Ice shelves around Antarctica can provide back stress for outlet glaciers and control ice sheet mass loss. They often contain narrow bands of thin ice termed ice shelf channels. Ice shelf channel ...morphology can be interpreted through surface depressions and exhibits junctions and deflections from flowlines. Using ice flow modeling and radar, we investigate ice shelf channels in the Roi Baudouin Ice Shelf. These are aligned obliquely to the prevailing easterly winds. In the shallow radar stratigraphy, syncline and anticline stacks occur beneath the upwind and downwind side, respectively. The structures are horizontally and vertically coherent, except near an ice shelf channel junction where patterns change structurally with depth. Deeper layers truncate near basal incisions. Using ice flow modeling, we show that the stratigraphy is ∼9 times more sensitive to atmospheric variability than to oceanic variability. This is due to the continual adjustment toward flotation. We propose that syncline‐anticline pairs in the shallow stratigraphy are caused by preferential snow deposition on the windward side and wind erosion at the downwind side. This drives downwind deflection of ice shelf channels of several meters per year. The depth variable structures indicate formation of an ice shelf channel junction by basal melting. We conclude that many ice shelf channels are seeded at the grounding line. Their morphology farther seaward is shaped on different length scales by ice dynamics, the ocean, and the atmosphere. These processes act on finer (subkilometer) scales than are captured by most ice, atmosphere, and ocean models, yet the dynamics of ice shelf channels may have broader implications for ice shelf stability.
Plain Language Summary
Ice flows from Antarctica's interior toward the coast. At the contact point between ice and ocean, the ice becomes afloat and forms fast‐flowing ice shelves. Snowfall continuously accumulates at the ice shelf surface, and at the ice shelf bottom the relatively warm ocean water can melt ice from below. Ice shelves sometimes exhibit a network of surface depressions resembling a river network. At the base, the depressions are accompanied by large incisions termed ice shelf channels. Using radar as a tool for echolocation, we investigate how the shape of this network is formed. We find that snow preferentially collects in the upwind side of the surface depressions. This makes ice shelf channels move to the downwind side. We also find that ice shelf channels can form junctions through localized ocean melting. This is important because it helps us to better understand how the Antarctic ice sheet interacts with the surrounding ocean.
Key Points
The radar stratigraphy in ice shelves is 9 times more sensitive to variability in snow deposition than to variability in basal melting
Some ice shelf channels at Roi Baudouin Ice Shelf deflect from flowlines; the radar stratigraphy reflects related processes
Variable snow deposition causes slow deflection, and basal melting can form ice shelf channel junctions far from the grounding line
Background
The incidence of colorectal cancer in adults younger than age 50 has increased with rates expected to continue to increase over the next decade. The objective of this study is to examine ...the survival benefit of surgical resection (primary and/or metastatic) versus palliative therapy in this patient population.
Methods
We identified 6708 young adults aged 18–45 years diagnosed with metastatic colorectal cancer (mCRC) from 2004 to 2015 from the SEER database. Overall survival (OS) was analyzed using Kaplan–Meier estimation, log rank test, and multivariate Cox proportional hazards model.
Results
Sixty‐three percent of patients in our study underwent primary tumor resection (PTR), with 40% undergoing PTR alone and 23% undergoing both resection of primary disease and metastasectomy. The median OS for patients who underwent both PTR and metastasectomy was 36 months, compared to 13 months for those who did not receive any surgical intervention. The multivariate analysis showed significant OS benefit of receiving both PTR and metastasectomy (HR 0.34, 95% CI: 0.31–0.37, p < 0.001) compared to palliative therapy. Undergoing PTR only and metastasectomy only were also associated with improved OS (HR 0.46, 95% CI: 0.43–0.49, p < 0.001 and HR 0.64, 95% CI: 0.55–0.76, p < 0.001, respectively).
Conclusion
This is the largest observational study to evaluate survival outcomes in young‐onset mCRC patients and the role of surgical intervention of the primary and/or metastatic site. Our study provides evidence of statistically significant increase in OS for young mCRC patients who undergo surgical intervention of the primary and/or metastatic site.
The incidence of colorectal cancer in adults younger than age 50 has increased with rates expected to continue to increase over the next decade. The objective of this study is to examine the survival benefit of surgical resection (primary and/or metastatic) vs palliative therapy in this patient population. Our study provides evidence of statistically significant increase in OS for young mCRC patients who undergo surgical intervention of the primary and/or metastatic site.
In this paper, effects of birefringence on radio waves obliquely propagating though polar ice sheets are examined to facilitate interpretations of bistatic and side-looking radar data. A formalism ...applicable for arbitrary radar configurations is developed to predict the returned power from within and beneath the ice sheets that have arbitrary alignments of ice crystals (ice fabrics). We applied this formalism to a range of ice fabrics found in ice cores and assessed the effects of birefringence in terms of ray-path configurations, ice fabrics, and radar frequency. Predicted frequency dependence of the bed return power replicates prominent features observed at Greenland NGRIP ice-core site. Results show that birefringence in ice of 1 km or more thickness with strong (weak) fabric can reduce the power returned from the bed 2 dB or more at frequencies higher than 200 MHz (20 MHz) as compared to isotropic ice. This suggests that quantitative interpretation of the power returned from the bed requires careful assessment of birefringence almost everywhere over the ice sheets. Application of this formalism also suggests a radar-frequency range usable for attenuation measurements, possible effects of fabric on synthetic aperture radar processing, and a feasibility of remote sensing of ice fabric.
We present results of a multi-methodological approach to characterize the flow regime of West Ragnhild Glacier, the widest glacier in Dronning Maud Land, Antarctica. A new airborne radar survey ...points to substantially thicker ice (>2000 m) than previously thought. With a discharge estimate of 13–14 Gt yr−1, West Ragnhild Glacier thus becomes of the three major outlet glaciers in Dronning Maud Land. Its bed topography is distinct between the upstream and downstream section: in the downstream section (<65 km upstream of the grounding line), the glacier overlies a wide and flat basin well below the sea level, while the upstream region is more mountainous. Spectral analysis of the bed topography also reveals this clear contrast and suggests that the downstream area is sediment covered. Furthermore, bed-returned power varies by 30 dB within 20 km near the bed flatness transition, suggesting that the water content at bed/ice interface increases over a short distance downstream, hence pointing to water-rich sediment. Ice flow speed observed in the downstream part of the glacier (~250 m yr−1) can only be explained through very low basal friction, leading to a substantial amount of basal sliding in the downstream 65 km of the glacier. All the above lines of evidence (sediment bed, wetness and basal motion) and the relatively flat grounding zone give the potential for West Ragnhild Glacier to be more sensitive to external forcing compared to other major outlet glaciers in this region, which are more stable due to their bed geometry (e.g. Shirase Glacier).
Hepatitis C virus (HCV) cirrhosis is the leading indication for liver transplantation in the United States, although nonalcoholic steatohepatitis (NASH) is on the rise. Increasingly effective HCV ...antivirals are available, but their association with diagnosis-specific liver transplantation rates and early graft survival is not known.
The Scientific Registry of Transplant Recipients database records were retrospectively stratified by HCV antiviral era: interferon (2003-2010), protease inhibitors (2011-2013), and direct-acting antivirals (2014 to present). Kaplan-Meier, χ
, and multivariable Cox proportional hazards regression models evaluated the effects of antiviral era and etiology of liver disease on transplantation rates and graft survival over 3 years.
Liver transplants for HCV decreased (35.3% to 23.6%), whereas those for NASH and alcoholic liver disease increased (5.8% to 16.5% and 15.6% to 24.0%) with each advancing era (all
< 0.05). Early graft survival improved with each advancing era for HCV but not for hepatitis B virus, NASH, or alcoholic liver disease (multivariable model era by diagnosis interaction
< 0.001). Era-specific multivariable models demonstrated that the risk of early graft loss for NASH was 22% lower than for HCV in the interferon era (hazard ratio, 0.78; 95% confidence interval, 0.64-0.96;
= 0.02) but risks associated with these diagnoses did not differ significantly in the protease inhibitor (
= 0.06) or direct-acting antiviral eras (
= 0.08).
Increasing effectiveness of HCV antivirals corresponds with decreased rates of liver transplantation for HCV and improved early graft survival. As the rates of liver transplant for NASH continue to increase, focus will be needed on the prevention and effective therapies for this disease.
Aim
To investigate the effects of tenascin‐C (TN‐C) on cultured rat dental pulp cells in relation to the expression of Notch signalling.
Methodology
Subcultured dental pulp cells derived from rat ...incisors were seeded both in wells and on plastic coverslips coated with various concentrations of recombinant human TN‐C. Expression of bone‐related mRNA was then analysed by RT‐PCR and observed by immunohistochemical staining. Encoding of Notch1 and Notch2 (markers of initial differentiation of odontoblast‐like cells), alkaline phosphatase (ALP), osteopontin (OPN) and osteocalcin (OCN) (markers of mineralization) was investigated. Non‐TN‐C‐coated wells were used as controls. Primary antibodies to Notch1, ALP and OCN were used for immunofluorescence staining, and ALP activity was evaluated. Data were compared using Student's t‐test.
Results
Cell proliferation rate in the experimental groups was significantly higher (P < 0.05) than that in the control group at 72 h. Expression of Notch1, Notch2, ALP, OPN and OCN mRNAs was significantly higher (P < 0.05) in the experimental group than that in the control group. Strongly positive staining for Notch1, ALP and OCN was observed in the experimental group. ALP activity was significantly higher (P < 0.01) in the experimental group than in the control group at 24 h.
Conclusion
TN‐C promoted differentiation of rat dental pulp cells by the activation of Notch.
ABSTRACT In order to investigate the origin of quasars, we estimate the bias factor for low-luminosity quasars at high redshift for the first time. In this study, we use the two-point angular ...cross-correlation function (CCF) for both low-luminosity quasars at and Lyman-break galaxies (LBGs). Our sample consists of both 25 low-luminosity quasars (16 objects are spectroscopically confirmed low-luminosity quasars) in the redshift range and 835 color-selected LBGs with at z ∼ 4 in the COSMOS field. We have performed our analysis for the following two quasar samples: (1) the spectroscopic sample (the 16 quasars confirmed by spectroscopy), and (2) the total sample (the 25 quasars including 9 quasars with photometric redshifts). The bias factor for low-luminosity quasars at z ∼ 4 is derived by utilizing the quasar-LBG CCF and the LBG auto-correlation function. We then obtain the 86% upper limits of the bias factors for low-luminosity quasars, which are 5.63 and 10.50 for the total and the spectroscopic samples, respectively. These bias factors correspond to the typical dark matter halo masses, log 12.7 and 13.5, respectively. This result is not inconsistent with the predicted bias for quasars that is estimated by the major merger models.
We present the result of our low-luminosity quasar survey in the redshift range of 4.5 <, ~ z <, ~ 5.5 in the COSMOS field. Using the COSMOS photometric catalog, we selected 15 quasar candidates with ...22 < i' < 24 at z ~ 5 that are ~3 mag fainter than the Sloan Digital Sky Survey quasars in the same redshift range. We obtained optical spectra for 14 of the 15 candidates using FOCAS on the Subaru Telescope and did not identify any low-luminosity type-1 quasars at z ~ 5, while a low-luminosity type-2 quasar at z ~ 5.07 was discovered. In order to constrain the faint end of the quasar luminosity function at z ~ 5, we calculated the 1sigma confidence upper limits of the space density of type-1 quasars. As a result, the 1sigma confidence upper limits on the quasar space density are Phi < 1.33 x 10 super(-7) Mpc super(-3) mag super(-1) for -24.52 < M sub(1450) < -23.52 and Phi < 2.88 x 10 super(-7) Mpc super(-3) mag super(-1) for -23.52 < M sub(1450) < -22.52. The inferred 1sigma confidence upper limits of the space density are then used to provide constraints on the faint-end slope and the break absolute magnitude of the quasar luminosity function at z ~ 5. We find that the quasar space density decreases gradually as a function of redshift at low luminosity (M sub(1450) ~ -23), being similar to the trend found for quasars with high luminosity (M sub(1450) < -26). This result is consistent with the so-called downsizing evolution of quasars seen at lower redshifts.
In order to better understand the spatial distribution of subglacial environments, ground-based radar profiling data were analyzed for a total distance of ~ 3300 km across Dronning Maud Land, East ...Antarctica. The relationship between geometrically corrected bed returned power PcbeddB in decibels and ice thickness H was examined. When H is smaller than a~critical value that varies according to location, PcbeddB tends to decrease relatively smoothly with increasing H, which is explicable primarily by the cumulative effect of dielectric attenuation within the ice. However, at locations where H is larger than the critical H values, anomalous increases and fluctuations in PcbeddB were observed, regardless of the choice of radar frequency or radar-pulse width. In addition, the amplitude of the fluctuations often range 10 ~ 20 dB. We argue that the anomalous increases are caused by higher bed reflectivity associated with the existence of subglacial water. We used these features to delineate frozen and temperate beds. Approximately two-thirds of the investigated area was found to have a temperate bed. The beds of the inland part of the ice sheet tend to be temperate, with the exception of subglacial high mountains. In contrast, the beds of coastal areas tend to be frozen, with the exception of fast-flowing ice on the subglacial lowland or troughs. We argue that this new analytical method can be applied to other regions.
BACKGROUND:Intrahepatic cholangiocarcinoma (iCCA) is a contraindication to liver transplantation (LT) in most centers worldwide. Therefore, only a few such cases have been performed in each ...individual center and the need for a systematic review and meta-analysis to cumulatively pool these results is apparent.
METHODS:A systematic literature review was conducted using the MEDLINE and Cochrane Library databases according to the PRISMA statement (end-of-search dateMay 29, 2020). Meta-analyses of proportions were conducted to pool the overall survival (OS), recurrence-free survival (RFS), and overall recurrence rates using the random-effects model. Meta-regression was utilized to examine cirrhosis and incidental diagnosis as confounders on OS and RFS.
RESULTS:Eighteen studies comprising 355 patients and a registry study of 385 patients were included. The pooled 1-, 3-, and 5-year OS rates were 75% (95%CI64%-84%), 56% (95%CI46%-67%), and 42% (95%CI29%-55%), respectively. The pooled 1-, 3-, and 5-year RFS rates were 70% (95%CI63%-75%), 49% (95%CI41%-57%), and 38% (95%CI27%-50%), respectively. Cirrhosis was positively associated with RFS, while incidental diagnosis was not. Neither cirrhosis nor incidental diagnosis were associated with OS. The pooled overall recurrence rate was 43% (95%CI33%-53%) over a mean follow-up of 40.6±37.7 months. Patients with very early (single ≤ 2 cm) iCCA exhibited superior pooled 5-year RFS (67%, 95%CI47%-86%) versus advanced iCCA (34%, 95%CI23%-46%).
CONCLUSIONS:Cirrhotics with very early iCCA or carefully selected patients with advanced iCCA after neoadjuvant therapy may benefit from LT under research protocols.
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