bluuebunny/crossref_metadata_2025 huggingface dataset:
Dose equations for shift‐variant CT acquisition modes using variable pitch, tube current, and aperture, and the meaning of their associated CTDIvol
Authors: Dixon Robert L. , Boone John M. , Kraft Robert A.
Published: October 2014

Purpose:

With the increasing clinical use of shift‐variant CT protocols involving tube current modulation (TCM), variable pitch or pitch modulation (PM), and variable aperture a(t), the interpretation of the scanner‐reported CTDIvol is called into question. This was addressed for TCM in their previous paper published by Dixon and Boone [Med. Phys. 40, 111920 (14pp.) (2013)] and is extended to PM and concurrent TCM/PM as well as variable aperture in this work.

Methods:

Rigorous convolution equations are derived to describe the accumulated dose distributions for TCM, PM, and concurrent TCM/PM. A comparison with scanner‐reported CTDIvol formulae clearly identifies the source of their differences with the traditional CTDIvol. Dose distribution simulations using the convolution are provided for a variety of TCM and PM scenarios including a helical shuttle used for perfusion studies (as well as constant mA)—all having the same scanner‐reported CTDIvol. These new convolution simulations for TCM are validated by comparison with their previous discrete summations.

Results:

These equations show that PM is equivalent to TCM if the pitch variation p(z) is proportional to 1/i(z), where i(z) is the local tube current. The simulations show that the local dose at z depends only weakly on the local tube current i(z) or local pitch p(z) due to scatter from all other locations along z, and that the “local CTDIvol(z)” or “CTDIvol per slice” do not represent a local dose but rather only a relative i(z) or p(z). The CTDI‐paradigm does not apply to shift‐variant techniques and the scanner‐reported CTDIvol for the same lacks physical significance and relevance.

Conclusions:

While the traditional CTDIvol at constant tube current and pitch conveys useful information (the peak dose at the center of the scan length), CTDIvol for shift‐variant techniques (TCM or PM) conveys no useful information about the associated dose distribution it purportedly represents. On the other hand, the total energy absorbed E (“integral dose”) as well as its surrogate DLP remain robust (invariant) with respect to shift‐variance, depending only on the total mAs = 〈i〉t0 accumulated during the total beam‐on time t0 and aperture a, where 〈i〉 is the average current.
Validation of a stereo camera system to quantify brain deformation due to breathing and pulsatility
Authors: Faria Carlos , Sadowsky Ofri , Bicho Estela , Ferrigno Giancarlo , Joskowicz Leo , Shoham Moshe , Vivanti Refael , De Momi Elena
Published: October 2014

Purpose:

A new stereo vision system is presented to quantify brain shift and pulsatility in open‐skull neurosurgeries.

Methods:

The system is endowed with hardware and software synchronous image acquisition with timestamp embedding in the captured images, a brain surface oriented feature detection, and a tracking subroutine robust to occlusions and outliers. A validation experiment for the stereo vision system was conducted against a gold‐standard optical tracking system, Optotrak CERTUS. A static and dynamic analysis of the stereo camera tracking error was performed tracking a customized object in different positions, orientations, linear, and angular speeds.

Results:

The system is able to detect an immobile object position and orientation with a maximum error of 0.5 mm and 1.6° in all depth of field, and tracking a moving object until 3 mm/s with a median error of 0.5 mm. Three stereo video acquisitions were recorded from a patient, immediately after the craniotomy. The cortical pulsatile motion was captured and is represented in the time and frequency domain. The amplitude of motion of the cloud of features’ center of mass was inferior to 0.8 mm. Three distinct peaks are identified in the fast Fourier transform analysis related to the sympathovagal balance, breathing, and blood pressure with 0.03–0.05, 0.2, and 1 Hz, respectively.

Conclusions:

The stereo vision system presented is a precise and robust system to measure brain shift and pulsatility with an accuracy superior to other reported systems.
A computational study of the effect of intraglottal vortex-induced negative pressure on vocal fold vibration
Authors: Farahani Mehrdad H. , Zhang Zhaoyan
Published: October 2014

Recent studies reported the formation of intraglottal vortices for medium and high subglottal pressures in excised-larynx experiments, and hypothesized that the suction force created by these vortices might affect vocal fold vibration. However, high subglottal pressures often lead to large vocal fold elastic recoil forces, and it is unclear if the vortex-induced suction force is large enough compared with the elastic recoil force to have noticeable effects on vocal fold vibration. In this study, the validity of this hypothesis was examined using a computational model. The results suggest that intraglottal vortices might only have small effects on vocal fold vibration.
Protein kinase D2 is a digital amplifier of T cell receptor–stimulated diacylglycerol signaling in naïve CD8
+
T cells
Authors: Navarro María N. , Feijoo-Carnero Carmen , Arandilla Alba Gonzalez , Trost Matthias , Cantrell Doreen A.
Published: October 2014

The kinase PKD2 matches the immune response to the intensity of T cell receptor stimulation.
Hedgehog: From Foe to Friend in the Battle Against Bladder Cancer
Authors: Ferrarelli Leslie K.
Published: October 2014

Hedgehog signaling promotes bladder cancer formation, but the loss of hedgehog-mediated stroma-tumor crosstalk contributes to disease progression.
Transporting the Calcium Signal to the Nucleus
Authors: Gough Nancy R.
Published: October 2014

CaMKIIγ delivers Ca
2+
/CaM from voltage-gated calcium channels to the nucleus.
Identification of VIM-2-Producing Pseudomonas aeruginosa from Tanzania Is Associated with Sequence Types 244 and 640 and the Location of
bla
VIM-2
in a TniC Integron
Authors: Moyo Sabrina , Haldorsen Bjørg , Aboud Said , Blomberg Bjørn , Maselle Samuel Y. , Sundsfjord Arnfinn , Langeland Nina , Samuelsen Ørjan
Published: October 2014

Epidemiological data on carbapenemase-producing Gram-negative bacteria on the African continent are limited. Here, we report the identification of VIM-2-producing
Pseudomonas aeruginosa
isolates in Tanzania. Eight out of 90 clinical isolates of
P. aeruginosa
from a tertiary care hospital in Dar es Salaam were shown to harbor
bla
VIM-2
. The
bla
VIM-2
-positive isolates belonged to two different sequence types (ST), ST244 and ST640, with
bla
VIM-2
located in an unusual integron structure lacking the 3′ conserved region of
qac
Δ
E1-sul1
.
JPC-2997, a New Aminomethylphenol with High
In Vitro
and
In Vivo
Antimalarial Activities against Blood Stages of Plasmodium
Authors: Birrell Geoffrey W. , Chavchich Marina , Ager Arba L. , Shieh Hong-Ming , Heffernan Gavin D. , Zhao Wenyi , Krasucki Peter E. , Saionz Kurt W. , Terpinski Jacek , Schiehser Guy A. , Jacobus Laura R. , Shanks G. Dennis , Jacobus David P. , Edstein Michael D.
Published: October 2014

4-(
tert
-Butyl)-2-((
tert
-butylamino)methyl)-6-(6-(trifluoromethyl)pyridin-3-yl)-phenol (JPC-2997) is a new aminomethylphenol compound that is highly active
in vitro
against the chloroquine-sensitive D6, the chloroquine-resistant W2, and the multidrug-resistant TM90-C2B
Plasmodium falciparum
lines, with 50% inhibitory concentrations (IC
50s
) ranging from 7 nM to 34 nM. JPC-2997 is >2,500 times less cytotoxic (IC
50
s > 35 μM) to human (HepG2 and HEK293) and rodent (BHK) cell lines than the D6 parasite line. In comparison to the chemically related WR-194,965, a drug that had advanced to clinical studies, JPC-2997 was 2-fold more active
in vitro
against
P. falciparum
lines and 3-fold less cytotoxic. The compound possesses potent
in vivo
suppression activity against
Plasmodium berghei
, with a 50% effective dose (ED
50
) of 0.5 mg/kg of body weight/day following oral dosing in the Peters 4-day test. The radical curative dose of JPC-2997 was remarkably low, at a total dose of 24 mg/kg, using the modified Thompson test. JPC-2997 was effective in curing three
Aotus
monkeys infected with a chloroquine- and pyrimethamine-resistant strain of
Plasmodium vivax
at a dose of 20 mg/kg daily for 3 days. At the doses administered, JPC-2997 appeared to be well tolerated in mice and monkeys. Preliminary studies of JPC-2997 in mice show linear pharmacokinetics over the range 2.5 to 40 mg/kg, a low clearance of 0.22 liters/h/kg, a volume of distribution of 15.6 liters/kg, and an elimination half-life of 49.8 h. The high
in vivo
potency data and lengthy elimination half-life of JPC-2997 suggest that it is worthy of further preclinical assessment as a partner drug.
A Continuous Enzyme-Coupled Assay for Triphosphohydrolase Activity of HIV-1 Restriction Factor SAMHD1
Authors: Arnold Laurence H. , Kunzelmann Simone , Webb Martin R. , Taylor Ian A.
Published: October 2014

The development of deoxynucleoside triphosphate (dNTP)-based drugs requires a quantitative understanding of any inhibition, activation, or hydrolysis by off-target cellular enzymes. SAMHD1 is a regulatory dNTP-triphosphohydrolase that inhibits HIV-1 replication in human myeloid cells. We describe here an enzyme-coupled assay for quantifying the activation, inhibition, and hydrolysis of dNTPs, nucleotide analogues, and nucleotide analogue inhibitors by triphosphohydrolase enzymes. The assay facilitates mechanistic studies of triphosphohydrolase enzymes and the quantification of off-target effects of nucleotide-based antiviral and chemotherapeutic agents.
The Investigational Agent E1210 Is Effective in Treatment of Experimental Invasive Candidiasis Caused by Resistant Candida albicans
Authors: Wiederhold Nathan P. , Najvar Laura K. , Fothergill Annette W. , McCarthy Dora I. , Bocanegra Rosie , Olivo Marcos , Kirkpatrick William R. , Everson Michael P. , Duncanson Frederick P. , Patterson Thomas F.
Published: October 2014

The
in vitro
and
in vivo
activity of the inositol acyltransferase inhibitor E1210 was evaluated against echinocandin-resistant
Candida albicans
. E1210 demonstrated potent
in vitro
activity, and in mice with invasive candidiasis caused by echinocandin-resistant
C. albicans
, oral doses of 10 and 40 mg E1210/kg of body weight twice daily significantly improved survival and reduced fungal burden compared to those of controls and mice treated with caspofungin (10 mg/kg/day). These results demonstrate the potential use of E1210 against resistant
C. albicans
infections.
Oxidative Stress Enhances Cephalosporin Resistance of Enterococcus faecalis through Activation of a Two-Component Signaling System
Authors: Djorić Dušanka , Kristich Christopher J.
Published: October 2014

Enterococcus faecalis
is a low-GC Gram-positive bacterium, a normal resident of the gastrointestinal (GI) tract, and an important hospital-acquired pathogen. An important risk factor for hospital-acquired enterococcal infections is prior therapy with broad-spectrum cephalosporins, antibiotics that impair cell wall biosynthesis by inhibiting peptidoglycan cross-linking. Enterococci are intrinsically resistant to cephalosporins; however, environmental factors that modulate cephalosporin resistance have not been described. While searching for the genetic determinants of cephalosporin resistance in
E. faecalis
, we unexpectedly discovered that oxidative stress, whether from external sources or derived from endogenous metabolism, drives enhanced intrinsic resistance to cephalosporins. A particular source of oxidative stress, H
2
O
2
, activates signaling through the CroR-CroS two-component signaling system, a known determinant of cephalosporin resistance in
E. faecalis
. We find that CroR-CroS is required for adaptation to H
2
O
2
stress and that H
2
O
2
potentiates the activities of cephalosporins against
E. faecalis
when the CroR-CroS signaling system is nonfunctional. Rather than directly detecting H
2
O
2
, our data suggest that the CroR-CroS system responds to cell envelope damage caused by H
2
O
2
exposure in order to promote cell envelope repair and enhanced cephalosporin resistance.
The
rv1184c
Locus Encodes Chp2, an Acyltransferase in Mycobacterium tuberculosis Polyacyltrehalose Lipid Biosynthesis
Authors: Touchette Megan H. , Holsclaw Cynthia M. , Previti Mary L. , Solomon Viven C. , Leary Julie A. , Bertozzi Carolyn R. , Seeliger Jessica C.
Published: October 2014

Trehalose glycolipids are found in many bacteria in the suborder
Corynebacterineae
, but methyl-branched acyltrehaloses are exclusive to virulent species such as the human pathogen
Mycobacterium tuberculosis
. In
M. tuberculosis
, the acyltransferase PapA3 catalyzes the formation of diacyltrehalose (DAT), but the enzymes responsible for downstream reactions leading to the final product, polyacyltrehalose (PAT), have not been identified. The PAT biosynthetic gene locus is similar to that of another trehalose glycolipid, sulfolipid 1. Recently, Chp1 was characterized as the terminal acyltransferase in sulfolipid 1 biosynthesis. Here we provide evidence that the homologue Chp2 (Rv1184c) is essential for the final steps of PAT biosynthesis. Disruption of
chp2
led to the loss of PAT and a novel tetraacyltrehalose species, TetraAT, as well as the accumulation of DAT, implicating Chp2 as an acyltransferase downstream of PapA3. Disruption of the putative lipid transporter MmpL10 resulted in a similar phenotype. Chp2 activity thus appears to be regulated by MmpL10 in a relationship similar to that between Chp1 and MmpL8 in sulfolipid 1 biosynthesis. Chp2 is localized to the cell envelope fraction, consistent with its role in DAT modification and possible regulatory interactions with MmpL10. Labeling of purified Chp2 by an activity-based probe was dependent on the presence of the predicted catalytic residue Ser141 and was inhibited by the lipase inhibitor tetrahydrolipstatin (THL). THL treatment of
M. tuberculosis
resulted in selective inhibition of Chp2 over PapA3, confirming Chp2 as a member of the serine hydrolase superfamily. Efforts to produce
in vitro
reconstitution of acyltransferase activity using straight-chain analogues were unsuccessful, suggesting that Chp2 has specificity for native methyl-branched substrates.
Where To Begin? Mapping Transcription Start Sites Genome-Wide in Escherichia coli
Authors: Wade Joseph T.
Published: October 2014

Recent genome-wide studies of bacterial transcription have revealed large numbers of promoters located inside genes. In this issue of the
Journal of Bacteriology
,
Thomason and colleagues
(J. Bacteriol. 197:18–28, 2015, doi:
10.1128/JB.02096-14
) map transcription start sites in
Escherichia coli
on an unprecedented scale. This work provides important insights into the regulation of transcripts that initiate inside genes and sources of variability between studies aimed at identifying these RNAs.
A novel method of adverse event detection can accurately identify venous thromboembolisms (VTEs) from narrative electronic health record data
Authors: Rochefort Christian M , Verma Aman D , Eguale Tewodros , Lee Todd C , Buckeridge David L
Published: October 2014

Background Venous thromboembolisms (VTEs), which include deep vein thrombosis (DVT) and pulmonary embolism (PE), are associated with significant mortality, morbidity, and cost in hospitalized patients. To evaluate the success of preventive measures, accurate and efficient methods for monitoring VTE rates are needed. Therefore, we sought to determine the accuracy of statistical natural language processing (NLP) for identifying DVT and PE from electronic health record data.

Methods We randomly sampled 2000 narrative radiology reports from patients with a suspected DVT/PE in Montreal (Canada) between 2008 and 2012. We manually identified DVT/PE within each report, which served as our reference standard. Using a bag-of-words approach, we trained 10 alternative support vector machine (SVM) models predicting DVT, and 10 predicting PE. SVM training and testing was performed with nested 10-fold cross-validation, and the average accuracy of each model was measured and compared.

Results On manual review, 324 (16.2%) reports were DVT-positive and 154 (7.7%) were PE-positive. The best DVT model achieved an average sensitivity of 0.80 (95% CI 0.76 to 0.85), specificity of 0.98 (98% CI 0.97 to 0.99), positive predictive value (PPV) of 0.89 (95% CI 0.85 to 0.93), and an area under the curve (AUC) of 0.98 (95% CI 0.97 to 0.99). The best PE model achieved sensitivity of 0.79 (95% CI 0.73 to 0.85), specificity of 0.99 (95% CI 0.98 to 0.99), PPV of 0.84 (95% CI 0.75 to 0.92), and AUC of 0.99 (95% CI 0.98 to 1.00).

Conclusions Statistical NLP can accurately identify VTE from narrative radiology reports.
Hypertensive urgency: an important aetiology of rebound hypertension
Authors: Malaty John , Malaty Irene A
Published: October 2014

A 46-year-old African-American man with a history of hypertension, end-stage kidney disease (on haemodialysis) and previous cocaine misuse presented to the emergency room with a sudden onset of severe headache and diaphoresis without other neurological or cardiovascular signs/symptoms. He checked his blood pressure at home and found it to be 230/130. It did not improve despite taking two serial doses of oral clonidine 0.3 mg. Evaluation with head CT and lumbar puncture demonstrated no acute intracranial process, such as subarachnoid haemorrhage. These symptoms started after he took Libido-Max, an over-the-counter supplement for erectile dysfunction. This supplement includes yohimbine, an α-2 antagonist, which counteracts the effects of oral clonidine, one of his routine antihypertensive medications. This led to rebound hypertension and made his hypertensive urgency resistant to oral clonidine. He was successfully treated with intravenous labetalol and his symptoms quickly resolved after lowering of his blood pressure.
Distinctive features of stump volume change in a fresh lower limb amputee with Parkes-Weber syndrome
Authors: Yahata Tetsutaro , Takeuchi Akihiko , Yoshida Shinya , Tsuchiya Hiroyuki
Published: October 2014

A 23-year-old man with Parkes-Weber syndrome suffered ischaemia on the toes of his left foot with overactive high-shunting. The symptoms were refractory and persistent, and trans-tibial amputation was finally performed; all detectable active lesions that had been involved by arteriovenous shunts were removed. Marked stump swelling was found a couple of times postoperatively when compression treatment was absent. Despite excessive enlargement, conventional compression treatment using elastic bandages was effective in suppressing the enlargement rapidly and in controlling the stump volume. Additionally, 8 months postoperatively, stump enlargement has not recurred using silicone liner as compressive measures. We speculated that marked stump swelling may have been caused by postoperative temporal venous congestion due to the residual varicosities in the stump. Excessive volume change of the stump confused us and stagnated prosthetic rehabilitation. Recognition of such clinical characteristics will facilitate smooth and favourable prosthetic rehabilitation in fresh amputees with Parkes-Weber syndrome.
Lingual thyroid in a young female: role of imaging
Authors: Suthar Pokhraj Prakashchandra , Mahajan Shivani , Rana Prakash Jagdishchandra , Patel Narottam Ambavibhai
Published: October 2014

A 12-year-old girl presented with dysphagia and a feeling of fullness in the throat. On examination a midline smooth, rubbery and reddish mass was seen at the base of the tongue, which moved with deglutination and protrusion of the tongue. A thyroid function test was within normal limits. On ultrasonography, absences of thyroid gland in its normal position with a smooth-contoured, round-shaped nodular mass at the tongue base with internal vascularity within. The mass was hyperdense and homogeneously enhancing on postcontrast. A clinical diagnosis of ectopic lingual was made based on the ultrasonography and CT scan features.
The long term results of vertebral artery ostium stenting in a single center
Authors: Sun Xuan , Ma Ning , Wang Bo , Mo Dapeng , Gao Feng , Xu Xiaotong , Liu Lian , Song Ligang , Miao Zhongrong
Published: October 2014

Background and purpose

The long term results of vertebral artery ostium (VAO) stenting remain uncertain. We sought to evaluate the incidence and risk factors for recurrent ischemic events on long term follow-up in patients who have undergone VAO stenting.

Methods

190 consecutive patients who had undergone a total of 202 stenting procedures for symptomatic atherosclerotic VAO stenosis between January 2011 and December 2012 were screened. Baseline demographics of the patients and morphological features of VAO were recorded. The primary outcome events analyzed included recurrent transient ischemic attack (TIA), stroke, and vascular related mortality. Risk factors for these recurrent events were identified. Other outcome events analyzed included in-stent restenosis (ISR) ≥50% and stent fracture noted on follow-up.

Results

Of the 188 patients with available follow-up data (mean follow-up period 16.7 months), 34 patients suffered recurrent TIAs (18.1%); none had stroke or death. 40 patients were found to have ISR (21.2%) and nine patients had stent fracture (4.7%). Patients with recurrent events were significantly more likely to have ISR, stent fracture, vessel tortuosity, and hyperlipidemia than patients without recurrent events.

Conclusions

Stenting for VAO stenosis seems to be safe and efficacious. The majority of recurrent events were TIAs, which may be related to ISR, stent fracture, vessel tortuosity, and hyperlipidemia.
Mesenchymal stem cells: mechanisms and role in bone regeneration
Authors: Qin Yunhao , Guan Junjie , Zhang Changqing
Published: October 2014

Stimulating bone growth and regeneration, especially in patients with delayed union or non-union of bone, is a challenge for orthopaedic surgeons. Treatments employed for bone regeneration are based on the use of cells, biomaterials and factors. Among these therapies, cell treatment with mesenchymal stem cells (MSCs) has a number of advantages as MSCs: (1) are multipotent cells that can migrate to sites of injury; (2) are capable of suppressing the local immune response; and (3) are available in large quantities from the patients themselves. MSC therapies have been used for stimulating bone regeneration in animal models and in patients. Methods of application range from direct MSC injection, seeding MSCs on synthetic scaffolds, the use of gene-modified MSCs, and hetero-MSCs application. However, only a small number of these cell-based strategies are in clinical use, and none of these treatments has become the gold standard treatment for delayed or non-union of bone.
CP violation of $B_{d}-{\bar B}_{d}$ mixing in supersymmetry with gauged baryon and lepton numbers
Authors: Sun Fei , Feng Tai-Fu , Gao Tie-Jun , Zhang Hai-Bin , Zhao Shu-Min
Published: October 2014

We analyze the CP asymmetry in flavor-specific decays [Formula: see text] for the [Formula: see text] mixing in the extension of the minimal supersymmetric standard model where baryon and lepton numbers are local gauge symmetries (BLMSSM). Considering the constraint of a 125 GeV Higgs, the numerical results indicate that the theoretical prediction of [Formula: see text] agrees with the current experimental result. For certain parameter sets, the BLMSSM contributions can be sizeable in [Formula: see text] mixing and CP asymmetry in B decays, which may help understand questions in cosmology.
Peierls brackets in non-Lagrangian field theory
Authors: Sharapov A. A.
Published: October 2014

The concept of Lagrange structure allows one to systematically quantize the Lagrangian and non-Lagrangian dynamics within the path-integral approach. In this paper, I show that any Lagrange structure gives rise to a covariant Poisson bracket on the space of solutions to the classical equations of motion, be they Lagrangian or not. The bracket generalize the well-known Peierls' bracket construction and make a bridge between the path-integral and the deformation quantization of non-Lagrangian dynamics.
Nonlinear Beam-Column Element Under Consistent Deformation
Authors: Tang Yi Qun , Zhou Zhi Hua , Chan Siu Lai
Published: October 2014

A new nonlinear beam-column element capable of considering the shear deformation is proposed under the concept of consistent deformation. For the traditional displacement interpolation function, the beam-column element produces membrane locking under large deformation and shear locking when the element becomes slender. To eliminate the membrane and shear locking, force equilibrium equations are employed to derive the displacement function. Numerical examples herein show that membrane locking in the traditional nonlinear beam-column element could cause a considerable error. Comparison of the present improved formulae based on the Timoshenko beam theory with that based on the Euler–Bernoulli beam theory indicates that the present approach requires several additional parameters to consider shear deformation and it is suitable for computer analysis readily for incorporation into the frames analysis software using the co-rotational approach for large translations and rotations. The examples confirm that the proposed element has higher accuracy and numerical efficiency.
LIMIT STATE EVALUATION OF STEEL-REINFORCED CONCRETE ELEMENTS BY VON MISES AND MENÉTREY–WILLAM-TYPE YIELD CRITERIA
Authors: PISANO A. A. , FUSCHI P. , DE DOMENICO D.
Published: October 2014

An advanced version of a recently developed numerical limit analysis procedure for the prediction of peak loads and failure modes of steel-reinforced concrete elements is proposed. The modified procedure allows to take into account possible yielding of reinforcement thus capturing the actual behavior at the collapse of both steel and concrete. This implies a finite element (FE) modeling of the reinforced concrete (RC) elements in which concrete is governed by a Menétrey–Willam-type yield criterion, with cap in compression, while steel bars are governed by a von Mises yield criterion. The peak load of a wide range of RC structures whose behavior at ultimate state is dominated either by the concrete crushing or by the steel bars yielding is then predicted with a very good accuracy.
ON FRACTURE CRITERIA FOR BI-MATERIAL CORNERS
Authors: JI XING
Published: October 2014

The prediction of crack nucleation near interface end in bi-material corners with definite wedge angles is fairly established. It takes Irwin-like form involving the stress intensity factor. Such a criterion requires the stress intensity factor of bi-material corners with same dimension, but the dimension of stress intensity factor of bi-material corner depends on wedge angles. The paper aims at the dimension problem. Particular attentions are paid to both the rigorous and asymptotic solutions of bi-material corners, because the asymptotic solution describes the stress singularity with stress intensity factor, and the rigorous solution describes the stress singularity with stress components. Studies on solutions of edge-bonded quarter and quarter planes and edge-bonded half and quarter planes lead to the following results. A unique point is found which divides the interfacial shear stress curve into an asymptotic part and a basic part. This point is called the transition point. Then, a relation between the stress intensity factor in the asymptotic part and the interfacial shear stress at the transition point is derived. This relation enables a fracture criterion of Irwin-like form for edge-bonded quarter and quarter planes and edge-bonded half and quarter planes to be formulated. To formulate a unified fracture criterion for arbitrary bi-material corners, further works are needed.
Constituents of potential concern for human health risk assessment of petroleum fuel releases
Authors: Bowers Richard L. , Smith Jonathan W. N.
Published: October 2014

When petroleum-based vehicle fuels are released to the subsurface environment, only a small number of chemical constituents typically account for a large majority of human health risks associated with potential exposures to affected soil, soil gas or groundwater. In other words, the risk ‘footprint’ of most fuel constituents is most often contained within the footprint of key risk-driving constituents of potential concern (COPCs). Therefore, assessment and management of an appropriate set of COPCs can support robust management of all potential risks and eliminate unnecessary chemical analyses and evaluation of constituents that rarely (or never) give rise to unacceptable human health risks. This paper presents an approach for identifying COPCs for petroleum fuel releases, based on internationally adopted human health risk assessment practices and available information on fuel composition and chemical toxicity. COPCs are identified as all constituents that could potentially give rise to unacceptable human health risks, based on theoretical upper-bound exposure estimates for exposure pathways. COPC lists are presented to guide the investigation and evaluation of risks at sites where releases of petrol, diesel, and kerosene/jet fuel have occurred. Such lists are generically applicable and may underpin site-specific evaluation of environmental conditions and associated risks.

Supplementary materials:

Risk equations, input definitions and values, the physical–chemical properties of the fuel components, human health criteria, complete results and rankings of the calculated risk values are available at
http://www.geolsoc.org.uk/SUP18789
.
Coupling ground-penetrating radar and flowmeter investigations for the characterization of a fissured aquifer
Authors: Godio A. , Basiricò S. , Crosta G. B. , Frattini P. , Villa A.
Published: October 2014

We test the integration of ground-penetrating radar (GPR) borehole investigation and electromagnetic flowmeter surveys to characterize fissured or complex aquifers. Borehole GPR investigation allows assessment of the lateral continuity of the porous and permeable zones between closely spaced boreholes, whereas flowmeter tests are adopted to identify the inflow–outflow zones in the boreholes. We apply the coupled approach in a portion (between 10 and 20 m below ground surface) of a complex aquifer hosted in a calcareous–gypsiferous formation. The hydro-geophysical characterization was aimed to detect the most conductive levels and to estimate the hydrodynamic properties of the aquifer. The integration of single-hole flowmeters and GPR measurements accurately distinguished different productive levels of high porosity and permeability in the aquifer. Two aquifer systems characterized by a complex geometry of fissures and permeable layers have been recognized, establishing the role of the drilled boreholes in the short-circuiting of the two systems. Interpretation of the GPR survey in cross-hole configuration gave values of total porosity of the order of 0.35 and 0.5 in the two more productive levels, which were detected by the flowmeter investigation.
Ground instability detection using PS-InSAR in Lanzhou, China
Authors: Zeng R. Q. , Meng X. M. , Wasowski J. , Dijkstra T. , Bovenga F. , Xue Y. T. , Wang S. Y.
Published: October 2014

This paper reports on the application of radar satellite data and Persistent Scatterer Interferometry (PS-InSAR) techniques for the detection of ground deformation in the semi-arid loess region of Lanzhou, northwestern China. Compared with Synthetic Aperture Radar Interferometry (InSAR), PS-InSAR overcomes the problems of temporal and geometric de-correlation and atmospheric heterogeneities by identifying persistent radar targets (PS) in a series of interferograms. The SPINUA algorithm was used to process 40 ENVISAT ASAR images for the study period 2003–2010. The analysis resulted in the identification of over 140000 PS in the greater Lanzhou area covering some 300 km
2
. The spatial distribution of moving radar targets was checked during a field campaign and highlights the range of ground instability problems that the Lanzhou area faces as urban expansion continues to accelerate. The PS-InSAR application detected ground deformations with rates up to 10 mm a
−1
; it resulted in the detection of previously unknown unstable slopes and two areas of subsidence.
Fast Compressed Tries through Path Decompositions
Authors: Grossi Roberto , Ottaviano Giuseppe
Published: October 2014

Tries are popular data structures for storing a set of strings, where common prefixes are represented by common root-to-node paths. More than 50 years of usage have produced many variants and implementations to overcome some of their limitations. We explore new succinct representations of path-decomposed tries and experimentally evaluate the corresponding reduction in space usage and memory latency, comparing with the state of the art. We study the following applications: compressed string dictionary and monotone minimal perfect hash for strings.

In compressed string dictionary, we obtain data structures that outperform other state-of-the-art compressed dictionaries in space efficiency while obtaining predictable query times that are competitive with data structures preferred by the practitioners. On real-world datasets, our compressed tries obtain the smallest space (except for one case) and have the fastest lookup times, whereas access times are within 20% slower than the best-known solutions.

In monotone minimal perfect hash for strings, our compressed tries perform several times faster than other trie-based monotone perfect hash functions while occupying nearly the same space. On real-world datasets, our tries are approximately 2 to 5 times faster than previous solutions, with a space occupancy less than 10% larger.
From wax tablets to touchscreens
Authors: Kristensson Per Ola
Published: October 2014

How we can enable users to transmit text to mobile and ubiquitous computer systems as quickly and as accurately as possible.
Detecting influencers in social media discussions
Authors: Rosenthal Sara
Published: October 2014

Knowing who's influential can help when planning political campaigns, advertising strategies, or even combating terrorism; and now research into influence detection promises to automate such detection.
Introduction to the Special Issue on Machine Learning for Multiple Modalities in Interactive Systems and Robots
Authors: Cuayáhuitl Heriberto , Frommberger Lutz , Dethlefs Nina , Raux Antoine , Marge Mathew , Zender Hendrik
Published: October 2014

This special issue highlights research articles that apply machine learning to robots and other systems that interact with users through more than one modality, such as speech, gestures, and vision. For example, a robot may coordinate its speech with its actions, taking into account (audio-)visual feedback during their execution. Machine learning provides interactive systems with opportunities to improve performance not only of individual components but also of the system as a whole. However, machine learning methods that encompass multiple modalities of an interactive system are still relatively hard to find. The articles in this special issue represent examples that contribute to filling this gap.
SCORPIO
Authors: Daya Bhavya K. , Chen Chia-Hsin Owen , Subramanian Suvinay , Kwon Woo-Cheol , Park Sunghyun , Krishna Tushar , Holt Jim , Chandrakasan Anantha P. , Peh Li-Shiuan
Published: October 2014

In the many-core era, scalable coherence and on-chip interconnects are crucial for shared memory processors. While snoopy coherence is common in small multicore systems, directory-based coherence is the de facto choice for scalability to many cores, as snoopy relies on ordered interconnects which do not scale. However, directory-based coherence does not scale beyond tens of cores due to excessive directory area overhead or inaccurate sharer tracking. Prior techniques supporting ordering on arbitrary unordered networks are impractical for full multicore chip designs

We present SCORPIO, an ordered mesh Network-on-Chip (NoC) architecture with a separate fixed-latency, bufferless network to achieve distributed global ordering. Message delivery is decoupled from the ordering, allowing messages to arrivein any order and at any time, and still be correctly ordered. The architecture is designed to plug-and-play with existing multicore IP and with practicality, timing, area, and power as top concerns. Full-system 36 and 64-core simulations on SPLASH-2 and PARSEC benchmarks show an average application runtime reduction of 24.1% and 12.9%, in comparison to distributed directory and AMD HyperTransport coherence protocols, respectively

The SCORPIO architecture is incorporated in an 11 mm-by-13mm chip prototype, fabricated in IBM 45nm SOI technology, comprising 36 Freescale e200 Power ArchitectureTMcores with private L1 and L2 caches interfacing with the NoC via ARM AMBA, along with two Cadence on-chip DDR2 controllers. The chip prototype achieves a post synthesis operating frequency of 1 GHz (833MHz post-layout) with an estimated power of 28.8W (768mW per tile), while the network consumes only 10% of tile area and 19 % of tile power.
Avoiding core's DUE & SDC via acoustic wave detectors and tailored error containment and recovery
Authors: Upasani Gaurang , Vera Xavier , González Antonio
Published: October 2014

The trend of downsizing transistors and operating voltage scaling has made the processor chip more sensitive against radiation phenomena making soft errors an important challenge. New reliability techniques for handling soft errors in the logic and memories that allow meeting the desired failures-in-time (FIT) target are key to keep harnessing the benefits of Moore's law. The failure to scale the soft error rate caused by particle strikes, may soon limit the total number of cores that one may have running at the same time

This paper proposes a light-weight and scalable architecture to eliminate silent data corruption errors (SDC) and detected unrecoverable errors (DUE) of a core. The architecture uses acoustic wave detectors for error detection. We propose to recover by confining the errors in the cache hierarchy, allowing us to deal with the relatively long detection latencies. Our results show that the proposed mechanism protects the whole core (logic, latches and memory arrays) incurring performance overhead as low as 0.60%
HELIX-RC
Authors: Campanoni Simone , Brownell Kevin , Kanev Svilen , Jones Timothy M. , Wei Gu-Yeon , Brooks David
Published: October 2014

Data dependences in sequential programs limit parallelization because extracted threads cannot run independently. Although thread-level speculation can avoid the need for precise dependence analysis, communication overheads required to synchronize actual dependences counteract the benefits of parallelization. To address these challenges, we propose a lightweight architectural enhancement co-designed with a parallelizing compiler, which together can decouple communication from thread execution. Simulations of these approaches, applied to a processor with 16 Intel Atom-like cores, show an average of 6.85x performance speedup for six SPEC CINT2000 benchmarks
HIOS
Authors: Jung Myoungsoo , Choi Wonil , Srikantaiah Shekhar , Yoo Joonhyuk , Kandemir Mahmut T.
Published: October 2014

Garbage collection (GC) and resource contention on I/O buses (channels) are among the critical bottlenecks in Solid State Disks (SSDs) that cannot be easily hidden. Most existing I/O scheduling algorithms in the host interface logic (HIL) of state-of-the-art SSDs are oblivious to such low-level performance bottlenecks in SSDs. As a result, SSDs may violate quality of service (QoS) requirements by not being able to meet the deadlines of I/O requests. In this paper, we propose a novel host interface I/O scheduler that is both GC-aware and QoS-aware. The proposed scheduler redistributes the GC overheads across non-critical I/O requests and reduces channel resource contention. Our experiments with workloads from various application domains reveal that the proposed scheduler reduces the standard deviation for latency over stateof- the-art I/O schedulers used in the HIL by 52.5%, and the worst-case latency by 86.6%. In addition, for I/O requests with sizes smaller than a superpage, our proposed scheduler avoids channel resource conflicts and reduces latency by 29.2% compared to the state-of-the-art
SleepScale
Authors: Liu Yanpei , Draper Stark C. , Kim Nam Sung
Published: October 2014

Power consumption in data centers has been growing significantly in recent years. To reduce power, servers are beingequipped with increasingly sophisticated power management mechanisms. Different mechanisms offer dramatically different trade-offs between power savings and performance penalties. Considering the complexity, variety, and temporallyvarying nature of the applications hosted in a typical data center, intelligently determining which power management policy to use and when is a complicated task.

In this paper we analyze a system model featuring both performance scaling and low-power states. We reveal the interplay between performance scaling and low-power states via intensive simulation and analytic verification. Based on the observations, we present SleepScale, a runtime power management tool designed to efficiently exploit existing power control mechanisms. At run time, SleepScale characterizes power consumption and quality-of-service (QoS) for each lowpower state and frequency setting, and selects the best policy for a given QoS constraint. We evaluate SleepScale using workload traces from data centers and achieve significant power savings relative to conventional power management strategies
Row-buffer decoupling
Authors: O Seongil , Son Young Hoon , Kim Nam Sung , Ahn Jung Ho
Published: October 2014

Modern DRAM devices for the main memory are structured to have multiple banks to satisfy ever-increasing throughput, energy-efficiency, and capacity demands. Due to tight cost constraints, only one row can be buffered (opened) per bank and actively service requests at a time, while the row must be deactivated (closed) before a new row is stored into the row buffers. Hasty deactivation unnecessarily re-opens rows for otherwise row-buffer hits while hindsight accompanies the deactivation process on the critical path of accessing data for row-buffer misses. The time to (de)activate a row is comparable to the time to read an open row while applications are often sensitive to DRAM latency. Hence, it is critical to make the right decision on when to close a row. However, the increasing number of banks per DRAM device over generations reduces the number of requests per bank. This forces a memory controller to frequently predict when to close a row due to a lack of information on future requests, while the dynamic nature of memory access patterns limits the prediction accuracy

In this paper, we propose a novel DRAM microarchitecture that can eliminate the need for any prediction. First, we identify that precharging the bitlines dominates the deactivate time, while sense amplifiers that work as a row buffer are physically coupled with the bitlines such that a single command precharges both bitlines and sense amplifiers simultaneously. By decoupling the bitlines from the row buffers using isolation transistors, the bitlines can be precharged right after a row becomes activated. Therefore, only the sense amplifiers need to be precharged for a miss in most cases, taking an order of magnitude shorter time than the conventional deactivation process. Second, we show that this row-buffer decoupling enables internal DRAM ?-operations to be separated and recombined, which can be exploited by memory controllers to make the main memory system more energy efficient. Our experiments demonstrate that row-buffer decoupling improves the geometric mean of the instructions per cycle and MIPS2/W by 14% and 29%, respectively, for memory-intensive SPEC CPU2006 applications
Increasing off-chip bandwidth in multi-core processors with switchable pins
Authors: Chen Shaoming , Hu Yue , Zhang Ying , Peng Lu , Ardonne Jesse , Irving Samuel , Srivastava Ashok
Published: October 2014

Off-chip memory bandwidth has been considered as one of the major limiting factors to processor performance, especially for multi-cores and many-cores. Conventional processor design allocates a large portion of off-chip pins to deliver power, leaving a small number of pins for processor signal communication. We observed that the processor requires much less power than that can be supplied during memory intensive stages. This is due to the fact that the frequencies of processor cores waiting for data to be fetched from off-chip memories can be scaled down in order to save power without degrading performance. In this work, motivated by this observation, we propose a dynamic pin switch technique to alleviate the bandwidth limitation issue. The technique is introduced to dynamically exploit the surplus pins for power delivery in the memory intensive phases and uses them to provide extra bandwidth for the program executions, thus significantly boosting the performance
OmniOrder
Authors: Qian Xuehai , Sahelices Benjamin , Torrellas Josep
Published: October 2014

Effective execution of atomic blocks of instructions (also called transactions) can enhance the performance and programmability of multiprocessors. Atomic blocks can be demarcated in software as in Transactional Memory (TM) or dynamically generated by the hardware as in aggressive implementations of strict memory consistency. In most current designs, when two atomic blocks conflict, one is squashed -- a performance loss that is often unnecessary.

To avoid this waste, this paper presents OmniOrder, the first design that efficiently executes conflicting atomic blocks concurrently in a directory-based coherence environment. The idea is to keep only non-speculative data in the caches and, when the cache coherence protocol transfers a line, include in the message the history of speculative updates to the line. The coherence protocol transitions are unmodified. We evaluate OmniOrder with 64-core simulations. In a TM environment, OmniOrder reduces the execution time of the STAMP applications by an average of 18.4% over a scheme that squashes on conflict. In an environment with SC enforcement with speculation, we run 11 programs that implement concurrent algorithms. OmniOrder reduces the programs' execution time by an average of 15.3% relative to a scheme that squashes on conflict. Finally, OmniOrder's communication overhead of transferring the history of speculative updates is negligible
The CHERI capability model
Authors: Woodruff Jonathan , Watson Robert N.M. , Chisnall David , Moore Simon W. , Anderson Jonathan , Davis Brooks , Laurie Ben , Neumann Peter G. , Norton Robert , Roe Michael
Published: October 2014

Motivated by contemporary security challenges, we reevaluate and refine capability-based addressing for the RISC era. We present CHERI, a hybrid capability model that extends the 64-bit MIPS ISA with byte-granularity memory protection. We demonstrate that CHERI enables language memory model enforcement and fault isolation in hardware rather than software, and that the CHERI mechanisms are easily adopted by existing programs for efficient in-program memory safety. In contrast to past capability models, CHERI complements, rather than replaces, the ubiquitous page-based protection mechanism, providing a migration path towards deconflating data-structure protection and OS memory management. Furthermore, CHERI adheres to a strict RISC philosophy: it maintains a load-store architecture and requires only singlecycle instructions, and supplies protection primitives to the compiler, language runtime, and operating system. We demonstrate a mature FPGA implementation that runs the FreeBSD operating system with a full range of software and an open-source application suite compiled with an extended LLVM to use CHERI memory protection. A limit study compares published memory safety mechanisms in terms of instruction count and memory overheads. The study illustrates that CHERI is performance-competitive even while providing assurance and greater flexibility with simpler hardware