Context.
The formation of planets is expected to be enhanced around snowlines in protoplanetary disks, in particular around the water snowline. Moreover, freeze-out of abundant volatile species in ...disks alters the chemical composition of the planet-forming material. However, the close proximity of the water snowline to the host star combined with the difficulty of observing water from Earth makes a direct detection of the water snowline in protoplanetary disks challenging. HCO
+
is a promising alternative tracer of the water snowline. The destruction of HCO
+
is dominated by gas-phase water, leading to an enhancement in the HCO
+
abundance once water is frozen out.
Aims.
Following earlier observed correlations between water and H
13
CO
+
emission in a protostellar envelope, the aim of this research is to investigate the validity of HCO
+
and the optically thin isotopologue H
13
CO
+
as tracers of the water snowline in protoplanetary disks and the required sensitivity and resolution to observationally confirm this.
Methods.
A typical Herbig Ae disk structure is assumed, and its temperature structure is modelled with the thermochemical code
DALI
. Two small chemical networks are then used and compared to predict the HCO
+
abundance in the disk: one without water and one including water. Subsequently, the corresponding emission profiles are modelled for the
J
= 2−1 transition of H
13
CO
+
and HCO
+
, which provides the best balance between brightness and the optical depth effects of the continuum emission and is less affected by blending with complex molecules. Models are then compared with archival ALMA data.
Results.
The HCO
+
abundance jumps by two orders of magnitude over a radial range of 2 AU outside the water snowline, which in our model is located at 4.5 AU. We find that the emission of H
13
CO
+
and HCO
+
is ring-shaped due to three effects: destruction of HCO
+
by gas-phase water, continuum optical depth, and molecular excitation effects. Comparing the radial emission profiles for
J
= 2−1 convolved with a 0′′.05 beam reveals that the presence of gas-phase water causes an additional drop of only ~13 and 24% in the centre of the disk for H
13
CO
+
and HCO
+
, respectively. For the much more luminous outbursting source V883 Ori, our models predict that the effects of dust and molecular excitation do not limit HCO
+
as a snowline tracer if the snowline is located at radii larger than ~40 AU. Our analysis of recent archival ALMA band 6 observations of the
J
= 3−2 transition of HCO
+
is consistent with the water snowline being located around 100 AU, further out than was previously estimated from an intensity break in the continuum emission.
Conclusions.
The HCO
+
abundance drops steeply around the water snowline, when water desorbs in the inner disk, but continuum optical depth and molecular excitation effects conceal the drop in HCO
+
emission due to the water snowline. Therefore, locating the water snowline with HCO
+
observations in disks around Herbig Ae stars is very difficult, but it is possible for disks around outbursting stars such as V883 Ori, where the snowline has moved outwards.
Most patients with advanced pancreas cancer experience pain and must limit their daily activities because of tumor-related symptoms. To date, no treatment has had a significant impact on the disease. ...In early studies with gemcitabine, patients with pancreas cancer experienced an improvement in disease-related symptoms. Based on those findings, a definitive trial was performed to assess the effectiveness of gemcitabine in patients with newly diagnosed advanced pancreas cancer.
One hundred twenty-six patients with advanced symptomatic pancreas cancer completed a lead-in period to characterize and stabilize pain and were randomized to receive either gemcitabine 1,000 mg/m2 weekly x 7 followed by 1 week of rest, then weekly x 3 every 4 weeks thereafter (63 patients), or to fluorouracil (5-FU) 600 mg/m2 once weekly (63 patients). The primary efficacy measure was clinical benefit response, which was a composite of measurements of pain (analgesic consumption and pain intensity), Karnofsky performance status, and weight. Clinical benefit required a sustained (> or = 4 weeks) improvement in at least one parameter without worsening in any others. Other measures of efficacy included response rate, time to progressive disease, and survival.
Clinical benefit response was experienced by 23.8% of gemcitabine-treated patients compared with 4.8% of 5-FU-treated patients (P = .0022). The median survival durations were 5.65 and 4.41 months for gemcitabine-treated and 5-FU-treated patients, respectively (P = .0025). The survival rate at 12 months was 18% for gemcitabine patients and 2% for 5-FU patients. Treatment was well tolerated.
This study demonstrates that gemcitabine is more effective than 5-FU in alleviation of some disease-related symptoms in patients with advanced, symptomatic pancreas cancer. Gemcitabine also confers a modest survival advantage over treatment with 5-FU.
The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This ...Letter reports results from LUX-ZEPLIN's first search for weakly interacting massive particles (WIMPs) with an exposure of 60 live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9 GeV/c^{2}. The most stringent limit is set for spin-independent scattering at 36 GeV/c^{2}, rejecting cross sections above 9.2×10^{-48} cm at the 90% confidence level.
The recently developed Social Exclusion Index for Health Surveys (SEI-HS) revealed particularly strong social exclusion in non-Western immigrant groups compared to the native Dutch population. To ...qualify such results, cross-cultural validation of the SEI-HS in non-Western immigrant groups is called for.
A sequential explanatory mixed methods design was used, employing quantitative data from the Netherlands Public Health Monitor along with qualitative interviews. Data from 1,803 adults aged 19 years or older of Surinamese, 1,009 of Moroccan and 1,164 of Turkish background and 19,318 native Dutch living in the four largest cities in the Netherlands were used to test the factorial structure of the SEI-HS and differential item functioning across immigrant groups. Additionally, 52 respondents with a high score on the SEI-HS and from different background were interviewed on the item content of the SEI-HS and subjective feelings of exclusion. For each SEI-HS item the semantic, conceptual and contextual connotations were coded and compared between the immigrant groups and native Dutch.
High levels of social exclusion were found in 20.0% of the urban population of Surinamese origin, 20.9% of Moroccan, 28.7% of Turkish and 4.2% of native Dutch origin. The 4-factor structure of the SEI-HS was confirmed in all three immigrant groups. None of the items demonstrated substantial differential item functioning in relation to immigration background. The interviews uncovered some methodological shortcomings, but these did not substantially impact the observed excess of social exclusion in immigrant groups.
The present study provides evidence in support of the validity of the SEI-HS in adults of Surinamese, Moroccan and Turkish background and confirms the major social exclusion of these immigrant groups in the main cities in the Netherlands. Policy measures to enhance social inclusion and reduce exclusion are urgently needed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Context. Snowlines in protoplanetary disks play an important role in planet formation and composition. Since the CO snowline is difficult to observe directly with CO emission, its location has been ...inferred in several disks from spatially resolved ALMA observations of DCO+ and N2H+. Aims. N2H+ is considered to be a good tracer of the CO snowline based on astrochemical considerations predicting an anti-correlation between N2H+ and gas-phase CO. In this work, the robustness of N2H+ as a tracer of the CO snowline is investigated. Methods. A simple chemical network was used in combination with the radiative transfer code LIME to model the N2H+ distribution and corresponding emission in the disk around TW Hya. The assumed CO and N2 abundances, corresponding binding energies, cosmic ray ionization rate, and degree of large-grain settling were varied to determine the effects on the N2H+ emission and its relation to the CO snowline. Results. For the adopted physical structure of the TW Hya disk and molecular binding energies for pure ices, the balance between freeze-out and thermal desorption predicts a CO snowline at 19 AU, corresponding to a CO midplane freeze-out temperature of 20 K. The N2H+ column density, however, peaks 5–30 AU outside the snowline for all conditions tested. In addition to the expected N2H+ layer just below the CO snow surface, models with an N2/CO ratio ≳0.2 predict an N2H+ layer higher up in the disk due to a slightly lower photodissociation rate for N2 as compared to CO. The influence of this N2H+ surface layer on the position of the emission peak depends on the total CO and N2 abundances and the disk physical structure, but the emission peak generally does not trace the column density peak. A model with a total (gas plus ice) CO abundance of 3 × 10-6 with respect to H2 fits the position of the emission peak previously observed for the TW Hya disk. Conclusions. The relationship between N2H+ and the CO snowline is more complicated than generally assumed: for the investigated parameters, the N2H+ column density peaks at least 5 AU outside the CO snowline. Moreover, the N2H+ emission can peak much further out, as far as ~50 AU beyond the snowline. Hence, chemical modeling, as performed here, is necessary to derive a CO snowline location from N2H+ observations.
Advances in satellite sensors have provided new datasets for monitoring air quality at urban and regional scales. Qualitative true color images and quantitative aerosol optical depth data from the ...Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the Terra satellite were compared with ground-based particulate matter data from US Environmental Protection Agency (EPA) monitoring networks covering the period from 1 April to 30 September, 2002. Using both imagery and statistical analysis, satellite data enabled the determination of the regional sources of air pollution events, the general type of pollutant (smoke, haze, dust), the intensity of the events, and their motion. Very high and very low aerosol optical depths were found to be eliminated by the algorithm used to calculate the MODIS aerosol optical depth data. Correlations of MODIS aerosol optical depth with ground-based particulate matter were better in the eastern and Midwest portion of the United States (east of 100°W). Data were patchy and had poorer correlations in the western US, although the correlation was dependent on location. This variability is likely due to a combination of the differences between ground-based and column average datasets, regression artifacts, variability of terrain, and MODIS cloud mask and aerosol optical depth algorithms. Preliminary analysis of the algorithms indicated that aerosol optical depth measurements calculated from the sulfate-rich aerosol model may be more useful in predicting ground-based particulate matter levels, but further analysis would be required to verify the effect of the model on correlations. Overall, the use of satellite sensor data such as from MODIS has significant potential to enhance air quality monitoring over synoptic and regional scales.
Nitrogen oxides (NOx) have fallen steadily across the US over the last 15 years. At the same time, NOx concentrations decrease on weekends relative to weekdays, largely without co-occurring changes ...in other gas-phase emissions, due to patterns of diesel truck activities. These trends taken together provide two independent constraints on the role of NOx in the nonlinear chemistry of atmospheric oxidation. In this context, we interpret interannual trends in wintertime ammonium nitrate (NH4NO3) in the San Joaquin Valley of California, a location with the worst aerosol pollution in the US and where a large portion of aerosol mass is NH4NO3. Here, we show that NOx reductions have simultaneously decreased nighttime and increased daytime NH4NO3 production over the last decade. We find a substantial decrease in NH4NO3 since 2000 and conclude that this decrease is due to reduced nitrate radical-initiated production at night in residual layers that are decoupled from fresh emissions at the surface. Further reductions in NOx are imminent in California, and nationwide, and we make a quantitative prediction of the response of NH4NO3. We show that the combination of rapid chemical production and efficient NH4NO3 loss via deposition of gas-phase nitric acid implies that high aerosol days in cities in the San Joaquin Valley air basin are responsive to local changes in NOx within those individual cities. Our calculations indicate that large decreases in NOx in the future will not only lower wintertime NH4NO3 concentrations but also cause a transition in the dominant NH4NO3 source from nighttime to daytime chemistry.
The classical Richtmyer-Meshkov instability (RMI) is a hydrodynamic instability characterizing the evolution of an interface following shock loading. In contrast to other hydrodynamic instabilities ...such as Rayleigh-Taylor, it is known for being unconditionally unstable: regardless of the direction of shock passage, any deviations from a flat interface will be amplified. In this article, we show that for negative Atwood numbers, there exist special sequences of shocks which result in a nearly perfectly suppressed instability growth. We demonstrate this principle computationally and experimentally with stepped fliers and phase transition materials. A fascinating immediate corollary is that in specific instances, a phase-transitioning material may self-suppress RMI.
This study evaluates the efficacy of capecitabine using data from a large, well-characterised population of patients with metastatic colorectal cancer (mCRC) treated in two identically designed phase ...III studies. A total of 1207 patients with previously untreated mCRC were randomised to either oral capecitabine (1250 mg m(-2) twice daily, days 1-14 every 21 days; n=603) or intravenous (i.v.) bolus 5-fluorouracil/leucovorin (5-FU/LV; Mayo Clinic regimen; n=604). Capecitabine demonstrated a statistically significant superior response rate compared with 5-FU/LV (26 vs 17%; P<0.0002). Subgroup analysis demonstrated that capecitabine consistently resulted in superior response rates (P<0.05), even in patient subgroups with poor prognostic indicators. The median time to response and duration of response were similar and time to progression (TTP) was equivalent in the two arms (hazard ratio (HR) 0.997, 95% confidence interval (CI) 0.885-1.123, P=0.95; median 4.6 vs 4.7 months with capecitabine and 5-FU/LV, respectively). Multivariate Cox regression analysis identified younger age, liver metastases, multiple metastases and poor Karnofsky Performance Status as independent prognostic indicators for poor TTP. Overall survival was equivalent in the two arms (HR 0.95, 95% CI 0.84-1.06, P=0.48; median 12.9 vs 12.8 months, respectively). Capecitabine results in superior response rate, equivalent TTP and overall survival, an improved safety profile and improved convenience compared with i.v. 5-FU/LV as first-line treatment for MCRC. For patients in whom fluoropyrimidine monotherapy is indicated, capecitabine should be strongly considered. Following encouraging results from phase I and II trials, randomised trials are evaluating capecitabine in combination with irinotecan, oxaliplatin and radiotherapy. Capecitabine is a suitable replacement for i.v. 5-FU as the backbone of colorectal cancer therapy.
A method was developed for registering three-dimensional knee implant models to single plane X-ray fluoroscopy images. We use a direct image-to-image similarity measure, taking advantage of the speed ...of modern computer graphics workstations to quickly render simulated (predicted) images. As a result, the method does not require an accurate segmentation of the implant silhouette in the image (which can be prone to errors). A robust optimization algorithm (simulated annealing) is used that can escape local minima and find the global minimum (true solution). Although we focus on the analysis of total knee arthroplasty (TKA) in this paper, the method can be (and has been) applied to other implanted joints, including, but not limited to, hips, ankles, and temporomandibular joints. Convergence tests on an in vivo image show that the registration method can reliably find poses that are very close to the optimal (i.e., within 0.4/spl deg/ and 0.1 mm), even from starting poses with large initial errors. However, the precision of translation measurement in the Z (out-of-plane) direction is not as good. We also show that the method is robust with respect to image noise and occlusions. However, a small amount of user supervision and intervention is necessary to detect cases when the optimization algorithm falls into a local minimum. Intervention is required less than 5% of the time when the initial starting pose is reasonably close to the correct answer, but up to 50% of the time when the initial starting pose is far away. Finally, extensive evaluations were performed on cadaver images to determine accuracy of relative pose measurement. Comparing against data derived from an optical sensor as a "gold standard," the overall root-mean-square error of the registration method was approximately 1.5/spl deg/ and 0.65 mm (although Z translation error was higher). However, uncertainty in the optical sensor data may account for a large part of the observed error.
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