bluuebunny/crossref_metadata_2025 huggingface dataset:
Stein's Method for Mean Field Approximations in Light and Heavy Traffic Regimes
Authors: Ying Lei
Published: March 2018

Mean-field analysis is an analytical method for understanding large-scale stochastic systems such as large-scale data centers and communication networks. The idea is to approximate the stationary distribution of a large-scale stochastic system using the equilibrium point (called the mean-field limit) of a dynamical system (called the mean-field model). This approximation is often justified by proving the weak convergence of stationary distributions to its mean-field limit. Most existing mean-field models concerned the light-traffic regime where the load of the system, denote by ρ, is strictly less than one and is independent of the size of the system. This is because a traditional mean-field model represents the limit of the corresponding stochastic system. Therefore, the load of the mean-field model is ρ= limN→ ∞ρ(N), where ρ(N)is the load of the stochastic system of sizeN.Now if ρ(N)→ 1asN→ ∞ (i.e., in the heavy-traffic regime), then ρ=1. For most systems, the mean-field limits when ρ=1 are trivial and meaningless. To overcome this difficulty of traditional mean-field models, this paper takes a different point of view on mean-field models. Instead of regarding a mean-field model as the limiting system of large-scale stochastic system, it views the equilibrium point of the mean-field model, called a mean-field solution, simply as an approximation of the stationary distribution of the finite-size system. Therefore both mean-field models and solutions can be functions ofN.This paper first outlines an analytical method to bound the approximation error based on Stein's method and the perturbation theory. We further present two examples: theM/M/Nqueueing system and the supermarket model under the power-of-two-choices algorithm. For both applications, the method enables us to characterize the system performance under a broad range of traffic loads. For the supermarket model, this is the first paper that rigorously quantifies the steady-state performance of the-power-of-two-choices in the heavy-traffic regime. These results in the heavy-traffic regime cannot be obtained using the traditional mean-field analysis and the interchange of the limits.
Characterizing and Modeling Patching Practices of Industrial Control Systems
Authors: Wang Brandon , Li Xiaoye , de Aguiar Leandro P. , Menasche Daniel S. , Shafiq Zubair
Published: March 2018

Industrial Control Systems (ICS) are widely deployed in mission critical infrastructures such as manufacturing, energy, and transportation. The mission critical nature of ICS devices poses important security challenges for ICS vendors and asset owners. In particular, the patching of ICS devices is usually deferred to scheduled production outages so as to prevent potential operational disruption of critical systems. Unfortunately, anecdotal evidence suggests that ICS devices are riddled with security vulnerabilities that are not patched in a timely manner, which leaves them vulnerable to exploitation by hackers, nation states, and hacktivist organizations.

In this paper, we present the results from our longitudinal measurement and characterization study of ICS patching behavior. Our study is based on IP scan data collected from Shodan over the duration of three years for more than 500 known industrial ICS protocols and products. Our longitudinal measurements reveal the impact of vulnerability disclosures on ICS patching. Our analysis of more than 100 thousand Internet-exposed ICS devices reveals that about 50% upgrade to newer patched versions within 60 days of a vulnerability disclosure. Based on our measurement and analysis, we further propose a variation of the Bass model to forecast the patching behavior of ICS devices. The evaluation shows that our proposed models have comparable prediction accuracy when contrasted against traditional ARIMA timeseries forecasting models, while requiring less parameters and being amenable to direct physical interpretation.
A Case Study in Power Substation Network Dynamics
Authors: Formby David , Walid Anwar , Beyah Raheem
Published: March 2018

The modern world is becoming increasingly dependent on computing and communication technology to function, but unfortunately its application and impact on areas such as critical infrastructure and industrial control system (ICS) networks remains to be thoroughly studied. Significant research has been conducted to address the myriad security concerns in these areas, but they are virtually all based on artificial testbeds or simulations designed on assumptions about their behavior either from knowledge of traditional IT networking or from basic principles of ICS operation. In this work, we provide the most detailed characterization of an example ICS to date in order to determine if these common assumptions hold true. A live power distribution substation is observed over the course of two and a half years to measure its behavior and evolution over time. Then, a horizontal study is conducted that compared this behavior with three other substations from the same company. Although most predictions were found to be correct, some unexpected behavior was observed that highlights the fundamental differences between ICS and IT networks including round trip times dominated by processing speed as opposed to network delay, several well known TCP features being largely irrelevant, and surprisingly large jitter from devices running real-time operating systems. The impact of these observations is discussed in terms of generality to other embedded networks, network security applications, and the suitability of the TCP protocol for this environment.
Design-Induced Latency Variation in Modern DRAM Chips
Authors: Lee Donghyuk , Khan Samira , Subramanian Lavanya , Ghose Saugata , Ausavarungnirun Rachata , Pekhimenko Gennady , Seshadri Vivek , Mutlu Onur
Published: March 2018

Variation has been shown to exist across the cells within a modern DRAM chip. Prior work has studied and exploited several forms of variation, such as manufacturing-process- or temperature-induced variation. We empirically demonstrate a new form of variation that exists within a real DRAM chip, induced by the design and placement of different components in the DRAM chip: different regions in DRAM, based on their relative distances from the peripheral structures, require different minimum access latencies for reliable operation. In particular, we show that in most real DRAM chips, cells closer to the peripheral structures can be accessed much faster than cells that are farther. We call this phenomenon design-induced variation in DRAM. Our goals are to i) understand design-induced variation that exists in real, state-of-the-art DRAM chips, ii) exploit it to develop low-cost mechanisms that can dynamically find and use the lowest latency at which to operate a DRAM chip reliably, and, thus, iii) improve overall system performance while ensuring reliable system operation.

To this end, we first experimentally demonstrate and analyze designed-induced variation in modern DRAM devices by testing and characterizing 96 DIMMs (768 DRAM chips). Our characterization identifies DRAM regions that are vulnerable to errors, if operated at lower latency, and finds consistency in their locations across a given DRAM chip generation, due to design-induced variation. Based on our extensive experimental analysis, we develop two mechanisms that reliably reduce DRAM latency. First, DIVA Profiling uses runtime profiling to dynamically identify the lowest DRAM latency that does not introduce failures. DIVA Profiling exploits design-induced variation and periodically profiles only the vulnerable regions to determine the lowest DRAM latency at low cost. It is the first mechanism to dynamically determine the lowest latency that can be used to operate DRAM reliably. DIVA Profiling reduces the latency of read/write requests by 35.1%/57.8%, respectively, at 55°C. Our second mechanism, DIVA Shuffling, shuffles data such that values stored in vulnerable regions are mapped to multiple error-correcting code (ECC) codewords. As a result, DIVA Shuffling can correct 26% more multi-bit errors than conventional ECC. Combined together, our two mechanisms reduce read/write latency by 40.0%/60.5%, which translates to an overall system performance improvement of 14.7%/13.7%/13.8% (in 2-/4-/8-core systems) across a variety of workloads, while ensuring reliable operation.
A Survey of Augmented, Virtual, and Mixed Reality for Cultural Heritage
Authors: Bekele Mafkereseb Kassahun , Pierdicca Roberto , Frontoni Emanuele , Malinverni Eva Savina , Gain James
Published: March 2018

A multimedia approach to the diffusion, communication, and exploitation of Cultural Heritage (CH) is a well-established trend worldwide. Several studies demonstrate that the use of new and combined media enhances how culture is experienced. The benefit is in terms of both number of people who can have access to knowledge and the quality of the diffusion of the knowledge itself. In this regard, CH uses augmented-, virtual-, and mixed-reality technologies for different purposes, including education, exhibition enhancement, exploration, reconstruction, and virtual museums. These technologies enable user-centred presentation and make cultural heritage digitally accessible, especially when physical access is constrained. A number of surveys of these emerging technologies have been conducted; however, they are either not domain specific or lack a holistic perspective in that they do not cover all the aspects of the technology. A review of these technologies from a cultural heritage perspective is therefore warranted. Accordingly, our article surveys the state-of-the-art in augmented-, virtual-, and mixed-reality systems as a whole and from a cultural heritage perspective. In addition, we identify specific application areas in digital cultural heritage and make suggestions as to which technology is most appropriate in each case. Finally, the article predicts future research directions for augmented and virtual reality, with a particular focus on interaction interfaces and explores the implications for the cultural heritage domain.
Censored Demand Estimation in Retail
Authors: Amjad Muhammad J. , Shah Devavrat
Published: March 2018

In this paper, the question of interest is estimating
true
demand of a product at a given store location and time period in the retail environment based on a
single
noisy and potentially censored observation. To address this question, we introduce a %non-parametric framework to make inference from multiple time series. Somewhat surprisingly, we establish that the algorithm introduced for the purpose of "matrix completion" can be used to solve the relevant inference problem. Specifically, using the Universal Singular Value Thresholding (USVT) algorithm [7], we show that our estimator is consistent: the average mean squared error of the estimated average demand with respect to the true average demand goes to
0
as the number of store locations and time intervals increase to $\infty$. We establish naturally appealing properties of the resulting estimator both analytically as well as through a sequence of instructive simulations. Using a real dataset in retail (Walmart), we argue for the practical relevance of our approach.
A Refined Mean Field Approximation
Authors: Gast Nicolas , Van Houdt Benny
Published: March 2018

Mean field models are a popular means to approximate large and complex stochastic models that can be represented as N interacting objects. Recently it was shown that under very general conditions the steady-state expectation of any performance functional converges at rate O(1/N) to its mean field approximation. In this paper we establish a result that expresses the constant associated with this 1/N term. This constant can be computed easily as it is expressed in terms of the Jacobian and Hessian of the drift in the fixed point and the solution of a single Lyapunov equation. This allows us to propose a refined mean field approximation. By considering a variety of applications, that include coupon collector, load balancing and bin packing problems, we illustrate that the proposed refined mean field approximation is significantly more accurate that the classic mean field approximation for small and moderate values of N: relative errors are often below 1% for systems with N=10.
On Non-Preemptive VM Scheduling in the Cloud
Authors: Psychas Konstantinos , Ghaderi Javad
Published: March 2018

We study the problem of scheduling VMs (Virtual Machines) in a distributed server platform, motivated by cloud computing applications. The VMs arrive dynamically over time to the system, and require a certain amount of resources (e.g. memory, CPU, etc) for the duration of their service. To avoid costly preemptions, we consider non-preemptive scheduling: Each VM has to be assigned to a server which has enough residual capacity to accommodate it, and once a VM is assigned to a server, its service
cannot
be disrupted (preempted). Prior approaches to this problem either have high complexity, require synchronization among the servers, or yield queue sizes/delays which are excessively large. We propose a non-preemptive scheduling algorithm that resolves these issues. In general, given an approximation algorithm to Knapsack with approximation ratio
r
, our scheduling algorithm can provide
rβ
fraction of the throughput region for
β < r
. In the special case of a greedy approximation algorithm to Knapsack, we further show that this condition can be relaxed to
β<1
. The parameters
β
and
r
can be tuned to provide a trade-off between achievable throughput, delay, and computational complexity of the scheduling algorithm. Finally extensive simulation results using both synthetic and real traffic traces are presented to verify the performance of our algorithm.
Performance of Balanced Fairness in Resource Pools
Authors: Bonald Thomas , Comte Céline , Mathieu Fabien
Published: March 2018

Understanding the performance of a pool of servers is crucial for proper dimensioning. One of the main challenges is to take into account the complex interactions between servers that are pooled to process jobs. In particular, a job can generally not be processed by any server of the cluster due to various constraints like data locality. In this paper, we represent these constraints by some assignment graph between jobs and servers. We present a recursive approach to computing performance metrics like mean response times when the server capacities are shared according to balanced fairness. While the computational cost of these formulas can be exponential in the number of servers in the worst case, we illustrate their practical interest by introducing broad classes of pool structures that can be exactly analyzed in polynomial time. This extends considerably the class of models for which explicit performance metrics are accessible.
The CSI Framework for Compiler-Inserted Program Instrumentation
Authors: Schardl Tao B. , Denniston Tyler , Doucet Damon , Kuszmaul Bradley C. , Lee I-Ting Angelina , Leiserson Charles E.
Published: March 2018

The CSI framework provides comprehensive static instrumentation that a compiler can insert into a program-under-test so that dynamic-analysis tools - memory checkers, race detectors, cache simulators, performance profilers, code-coverage analyzers, etc. - can observe and investigate runtime behavior. Heretofore, tools based on compiler instrumentation would each separately modify the compiler to insert their own instrumentation. In contrast, CSI inserts a standard collection of instrumentation hooks into the program-under-test. Each CSI-tool is implemented as a library that defines relevant hooks, and the remaining hooks are "nulled" out and elided during either compile-time or link-time optimization, resulting in instrumented runtimes on par with custom instrumentation. CSI allows many compiler-based tools to be written as simple libraries without modifying the compiler, lowering the bar for the development of dynamic-analysis tools.

We have defined a standard API for CSI and modified LLVM to insert CSI hooks into the compiler's internal representation (IR) of the program. The API organizes IR objects - such as functions, basic blocks, and memory accesses - into flat and compact ID spaces, which not only simplifies the building of tools, but surprisingly enables faster maintenance of IR-object data than do traditional hash tables. CSI hooks contain a "property" parameter that allows tools to customize behavior based on static information without introducing overhead. CSI provides "forensic" tables that tools can use to associate IR objects with source-code locations and to relate IR objects to each other.

To evaluate the efficacy of CSI, we implemented six demonstration CSI-tools. One of our studies shows that compiling with CSI and linking with the "null" CSI-tool produces a tool-instrumented executable that is as fast as the original uninstrumented code. Another study, using a CSI port of Google's ThreadSanitizer, shows that the CSI-tool rivals the performance of Google's custom compiler-based implementation. All other demonstration CSI tools slow down the execution of the program-under-test by less than 70%.
Efficient and Scalable Graph Parallel Processing With Symbolic Execution
Authors: Zheng Long , Liao Xiaofei , Jin Hai
Published: March 2018

Existing graph processing essentially relies on the underlying iterative execution with synchronous (Sync) and/or asynchronous (Async) engine. Nevertheless, they both suffer from a wide class of inherent serialization arising from data interdependencies within a graph.

In this article, we present SymGraph, a judicious graph engine with symbolic iteration that enables the parallelism of dependent computation on vertices. SymGraph allows using abstract symbolic value (instead of the concrete value) for the computation if the desired data is unavailable. To maximize the potential of symbolic iteration, we propose a chain of tailored sophisticated techniques, enabling SymGraph to scale out with a new milestone of efficiency for large-scale graph processing. We evaluate SymGraph in comparison to Sync, Async, and a hybrid of Sync and Async engines. Our results on 12 nodes show that SymGraph outperforms all three graph engines by 1.93x (vs. Sync), 1.98x (vs. Async), and 1.57x (vs. Hybrid) on average. In particular, the performance for PageRank on 32 nodes can be dramatically improved by 16.5x (vs. Sync), 23.3x (vs. Async), and 12.1x (vs. Hybrid), respectively. The efficiency of SymGraph is also validated with at least one order of magnitude improvement in contrast to three specialized graph systems (Naiad, GraphX, and PGX.D).
RAPL in Action
Authors: Khan Kashif Nizam , Hirki Mikael , Niemi Tapio , Nurminen Jukka K. , Ou Zhonghong
Published: March 2018

To improve energy efficiency and comply with the power budgets, it is important to be able to measure the power consumption of cloud computing servers. Intel’s Running Average Power Limit (RAPL) interface is a powerful tool for this purpose. RAPL provides power limiting features and accurate energy readings for CPUs and DRAM, which are easily accessible through different interfaces on large distributed computing systems. Since its introduction, RAPL has been used extensively in power measurement and modeling. However, the advantages and disadvantages of RAPL have not been well investigated yet. To fill this gap, we conduct a series of experiments to disclose the underlying strengths and weaknesses of the RAPL interface by using both customized microbenchmarks and three well-known application level benchmarks:
Stream
,
Stress-ng
, and
ParFullCMS
. Moreover, to make the analysis as realistic as possible, we leverage two production-level power measurement datasets from the
Taito
, a supercomputing cluster of the Finnish Center of Scientific Computing and also replicate our experiments on Amazon EC2. Our results illustrate different aspects of RAPL and document the findings through comprehensive analysis. Our observations reveal that RAPL readings are highly correlated with plug power, promisingly accurate enough, and have negligible performance overhead. Experimental results suggest RAPL can be a very useful tool to measure and monitor the energy consumption of servers without deploying any complex power meters. We also show that there are still some open issues, such as driver support, non-atomicity of register updates, and unpredictable timings that might weaken the usability of RAPL in certain scenarios. For such scenarios, we pinpoint solutions and workarounds.
Complexity of Coloring Random Graphs
Authors: Mann Zoltán Ádám
Published: March 2018

It is known that the problem of deciding
k
-colorability of a graph exhibits an easy-hard-easy pattern,—that is, the average-case complexity for backtrack-type algorithms, as a function of
k
, has a peak. This complexity peak is either at
k
= χ − 1 or
k
= χ, where χ is the chromatic number of the graph. However, the behavior around the complexity peak is poorly understood. In this article, we use list coloring to model coloring with a fractional number of colors between χ − 1 and χ. We present a comprehensive computational study on the complexity of backtrack-type graph coloring algorithms in this critical range. According to our findings, an easy-hard-easy pattern can be observed on a finer scale between χ − 1 and χ as well. The highest complexity found this way can be higher than for any integer value of
k
. It turns out that the complexity follows an alternating three-dimensional pattern; understanding this pattern is very important for benchmarking purposes. Our results also answer the previously open question whether coloring with χ − 1 or with χ colors is harder: this depends on the location of the maximal fractional complexity.
Bounded Query Rewriting Using Views
Authors: Cao Yang , Fan Wenfei , Geerts Floris , Lu Ping
Published: March 2018

A query
Q
in a language
L
has a
bounded rewriting
using a set of L-definable views if there exists a query
Q
′
in
L
such that given any dataset
D
,
Q
(
D
) can be computed by
Q
′
that accesses only cached views and a small fraction
D

Q

of
D
. We consider datasets
D
that satisfy a set of access constraints, which are a combination of simple cardinality constraints and associated indices, such that the size |
D

Q

| of
D

Q

and the time to identify
D

Q

are independent of |
D
|, no matter how big
D
is.

In this article, we study the problem for deciding whether a query has a bounded rewriting given a set
V
of views and a set
A
of access constraints. We establish the complexity of the problem for various query languages
L
, from Σ
3
p
-complete for conjunctive queries (CQ) to undecidable for relational algebra (FO). We show that the intractability for CQ is rather robust even for acyclic CQ with fixed
V
and
A
, and characterize when the problem is in PTIME. To make practical use of bounded rewriting, we provide an effective syntax for FO queries that have a bounded rewriting. The syntax characterizes a key subclass of such queries without sacrificing the expressive power, and can be checked in PTIME. Finally, we investigate
L
1
-to-
L
2
bounded rewriting, when
Q
in
L
1
is allowed to be rewritten into a query
Q
′
in another language
L
2
. We show that this relaxation does not simplify the analysis of bounded query rewriting using views.
Online Harassment and Content Moderation
Authors: Jhaver Shagun , Ghoshal Sucheta , Bruckman Amy , Gilbert Eric
Published: March 2018

Online harassment is a complex and growing problem. On Twitter, one mechanism people use to avoid harassment is the
blocklist
, a list of accounts that are preemptively blocked from interacting with a subscriber. In this article, we present a rich description of Twitter blocklists – why they are needed, how they work, and their strengths and weaknesses in practice. Next, we use blocklists to interrogate online harassment – the forms it takes, as well as tactics used by harassers. Specifically, we interviewed both people who use blocklists to protect themselves, and people who are blocked by blocklists. We find that users are not adequately protected from harassment, and at the same time, many people feel that they are blocked unnecessarily and unfairly. Moreover, we find that not all users agree on what constitutes harassment. Based on our findings, we propose design interventions for social network sites with the aim of protecting people from harassment, while preserving freedom of speech.
Nitrate Transport, Signaling, and Use Efficiency
Authors: Wang Ya-Yun , Cheng Yu-Hsuan , Chen Kuo-En , Tsay Yi-Fang
Published: March 2018

Nitrogen accounts for approximately 60% of the fertilizer consumed each year; thus, it represents one of the major input costs for most nonlegume crops. Nitrate is one of the two major forms of nitrogen that plants acquire from the soil. Mechanistic insights into nitrate transport and signaling have enabled new strategies for enhancing nitrogen utilization efficiency, for lowering input costs for farming, and, more importantly, for alleviating environmental impacts (e.g., eutrophication and production of the greenhouse gas N2O). Over the past decade, significant progress has been made in understanding how nitrate is acquired from the surroundings, how it is efficiently distributed into different plant tissues in response to environmental changes, how nitrate signaling is perceived and transmitted, and how shoot and root nitrogen status is communicated. Several key components of these processes have proven to be novel tools for enhancing nitrate- and nitrogen-use efficiency. In this review, we focus on the roles of NRT1 and NRT2 in nitrate uptake and nitrate allocation among different tissues; we describe the functions of the transceptor NRT1.1, transcription factors, and small signaling peptides in nitrate signaling and tissue communication; and we compile the new strategies for improving nitrogen-use efficiency.
Ribosome-Targeting Antibiotics: Modes of Action, Mechanisms of Resistance, and Implications for Drug Design
Authors: Lin Jinzhong , Zhou Dejian , Steitz Thomas A. , Polikanov Yury S. , Gagnon Matthieu G.
Published: March 2018

Genetic information is translated into proteins by the ribosome. Structural studies of the ribosome and of its complexes with factors and inhibitors have provided invaluable information on the mechanism of protein synthesis. Ribosome inhibitors are among the most successful antimicrobial drugs and constitute more than half of all medicines used to treat infections. However, bacterial infections are becoming increasingly difficult to treat because the microbes have developed resistance to the most effective antibiotics, creating a major public health care threat. This has spurred a renewed interest in structure-function studies of protein synthesis inhibitors, and in few cases, compounds have been developed into potent therapeutic agents against drug-resistant pathogens. In this review, we describe the modes of action of many ribosome-targeting antibiotics, highlight the major resistance mechanisms developed by pathogenic bacteria, and discuss recent advances in structure-assisted design of new molecules.
Crystal Engineering for Catalysis
Authors: Rimer Jeffrey D. , Chawla Aseem , Le Thuy T.
Published: March 2018

Crystal engineering relies upon the ability to predictively control intermolecular interactions during the assembly of crystalline materials in a manner that leads to a desired (and predetermined) set of properties. Economics, scalability, and ease of design must be leveraged with techniques that manipulate the thermodynamics and kinetics of crystal nucleation and growth. It is often challenging to exact simultaneous control over multiple physicochemical properties, such as crystal size, habit, chirality, polymorph, and composition. Engineered materials often rely upon postsynthesis (top-down) processes to introduce properties that would otherwise be challenging to attain through direct (bottom-up) approaches. We discuss the application of crystal engineering to heterogeneous catalysts with a focus on four general themes: ( a) tailored nanocrystal size, ( b) controlled environments surrounding active sites, ( c) tuned morphology with well-defined facets, and ( d) hierarchical materials with disparate pore size and active site distributions. We focus on nonporous materials, including metals and metal oxides, and two classes of porous materials: zeolites and metal organic frameworks. We review novel synthesis methods involving synergistic experimental and computational design approaches, the challenges facing catalyst development, and opportunities for future advancement in crystal engineering.
Protein tyrosine phosphatase 1B inactivation limits aging-associated heart failure in mice
Authors: Besnier Marie , Coquerel David , Favre Julie , Dumesnil Anais , Guerrot Domique , Remy-Jouet Isabelle , Mulder Paul , Djerada Zoubir , Tamion Fabienne , Richard Vincent , Ouvrard-Pascaud Antoine
Published: March 2018

We have previously shown that protein tyrosine phosphatase 1B (PTP1B) inactivation in mice [PTP1B-deficient (PTP1B−/−) mice] improves left ventricular (LV) angiogenesis, perfusion, remodeling, and function and limits endothelial dysfunction after myocardial infarction. However, whether PTP1B inactivation slows aging-associated cardiovascular dysfunction remains unknown. Wild-type (WT) and PTP1B−/− mice were allowed to age until 18 mo. Compared with old WT mice, in which aging increased the LV mRNA expression of PTP1B, old PTP1B−/− mice had 1) reduced cardiac hypertrophy with decreased LV mRNA levels of hypertrophic markers and atrial and brain natriuretic peptides, 2) lower LV fibrosis (collagen: 16 ± 3% in WT mice and 5 ± 3% in PTP1B−/− mice, P < 0.001) with decreased mRNA levels of transforming growth-factor-β1 and matrix metalloproteinase-2, and 3) higher LV capillary density and lower LV mRNA level of hypoxic inducible factor-1α, which was associated over time with a higher rate of proangiogenic M2 type macrophages and a stable LV mRNA level of VEGF receptor-2. Echocardiography revealed an age-dependent LV increase in end-diastolic volume in WT mice together with alterations of fractional shortening and diastole (transmitral Doppler E-to-A wave ratio). Invasive hemodynamics showed better LV systolic contractility and better diastolic compliance in old PTP1B−/− mice (LV end-systolic pressure-volume relation: 13.9 ± 0.9 in WT mice and 18.4 ± 1.6 in PTP1B−/− mice; LV end-diastolic pressure-volume relation: 5.1 ± 0.8 mmHg/relative volume unit in WT mice and 1.2 ± 0.3 mmHg/relative volume unit in PTP1B−/− mice, P < 0.05). In addition, old PTP1B−/− mice displayed a reduced amount of LV reactive oxygen species. Finally, in isolated resistance mesenteric arteries, PTP1B inactivation reduced aging-associated endothelial dysfunction (flow-mediated dilatation: −0.4 ± 2.1% in WT mice and 8.2 ± 2.8% in PTP1B−/− mice, P < 0.05). We conclude that PTP1B inactivation slows aging-associated LV remodeling and dysfunction and reduces endothelial dysfunction in mesenteric arteries.

NEW & NOTEWORTHY The present study shows that protein tyrosine phosphatase 1B inactivation in aged mice improves left ventricular systolic and diastolic function associated with reduced adverse cardiac remodeling (hypertrophy, fibrosis, and capillary rarefaction) and limits vascular endothelial dysfunction. This suggests that protein tyrosine phosphatase 1B inhibition could be an interesting treatment approach in age-related cardiovascular dysfunction.
Cohesin RAD21 Gene Promoter Methylation in Patients with Chronic Lymphocytic Leukemia
Authors: Ioannidou Agapi , Zachaki Sophia , Karakosta Maria , Daraki Aggeliki , Roussou Paraskevi , Manola Kalliopi N.
Published: March 2018

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in adults and is characterized by the presence of specific cytogenetic abnormalities. CLL research has been focused on epigenetic processes like gene promoter methylation of CpG islands. In the present study, the methylation status of the RAD21 gene is studied and associated with cytogenetic findings in CLL patients in order to investigate its possible implication in CLL pathogenesis and the formation of CLL chromosomal abnormalities.
Evaluation of Collateral Source Characteristics With 3‐Dimensional Analysis Using Micro–X‐Ray Computed Tomography
Authors: Arima Yuichiro , Hokimoto Seiji , Tabata Noriaki , Nakagawa Osamu , Oshima Asahi , Matsumoto Yosuke , Sato Takahiro , Mukunoki Toshifumi , Otani Jun , Ishii Masanobu , Uchikawa Michie , Yamamoto Eiichiro , Izumiya Yasuhiro , Kaikita Koichi , Ogawa Hisao , Nishiyama Koichi , Tsujita Kenichi
Published: March 2018

Background

Collateral arteries provide an alternative blood supply and protect tissues from ischemic damage in patients with peripheral artery disease. However, the mechanism of collateral artery development is difficult to validate.

Methods and Results

Collateral arteries were visualized using micro–x‐ray computed tomography. Developmental characteristics were assessed using confocal microscopy. We conducted a single‐center, retrospective, observational study and assessed the dilatation of collateral arteries on ischemic sides. We quantified the vascular volume in both ischemic and nonischemic legs. A prominent increase in vascular volume was observed in the ischemic leg using a murine hind‐limb ischemia model. We also performed qualitative assessment and confirmed that the inferior gluteal artery functioned as a major collateral source. Serial analysis of murine hind‐limb vessel development revealed that the inferior gluteal artery was a remnant of the ischial artery, which emerged as a representative vessel on the dorsal side during hind‐limb organogenesis. We retrospectively analyzed consecutive patients who were admitted for the diagnosis or treatment of peripheral artery disease. The diameter of the inferior gluteal artery on the ischemic side showed significant dilatation compared with that on the nonischemic side.

Conclusions

Our findings indicate that an embryonic remnant artery can become a collateral source under ischemic conditions. Flow enhancement in the inferior gluteal artery might become a novel therapeutic approach for patients with peripheral artery disease.
Prevalence, Causes, and Predictors of 30‐Day Readmissions Following Hospitalization With Acute Myocardial Infarction Complicated By Cardiogenic Shock: Findings From the 2013–2014 National Readmissions Database
Authors: Mahmoud Ahmed N. , Elgendy Islam Y. , Mojadidi Mohammad K. , Wayangankar Siddharth A. , Bavry Anthony A. , Anderson R. David , Jneid Hani , Pepine Carl J.
Published: March 2018

Background

Prior studies have shown that survivors of acute myocardial infarction (
AMI
) complicated by cardiogenic shock are likely to have increased risk of readmissions in the early post‐discharge period. However, the contemporary prevalence, reasons, and predictors of 30‐day readmissions are not well known.

Methods and Results

Hospitalizations for a primary diagnosis of
AMI
complicated by cardiogenic shock, and discharged alive, were identified in the 2013 and 2014 Nationwide Readmissions Databases. Prevalence and reasons for 30‐day unplanned readmissions were investigated. A hierarchical logistic regression model was used to identify independent predictors of 30‐day readmissions. Among 1 116 933 patient hospitalizations with
AMI
, 39 807 (3.6%) had cardiogenic shock and were discharged alive. Their 30‐day readmission rate was 18.6%, with a median time for readmission 10 days post discharge. Predictors of readmission included: non–
ST
‐segment elevation myocardial infarction, female sex, low‐income status, nonprivate insurance, chronic renal failure, long‐term ventricular assist device or intra‐aortic balloon placement, and tachyarrhythmia. The majority of readmissions were attributable to cardiac‐related causes (52%); heart failure being the most frequent cardiac cause (39% of all cardiac causes). Noncardiac‐related readmissions included infections (14.9%), bleeding (5.3%), and respiratory causes (4.9%). The median cost per readmission was $9473
US
dollars ($5037–20 199).

Conclusions

Among survivors of
AMI
complicated by cardiogenic shock who were discharged from hospital, almost 1 in 5 are readmitted at 30 days, mainly because of cardiac reasons such as heart failure and new
AMI
. The risk of readmission was associated with certain baseline patient/hospital characteristics.
R2P and the Prevention of Mass Atrocities: A Child-Centric Approach
Authors: Jacob Cecilia
Published: March 2018

Prevention has taken centre-stage in present discussions around both United Nations reform and the r2p implementation agenda. Contemporary humanitarian crises from Myanmar to Yemen reinforce the horrendous atrocities that children face during periods of armed conflict and mass political upheaval to which the prevention agenda is geared. This article considers the atrocity prevention dimension of r2p; it describes changes in both understanding around the dynamics of political violence and strategies for targeting civilians in contemporary conflicts over the past two decades, situates children in the broader social context of mass political violence, and identifies strategies for incorporating a child-centric lens into the existing atrocity prevention toolkit. It argues that while the children and armed conflict agenda strengthens atrocity prevention efforts in relation to children’s specific experiences in violent conflict, it does not serve as an adequate proxy for a child-centric approach to atrocity prevention through both structural and targeted measures.
Evidence from Australian mesic zone dung beetles supports their Gondwanan origin and Mesozoic diversification of the Scarabaeinae
Authors: Gunter Nicole L. , Monteith Geoff B. , Cameron Stephen L. , Weir Tom A.
Published: March 2018

The evolution of dung beetles remains contentious with two hypotheses reflecting Cretaceous and Paleogene origins driven by different methods. We explore biogeographic evidence and phylogeographic origins against vicariance and dispersal scenarios that attribute to the four elements of the Australian fauna using a multi-gene approach. Maximum-likelihood and Bayesian analyses supported the Australasian clade, composed of almost all Australian, New Caledonian and New Zealand endemic genera (to the exclusion of Boletoscapter). Two Australian lineages with east-west splits and few lineages with restricted, non-overlapping distrbution were identified, and biogeography models provided evidence that vicariance and founder event speciation are important processes in the diversification of Australasian scarabaeines. Our phylogenetic results are largely congruent with a mid-Cretaceous origin of the Australasian clade, the tectonic history of Gondwanaland and climatic history of the Australian continent, and provide compelling evidence that Australian dung beetles are a relictual fauna whose history is linked to mesic zone fragmentation.
Two new species of freshwater crayfish of the genus Faxonius (Decapoda: Cambaridae) from the Ozark Highlands of Arkansas and Missouri
Authors: FETZNER JAMES W. JR. , TAYLOR CHRISTOPHER A.
Published: March 2018

Two new species of freshwater crayfish are described from the Ozarks Plateau of northern Arkansas and southern Missouri. Both species are restricted to the mainstem of rocky streams that are at least fourth-order or greater in size. Recent genetic and morphological investigations of the coldwater crayfish, Faxonius eupunctus Williams, 1952, indicated that it was actually composed of several undescribed species. Faxonius eupunctus is herein restricted to just the Eleven Point River system. Faxonius roberti, new species is found in the mainstem of the Spring and Strawberry river systems in northern Arkansas. It differs from F. eupunctus by lacking a male Form-I gonopod with a distal spatulate mesial process, and presence of two spines on the dorsal side of the merus, where F. eupunctus typically has 1 spine. Faxonius wagneri, new species is known from a 54 mile (86 km) stretch of the Eleven Point River mainstem, ranging from just southeast of Greer, Missouri to just north of Birdell, Arkansas. Faxonius wagneri can be differentiated from both F. eupunctus and Faxonius roberti sp. nov. by using the male Form-I and Form-II gonopods, the shape of the chelae, and the female annulus ventralis. In F. wagneri, the terminal elements of the first pleopod are almost twice as long as those in F. eupunctus and F. roberti, with the tips of the appendage reaching the posterior base of the first perieopod when the abdomen is flexed forward, whereas, in the other two species, these elements only reach the base of the second pereiopod. The species also possesses two spines on the dorsal side of the merus of the first pereiopod, which helps distinguish it from F. eupunctus.
Morphological examination and phylogenetic analysis clarify the taxonomic status of Cuban Longior Travassos & Kloss, 1958 (Nematoda: Thelastomatoidea: Hystrignathidae)
Authors: MORFFE JANS , GARCÍA NAYLA , BREUGELMANS KARIN , ADAMS BYRON J.
Published: March 2018

The status of Longior alius García & Coy, 1994 (Nematoda: Thelastomatoidea: Hystrignathidae) is discussed on the basis of new material obtained from its type host Antillanax pertyi (Kaup, 1869) (Coleoptera: Passalidae) from Limonar, Guantánamo province, Cuba, near the type locality. Based on morphological and molecular studies L. alius is considered synonymous with L. longior Morffe & García, 2011. L. longior and L. similis Morffe, García & Ventosa, 2009 are redescribed and illustrated with the aid of SEM. New locality records for both species are given. The conspecificity of females and males of both species is supported by comparison of the D2-D3 segment of the 28S LSU rDNA. The inter-specific differences and phylogenetic position of L. longior and L. similis are discussed.
Bringing taxonomy to school kids: Aedokritus adotivae sp. n. from Amazon
(Diptera: Chironomidae)
Authors: PINHO LUIZ CARLOS
Published: March 2018

Children curiosity about how taxonomy works led me to ask for their help to choose a name for a new species of Aedokritus Roback from Pará State (Brazilian Amazon). Aedokritus adotivae sp. n. is here described based on male adults. A key to species of the genus is provided.
Using the GOES-16 Split Window Difference to Detect a Boundary prior to Cloud Formation
Authors: Lindsey Daniel T. , Bikos Dan , Grasso Lewis
Published: March 2018

Geostationary Operational Environmental Satellite-16 (GOES-16) was launched into geostationary orbit in late 2016 and began providing unprecedented spatial and temporal resolution imagery early in 2017. Its Advanced Baseline Imager has additional spectral bands including two in the “clear” window and “dirty window” portion of the infrared spectrum, and the difference of these two bands, sometimes called the split window difference, provides unique information about low-level water vapor. Under certain conditions, low-level convergence along a boundary can cause local water vapor pooling, and the signal of this pooling can sometimes be detected by GOES-16 prior to any cloud formation. This case study from 15 June 2017 illustrates how the technique might be used in an operational forecast setting. A boundary in western Kansas was detected using the split window difference more than 2 h before the first cloud formed.
Tibetan Plateau Impacts on Global Dust Transport in the Upper Troposphere
Authors: Xu Chao , Ma Yaoming , Yang Kun , You Chao
Published: March 2018

Dust is a major component of atmospheric aerosol worldwide, greatly affecting regional and global climate. In this study dust aerosol optical depth (DAOD) and dust mass fluxes (DMF) were evaluated at different altitudes using measurements by the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) and ERA-Interim data from March through May (MAM) for the period 2007–16. Significantly higher upper-tropospheric (above ~8 km) dust loads and DMF downstream of the Tibetan Plateau (TP) relative to those over other major dust sources of the Northern Hemisphere were found during spring. A DMF magnitude of 1010 g integrated across a 2°-latitude segment during spring was estimated downstream of the TP in the upper troposphere. A dust belt can be clearly seen at altitudes higher than 6 km over the downwind direction of the TP at latitudes of around 30°–40°N, crossing the Pacific Ocean and extending to North America during spring. A pathway for transporting dust aerosols into the upper troposphere is proposed, as follows. Dust is uplifted to the midtroposphere over the source regions; then, frequent, deep, dry convection prevailing over the TP during spring can cause convective overshooting that uplifts the dust aerosols to the upper troposphere. The TP thus acts as a channel for transporting dust from the lower atmosphere to the upper troposphere, enabling the long-range zonal transport of dust around the Northern Hemisphere.
Spatial Distribution of Diurnal Rainfall Variation in Summer over China
Authors: Zhu Liming , Liu Junzhi , Zhu A-Xing , Sheng Meiling , Duan Zheng
Published: March 2018

Diurnal rainfall variation plays an important role in the characterization of regional climate. Most existing research used predefined region boundaries to study the spatial differences of diurnal rainfall variation, which depends on experiential knowledge and is somewhat subjective. In this study, the k-means clustering algorithm was used to mine the spatial distribution of diurnal rainfall variation from gridded precipitation data over China. First, clustering was conducted according to the hourly rainfall frequency at each grid cell. A cluster number large enough to find the main types of diurnal rainfall variation was used. Then similar clusters were merged according to the peak time and amplitude of the diurnal rainfall variation. Each merged cluster corresponds to one type of diurnal variation, and the locations of grid cells in each merged cluster form the spatial distribution. Thus, the classification maps of diurnal rainfall variation can be obtained. From the spatial distribution maps, the conclusions of existing research (e.g., the distribution of well-known nocturnal rainfall in southwestern China, the prevailing afternoon rainfall regions) were confirmed. Some new findings were found, such as the spatial patterns of nocturnal rainfall regions along slopes of the macroterrain and the different types of diurnal rainfall variation in the North China Plain. The diurnal rainfall variation in some regions also shows a close relationship with land cover. The results of this study can provide valuable information for further mechanism studies, and the proposed approach can serve as a useful tool for studies on diurnal rainfall variation in other regions.
Assessment and propagation of mechanical property uncertainties in fatigue life prediction of composite laminates
Authors: Castro Oscar , Branner Kim , Dimitrov Nikolay
Published: March 2018

A probabilistic model for estimating the fatigue life of laminated composite materials considering the uncertainty in their mechanical properties is developed. The uncertainty in the material properties is determined from fatigue coupon tests. Based on this uncertainty, probabilistic constant life diagrams are developed which can efficiently estimate probabilistic ɛ-N curves at any load level and stress ratio. The probabilistic ɛ-N curve information is used in a reliability analysis for fatigue limit state proposed for estimating the probability of failure of composite laminates under variable amplitude loading cycles. Fatigue life predictions of unidirectional and multi-directional glass/epoxy laminates are carried out to validate the proposed model against experimental data. The probabilistic fatigue behavior of laminates is analyzed under constant amplitude loading conditions as well as under both repeated block tests and spectral fatigue using the WISPER, WISPERX, and NEW WISPER load sequences for wind turbine blades.