bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling and mapping permafrost at high spatial resolution in Wapusk National Park, Hudson Bay Lowlands1This article is one of a series of papers published in this CJES Special Issue on the theme ofFundamental and applied research on permafrost in Canada.2Earth Science Sector Contribution 20110058.
Authors: Zhang Yu , Li Junhua , Wang Xiping , Chen Wenjun , Sladen Wendy , Dyke Larry , Dredge Lynda , Poitevin Jean , McLennan Donald , Stewart Heather , Kowalchuk Sheldon , Wu Wanli , Kershaw G. Peter , Brook Ryan K. 
Published: July 2012

Most spatial modelling of permafrost distribution and dynamics has been conducted at half-degree latitude/longitude or coarser resolution. Such coarse results are difficult to use for land managers and ecologists. Here we mapped permafrost distribution at 30 m × 30 m resolution for a region in the northwest Hudson Bay Lowlands using a process-based model. Land-cover types and leaf area indices were derived from Landsat imagery; peat thickness was estimated from elevation based on field measurements; and climate data were interpolated from station observations. The modelled active-layer thickness and permafrost extent compared well with field observations, demonstrating that modelling and mapping permafrost at a high spatial resolution is practical for terrains such as these lowlands. The map portrayed large variations in active-layer thickness, with land-cover type and peat thickness being the most important controlling variables. The modelled active-layer thickness on average increased by 37% during the twentieth century due to increases in air temperature and precipitation, and permafrost disappeared in some southern areas. The spatial scale of the permafrost maps developed in this study is close to that of the ecosystem and landscape features; therefore, the results are useful for land management and ecosystem assessment.
The Power of Simple Tabulation Hashing
Authors: Pǎtraşcu Mihai , Thorup Mikkel 
Published: July 2012

Randomized algorithms are often enjoyed for their simplicity, but the hash functions used to yield the desired theoretical guarantees are often neither simple nor practical. Here we show that the simplest possible tabulation hashing provides unexpectedly strong guarantees.

The scheme itself dates back to Zobrist in 1970 who used it for game playing programs. Keys are viewed as consisting of
c
characters. We initialize
c
tables
H
1, ...,
H
c
mapping characters to random hash codes. A key
x
= (
x
1
, ...,
x
c
) is hashed to
H
1[
x
1] ⊕ ⋯ ⊕
H
c
[
x
c
], where ⊕ denotes bit-wise exclusive-or.

While this scheme is not even 4-independent, we show that it provides many of the guarantees that are normally obtained via higher independence, for example, Chernoff-type concentration, min-wise hashing for estimating set intersection, and cuckoo hashing.
How to approximate optimal auctions
Authors: Haghpanah Nima , Immorlica Nicole , Mirrokni Vahab , Munagala Kamesh 
Published: July 2012

Bayesian auction design investigates how to sell scarce resources to agents with private values drawn according to known distributions. A natural objective in this setting is revenue maximization. The seminal work of Roger Myerson presents a recipe for designing revenue-maximizing auctions in single-parameter settings. Myerson defines a function that maps each agent's value to a new number called the
virtual value
. The optimal auction then chooses the solution with maximum virtual surplus subject to the feasibility constraints. Often this underlying optimization problem is NP-hard and is complicated by the fact that virtual values may be negative. Prior work approximates the optimal auction by approximating this optimization problem. Such a solution can be interpreted as approximating the optimal auction point-wise, i.e., for each realization of values the revenue of the derived auction is close to that of the Myerson auction. In this letter, we suggest a different approach:

Approximate the maximum virtual surplus on average with respect to the induced virtual value distributions
.

Our approach has the advantage that sometimes the point-wise optimization problem is not approximable to within any reasonable factor. However, by leveraging the fact that any distribution of virtual values has non-negative expectation, it is sometimes possible to get good average-case approximations. Furthermore, the optimal auction is itself an average-case guarantee: it maximizes the revenue on average with respect to the distributions, but it may lose substantial revenue on certain value profiles. Thus our average-case guarantee is without loss of generality.
We showcase our approach using the problem of selling goods with positive network externalities. For this problem, the underlying optimization problem is inapproximable, yet with our approach we are able to prove that a natural greedy auction is a constant-factor approximation.
Baseline Tumor Oxygen Saturation Correlates with a Pathologic Complete Response in Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy
Authors: Ueda Shigeto , Roblyer Darren , Cerussi Albert , Durkin Amanda , Leproux Anais , Santoro Ylenia , Xu Shanshan , O'Sullivan Thomas D. , Hsiang David , Mehta Rita , Butler John , Tromberg Bruce J. 
Published: July 2012

AbstractTissue hemoglobin oxygen saturation (i.e., oxygenation) is a functional imaging endpoint that can reveal variations in tissue hypoxia, which may be predictive of pathologic response in subjects undergoing neoadjuvant chemotherapy. In this study, we used diffuse optical spectroscopic imaging (DOSI) to measure concentrations of oxyhemoglobin (ctO2Hb), deoxy-hemoglobin (ctHHb), total Hb (ctTHb = ctO2Hb + ctHHb), and oxygen saturation (stO2 = ctO2Hb/ctTHb) in tumor and contralateral normal tissue from 41 patients with locally advanced primary breast cancer. Measurements were acquired before the start of neoadjuvant chemotherapy. Optically derived parameters were analyzed separately and in combination with clinical biomarkers to evaluate correlations with pathologic response. Discriminant analysis was conducted to determine the ability of optical and clinical biomarkers to classify subjects into response groups. Twelve (28.6%) of 42 tumors achieved pathologic complete response (pCR) and 30 (71.4%) were non-pCR. Tumor measurements in pCR subjects had higher stO2 levels (median 77.8%) than those in non-pCR individuals (median 72.3%, P = 0.01). There were no significant differences in baseline ctO2Hb, ctHHb, and ctTHb between response groups. An optimal tumor oxygenation threshold of stO2 = 76.7% was determined for pCR versus non-pCR (sensitivity = 75.0%, specificity = 73.3%). Multivariate discriminant analysis combining estrogen receptor staining and stO2 further improved the classification of pCR versus non-pCR (sensitivity = 100%, specificity = 85.7%). These results show that elevated baseline tumor stO2 are correlated with a pCR. Noninvasive DOSI scans combined with histopathology subtyping may aid in stratification of individual patients with breast cancer before neoadjuvant chemotherapy. Cancer Res; 72(17); 4318–28. ©2012 AACR.
The Novel BCR-ABL and FLT3 Inhibitor Ponatinib Is a Potent Inhibitor of the MDR-Associated ATP-Binding Cassette Transporter ABCG2
Authors: Sen Rupashree , Natarajan Karthika , Bhullar Jasjeet , Shukla Suneet , Fang Hong-Bin , Cai Ling , Chen Zhe-Sheng , Ambudkar Suresh V. , Baer Maria R. 
Published: July 2012

AbstractPonatinib is a novel tyrosine kinase inhibitor with potent activity against BCR-ABL with mutations, including T315I, and also against fms-like tyrosine kinase 3. We tested interactions between ponatinib at pharmacologically relevant concentrations of 50 to 200 nmol/L and the MDR-associated ATP-binding cassette (ABC) proteins ABCB1, ABCC1, and ABCG2. Ponatinib enhanced uptake of substrates of ABCG2 and ABCB1, but not ABCC1, in cells overexpressing these proteins, with a greater effect on ABCG2 than on ABCB1. Ponatinib potently inhibited [125I]-IAAP binding to ABCG2 and ABCB1, indicating binding to their drug substrate sites, with IC50 values of 0.04 and 0.63 μmol/L, respectively. Ponatinib stimulated ABCG2 ATPase activity in a concentration-dependent manner and stimulated ABCB1 ATPase activity at low concentrations, consistent with it being a substrate of both proteins at pharmacologically relevant concentrations. The ponatinib IC50 values of BCR-ABL–expressing K562 cells transfected with ABCB1 and ABCG2 were approximately the same as and 2-fold higher than that of K562, respectively, consistent with ponatinib being a substrate of both proteins, but inhibiting its own transport, and resistance was also attenuated to a small degree by ponatinib-induced downregulation of ABCB1 and ABCG2 cell-surface expression on resistant K562 cells. Ponatinib at pharmacologically relevant concentrations produced synergistic cytotoxicity with ABCB1 and ABCG2 substrate chemotherapy drugs and enhanced apoptosis induced by these drugs, including daunorubicin, mitoxantrone, topotecan, and flavopiridol, in cells overexpressing these transport proteins. Combinations of ponatinib and chemotherapy drugs warrant further testing. Mol Cancer Ther; 11(9); 2033–44. ©2012 AACR.
CD36 Repression Activates a Multicellular Stromal Program Shared by High Mammographic Density and Tumor Tissues
Authors: DeFilippis Rosa Anna , Chang Hang , Dumont Nancy , Rabban Joseph T. , Chen Yunn-Yi , Fontenay Gerald V. , Berman Hal K. , Gauthier Mona L. , Zhao Jianxin , Hu Donglei , Marx James J. , Tjoe Judy A. , Ziv Elad , Febbraio Maria , Kerlikowske Karla , Parvin Bahram , Tlsty Thea D. 
Published: July 2012

AbstractAlthough high mammographic density is considered one of the strongest risk factors for invasive breast cancer, the genes involved in modulating this clinical feature are unknown. Tissues of high mammographic density share key histologic features with stromal components within malignant lesions of tumor tissues, specifically low adipocyte and high extracellular matrix (ECM) content. We show that CD36, a transmembrane receptor that coordinately modulates multiple protumorigenic phenotypes, including adipocyte differentiation, angiogenesis, cell–ECM interactions, and immune signaling, is greatly repressed in multiple cell types of disease-free stroma associated with high mammographic density and tumor stroma. Using both in vitro and in vivo assays, we show that CD36 repression is necessary and sufficient to recapitulate the above-mentioned phenotypes observed in high mammographic density and tumor tissues. Consistent with a functional role for this coordinated program in tumorigenesis, we observe that clinical outcomes are strongly associated with CD36 expression.Significance: CD36 simultaneously controls adipocyte content and matrix accumulation and is coordinately repressed in multiple cell types within tumor and high mammographic density stroma, suggesting that activation of this stromal program is an early event in tumorigenesis. Levels of CD36 and extent of mammographic density are both modifiable factors that provide potential for intervention. Cancer Discov; 2(9); 826–39. ©2012 AACR.Read the Commentary on this article by DeClerck, p. 772.This article is highlighted in the In This Issue feature, p. 753.
Repolarization Changes Underlying Long-Term Cardiac Memory Due to Right Ventricular Pacing
Authors: Marrus Scott B. , Andrews Christopher M. , Cooper Daniel H. , Faddis Mitchell N. , Rudy Yoram 
Published: July 2012

Background—
Cardiac memory refers to the observation that altered cardiac electrical activation results in repolarization changes that persist after the restoration of a normal activation pattern. Animal studies, however, have yielded disparate conclusions, both regarding the spatial pattern of repolarization changes in cardiac memory and the underlying mechanisms. The present study was undertaken to produce 3-dimensional images of the repolarization changes underlying long-term cardiac memory in humans.

Methods and Results—
Nine adult subjects with structurally normal hearts and dual-chamber pacemakers were enrolled in the study. Noninvasive electrocardiographic imaging was used before and after 1 month of ventricular pacing to reconstruct epicardial activation and repolarization patterns. Eight subjects exhibited cardiac memory in response to ventricular pacing. In all subjects, ventricular pacing resulted in a prolongation of the activation recovery interval (a surrogate for action potential duration) in the region close to the site of pacemaker-induced activation from 228.4±7.6 ms during sinus rhythm to 328.3±6.2 ms during cardiac memory. As a consequence, increases are observed in both apical-basal and right-left ventricular gradients of repolarization, resulting in a significant increase in the dispersion of repolarization.

Conclusions—
These results demonstrate that electrical remodeling in response to ventricular pacing in human subjects results in action potential prolongation near the site of abnormal activation and a marked dispersion of repolarization. This dispersion of repolarization is potentially arrhythmogenic and, intriguingly, was less evident during continuous right ventricular pacing, suggesting the novel possibility that continuous right ventricular pacing at least partially suppresses pacemaker-induced cardiac memory.
Molecular Insights into Arrhythmogenic Right Ventricular Cardiomyopathy Caused by Plakophilin-2 Missense Mutations
Authors: Kirchner Florian , Schuetz Anja , Boldt Leif-Hendrik , Martens Kristina , Dittmar Gunnar , Haverkamp Wilhelm , Thierfelder Ludwig , Heinemann Udo , Gerull Brenda 
Published: July 2012

Background—
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disorder mainly caused by dominant mutations in several components of the cardiac desmosome including plakophilin-2 (PKP2), the most prevalent disease gene. Little is known about the underlying genetic and molecular mechanisms of missense mutations located in the armadillo (ARM) domains of PKP2, as well as their consequences on human cardiac pathology.

Methods and Results—
We focused on in vivo and in vitro studies of the PKP2 founder mutation c.2386T>C (p.C796R), and demonstrated in cardiac tissue from 2 related mutation carriers a patchy expression pattern ranging from unchanged to totally absent immunoreactive signals of PKP2 and other desmosomal proteins. In vitro expression analysis of mutant PKP2 in cardiac derived HL-1 cells revealed unstable proteins that fail to interact with desmoplakin and are targeted by degradation involving calpain proteases. Bacterial expression, crystallization, and structural modeling of mutated proteins impacting different ARM domains and helices of PKP2 confirmed their instability and degradation, resulting in the same remaining protein fragment that was crystallized and used to model the entire ARM domain of PKP2.

Conclusions—
The p.C796R and other ARVC-related PKP2 mutations indicate loss of function effects by intrinsic instability and calpain proteases mediated degradation in in vitro model systems, suggesting haploinsufficiency as the most likely cause for the genesis of dominant ARVC due to mutations in PKP2.
In Vivo Noninvasive Characterization of Brown Adipose Tissue Blood Flow by Contrast Ultrasound in Mice
Authors: Baron David M. , Clerte Maeva , Brouckaert Peter , Raher Michael J. , Flynn Aidan W. , Zhang Haihua , Carter Edward A. , Picard Michael H. , Bloch Kenneth D. , Buys Emmanuel S. , Scherrer-Crosbie Marielle 
Published: July 2012

Background—
Interventions to increase brown adipose tissue (BAT) volume and activation are being extensively investigated as therapies to decrease the body weight in obese subjects. Noninvasive methods to monitor these therapies in animal models and humans are rare. We investigated whether contrast ultrasound (CU) performed in mice could detect BAT and measure its activation by monitoring BAT blood flow. After validation, CU was used to study the role of uncoupling protein 1 and nitric oxide synthases in the acute regulation of BAT blood flow.

Methods and Results—

Blood flow of interscapular BAT was assessed in mice (n=64) with CU by measuring the signal intensity of continuously infused contrast microbubbles. Blood flow of BAT estimated by CU was 0.5±0.1 (mean±SEM) dB/s at baseline and increased 15-fold during BAT stimulation by norepinephrine (1 µg·kg
−1
·min
−1
). Assessment of BAT blood flow using CU was correlated to that performed with fluorescent microspheres (
R
2
=0.86,
P
<0.001). To evaluate whether intact BAT activation is required to increase BAT blood flow, CU was performed in uncoupling protein 1–deficient mice with impaired BAT activation. Norepinephrine infusion induced a smaller increase in BAT blood flow in uncoupling protein 1–deficient mice than in wild-type mice. Finally, we investigated whether nitric oxide synthases played a role in acute norepinephrine-induced changes of BAT blood flow. Genetic and pharmacologic inhibition of nitric oxide synthase 3 attenuated the norepinephrine-induced increase in BAT blood flow.

Conclusions—
These results indicate that CU can detect BAT in mice and estimate BAT blood flow in mice with functional differences in BAT.
Cardiac Rehabilitation Attendance and Outcomes in Coronary Artery Disease Patients
Authors: Martin Billie-Jean , Hauer Trina , Arena Ross , Austford Leslie D. , Galbraith P. Diane , Lewin Adriane M. , Knudtson Merril L. , Ghali William A. , Stone James A. , Aggarwal Sandeep G. 
Published: July 2012

Background—
Cardiac rehabilitation (CR) is an efficacious yet underused treatment for patients with coronary artery disease. The objective of this study was to determine the association between CR completion and mortality and resource use.

Methods and Results—
We conducted a prospective cohort study of 5886 subjects (20.8% female; mean age, 60.6 years) who had undergone angiography and were referred for CR in Calgary, AB, Canada, between 1996 and 2009. Outcomes of interest included freedom from emergency room visits, hospitalization, and survival in CR completers versus noncompleters, adjusted for clinical covariates, treatment strategy, and coronary anatomy. Hazard ratios for events for CR completers versus noncompleters were also constructed. A propensity model was used to match completers to noncompleters on baseline characteristics, and each outcome was compared between propensity-matched groups. Of the subjects referred for CR, 2900 (49.3%) completed the program, and an additional 554 subjects started but did not complete CR. CR completion was associated with a lower risk of death, with an adjusted hazard ratio of 0.59 (95% confidence interval, 0.49–0.70). CR completion was also associated with a decreased risk of all-cause hospitalization (adjusted hazard ratio, 0.77; 95% confidence interval, 0.71–0.84) and cardiac hospitalization (adjusted hazard ratio, 0.68; 95% confidence interval, 0.55–0.83) but not with emergency room visits. Propensity-matched analysis demonstrated a persistent association between CR completion and reduced mortality.

Conclusions—
Among those coronary artery disease patients referred, CR completion is associated with improved survival and decreased hospitalization. There is a need to explore reasons for nonattendance and to test interventions to improve attendance after referral.
Land Surface Controls on Hydroclimatic Means and Variability
Authors: Koster Randal D. , P. Mahanama Sarith P. 
Published: July 2012

Abstract
Hydroclimatic means and variability are determined in large part by the control of soil moisture on surface moisture fluxes, particularly evapotranspiration and runoff. This control is examined here using a simple water balance model and multidecadal observations covering the conterminous United States. Under the assumption that the relevant soil moisture–evapotranspiration and soil moisture–runoff relationships are, to first order, universal, the simple model illustrates the degree to which they interact to determine spatial distributions of hydroclimatic means and variability. In the process, the simple model provides estimates for the underlying relationships that operate in nature. The hydroclimatic sensitivities established with the simple water balance model can be used to evaluate more complex land surface models and to guide their further development, as demonstrated herein with an example.
The Formation of Nonzonal Jets over Sloped Topography
Authors: Boland Emma J. D. , Thompson Andrew F. , Shuckburgh Emily , Haynes Peter H. 
Published: July 2012

Abstract
Coherent jets are ubiquitous features of the ocean’s circulation, and their characteristics, such as orientation and energetics, may be influenced by topography. In this study, the authors introduce a large-scale, topographic slope with an arbitrary orientation into quasigeostrophic, doubly periodic, barotropic and baroclinic systems. In both systems, the flow organizes itself into coherent tilted nonzonal jets that are aligned perpendicular to the barotropic potential vorticity (PV) gradient. In the two-layer system, the upper layer, the lower layer, and the barotropic PV gradients all have different orientations and therefore the jets cross the layer-wise PV gradients. The fact that the jets cross layer-wise PV gradients and the requirement of conservation of PV for fluid parcels together results in the drift of the tilted jets across the domain. Like their zonal counterparts, the tilted jets exhibit strong transport anisotropy. The dynamical response to jet deflection is very strong in the two-layer baroclinic case, with eddy energy production increasing by orders of magnitude as the topographic slope becomes more zonal. This increase in eddy energy is also reflected in an increase in jet spacing and a reduction in strength of the across-jet transport barriers, shown using an effective diffusivity diagnostic. The dynamics identified here, while formally valid within the constraints of quasigeostrophic scalings, provide important insight into the sensitive relationship between flow orientation and flow stability in regions with broad topographic slopes.
The Wavenumber–Frequency Content of Resonantly Excited Equatorial Waves
Authors: Durland Theodore S. , Farrar J. Thomas 
Published: July 2012

Abstract
The theoretical resonant excitation of equatorial inertia–gravity waves and mixed Rossby–gravity waves is examined. Contrary to occasionally published expectations, solutions show that winds that are broadband in both zonal wavenumber and frequency do not in general produce peaks in the wavenumber–frequency spectrum of sea surface height (SSH) at wavenumbers associated with vanishing zonal group velocity.
Excitation of total wave energy in inertia–gravity modes by broadband zonal winds is virtually wavenumber independent when the meridional structure of the winds does not impose a bias toward negative or positive zonal wavenumbers. With increasing wavenumber magnitude |k|, inertia–gravity waves asymptote toward zonally propagating pure gravity waves, in which the magnitude of meridional velocity υ becomes progressively smaller relative to the magnitude of zonal velocity u and pressure p. When the total wave energy is independent of wavenumber, this effect produces a peak in |υ|2 near the wavenumber where group velocity vanishes, but a trough in |p|2 (or SSH variance). Another consequence of the shift toward pure gravity wave structure is that broadband meridional winds excite inertia–gravity modes progressively less efficiently as |k| increases and υ becomes less important to the wave structure. Broadband meridional winds produce a low-wavenumber peak in total wave energy leading to a subtle elevation of |p|2 at low wavenumbers, but this is due entirely to the decrease in the forcing efficiency of meridional winds with increasing |k|, rather than to the vanishing of the group velocity. Physical conditions that might alter the above conclusions are discussed.