2,852 research outputs found
Marine ice-sheet profiles and stability under Coulomb basal conditions
The behavior of marine-terminating ice sheets, such as the West Antarctic ice sheet, is of
interest due to the possibility of rapid grounding-line retreat and consequent catastrophic loss of ice.
Critical to modeling this behavior is a choice of basal rheology, where the most popular approach is to
relate the ice-sheet velocity to a power-law function of basal stress. Recent experiments, however,
suggest that near-grounding line tills exhibit Coulomb friction behavior. Here we address how Coulomb
conditions modify ice-sheet profiles and stability criteria. The basal rheology necessarily transitions to
Coulomb friction near the grounding line, due to low effective stresses, leading to changes in ice-sheet
properties within a narrow boundary layer. Ice-sheet profiles ‘taper off’ towards a flatter upper surface,
compared with the power-law case, and basal stresses vanish at the grounding line, consistent with
observations. In the Coulomb case, the grounding-line ice flux also depends more strongly on flotation
ice thickness, which implies that ice sheets are more sensitive to climate perturbations. Furthermore,
with Coulomb friction, the ice sheet grounds stably in shallower water than with a power-law rheology.
This implies that smaller perturbations are required to push the grounding line into regions of negative
bed slope, where it would become unstable. These results have important implications for ice-sheet
stability in a warming climate
Proximal phalanx shaft fracture with entrapment in the transverse retinacular ligament: a case report
We report the interesting case of a 33 years old male who underwent operative intervention for a left oblique proximal phalanx shaft fracture of the third finger which penetrated the transverse retinacular ligament (TRL). This patient required operative intervention due to entrapment of the bony fragment in the TRL which acted as a noose with traction on the fractured segment. The fracture was irreducible through a closed maneuver. The use of a dorsal approach allowed visualization of the fracture site and implementation of screws for fixation was deemed adequate secondary to the patient’s bone quality. He was placed in a volar splint at the conclusion of the case to allow for immobilization and protection of the repair. At follow-up, the patient’s radiographic images appeared appropriate and was progressing as expected. We report lessons learned from this case and describe a previously unreported fracture pattern and a possible method of reduction and fixation through a surgical approach in this report
Salter-Harris type II fracture of the middle phalanx with concomitant central slip injury in an 11 year old: a case report
An 11-year-old male sustained an irreducible, completely displaced epiphyseal fracture of the proximal interphalangeal joint (PIPJ) of the middle finger with an associated central slip injury. Central slip injuries occurring in conjunction with Salter-Harris type II middle phalanx fracture are rare entities, with no previously documented case. Our patient underwent open reduction, internal fixation through crossed-pins to achieve reduction and fixation. He was then splinted in extension for six weeks to allow healing of the central slip injury. At 1-year follow-up, the patient had full range-of-motion with no clinical indication of physeal disruption or growth arrest of the repaired digit. We demonstrate a case in which ephiphyseal fractures of the proximal interphalangeal joint with a concomitant central slip injury can safely be treated with open reduction internal fixation combined with a period of immobilization. We characterize a surgical method of reduction and fixation with splinted immobilization and describe lessons learned from this previously unreported case
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Spatial calibration of an optical see-through head-mounted display
We present here a method for calibrating an optical see-through Head Mounted Display (HMD) using techniques usually applied to camera calibration (photogrammetry). Using a camera placed inside the HMD to take pictures simultaneously of a tracked object and features in the HMD display, we could exploit established camera calibration techniques to recover both the intrinsic and extrinsic properties of the~HMD (width, height, focal length, optic centre and principal ray of the display). Our method gives low re-projection errors and, unlike existing methods, involves no time-consuming and error-prone human measurements, nor any prior estimates about the HMD geometry
Constrained MSSM favoring new territories: The impact of new LHC limits and a 125 GeV Higgs boson
We present an updated and extended global analysis of the Constrained MSSM
(CMSSM) taking into account new limits on supersymmetry from ~5/fb data sets at
the LHC. In particular, in the case of the razor limit obtained by the CMS
Collaboration we simulate detector efficiency for the experimental analysis and
derive an approximate but accurate likelihood function. We discuss the impact
on the global fit of a possible Higgs boson with mass near 125 GeV, as implied
by recent data, and of a new improved limit on BR(B_s->\mu\mu). We identify
high posterior probability regions of the CMSSM parameters as the
stau-coannihilation and the A-funnel region, with the importance of the latter
now being much larger due to the combined effect of the above three LHC results
and of dark matter relic density. We also find that the focus point region is
now disfavored. Ensuing implications for superpartner masses favor even larger
values than before, and even lower ranges for dark matter spin-independent
cross section, \sigma^{SI}_p<10^{-9} pb. We also find that relatively minor
variations in applying experimental constraints can induce a large shift in the
location of the best-fit point. This puts into question the robustness of
applying the usual chisquare approach to the CMSSM. We discuss the
goodness-of-fit and find that, while it is difficult to calculate a p-value,
the g-2 constraint makes, nevertheless, the overall fit of the CMSSM poor. We
consider a scan without this constraint, and we allow \mu\ to be either
positive or negative. We find that the global fit improves enormously for both
signs of \mu, with a slight preference for \mu<0 caused by a better fit to
BR(b->s\gamma) and BR(B_s->\mu\mu).Comment: 24 pages, 17 figures. PRD-approved version; Higgs bounds case removed
as obsolete in light of the Higgs discover
Submillimetre observations of WISE-selected high-redshift, luminous, dusty galaxies
We present SCUBA-2 850um submillimetre (submm) observations of the fields of
10 dusty, luminous galaxies at z ~ 1.7 - 4.6, detected at 12um and/or 22um by
the WISE all-sky survey, but faint or undetected at 3.4um and 4.6um; dubbed
hot, dust-obscured galaxies (Hot DOGs). The six detected targets all have total
infrared luminosities greater than 10^13 L_sun, with one greater than 10^14
L_sun. Their spectral energy distributions (SEDs) are very blue from
mid-infrared to submm wavelengths and not well fitted by standard AGN SED
templates, without adding extra dust extinction to fit the WISE 3.4um and 4.6um
data. The SCUBA-2 850um observations confirm that the Hot DOGs have less cold
and/or more warm dust emission than standard AGN templates, and limit an
underlying extended spiral or ULIRG-type galaxy to contribute less than about
2% or 55% of the typical total Hot DOG IR luminosity, respectively. The two
most distant and luminous targets have similar observed submm to mid-infrared
ratios to the rest, and thus appear to have even hotter SEDs. The number of
serendipitous submm galaxies (SMGs) detected in the 1.5-arcmin-radius SCUBA-2
850um maps indicates there is a significant over-density of serendipitous
sources around Hot DOGs. These submm observations confirm that the
WISE-selected ultra-luminous galaxies have very blue mid-infrared to submm
SEDs, suggesting that they contain very powerful AGN, and are apparently
located in unusual arcmin-scale overdensities of very luminous dusty galaxies.Comment: 12 pages, 8 figures, 3 tables, accepted for publication in MNRA
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