bluuebunny/crossref_metadata_2025 huggingface dataset:
TH‐EF‐207A‐06: High‐Resolution Optical‐CT/ECT Imaging of Unstained Mice Femur, Brain, Spleen, and Tumor
Authors: Yoon S , Boss M , Birer S , Dewhirst M , Oldham M
Published: July 2016

Purpose:

Optical transmission and emission computed tomography (optical‐CT/ECT) provides high‐resolution 3D attenuation and emission maps in unsectioned large (∼1cm3) ex vivo tissue samples at a resolution of 12.9µm3 per voxel. Here we apply optical‐CT/ECT to investigate high‐resolution structure and auto‐fluorescence in a range of optically cleared mice organs, including, for the first time, mouse bone (femur), opening the potential for study of bone metastasis and bone‐mediated immune response.

Methods:

Three BALBc mice containing 4T1 flank tumors were sacrificed to obtain spleen, brain, tumor, and femur. Tissues were washed in 4% PFA, fixed in EtOH solution (for 5, 10, 10, and 2 days respectively), and then optically cleared for 3 days in BABBs. The femur was also placed in 0.25M aqueous EDTA for 15–30 days to remove calcium. Optical‐CT/ECT attenuation and emission maps at 633nm (the latter using 530nm excitation light) were obtained for all samples. Bi‐telecentric optical‐CT was compared side‐by‐side with conventional optical projection tomography (OPT) imaging to evaluate imaging capability of these two rival techniques.

Results:

Auto‐fluorescence mapping of femurs reveals vasculatures and fluorescence heterogeneity. High signals (A.U.=10) are reported in the medullary cavity but not in the cortical bone (A.U.=1). The brain strongly and uniform auto‐fluoresces (A.U.=5). Thick, optically dense organs such as the spleen and the tumor (0.12, 0.46OD/mm) are reconstructed at depth without significant loss of resolution, which we attribute to the bi‐telecentric optics of optical‐CT. The attenuation map of tumor reveals vasculature, attenuation heterogeneity, and possibly necrotic tissue.

Conclusion:

We demonstrate the feasibility of optical‐CT/ECT imaging of un‐sectioned mice bones (femurs) and spleen with high resolution. This result, and the characterization of unstained organs, are important steps enabling future studies involving optical‐CT/ECT applied to study metastasis and immunologic responses via fluorescence staining.
TH‐E‐209‐03: Development of An In‐House CT Dose Monitoring and Management System Based On Open‐Source Software Resources ‐‐ Pearls and Pitfalls
Authors: Zhang D.
Published: July 2016

Radiation dose monitoring solutions have opened up new opportunities for medical physicists to be more involved in modern clinical radiology practices. In particular, with the help of comprehensive radiation dose data, data‐driven protocol management and informed case follow up are now feasible.

Significant challenges remain however and the problems faced by medical physicists are highly heterogeneous. Imaging systems from multiple vendors and a wide range of vintages co‐exist in the same department and employ data communication protocols that are not fully standardized or implemented making harmonization complex.

Many different solutions for radiation dose monitoring have been implemented by imaging facilities over the past few years. Such systems are based on commercial software, home‐grown IT solutions, manual PACS data dumping, etc., and diverse pathways can be used to bring the data to impact clinical practice. The speakers will share their experiences with creating or tailoring radiation dose monitoring/management systems and procedures over the past few years, which vary significantly in design and scope.

Topics to cover: (1) fluoroscopic dose monitoring and high radiation event handling from a large academic hospital; (2) dose monitoring and protocol optimization in pediatric radiology; and (3) development of a home‐grown IT solution and dose data analysis framework.

Learning Objectives:

Describe the scope and range of radiation dose monitoring and protocol management in a modern radiology practice

Review examples of data available from a variety of systems and how it managed and conveyed.

Reflect on the role of the physicist in radiation dose awareness.
TH‐F‐209‐00: Pitfalls: Reliability and Performance of Diagnostic X‐Ray Sources
Authors: Behling Rolf
Published: July 2016

Purpose:

Performance and reliability of medical X‐ray tubes for imaging are crucial from an ethical, clinical and economic perspective. This lecture will deliver insight into the aspects to consider during the decision making process to invest in X‐ray imaging equipment. Outdated metric still hampers realistic product comparison. It is time to change this and to comply with latest standards, which consider current technology. Failure modes and ways to avoid down‐time of the equipment shall be discussed. In view of the increasing number of interventional procedures and the hazards associated with ionizing radiation, toxic contrast agents, and the combination thereof, the aspect of system reliability is of paramount importance.

Methods:

A comprehensive picture of trends for different modalities (CT, angiography, general radiology) has been drawn and led to the development of novel X‐ray tube technology.

Results:

Recent X‐ray tubes feature enhanced reliability and unprecedented performance. Relevant metrics for product comparison still have to be implemented in practice.

Conclusion:

The speed of scientific and industrial development of new diagnostic and therapeutic X‐ray sources remains tremendous. Still, users suffer from gaps between desire and reality in day‐to‐day diagnostic routine. X‐ray sources are still limiting cutting‐edge medical procedures. Side‐effects of wear and tear, limitations of the clinical work flow, costs, the characteristics of the X‐ray spectrum and others topics need to be further addressed. New applications and modalities, like detection‐based color‐resolved X‐ray and phase‐contrast / dark‐field imaging will impact the course of new developments of X‐ray sources.

Learning Objectives:

Understand the basic requirements on medical diagnostic X‐ray sources per modality

Learn to select the optimal equipment employing state‐of‐the‐art metric

Know causes of failures, depending on the way X‐ray sources are operated

Understand methods to remediate critical situations

Understand the meaning of different warranty models

I am employee of Royal Philips; R. Behling, No external funding. I am employee of Royal Philips.
TH‐F‐209‐01: Pitfalls: Reliability and Performance of Diagnostic X‐Ray Sources
Authors: Behling R.
Published: July 2016

Purpose:

Performance and reliability of medical X‐ray tubes for imaging are crucial from an ethical, clinical and economic perspective. This lecture will deliver insight into the aspects to consider during the decision making process to invest in X‐ray imaging equipment. Outdated metric still hampers realistic product comparison. It is time to change this and to comply with latest standards, which consider current technology. Failure modes and ways to avoid down‐time of the equipment shall be discussed. In view of the increasing number of interventional procedures and the hazards associated with ionizing radiation, toxic contrast agents, and the combination thereof, the aspect of system reliability is of paramount importance.

Methods:

A comprehensive picture of trends for different modalities (CT, angiography, general radiology) has been drawn and led to the development of novel X‐ray tube technology.

Results:

Recent X‐ray tubes feature enhanced reliability and unprecedented performance. Relevant metrics for product comparison still have to be implemented in practice.

Conclusion:

The speed of scientific and industrial development of new diagnostic and therapeutic X‐ray sources remains tremendous. Still, users suffer from gaps between desire and reality in day‐to‐day diagnostic routine. X‐ray sources are still limiting cutting‐edge medical procedures. Side‐effects of wear and tear, limitations of the clinical work flow, costs, the characteristics of the X‐ray spectrum and others topics need to be further addressed. New applications and modalities, like detection‐based color‐resolved X‐ray and phase‐contrast / dark‐field imaging will impact the course of new developments of X‐ray sources.

Learning Objectives:

Understand the basic requirements on medical diagnostic X‐ray sources per modality

Learn to select the optimal equipment employing state‐of‐the‐art metric

Know causes of failures, depending on the way X‐ray sources are operated

Understand methods to remediate critical situations

Understand the meaning of different warranty models

I am employee of Royal Philips; R. Behling, No external funding. I am employee of Royal Philips.
An
RYR1
mutation associated with malignant hyperthermia is also associated with bleeding abnormalities
Authors: Lopez Rubén J. , Byrne Susan , Vukcevic Mirko , Sekulic-Jablanovic Marijana , Xu Lifen , Brink Marijke , Alamelu Jay , Voermans Nicol , Snoeck Marc , Clement Emma , Muntoni Francesco , Zhou Haiyan , Radunovic Aleksandar , Mohammed Shehla , Wraige Elizabeth , Zorzato Francesco , Treves Susan , Jungbluth Heinz
Published: July 2016

Gain-of-function
RYR1
mutations cause increased Ca
2+
sparks in vascular smooth muscle cells and prolong bleeding.
Research funding for addressing tobacco-related disease: an analysis of UK investment between 2008 and 2012
Authors: Hall Mary , Bogdanovica Ilze , Britton John
Published: July 2016

Introduction

Tobacco use is the leading cause of preventable death in the UK. However, research spending on tobacco-related disease, and particularly smoking prevention, is thought to be low. We therefore aimed to assess the relation between tobacco-related research investment and disease burden from 2008 to 2012.

Methods

We used the Health Research Classification System to classify UK government and charitable research funding by broad health category and then by tobacco prevention research and 18 WHO defined tobacco-related diseases. We used UK mortality figures to calculate disease-specific tobacco attributable deaths and then compared disease specific and tobacco prevention research investment with all cause and tobacco attributable mortality over the 5-year period and as annual averages.

Results

12 922 research grants were identified with a total value of £6.69bn, an annual average of £1.34bn. Annually an average of 110 000 people die from tobacco-related disease, approximately 20% of total deaths. £130m is invested in researching tobacco-related disease each year and £5m on tobacco prevention, 10.8% and 0.42% of total annual research funding, respectively. Prevention research equated to an annual average of £46 per tobacco attributable death or one pound for every £29 spent on tobacco-related disease. Funding varied widely for diseases with different numbers of deaths (eg, lung cancer £68 per all cause death, cervical cancer £2500), similar numbers of deaths (leukaemia £983 per death, stomach cancer £43) or similar numbers of tobacco attributable deaths (eg, colorectal cancer £5k, pancreatic cancer £670, bladder cancer £340).

Conclusions

Tobacco-related research funding is not related to burden of disease or level of risk. As a result certain diseases receive a disproportionately low level of research funding and disease prevention funding is even lower.
Adjuvant therapy for highly malignant canine mammary tumours: Cox‐2 inhibitor versus chemotherapy: a case–control prospective study
Authors: Arenas C. , Peña L. , Granados‐Soler J. L. , Pérez‐Alenza M. D.
Published: July 2016

Cyclooxygenase‐2 (Cox‐2) enzyme participates in different steps of the carcinogenetic process and in canine mammary tumours (CMTs), a high expression of Cox‐2 is associated with malignancy and tumour angiogenesis. The objectives of the study were to evaluate the disease‐free survival (DFS) and overall survival (OS) of a Cox‐2 inhibitor as adjuvant therapy in dogs with highly malignant (HM)‐CMTs and compare it with that of dogs treated with chemotherapy and with control dogs. Twenty‐eight dogs were prospectively included. After surgery, dogs were alternatively allocated into two treatment groups (chemotherapy with mitoxantrone n=8; Cox‐2 inhibitor, firocoxib n=7). Control group (n=13) included dogs whose owners rejected adjuvant therapy. All dogs were followed up for two years or until death. The DFS was significantly higher in dogs that received adjuvant treatment (mitoxantrone or firocoxib) (P=0.030) than in control dogs. Dogs on firocoxib treatment had significantly higher DFS (P=0.015) and OS (P=0.048) than control dogs. The DFS and OS of dogs on mitoxantrone treatment were not statistically different from controls. In conclusion, this study supports the use of firocoxib for the treatment of HM‐CMTs. Further studies are needed to compare the efficacy of chemotherapy drugs versus Cox‐2 inhibitors as adjuvant treatment in these cases.
Azuki bean (Vigna angularis) extract reduces oxidative stress and stimulates autophagy in the kidneys of streptozotocin-induced early diabetic rats
Authors: Sato Shin , Kataoka Saori , Kimura Akane , Mukai Yuuka
Published: July 2016

Diabetic kidney disease is associated with oxidative stress, inflammation, and autophagy. The aim of this study was to investigate the effect of azuki bean (Vigna angularis) extract (ABE) on oxidative stress and autophagy in the kidneys of diabetic rats. Streptozotocin (STZ)-induced diabetic rats received 0, 10, or 40 mg/kg of ABE orally for 4 weeks, whereas vehicle-injected control rats received distilled water. Level of plasma glutathione and expression of heme oxygenase-1 (HO-1), p47phox (NADPH oxidase subunit), and markers associated with autophagy were examined. The glutathione level in the 40 mg/kg ABE-treated diabetic group (ABE-40 group) was higher than that of the untreated diabetic group (ABE-0 group). The HO-1 and p47phox protein expression levels of the ABE-40 group were lower (47% and 33%, respectively) than those of the ABE-0 group. The level of light chain 3B II (LC3B-II) was higher in the ABE-40 group than in the ABE-0 group. Protein levels of p62/sequestosome 1 (p62) in the ABE-40 group were lower than those in the ABE-0 group. Our results suggest that ABE may attenuate STZ-induced diabetic kidney injury by suppressing oxidative stress and (or) by upregulating autophagy.
MODERN MONETARY CIRCUIT THEORY, STABILITY OF INTERCONNECTED BANKING NETWORK, AND BALANCE SHEET OPTIMIZATION FOR INDIVIDUAL BANKS
Authors: LIPTON ALEXANDER
Published: July 2016

A modern version of monetary circuit theory with a particular emphasis on stochastic underpinning mechanisms is developed. It is explained how money is created by the banking system as a whole and by individual banks. The role of central banks as system stabilizers and liquidity providers is elucidated. It is shown how in the process of money creation banks become naturally interconnected. A novel extended structural default model describing the stability of the Interconnected banking network is proposed. The purpose of bank capital and liquidity is explained. Multi-period constrained optimization problem for bank balance sheet is formulated and solved in a simple case. Both theoretical and practical aspects are covered.
IPO Initial Excess Return in an Emerging Market: Evidence from Vietnam’s Stock Exchanges
Authors: Huang Shaio Yan , Lee Chao-Hsiung , Pan Lee-Hsien , Nguyen Thi Bich Hanh
Published: July 2016

Using data from 118 firms listed on the Ho Chi Minh and Hanoi Stock Exchanges from January 1, 2006 to June 30, 2010, we find that Vietnamese IPOs, which face high government regulation, are on average 1.92% underpriced during the initial 30-day trading period. Among these firms, the initial excess returns are 3.49%, 2.68%, and 2.27% for the manufacturing, information, and service industries, respectively, possibly due to favorable government policy toward industrialization. Moreover, the government’s policies regarding trade liberalization, state-owned enterprise privatization, and export-led industrialization are positively associated with IPO underpricing during the initial trading period. Consequently, IPO initial excess return is more pronounced in 2007, when Vietnam joined the World Trade Organization.
The Impact of Corporate Culture Disclosure on Performance: A Quantitative Approach
Authors: Guo Zhaorui , Chan Kam C. , Xue Yunkui
Published: July 2016

In this paper, we propose a quantitative approach to measure the extent of corporate culture disclosure. Using this new measure, we document that corporate culture disclosure and performance is positively correlated in terms of stock return, return on assets, cash flow, earnings growth, sales growth, return on sales, and turnover; corporate culture disclosure also helps to lower the negative impact of missing earnings benchmarks using a sample of Chinese firms. In addition, we find that the extent of corporate culture disclosure is negatively correlated with earnings management and operational risk exposure. Essentially, our comprehensive analysis provides a good illustration of using the method to measure corporate culture disclosure.
Corporate Governance and the Efficiency of Internal Capital Markets
Authors: Chen I-Ju
Published: July 2016

This study investigates whether the governance structure of a diversified firm affects its internal capital market and the associated investment efficiencies. We propose that managers of well-governed diversified firms are more subject to the disciplinary power of shareholders and thus are less likely to undertake the inefficient capital investment between divisions. We find that the small segment investment of well-governed diversified firms has less sensitivity with regard to cash flows, but is more sensitive to growth opportunities. Our empirical results suggest that governance mechanisms play an important role in capital allocation among divisions of diversified firms.
Sensitivity Analysis of Material Microstructure Effects on Predicted Crack Paths Using Finite Element Simulations
Authors: Jacob Anaïs , Mehmanparast Ali
Published: July 2016

The effects of microstructure, grain and grain boundary (GB) properties on predicted damage paths and indicative crack propagation direction have been examined for a polycrystalline material using mesoscale finite element simulations. Numerical analyses were carried out on a compact tension specimen geometry containing granular mesh structures with random grain shapes and sizes of average diameter 100[Formula: see text][Formula: see text]m. Nanoindentation tests were performed to investigate the dependency of mesoscale hardness measurements on the indentation location with respect to grain and GB regions. Finite element results have shown that under tensile loading conditions, the predicted damage paths are very sensitive to the granular mesh structure, GB properties and individual grain properties. Furthermore, finite element results have revealed that the cracking mode (i.e., transgranular/intergranular) and maximum crack deviation angle are strongly dependent on the material microstructures employed in simulations.
DAY-OF-THE-WEEK EFFECT IN US BIOTECHNOLOGY STOCKS — DO POLICY CHANGES AND ECONOMIC CYCLES MATTER?
Authors: CHATTERJEE SWARN , HUBBLE AMY
Published: July 2016

This study examines the presence of the day-of-the-week effect on daily returns of biotechnology stocks over a 16-year period from January 2002 to December 2015. Using daily returns from the NASDAQ Biotechnology Index (NBI), we find that the stock returns were the lowest on Mondays, and compared to the Mondays the stock returns were significantly higher on Wednesdays, Thursdays, and Fridays. The day-of-the-week effect on returns of biotechnology stocks remained significant even after controlling for the Fama–French and Carhart factors. Moreover, the results from using the asymmetric generalized autoregressive conditional heteroskedastic (GARCH) processes reveal that momentum and small-firm effect were positively associated with the market risk-adjusted returns of the biotechnology stocks during this period. The findings of our study suggest that active portfolio managers need to consider the day of the week, momentum, and small-firm effect when making trading decisions for biotechnology stocks. Implications for portfolio managers, small investors, scholars, and policymakers are included.
Algorithm 963
Authors: Escobar Marcos , Rudolph Benedikt , Zagst Rudi
Published: July 2016

We describe the implementation of a parameter estimation method suitable for models commonly used in quantitative finance. The Continuum-Generalized Method of Moments (CGMM) is a Generalized Method of Moments (GMM) type of methodology that applies a continuum of moment conditions to achieve the efficiency of a Maximum Likelihood method. Instead of the transition density, the more commonly available conditional characteristic function is used for estimation. We test the CGMM and a simpler version, called the CMM, on simulated time series to check the recovery of the parameters. We also applied CMM to two stochastic covariance models, the Wishart Affine Stochastic Correlation (WASC) model and the Principal Components Stochastic Volatility (PCSV) model. This illustrates the power of CGMM, as stochastic covariance models are generally hard to estimate. The estimation method is fully implemented in MATLAB.
Space-Efficient Approximations for Subset Sum
Authors: Gál Anna , Jang Jing-Tang , Limaye Nutan , Mahajan Meena , Sreenivasaiah Karteek
Published: July 2016

S
ubset
S
um
is a well-known NP-complete problem: given
t
∈
Z
+
and a set
S
of
m
positive integers, output YES if and only if there is a subset
S
′⊆
S
such that the sum of all numbers in
S
′ equals
t
. The problem and its search and optimization versions are known to be solvable in pseudopolynomial time in general.

We develop a one-pass deterministic streaming algorithm that uses space O(log
t
/ ε) and decides if some subset of the input stream adds up to a value in the range {(1 ± ϵ)
t
}. Using this algorithm, we design space-efficient fully polynomial-time approximation schemes (FPTAS) solving the search and optimization versions of S
ubset
S
um
. Our algorithms run in O(1 / ϵ
m
2
) time and O(1 / ϵ) space on unit-cost RAMs, where 1 + ϵ is the approximation factor. This implies constant space quadratic time FPTAS on unit-cost RAMs when ϵ is a constant. Previous FPTAS used space linear in
m
.

In addition, we show that on certain inputs, when a solution is located within a short prefix of the input sequence, our algorithms may run in sublinear time. We apply our techniques to the problem of finding balanced separators, and we extend our results to some other variants of the more general knapsack problem.

When the input numbers are encoded in unary, the decision version has been known to be in log space. We give streaming space lower and upper bounds for unary S
ubset
S
um
(USS). If the input length is
N
when the numbers are encoded in unary, we show that randomized
s
-pass streaming algorithms for exact S
ubset
S
um
need space Ω (√N/s) and give a simple deterministic two-pass streaming algorithm using O(√
N
log
N
) space.

Finally, we formulate an encoding under which USS is monotone and show that the exact and approximate versions in this formulation have monotone
O
(log
2
t
) depth Boolean circuits. We also show that any circuit using ε-approximator gates for S
ubset
S
um
under this encoding needs Ω(
n
/log
n
) gates to compute the disjointness function.
A Survey on Wireless Indoor Localization from the Device Perspective
Authors: Xiao Jiang , Zhou Zimu , Yi Youwen , Ni Lionel M.
Published: July 2016

With the marvelous development of wireless techniques and ubiquitous deployment of wireless systems indoors, myriad indoor location-based services (ILBSs) have permeated into numerous aspects of modern life. The most fundamental functionality is to pinpoint the location of the target via wireless devices. According to how wireless devices interact with the target, wireless indoor localization schemes roughly fall into two categories: device based and device free. In device-based localization, a wireless device (e.g., a smartphone) is attached to the target and computes its location through cooperation with other deployed wireless devices. In device-free localization, the target carries no wireless devices, while the wireless infrastructure deployed in the environment determines the target’s location by analyzing its impact on wireless signals.

This article is intended to offer a comprehensive state-of-the-art survey on wireless indoor localization from the device perspective. In this survey, we review the recent advances in both modes by elaborating on the underlying wireless modalities, basic localization principles, and data fusion techniques, with special emphasis on emerging trends in (1) leveraging smartphones to integrate wireless and sensor capabilities and extend to the social context for device-based localization, and (2) extracting specific wireless features to trigger novel human-centric device-free localization. We comprehensively compare each scheme in terms of accuracy, cost, scalability, and energy efficiency. Furthermore, we take a first look at intrinsic technical challenges in both categories and identify several open research issues associated with these new challenges.
Experimental Analysis of Space-Bounded Schedulers
Authors: Simhadri Harsha Vardhan , Blelloch Guy E. , Fineman Jeremy T. , Gibbons Phillip B. , Kyrola Aapo
Published: July 2016

The running time of nested parallel programs on shared-memory machines depends in significant part on how well the scheduler mapping the program to the machine is optimized for the organization of caches and processor cores on the machine. Recent work proposed “space-bounded schedulers” for scheduling such programs on the multilevel cache hierarchies of current machines. The main benefit of this class of schedulers is that they provably preserve locality of the program at every level in the hierarchy, which can result in fewer cache misses and better use of bandwidth than the popular work-stealing scheduler. On the other hand, compared to work stealing, space-bounded schedulers are inferior at load balancing and may have greater scheduling overheads, raising the question as to the relative effectiveness of the two schedulers in practice.

In this article, we provide the first experimental study aimed at addressing this question. To facilitate this study, we built a flexible experimental framework with separate interfaces for programs and schedulers. This enables a head-to-head comparison of the relative strengths of schedulers in terms of running times and cache miss counts across a range of benchmarks. (The framework is validated by comparisons with the Intel® Cilk™ Plus work-stealing scheduler.) We present experimental results on a 32-core Xeon® 7560 comparing work stealing, hierarchy-minded work stealing, and two variants of space-bounded schedulers on both divide-and-conquer microbenchmarks and some popular algorithmic kernels. Our results indicate that space-bounded schedulers reduce the number of L3 cache misses compared to work-stealing schedulers by 25% to 65% for most of the benchmarks, but incur up to 27% additional scheduler and load-imbalance overhead. Only for memory-intensive benchmarks can the reduction in cache misses overcome the added overhead, resulting in up to a 25% improvement in running time for synthetic benchmarks and about 20% improvement for algorithmic kernels. We also quantify runtime improvements varying the available bandwidth per core (the “bandwidth gap”) and show up to 50% improvements in the running times of kernels as this gap increases fourfold. As part of our study, we generalize prior definitions of space-bounded schedulers to allow for more practical variants (while still preserving their guarantees) and explore implementation tradeoffs.
Extremes of user experience and design thinking
Authors: Marcus Aaron
Published: July 2016

The
Interactions
website (interactions.acm.org) hosts a stable of bloggers who share insights and observations on HCI, often challenging current practices. Each issue we'll publish selected posts from some of the leading voices in the field.
On the design of the humanities
Authors: Mak Bonnie , Pollack Julia
Published: July 2016

This forum highlights conversations at the intersection of design methods and social studies of technology. By highlighting a diversity of perspectives on design interventions and programs, we aim to forge new connections between HCI design and communication, science and technology studies, and media studies scholarship.
--- Daniela Rosner, Editor
On the Viability of a Cloud Virtual Service Provider
Authors: Zheng Liang , Joe-Wong Carlee , Brinton Christopher G. , Tan Chee Wei , Ha Sangtae , Chiang Mung
Published: July 2016

Cloud service providers (CSPs) often face highly dynamic user demands for their resources, which can make it difficult for them to maintain consistent quality-of-service. Some CSPs try to stabilize user demands by offering sustained-use discounts to jobs that consume more instance-hours per month. These discounts present an opportunity for users to pool their usage together into a single ``job.'' In this paper, we examine the viability of a middleman, the cloud virtual service provider (CVSP), that rents cloud resources from a CSP and then resells them to users. We show that the CVSP's business model is only viable if the average job runtimes and thresholds for sustained-use discounts are sufficiently small; otherwise, the CVSP cannot simultaneously maintain low job waiting times while qualifying for a sustained-use discount. We quantify these viability conditions by modeling the CVSP's job scheduling and then use this model to derive users' utility-maximizing demands and the CVSP's profit-maximizing price, as well as the optimal number of instances that the CVSP should rent from the CSP. We verify our results on a one-month trace from Google's production compute cluster, through which we first validate our assumptions on the job arrival and runtime distributions, and then show that the CVSP is viable under these workload traces. Indeed, the CVSP can earn a positive profit without significantly impacting the CSP's revenue, indicating that the CSP and CVSP can coexist in the cloud market.
Hash, Don't Cache (the Page Table)
Authors: Yaniv Idan , Tsafrir Dan
Published: July 2016

Radix page tables as implemented in the x86-64 architecture incur a penalty of four memory references for address translation upon each TLB miss. These 4 references become 24 in virtualized setups, accounting for 5%--90% of the runtime and thus motivating chip vendors to incorporate page walk caches (PWCs). Counterintuitively, an ISCA 2010 paper found that radix page tables with PWCs are superior to hashed page tables, yielding up to 5x fewer DRAM accesses per page walk. We challenge this finding and show that it is the result of comparing against a suboptimal hashed implementation---that of the Itanium architecture. We show that, when carefully optimized, hashed page tables in fact outperform existing PWC-aided x86-64 hardware, shortening benchmark runtimes by 1%--27% and 6%--32% in bare-metal and virtualized setups, without resorting to PWCs. We further show that hashed page tables are inherently more scalable than radix designs and are better suited to accommodate the ever increasing memory size; their downside is that they make it more challenging to support such features as superpages.
Reverse Ranking by Graph Structure
Authors: Buchnik Eliav , Cohen Edith
Published: July 2016

Distances in a network capture relations between nodes and are the basis of centrality, similarity, and influence measures. Often, however, the relevance of a node u to a node v is more precisely measured not by the magnitude of the distance, but by the number of nodes that are closer to v than u. That is, by the
rank
of u in an ordering of nodes by increasing distance from v. We identify and address fundamental challenges in rank-based graph mining. We first consider single-source computation of reverse-ranks and design a "Dijkstra-like" algorithm which computes nodes in order of increasing approximate reverse rank while only traversing edges adjacent to returned nodes. We then define
reverse-rank influence
, which naturally extends reverse nearest neighbors influence [Korn and Muthukrishnan 2000] and builds on a well studied distance-based influence. We present near-linear algorithms for greedy approximate reverse-rank influence maximization. The design relies on our single-source algorithm. Our algorithms utilize near-linear preprocessing of the network to compute all-distance sketches. As a contribution of independent interest, we present a novel algorithm for computing these sketches, which have many other applications, on multi-core architectures.

We complement our algorithms by establishing the hardness of computing
exact
reverse-ranks for a single source and
exact
reverse-rank influence. This implies that when using near-linear algorithms, the small relative errors we obtain are the best we can currently hope for.

Finally, we conduct an experimental evaluation on graphs with tens of millions of edges, demonstrating both scalability and accuracy.
Optimizing TTL Caches under Heavy-Tailed Demands
Authors: Ferragut Andrés , Rodriguez Ismael , Paganini Fernando
Published: July 2016

In this paper we analyze the hit performance of cache systems that receive file requests with general arrival distributions and different popularities. We consider timer-based (TTL) policies, with differentiated timers over which we optimize. The optimal policy is shown to be related to the monotonicity of the hazard rate function of the inter-arrival distribution. In particular for decreasing hazard rates, timer policies outperform the static policy of caching the most popular contents. We provide explicit solutions for the optimal policy in the case of Pareto-distributed inter-request times and a Zipf distribution of file popularities, including a compact fluid characterization in the limit of a large number of files. We compare it through simulation with classical policies, such as least-recently-used and discuss its performance. Finally, we analyze extensions of the optimization framework to a line network of caches.
Improved Achievability and Converse Bounds for Erdos-Renyi Graph Matching
Authors: Cullina Daniel , Kiyavash Negar
Published: July 2016

We consider the problem of perfectly recovering the vertex correspondence between two correlated Erdos-Renyi (ER) graphs. For a pair of correlated graphs on the same vertex set, the correspondence between the vertices can be obscured by randomly permuting the vertex labels of one of the graphs. In some cases, the structural information in the graphs allow this correspondence to be recovered. We investigate the information-theoretic threshold for exact recovery, i.e. the conditions under which the entire vertex correspondence can be correctly recovered given unbounded computational resources. Pedarsani and Grossglauser provided an achievability result of this type. Their result establishes the scaling dependence of the threshold on the number of vertices. We improve on their achievability bound. We also provide a converse bound, establishing conditions under which exact recovery is impossible. Together, these establish the scaling dependence of the threshold on the level of correlation between the two graphs. The converse and achievability bounds differ by a factor of two for sparse, significantly correlated graphs.
On the Approximation Error of Mean-Field Models
Authors: Ying Lei
Published: July 2016

Mean-field models have been used to study large-scale and complex stochastic systems, such as large-scale data centers and dense wireless networks, using simple deterministic models (dynamical systems). This paper analyzes the approximation error of mean-field models for continuous-time Markov chains (CTMC), and focuses on mean-field models that are represented as finite-dimensional dynamical systems with a unique equilibrium point. By applying Stein's method and the perturbation theory, the paper shows that under some mild conditions, if the mean-field model is
globally asymptotically stable
and
locally exponentially stable
, the
mean square difference
between the stationary distribution of the stochastic system with size
M
and the equilibrium point of the corresponding mean-field system is
O(1/M).
The result of this paper establishes a general theorem for establishing the convergence and the approximation error (i.e., the rate of convergence) of a large class of CTMCs to their mean-field limit by mainly looking into the stability of the mean-field model, which is a deterministic system and is often easier to analyze than the CTMCs. Two applications of mean-field models in data center networks are presented to demonstrate the novelty of our results.
Using Predictions in Online Optimization
Authors: Chen Niangjun , Comden Joshua , Liu Zhenhua , Gandhi Anshul , Wierman Adam
Published: July 2016

We consider online convex optimization (OCO) problems with switching costs and noisy predictions. While the design of online algorithms for OCO problems has received considerable attention, the design of algorithms in the context of noisy predictions is largely open. To this point, two promising algorithms have been proposed: Receding Horizon Control (RHC) and Averaging Fixed Horizon Control (AFHC). The comparison of these policies is largely open. AFHC has been shown to provide better worst-case performance, while RHC outperforms AFHC in many realistic settings. In this paper, we introduce a new class of policies, Committed Horizon Control (CHC), that generalizes both RHC and AFHC. We provide average-case analysis and concentration results for CHC policies, yielding the first analysis of RHC for OCO problems with noisy predictions. Further, we provide explicit results characterizing the optimal CHC policy as a function of properties of the prediction noise, e.g., variance and correlation structure. Our results provide a characterization of when AFHC outperforms RHC and vice versa, as well as when other CHC policies outperform both RHC and AFHC.
Optimal Heavy-Traffic Queue Length Scaling in an Incompletely Saturated Switch
Authors: Maguluri Siva Theja , Burle Sai Kiran , Srikant R.
Published: July 2016

We consider an input queued switch operating under the MaxWeight scheduling algorithm. This system is interesting to study because it is a model for Internet routers and data center networks. Recently, it was shown that the MaxWeight algorithm has optimal heavy-traffic queue length scaling when all ports are uniformly saturated. Here we consider the case where a fraction of the ports are saturated and others are not (which we call the incompletely saturated case), and also the case where the rates at which the ports are saturated can be different. We use a recently developed drift technique to show that the heavy-traffic queue length under the MaxWeight scheduling algorithm has optimal scaling with respect to the switch size even in these cases.
Collaborative Filtering with Low Regret
Authors: Bresler Guy , Shah Devavrat , Voloch Luis Filipe
Published: July 2016

There is much empirical evidence that item-item collaborative filtering works well in practice. Motivated to understand this, we provide a framework to design and analyze various recommendation algorithms. The setup amounts to online binary matrix completion, where at each time a random user requests a recommendation and the algorithm chooses an entry to reveal in the user's row. The goal is to minimize regret, or equivalently to maximize the number of +1 entries revealed at any time. We analyze an item-item collaborative filtering algorithm that can achieve fundamentally better performance compared to user-user collaborative filtering. The algorithm achieves good "cold-start" performance (appropriately defined) by quickly making good recommendations to new users about whom there is little information.
Inference in OSNs via Lightweight Partial Crawls
Authors: Avrachenkov Konstantin , Ribeiro Bruno , Sreedharan Jithin K.
Published: July 2016

Are Online Social Network (OSN) A users more likely to form friendships with those with similar attributes? Do users at an OSN B score content more favorably than OSN C users? Such questions frequently arise in the context of Social Network Analysis (SNA) but often crawling an OSN network via its Application Programming Interface (API) is the only way to gather data from a third party. To date, these partial API crawls are the majority of public datasets and the synonym of lack of statistical guarantees in incomplete-data comparisons, severely limiting SNA research progress. Using regenerative properties of the random walks, we propose estimation techniques based on short crawls that have proven statistical guarantees. Moreover, our short crawls can be implemented in massively distributed algorithms. We also provide an adaptive crawler that makes our method parameter-free, significantly improving our statistical guarantees. We then derive the Bayesian approximation of the posterior of the estimates, and in addition, obtain an estimator for the expected value of node and edge statistics in an equivalent configuration model or Chung-Lu random graph model of the given network (where nodes are connected randomly) and use it as a basis for testing null hypotheses. The theoretical results are supported with simulations on a variety of real-world networks.
Spatial Multi-LRU Caching for Wireless Networks with Coverage Overlaps
Authors: Giovanidis Anastasios , Avranas Apostolos
Published: July 2016

This article introduces a novel family of decentralised caching policies for wireless networks, referred to as spatial multi-LRU. Based on these, cache inventories are updated in a way that provides content diversity to users that are covered by, and thus have access to, more than one station. Two variations are proposed, the multi-LRU-One and -All, which differ in the number of replicas inserted in the involved edge caches. Che-like approximations are proposed to accurately predict their hit probability under the Independent Reference Model (IRM). For IRM traffic multi-LRU-One outperforms multi-LRU-All, whereas when the traffic exhibits temporal locality the -All variation can perform better.
A Service System with Randomly Behaving On-demand Agents
Authors: Nguyen Lam M. , Stolyar Alexander L.
Published: July 2016

We consider a service system where agents (or, servers) are invited on-demand. Customers arrive as a Poisson process and join a customer queue. Customer service times are i.i.d. exponential. Agents' behavior is random in two respects. First, they can be invited into the system exogenously, and join the agent queue after a random time. Second, with some probability they rejoin the agent queue after a service completion, and otherwise leave the system. The objective is to design a real-time adaptive agent invitation scheme that keeps both customer and agent queues/waiting-times small. We study an adaptive scheme, which controls the number of pending agent invitations, based on queue-state feedback.

We study the system process fluid limits, in the asymptotic regime where the customer arrival rate goes to infinity. We use the machinery of switched linear systems and common quadratic Lyapunov functions to derive sufficient conditions for the local stability of fluid limits at the desired equilibrium point (with zero queues). We conjecture that, for our model, local stability is in fact sufficient for global stability of fluid limits; the validity of this conjecture is supported by numerical and simulation experiments. When the local stability conditions do hold, simulations show good overall performance of the scheme.
Time-Based Bandwidth Allocation for Heterogeneous Storage
Authors: Wang Hui , Varman Peter
Published: July 2016

Providing fairness and system efficiency are important, often conflicting, requirements when allocating shared resources. In a hybrid storage system the problem is complicated by the high variability in request service times, caused by speed differences between heterogeneous devices and workload-specific variations in access time within a device.

This paper describes a model for fair time-based resource allocation in a hybrid storage system that has better fairness and efficiency than traditional IOPS-based schemes. An analytical model is developed and an optimal algorithm for fairly allocating device times to applications while maximizing the system throughput or utilization is presented. The results are validated using Linux implementations.
Contrasting Effects of Replication in Parallel Systems
Authors: Poloczek Felix , Ciucu Florin
Published: July 2016

Task replication has recently been advocated as a practical solution to reduce latencies in parallel systems. In addition to several convincing empirical studies, analytical results have been provided, yet under some strong assumptions such as independent service times of the replicas, which may lend themselves to some contrasting and perhaps contriving behavior. For instance, under the independence assumption, an overloaded system can be stabilized by a replication factor, but can be sent back in overload through further replication. Motivated by the need to dispense with such common and restricting assumptions, which may cause unexpected behavior, we develop a unified and general theoretical framework to compute tight bounds on the distribution of response times in general replication systems. These results immediately lend themselves to the optimal number of replicas minimizing response time quantiles, depending on the parameters of the system (e.g., the degree of correlation amongst replicas).
Trading Discount for Reputation?
Authors: Xie Hong , Ma Richard T.B. , Lui John C.S.
Published: July 2016

We develop an optimization framework to trade short-term profits for reputation (i.e., reducing ramp-up time). We apply the stochastic bandits framework to design an online discounting mechanism which infers the optimal discount from a seller's historical transaction data. We conduct experiments on an eBay's dataset and show that our online discounting mechanism can trade 60% of the shortterm profits for reducing the ramp-up time by 40%.
Automated Test Location Selection For Cellular Network Upgrades
Authors: Qureshi Mubashir Adnan , Mahimkar Ajay , Qiu Lili , Ge Zihui , Puthenpura Sarat , Mir Nabeel , Ahuja Sanjeev
Published: July 2016

Cellular networks are constantly evolving due to frequent changes in radio access and end user equipment technologies, applications, and traffic. Network upgrades should be performed with extreme caution since millions of users heavily depend on the cellular networks. Before upgrading the entire network, it is important to conduct field evaluation of upgrades.The choice and number of field test locations have significant impact on the time-to-market and confidence in how well various network upgrades will work out in the rest of the network. We propose a novel approach -- Reflection to automatically determine where to conduct the upgrade field tests to accurately identify important features that affect the upgrade and predict for the performance of untested locations. We demonstrate its effectiveness using real traces collected from a major US cellular network as well as synthetic traces.