burton 1997, Atlas of Galactic Neutral Hydrogen, CUP) of Galactic
hydrogen, the HI signature of a large galaxy, moving at a recession velocity of
282 km/s, with respect to our Galaxy. Deep multicolor and spectroscopic optical
observations show the presence of star formation in scattered HII regions;
radio HI synthesis interferometry confirms that the galaxy is rich in HI and
has the rotation signature of a spiral galaxy; a submillimeter observation
failed to detect the CO molecule. The radio and optical evidence combined
suggest its classification as a low-surface-brightness spiral galaxy. It is
located in close spatial and kinematic proximity to the galaxy NGC 6946. The
newly-discovered galaxy, which we call Cepheus 1, is at a distance of about 6
Mpc. It is probably to be numbered amongst the nearest few LSB spirals.Comment: 13 page LaTeX, requires aastex, 4 GIF figures. Accepted for
publication in the AJ, January 199
H-alpha and Free-Free Emission from the WIM
Recent observations have found the ratio of H-alpha to free-free radio
continuum to be surprisingly high in the diffuse ionized ISM (the so-called
WIM), corresponding to an electron temperature of only ~3000K. Such low
temperatures were unexpected in gas that was presumed to be photoionized. We
consider a 3-component model for the observed diffuse emission, consisting of a
mix of (1) photoionized gas, (2) gas that is recombining and cooling, and (3)
cool H I gas. This model can successfully reproduce the observed intensities of
free-free continuum, H-alpha, and collisionally-excited lines such as NII 6583.
To reproduce the low observed value of free-free to H-alpha, the PAH abundance
in the photoionized regions must be lowered by a factor ~3, and ~20% of the
diffuse H-alpha must be reflected from dust grains, as suggested by Wood &
Reynolds (1999).Comment: 25 pages, 7 figures, 4 tables, single column, details of the
calculation and atomic physics added, accepted by Ap
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