bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational Studies on the Resistance of Penicillin‐Binding Protein 2B (PBP2B) of Wild‐type and Mutant Strains of Streptococcus pneumoniae Against β‐Lactam Antibiotics
Authors: Ramalingam Jothi , Vennila Jannet , Subbiah Parthasarathy
Published: March 2012

Mutations within transpeptidase domain of penicillin‐binding protein 2B of the strains of Streptococcus pneumoniae leads to resistance against β‐lactam antibiotics. To uncover the important residues responsible for sensitivity and resistance, the recently determined three dimensional structures of penicillin‐binding protein 2B of both wild‐type R6 (sensitive) and mutant 5204 (resistant) strains along with the predicted structures of other mutant strains G54, Hungary19A‐6 and SP195 were considered for the interaction study with β‐lactam antibiotics using induced‐fit docking of Schrödinger. Associated binding energies of the complexes and their intermolecular interactions in the binding site clearly show that the wild‐type R6 as sensitive, mutant strains 5204 and G54 as highly resistant, and the mutant strains Hungary19A‐6 and SP195 as intermediate resistant. The study also reveals that the mutant strains Hungary19A‐6 and SP195 exhibit intermediate resistant because of the existence of mutations till the intermediate 538th and 516th positions, respectively, and not till the end of the C‐terminus. Furthermore, our investigations show that if the mutations are extended till the end of the C terminus, then the antibiotic resistance of induced‐mutated strains increases from intermediate to high as in the strains 5204 and G54. The binding patterns obtained in the study are useful in designing potential inhibitors against multidrug resistant S. pneumoniae.
The influence of motivational language in the technologically mediated realm of telecommuters
Authors: Madlock Paul E.
Published: March 2012

The purpose of the current study was to extend organisational communication scholarship by examining the use of motivating language by supervisors of telecommuters and how motivating language influences telecommuters' perceptions of their supervisors' communication competence and their own communication satisfaction, job satisfaction, and organisational commitment. Participants included 177 full‐time telecommuters from a number of organisations across the US. The current findings indicate that supervisors of telecommuters tended to use the motivating language of direction giving (task oriented) most frequently followed by empathetic and meaning‐making language. Direction‐giving language was also indicated as the greatest predictor of communication and organisational outcomes. A discussion of the current findings coupled with options for future research is also offered.
Trust restoration: an examination of senior managers' attempt to rebuild employee trust
Authors: Pate Judy , Morgan‐Thomas Anna , Beaumont Phillip
Published: March 2012

This article advances discussions surrounding the extent to which senior management can rebuild damaged trust relationships in a context where the founding principle of respect had been contravened. More specifically, our article is concerned with a senior management team's attempt to regain trust through addressing workplace bullying. The study draws on a quantitative methodology where the population of the case study organisation were surveyed (n = 206) at two points in time (2004 and 2007). The findings revealed that managements’ actions had a significant effect on perceptions of bullying. T‐tests, however, provided only partial support for the notion that trust had improved as a result of management actions. In particular, there were significant differences in the levels of loyalty and benevolent motives and also openness, whereas no significant changes were observed for other dimensions of trust (integrity, competence, consistency and respect).
Evaluation of derived Coulter red blood cell parameters for the assessment of iron deficiency in adults with congenital heart disease
Authors: DOPSAJ V. , MIKOVIC‐GOLUBOVIC G. , MARTINOVIC J. , KALIMANOVSKA‐OSTRIC D.
Published: March 2012

Introduction:  The aim of our study was to evaluate derived red blood cell parameters in determining the presence of iron depletion and iron‐deficient erythropoiesis, as states that precede iron deficiency anemia, in adults with congenital heart disease.

Methods:  Eighty‐eight adults who were diagnosed with congenital heart disease were divided into two groups (cyanotic and acyanotic). In both groups, congenital heart disease patients were then divided into three subgroups: with iron depletion, with iron‐deficient erythropoiesis, and a control group. The following parameters were measured: complete blood count, reticulocytes, ferritin, soluble transferrin receptor, haptoglobin, lactate dehydrogenase, and calculated parameters: low hemoglobin density (LHD), red cell size factor (RSF), and microcytic anemia factor (MAF).

Results:  Discriminant analysis indicated statistically significant differences in the first discriminant function: Function 1 – body iron, LHD, MAF, sTfR, and RSF (P < 0.001) in patients with acyanotic congenital heart disease and significant differences in both discriminant functions in patients with cyanotic congenital heart disease: Function 1 – body iron, soluble transferrin receptor, LHD, RSF, MAF, lactate dehydrogenase, and haptoglobin (P = 0.008) and Function 2 – reticulocytes (#), immature reticulocyte fraction and reticulocytes (%) (P = 0.049).

Conclusions:  Beside parameters that describe iron metabolism dynamics (body iron and soluble transferrin receptor), LHD, indicator of hypochromia, have the highest potential to differentiate and classify iron deficiency in patients with congenital heart disease.
Production of recombinant nonstructural 1 protein in Escherichia coli for early detection of Japanese encephalitis virus infection
Authors: Tripathi Nagesh K. , Kumar Jyoti S. , Biswal Karttik C. , Rao P. V. Lakshmana
Published: March 2012

Japanese encephalitis is a major public health problem in South‐East Asia and Western Pacific countries. The recombinant nonstructural 1 (rNS1) protein of Japanese encephalitis virus is a potential diagnostic as well as vaccine candidate. Developments of cost‐effective and simple culture media as well as appropriate culture conditions are generally favourable for large‐scale production of recombinant proteins. The effects of medium composition and cultivation conditions on the production of rNS1 protein were investigated in shake flask culture as well as batch cultivation of Escherichia coli. Further, the fed‐batch process was also carried out for high cell density cultivation (HCDC) of E. coli expressing rNS1 protein. Isopropyl‐β‐d‐thiogalactopyranoside (IPTG) was used to induce the expression of rNS1 protein at ∼ 13 g dry cell weight per litre of culture. The final dry cell weight after fed‐batch cultivation was ∼ 17 g l−1. The Inclusion bodies were isolated and purified through affinity chromatography to give a final product yield of ∼ 142 mg l−1. The reactivity of purified protein was confirmed by Western blotting and Enzyme linked immunosorbent assay. These results show that rNS1 protein may be used as a diagnostic reagent or for further prophylactic studies. This approach of producing rNS1 protein in E. coli with high yield may also offer promising method for production of other viral recombinant proteins.
Multiple Roles and Stress Burden in Women: A Conceptual Model of Heart Disease Risk
Authors: TERRILL ALEXANDRA L. , GAROFALO JOHN P. , SOLIDAY ELIZABETH , CRAFT REBECCA
Published: March 2012

Coronary heart disease is the leading cause of mortality in adult women, and recent trends indicate that risk for women, particularly working mothers, has worsened during the last decade. The absence of a biological explanation for this gender discrepancy has led some to look to psychosocial risk factors. This literature review examines the effect of multiple roles on women's cardiovascular health. Further, a conceptual model of heart disease risk is proposed, which introduces background stress, a chronic stress burden, as a potential pathway between multiple roles and heart disease. Trends in the literature largely support the proposed conceptual model. Multiple roles that often place conflicting demands on women may affect health outcomes through an increase in total background stress.
Community‐Based Participatory Research Skills and Training Needs in a Sample of Academic Researchers from a Clinical and Translational Science Center in the Northeast
Authors: DiGirolamo Ann , Geller Alan C. , Tendulkar Shalini A. , Patil Pratima , Hacker Karen
Published: March 2012

Purpose: To determine the community‐based participatory research (CBPR) training interests and needs of researchers interested in CBPR to inform efforts to build infrastructure for conducting community‐engaged research.

Method: A 20‐item survey was completed by 127 academic health researchers at Harvard Medical School, Harvard School of Public Health, and Harvard affiliated hospitals.

Results: Slightly more than half of the participants reported current or prior experience with CBPR (58 %). Across all levels of academic involvement, approximately half of the participants with CBPR experience reported lacking skills in research methods and dissemination, with even fewer reporting skills in training of community partners. Regardless of prior CBPR experience, about half of the respondents reported having training needs in funding, partnership development, evaluation, and dissemination of CBPR projects. Among those with CBPR experience, more than one‐third of the participants wanted a mentor in CBPR; however only 19 % were willing to act as a mentor.

Conclusions: Despite having experience with CBPR, many respondents did not have the comprehensive package of CBPR skills, reporting a need for training in a variety of CBPR skill sets. Further, the apparent mismatch between the need for mentors and availability in this sample suggests an important area for development. Clin Trans Sci 2012; Volume #: 1–5
Outcomes of moderate sedation in paediatric dental patients
Authors: Özen B , Malamed SF , Cetiner S , Özalp N , Özer L , Altun C
Published: March 2012

Background:  The aim of this study was to evaluate the outcomes of moderate sedation with nitrous oxide/oxygen (N2O/O2) alone or combined with different dosages and administration routes of midazolam in uncooperative paediatric dental patients using the Bispectral Index System (BIS).

Methods:  This one‐year clinical study examined first‐visit moderate sedation performed in 240 healthy children aged 4–6 years. Subjects were randomly divided into four groups according to drug, route and dosage, as follows: Group 1 – 0.20 mg/kg midazolam (40 mg/ml) delivered intranasally; Group 2 – 0.75 mg/kg midazolam (15 mg/3 ml) delivered orally; Group 3 – 0.50 mg/kg midazolam (15 mg/3 ml) delivered orally. All children in these three groups also received inhalation sedation with 50%–50% N2O/O2, whereas children in Group 4 received inhalation sedation with 50%–50% N2O/O2 only. The outcome of sedation was evaluated as either ‘successful’, ‘failed’ or ‘not accepted’.

Results:  The highest success rate was found in Group 1 (0.20 mg/kg intranasally, 87%), followed by Group 2 (0.75 mg/kg orally, 79%). The overall mean success rate for all groups was 73%.

Conclusions:  Moderate sedation can be successfully used in the clinical management of paediatric dental patients, with both intranasal and oral sedation using midazolam in conjunction with nitrous oxide found to be effective methods.
Histology obtained by needle biopsy gives additional information on the prognosis of hepatocellular carcinoma
Authors: van Malenstein Hannah , Komuta Mina , Verslype Chris , Vandecaveye Vincent , Van Calster Ben , Topal Baki , Laleman Wim , Cassiman David , Van Steenbergen Werner , Aerts Raymond , Vanbeckevoort Dirk , Bielen Didier , Pirenne Jacques , van Pelt Jos , Roskams Tania , Nevens Frederik
Published: March 2012

Aim:  Hepatocellular carcinomas (HCC) have a strong biological heterogeneity. Current prognostic scores do not include histology. Information on the behavior of HCC based on histology has been characterized on retrospective data and large tissue specimens. We aimed to assess the additional value of needle biopsy and keratin 19 (K19) assessment in a prospective manner.

Methods:  Between 2003 and 2008, all patients with a confirmed diagnosis of HCC by a percutaneous or laparoscopic needle biopsy at the time of diagnosis, and of Barcelona Clinic Liver Cancer (BCLC) stage A, B or C, were included. The exclusion criterion was a palliative setting. Biopsies were scored for microvascular invasion, differentiation, K19, epithelial cell adhesion molecule and α‐fetoprotein staining. Clinical and radiological features were registered at time of biopsy. The added value of K19 was assessed using Cox proportional hazards regression.

Results:  Of 74 patients screened, we included 58 patients. Based on the BCLC, 41% presented with early disease (BCLC A), 16% with intermediate disease (BCLC B) and 43% with advanced disease (BCLC C). In nine patients (16%), K19 staining was positive. Median follow up was 54 months (range 1–74) and 43 patients (72%) died. BCLC classification predicted the prognosis accurately, but histology offered additional prognostic information. In multivariate analysis, K19 was a strong predictor of overall survival (hazard ratio 4.57, 95% confidence interval 1.86–10.6), which improved predictive performance. No needle tract dissemination was observed.

Conclusion:  Despite the possible problem of sampling error, needle biopsy offered additional prognostic information. This is especially the case for K19 staining.
Notch‐dependent expression of epithelial–mesenchymal transition markers in cholangiocytes after liver transplantation
Authors: Liu Xiaowei , Li Jun , Xiong Jun , Li Min , Zhang Yong , Zheng Qichang
Published: March 2012

Aim:  Epithelial–mesenchymal transition (EMT) has been identified in chronic cholestatic liver diseases, which are characterized by biliary proliferation and fibrosis. Activation of Notch signaling mediates EMT in a variety of epithelial cell types. In the present study, we investigated the role of Notch signaling in the regulation of EMT marker expression in cholangiocytes after liver transplantation.

Methods:  Orthotopic liver transplantation was performed in Sprague–Dawley rats. Liver tissues and isolated cholangiocytes were collected 1 week after transplantation. The expression of mesenchymal and biliary epithelial markers was evaluated by immunohistochemistry, quantitative polymerase chain reaction (PCR) and western blotting in liver sections and isolated cholangiocytes. Quantitative real‐time PCR and western blotting for Jagged1 and HES1 were utilized to evaluate the activation of Notch signaling. Proliferation and migration of cholangiocytes were assessed by 5‐bromodeoxyuridine and transwell assays, respectively. Cholangiocyte proliferation, migration and expression of EMT markers were also evaluated following the inhibition of Notch signaling with N,(N‐[3,5‐difluorophenacetyl]‐L‐alanyl)‐S‐phenylglycine t‐butylester (γ‐secretase inhibitor) and a Jagged1‐neutralizing antibody.

Results:  Expression of EMT markers by cholangiocytes was observed in liver grafts and isolated cholangiocytes obtained 1 week after transplantation. Inhibition of Notch signaling prevented the expression of EMT markers in bile ducts of liver sections and isolated cholangiocytes. Cholangiocyte proliferative and migratory capacities were also suppressed by the inhibition of Notch signaling.

Conclusion:  Activation of Notch signaling promotes cholangiocyte proliferation and expression of EMT markers after liver transplantation.
Localization of hepatocyte nuclear factor‐4α in the nucleolus and nucleus is regulated by its C‐terminus
Authors: Ogata Makiko , Awaji Takeo , Iwasaki Naoko , Fujimaki Risa , Takizawa Miho , Maruyama Kei , Bell Graeme I , Iwamoto Yasuhiko , Uchigata Yasuko
Published: March 2012

Aims/Introduction:  Mutations in hepatocyte nuclear factor‐4α (HNF4α) lead to various diseases, among which C‐terminal deletions of HNF4α are exclusively responsible for maturity onset diabetes of the young 1 (MODY1). MODY is an autosomal dominant disease characterized by a primary defect in insulin response to glucose, suggesting that the C‐terminus of HNF4α is important for pancreatic β‐cell function. To clarify the role of the C‐terminus of HNF4α, changes in cellular localization and the binding ability to its regulator were examined, specifically in the region containing Q268, which deletion causes MODY1.

Materials and Methods:  Cellular localization of mutant HNF4α were examined in monkey kidney 7 (COS7), Chinese hamster ovary, rat insulinoma and mouse insulinoma cells, and their binding activity to other proteins were examined by fluorescence resonance energy transfer (FRET) in COS7 cells.

Results:  Although wild‐type HNF4α was localized in the nucleoplasm in transfected cultured cells, Q268X‐HNF4α was located predominantly in the nucleolus. Deletion analysis of the C‐terminus of HNF4α showed that the S337X‐HNF4α mutant, and other mutants with shorter amino acid sequences (S337‐K194), were mostly localized in the nucleolus. HNF4α mutants with amino acid sequences shorter than the W192X‐HNF4α mutant gradually spread to the nucleoplasm in accordance with their lengths. The A250X‐HNF4α mutant was capable of causing the accumulation of HNF4α or the small heterodimer partner (SHP), one of the HNF4α regulators, in the nucleolus. However, the R154X‐HNF4α mutant did not have binding ability to wild‐type HNF4α or SHP, and thus was seen in the nucleus.

Conclusions:  The C‐terminus sites might play a key role in facilitating the nucleolar and subnucleolar localization of HNF4α. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2012.00210.x, 2012)
Prolonged hyperinsulinemia after subcutaneous injection of 2400 U regular insulin in a suicide attempt: Time course of serum insulin with frequent measurements
Authors: Hiromine Yoshihisa , Kawabata Yumiko , Yamauchi Takaaki , Noso Shinsuke , Babaya Naru , Harada Takeshi , Ito Hiroyuki , Ikegami Hiroshi
Published: March 2012

We studied the time course of serum insulin level in a patient who injected large amounts of regular insulin in an attempted suicide. A 58‐year‐old woman attempted suicide by subcutaneously injecting herself with 2400 U regular insulin. On arrival, the serum glucose level was 2.4 mmol/L (44 mg/dL) and the serum insulin level was 40,000 pmol/L (5700 μIU/mL). The serum insulin level was high, with a maximum of 110,000 pmol/L (16,000 μIU/mL) at 13 h after injection, followed by an initial rapid decrease and a subsequent slow decrease, with hyperinsulinemia lasting as long as 5 days after injection. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2012.00211.x, 2012)
Biorelevant in-vitro performance testing of orally administered dosage forms
Authors: Reppas Christos , Vertzoni Maria
Published: March 2012

Objectives

This review focuses on the evolution and current status of biorelevant media and hydrodynamics, and discusses the usefulness of biorelevant performance testing in the evaluation of specific dosage form related lumenal processes.

Key findings

During the last 15 years our knowledge of the gastrointestinal environment (including the lower gut) has improved dramatically and biorelevant media composition and, to a lesser extent, biorelevant hydrodynamics, have been refined. Biorelevant dissolution/release testing is useful for the evaluation of formulation and food effects on plasma levels after administration of immediate release dosage forms containing low solubility compounds and after administration of extended release products. Lumenal disintegration times of immediate release dosage forms and the bile acid sequestering activity of resins in the lumen can also be successfully forecasted with biorelevant in vitro testing.

Biorelevant in-vitro performance testing is an important tool for evaluating intralumenal dosage form performance. Since the formulation of new active pharmaceutical ingredients for oral delivery is more challenging than ever before, efforts to improve the predictability of biorelevant tests are expected to continue.
Total flavonoids of Bidens bipinnata L. a traditional Chinese medicine inhibits the production of inflammatory cytokines of vessel endothelial cells stimulated by sera from Henoch–Schönlein purpura patients
Authors: Bo Yan , Yuan Li-ping , Zhang Jian-jun , Meng Dei-di , Jing Han , Dai Han-jing
Published: March 2012

Objectives

Bidens bipinnata L. is well known as a traditional antipyretic, anti-inflammatory and anti-rheumatic medicine in China. This study was designed to evaluate the role of total extracted flavonoids from B. bipinnata (TFB) in inhibiting the production of inflammatory cytokines.

Methods

Human umbilical vein endothelial cells (HUVEC) were used to examine the effect of TFB on the production of inflammatory cytokines. The supernatant interleukin (IL)-8, tumour necrosis factor (TNF)-α and nitric oxide (NO) levels of HUVEC were measured with ELISA methods. Nuclear factor-kappaB (NF-κB) and fractalkine expression was evaluated by RT-PCR and Western blot methods, respectively.

Key findings

We observed that IL-8, TNF-α and NO release of HUVEC incubated with sera from active Henoch–Schönlein purpura (HSP) was significantly increased. TFB intervention may significantly suppressed the supernatant IL-8, TNF-α and NO levels of HUVEC. Similarly, TFB obviously suppressed the NF-κB and fractalkine mRNA and protein expression.

Conclusions

These results suggested that TFB may be useful for improving microvascular inflammation in HSP patients.
Withholding negative feedback: Is it about protecting the self or protecting others?
Authors: Jeffries Carla H. , Hornsey Matthew J.
Published: March 2012

The reluctance to deliver negative feedback to someone's face is widely documented. This research disentangles the extent to which this reluctance is motivated by a desire to protect the self as opposed to others. Participants assessed an essay written by someone with high, medium, or low self‐esteem. Assessment of the essay was most positive when the feedback was to be provided face‐to‐face, less positive when delivered anonymously, and least positive when it was not required to be delivered at all. This effect only emerged among participants low in self‐liking (but was unrelated to self‐competency). The self‐esteem of the essay writer had no effect on evaluations. The data lend support for a self‐protection motive and modest support for an other‐protection motive.
Distinct contributions by ionotropic purinoceptor subtypes to ATP‐evoked calcium signals in mouse parotid acinar cells
Authors: Bhattacharya Sumit , Verrill Douglas S. , Carbone Kristopher M. , Brown Stefanie , Yule David I. , Giovannucci David R.
Published: March 2012

Key points

There are two major ionotropic purinoceptor subtypes (ATP‐gated, non‐selective, Ca2+‐conducting ion channels) in the salivary gland.

Relatively little is known about the physiological roles of these purinoceptors regarding compartmentalization and selective activation, their contributions to the spatiotemporal properties of intracellular Ca2+ signals and their roles in regulating protein exocytosis and ion channel activity.

In this study, we investigated the subtype‐specific sub‐cellular distribution and functional characterization of purinoceptors in mouse parotid acinar cells.

Selective activation of ionotropic purinergic receptor subtypes was shown to evoke spatially distinct cytosolic Ca2+ signals as well as protein exocytosis.

This study identifies a subtype of ionotropic purinergic receptors as a potential therapeutic target for treatment of salivary gland hypofunction.
On a Robust Modeling of Piezo-Systems
Authors: Corbier Christophe , Boukari Abdou Fadel , Carmona Jean-Claude , Martinez Victor Alvarado , Moraru George , Malburet François
Published: March 2012

This paper proposes a new modeling approach which is experimentally validated on piezo-electric systems in order to provide a robust Black-box model for complex systems control. Industrial applications such as vibration control in machining and active suspension in transportation should be concerned by the results presented here. Generally one uses physical based approaches. These are interesting as long as the user cares about the nature of the system. However, sometimes complex phenomena occur in the system while there is not sufficient expertise to explain them. Therefore, we adopt identification methods to achieve the modeling task. Since the microdisplacements of the piezo-system sometimes generate corrupted data named observation outliers leading to large estimation errors, we propose a parameterized robust estimation criterion based on a mixed L2 – L1 norm with an extended range of a scaling factor to tackle efficiently these outliers. This choice is motivated by the high sensitivity of least-squares methods to the large estimation errors. Therefore, the role of the L1-norm is to make the L2-estimator more robust. Experimental results are presented and discussed.
Robust Tracking of a Class of Perturbed Nonlinear Systems via Multivariable Nested Sliding Mode Control
Authors: Adhami-Mirhosseini Aras , Yazdanpanah Mohammad J. , Khaki-Sedigh Ali
Published: March 2012

In this paper, a new methodology for robust controller design in nonlinear multivariable systems is suggested to guarantee asymptotic output tracking. The systems under consideration are perturbed by functionally bounded matched and unmatched uncertainties/perturbations and assumed to be described in the strict-feedback form. The main idea of the methodology is based on the combination of conventional sliding mode control and backstepping algorithm. The proposed controller called nested sliding mode controller that is obtained through a stepwise algorithm. It has the ability of rejecting nonvanishing perturbations by using dynamic switches, unlike conventional and other hierarchical sliding mode design methods. Performance is studied through theorems and verified by two numerical examples.
Comparative Study of Bond Graph Models for Hydraulic Transmission Lines With Transient Flow Dynamics
Authors: Yang Limin , Hals Jørgen , Moan Torgeir
Published: March 2012

The partial differential equation describing one-dimensional flow in a hydraulic pipeline with linear resistance can be approximated and solved numerically using different modal approaches. Modal models can be obtained either by using rational transfer functions (RTF) in the Laplace domain solution or by using separation of variables (SOV) techniques. The pipeline models have four possible input–output configurations: pressure inputs at both ends, flow rate inputs at both ends, and the two cases of mixed inputs. In this paper, modal bond graph representations for pipeline sections are reviewed, and new bond graphs are proposed for combinations of solution method and input–output configurations not yet presented in the literature. This includes bond graph representations for the two mixed input cases developed using the SOV technique, and bond graphs for the other two cases, pressure inputs or flow rate inputs, constructed on the basis of RTF solutions. Through numerical simulations of hydraulic single lines, the obtained models are compared to alternative models already established in the literature. It is shown that the modal models developed by the RTF and SOV methods have the same accuracy when the same number of modes is used. For both of these approaches, correction methods to maintain a high accuracy when truncating high-order modes are described, and also adapted to the bond graph form. Finally, simulation results for various line configurations are illustrated.
Peristaltic Flow of a Carreau Fluid in a Rectangular Duct
Authors: Nadeem S. , Akram Safia , Hayat T. , Hendi Awatif A.
Published: March 2012

In the present investigation we have studied the peristaltic flow of a Carreau fluid in a rectangular duct. The flow is investigated in the wave frame of reference moving with the velocity c away from the fixed frame. The peristaltic wave propagating on the horizontal side walls of a rectangular duct is studied under long wave length and low Reynolds number approximation. The analytical solutions of velocity and pressure gradient have been found under lubrication approach with the help of Homotopy perturbation method. Graphical results are displayed to see the behavior of various emerging parameters of Carreau fluid. The comparison of the present work is also made with the existing literature.
Intrinsic Finite Element Modeling of Nonlinear Dynamic Response in Helical Springs
Authors: Leamy Michael J.
Published: March 2012

This paper presents an efficient intrinsic finite element approach for modeling and analyzing the forced dynamic response of helical springs. The finite element treatment employs intrinsic curvature (and strain) interpolation and vice rotation (and displacement) interpolation and, thus, can accurately and efficiently represent initially curved and twisted beams with a sparse number of elements. The governing equations of motion contain nonlinearities necessary for large curvatures. In addition, a constitutive model is developed, which captures coupling due to nonzero initial curvature and strain. The method is employed to efficiently study dynamically-loaded helical springs. Convergence studies demonstrate that a sparse number of elements accurately capture spring dynamic response, with more elements required to resolve higher frequency content, as expected. Presented results also document rich, amplitude-dependent frequency response. In particular, moderate loading amplitudes lead to the presence of secondary resonances (not captured by linearized models), while large loading amplitudes lead to complex dynamics and transverse buckling.
Determination of Dislocation Interaction Strengths Using Discrete Dislocation Dynamics of Curved Dislocations
Authors: Alankar Alankar , Mastorakos Ioannis N. , Field David P. , Zbib Hussein M.
Published: March 2012

In latent interactions of dislocations, junction formation is one of the most important phenomena that contribute to the evolution of strength. In this work, the latent hardening coefficients for pure aluminum are estimated using 3D multiscale dislocation dynamics program (MDDP). Three well-known junction configurations, namely, the Hirth lock, the glissile junction, and the Lomer lock, are studied using 3D discrete dislocation dynamics simulations. The evolution of strength is discussed as a function of the resolved shear stress (RSS) and the number of junctions for the three junctions investigated. Hirth lock and Lomer lock are found to be the weakest and strongest junctions, respectively. Collinear reaction of dislocations does not form a junction but causes a higher strength than a Lomer lock. Quantitative and qualitative results are compared with those found in the literature.
Numerical Modeling of the Failure of Magnesium Tubes Under Compressive Loading
Authors: Rossiter Jonathan , Inal Kaan , Mishra Raja
Published: March 2012

A new finite element (FE) specific failure criterion utilizing hardening rates to quantify bending stress is implemented into the MAT_124 material model in the commercial software LS-DYNA to simulate fracture of extruded AZ31 and cast AM60 magnesium alloy tubes. The simulations are performed by requiring element erosion of hexahedral solid elements in a three-dimensional (3D) FE model when the failure criterion is satisfied at any point in the simulation. Experimental stress–strain curves from tensile and compression tests of the materials are used as inputs in the model. The simulations reproduce the measured load displacement data as well as general features of the experimental failure modes of round and rectangular tubes undergoing axial crush tests. The model is applied to investigate the effects of a variety of design features, such as varying tube wall thickness, preformed bulges, alternate bands of Al and Mg alloys, and cladding Al on magnesium, on the macroscopic strain to failure. The results show that adding multiple preformed bulges to the tubes can increase the strain to failure and reduce the force required to cause deformation. Adding a single bulge concentrates the strain causing reduced macroscopic strain to failure. Placing sections of reduced wall thickness or brazing in sections of aluminum causes stress concentrations which reduce the macroscopic strain to failure. Cladding aluminum onto the outside of the magnesium tube is shown to improve strain to failure.
Nanoscale Structural and Mechanical Characterization of MWCNT-Reinforced Polymer Composites
Authors: Leininger Wyatt , Wang Xinnan , Tangpong X. W. , McNea Marshall
Published: March 2012

In this study, the elastic modulus of 1 wt. % multiwalled carbon nanotube (MWCNT) reinforced epoxy composite was characterized using an in-house designed micro/nano tensile load stage in conjunction with an atomic force microscope (AFM). The surface of the nanocomposite was scanned by the AFM during intermittent tensile testing, and micro/nanoscale deformation was observed. The MWCNT reinforced nanocomposite exhibited a 23% increase in the measured elastic modulus compared with the pure epoxy. The elastic moduli of the nanocomposite were also predicted by the Halpin–Tsai and Hui–Shia models, and the former offered a better correlation with the experimental result when only the load bearing outer layer of the MWCNTs was considered. The combination of the load stage and AFM is capable of capturing the in situ deformation progress for small strain increments.
Molecular Dynamics Simulations of Diffusion of O2 and N2 Penetrants in Polydimethylsiloxane-Based Nanocomposites
Authors: Spearot Douglas E. , Sudibjo Alex , Ullal Varun , Huang Adam
Published: March 2012

Recently, metal particle polymer composites have been proposed as sensing materials for micro corrosion sensors. To design the sensors, a detailed understanding of diffusion through metal particle polymer composites is necessary. Accordingly, in this work molecular dynamics (MD) simulations are used to study the diffusion of O2 and N2 penetrants in metal particle polymer nanocomposites composed of an uncross-linked polydimethylsiloxane (PDMS) matrix with Cu nanoparticle inclusions. PDMS is modeled using a hybrid interatomic potential with explicit treatment of Si and O atoms along the chain backbone and coarse-grained methyl side groups. In most models examined in this work, MD simulations show that diffusion coefficients of O2 and N2 molecules in PDMS-based nanocomposites are lower than that in pure PDMS. Nanoparticle inclusions act primarily as geometric obstacles for the diffusion of atmospheric penetrants, reducing the available porosity necessary for diffusion, with instances of O2 and N2 molecule trapping also observed at or near the PDMS/Cu nanoparticle interfaces. In models with the smallest gap between Cu nanoparticles, MD simulations show that O2 and N2 diffusion coefficients are higher than that in pure PDMS at the lowest temperatures studied. This is due to PDMS chain confinement at low temperatures in the presence of the Cu nanoparticles, which induces low-density regions within the PDMS matrix. MD simulations show that the role of temperature on diffusion can be modeled using the Williams–Landel–Ferry equation, with parameters influenced by nanoparticle content and spacing.
Direct Observation of Crack Propagation in Copper–Niobium Multilayers
Authors: Hattar K. , Misra A. , Dosanjh M. R. F. , Dickerson P. , Robertson I. M. , Hoagland R. G.
Published: March 2012

The failure of a cross-sectional 65 nm-thick copper and 150 nm-thick niobium multilayer thin film was investigated via an in situ transmission electron microscopy straining experiment. The fracture of the free-standing multilayer films was associated with confined dislocation slip within layers containing and preceding the crack tip. Four crack hindrance mechanisms were observed to operate during crack propagation: microvoid formation, crack deviation, layer necking, and crack blunting. Failure was observed to occur across and through the copper and niobium layers but never within the interfaces or grain boundaries. These results are discussed relative to the length-scale-dependent deformation mechanisms of nanoscale metallic multilayers.
Elasto-Plastic Stresses in a Functionally Graded Rotating Disk
Authors: Jahromi Babak Haghpanah , Nayeb-Hashemi Hamid , Vaziri Ashkan
Published: March 2012

A numerical method based on the extension of the variable material property method was developed to obtain the elasto-plastic stress field in a functionally graded (FG) rotating disk. The method was applied to estimate the stress field in a metal–ceramic functionally graded solid disk. To establish the validity of the proposed method, results were compared with finite element results. Unlike uniform rotating disks, where yielding starts from the disk center, plasticity in FG disks can originate at any point. The effect of different metal–ceramic grading patterns as well as the relative elastic moduli and densities of the ceramic and metallic constituents on the developed stresses were studied. Reinforcement of a metal disk with ceramic particles, in both elastic and plastic regimes, can significantly influence the mechanical response of the disk such as the stress distribution and the critical angular velocities corresponding to the onset of plasticity in the disk and plastic disk. Disks with increasing ceramic content from inner to outer radius showed a more uniform von Mises stress distribution for a fixed value of total ceramic content. In contrast, disks with decreasing ceramic content from inner to outer radius had the lowest outer edge displacement for a fixed value of total ceramic content.
Comparisons of Constitutive Models for Steel Over a Wide Range of Temperatures and Strain Rates
Authors: Abed Farid , Makarem Fadi
Published: March 2012

This study investigates and compares several available plasticity models used to describe the thermomechanical behavior of structural steel subjected to complex loadings. The main purpose of this comparison is to select a proper constitutive model that can later be implemented into a finite element code to capture localizations (e.g., shear bands and necking) in steel and steel structures subjected to low- and high-velocity impact. Four well-known constitutive models for viscoplastic deformation of metals, i.e., Johnson–Cook (JC), Zerilli–Armstrong (ZA), Rusinek–Klepaczko (RK), and Voyiadjis–Abed (VA), have been investigated and compared with reference to existing deformation data of HSLA-65 and DH-36 steel conducted at low and high strain rates and various initial temperatures. The JC, ZA, and RK models reasonably describe the flow stress and the strain hardening behavior only in the certain ranges of strain, strain rate, and temperature for which the models were developed. This was attributed to the inaccurate assumptions used in developing these models. In contrast, the VA model most effectively describes the flow stress and strain hardening in which very good predictions are observed for the constitutive behavior of high strength steel over a wide range of strains, strain rates, and temperatures.
Modeling of Microchannel Hydroforming Process With Thin Metallic Sheets
Authors: Xu Zhutian , Peng Linfa , Yi Peiyun , Lai Xinmin
Published: March 2012

Micro/mesoscale metal sheet hydroforming (SHF) process is an efficient approach suitable for mass production to fabricate metal parts with micro/mesochannel features. In conventional sheet hydroforming process, the channel’s feature sizes (e.g., the channel width, fillet radius, etc.) are much greater than the sheet’s thickness, so that the influence of the fillet and the inhomogeneous stress/strain distribution through the thickness direction can be ignored. However, the influence becomes increasingly important, because the thickness of the sheet and the feature dimensions of the microchannel are in the same magnitude as the feature sizes of the material and tools reduced to micro/mesoscale. In this paper, an analytical model with consideration of the inhomogeneous stress/strain distribution was developed to predict the channel profile at different pressures in micro/mesohydroforming process. Plane-strain deformation behaviors in the section of the workpiece were studied, and the relation function between the pressure and the channel height was established. Via this function, the channel height could be accurately predicted for a given pressure. Furthermore, an experimental setup was prepared, hydroforming experiments using microchannel dies with various geometric dimensions were conducted, and the channel height of the workpieces was measured. It was found that the experimental results matched well with the simulation results, which confirmed the validity of the analytical model proposed in this study. It is expected that the model will be beneficial in the optimization of the microchannel hydroforming process.
A Novel Singular Finite Element on Mixed-Mode Dugdale Model Based Crack
Authors: Yao W. A. , Hu X. F.
Published: March 2012

The symplectic dual approach is employed to obtain the analytical solutions of displacements and stresses around the mixed-mode Dugdale crack tip. Based on the analytical solutions, a novel singular finite element is developed to study the problem. The singular finite element can be applied to determine the sizes of crack tip opening/sliding displacement of a mixed-mode Dugdale model. Numerical results obtained by the present method show excellent agreement with the existing analytical solutions.
Experimental Assessment of High Temperature Formability of Boron Steel Sheet Manufactured With a Spring Compound Bending Die
Authors: Li Yang , Jeon Yong-Phil , Kang Chung-Gil
Published: March 2012

Bending behavior occurs in the hot press forming process, resulting in many cases of failure during forming. To address the problem of cracking and improve the formability and mechanical properties of boron steel sheets in the bending process, an experiment has been carried out by using a spring compound bending die. Also, a comparison has been made between the traditional U-bending die and the spring compound bending die with regard to formability. The influence of the parameters for hot press forming such as the heating temperature, punch speed, and die radii on the mechanical properties and microstructure was analyzed by tension testing and metallographic observations.
Impact of mask absorber thickness on the focus shift effect in extreme ultraviolet lithography
Authors: Cao Yuting , Wang Xiangzhao , Tu Yuanying , Bu Peng
Published: March 2012

A focus shift is a common phenomenon in extreme ultraviolet lithography. It depends on the pattern pitch and has a significant effect on the process window. This work proposes an approximate but analytical method to investigate the focus shift effect using a modified thin mask model and the Hopkins formula of imaging. The source of the focus shift is identified, and the impact of the absorber thickness is discussed. The focus shift effect can be reduced and the process window can be improved by choosing the appropriate absorber thickness.
Hyperplexing: A Method for Higher-Order Multiplexed Quantitative Proteomics Provides a Map of the Dynamic Response to Rapamycin in Yeast
Authors: Dephoure Noah , Gygi Steven P.
Published: March 2012

A dual-labeling strategy enables high-throughput analysis of multiple samples by mass spectrometry.
Deconvolution of mTORC2 “in Silico”
Authors: Fingar Diane C. , Inoki Ken
Published: March 2012

Combining classic biochemical approaches with dynamic mathematical modeling elucidates a new model for insulin-mediated activation of mTORC2.
Reversing Decline?
Authors: Hurtley Stella M.
Published: March 2012

Bexarotene counters the effects of neurodegenerative disease in mice.
Detecting Injury to Infer Predators
Authors: Gough Nancy R.
Published: March 2012

Chondroitin sulfate released from injured fish triggers fear responses.
GAINing Autoproteolytic Activity
Authors: VanHook Annalisa M.
Published: March 2012

Structural analysis reveals how cell adhesion GPCRs and PKD proteins mediate autoproteolysis of the extracellular domain.
Gravity-Defying Peptides
Authors: VanHook Annalisa M.
Published: March 2012

Secreted peptides cooperate with auxin to drive gravitropic responses in plants.
Linking Aberrant Metabolism to Oncogenesis
Authors: Adler Elizabeth M.
Published: March 2012

Three papers explore the relationship between isocitrate dehydrogenase (IDH) mutation and glioma, with two implicating mutant IDH in aberrant methylation and the third linking (
R
)-2-hydroxyglutarate to degradation of hypoxia-inducible factor.
Correlative Time-Resolved Fluorescence Microscopy To Assess Antibiotic Diffusion-Reaction in Biofilms
Authors: Daddi Oubekka S. , Briandet R. , Fontaine-Aupart M.-P. , Steenkeste K.
Published: March 2012

The failure of antibiotics to inactivate
in vivo
pathogens organized in biofilms has been shown to trigger chronic infections. In addition to mechanisms involving specific genetic or physiological cell properties, antibiotic sorption and/or reaction with biofilm components may lessen the antibiotic bioavailability and consequently decrease their efficiency. To assess locally and accurately the antibiotic diffusion-reaction, we used for the first time a set of advanced fluorescence microscopic tools (fluorescence recovery after photobleaching, fluorescence correlation spectroscopy, and fluorescence lifetime imaging) that offer a spatiotemporal resolution not available with the commonly used time-lapse confocal imaging method. This set of techniques was used to characterize the dynamics of fluorescently labeled vancomycin in biofilms formed by two
Staphylococcus aureus
human isolates. We demonstrate that, at therapeutic concentrations of vancomycin, the biofilm matrix was not an obstacle to the diffusion-reaction of the antibiotic that can reach all cells through the biostructure.
Multiplex Real-Time PCR for Detection of an Epidemic KPC-Producing Klebsiella pneumoniae ST258 Clone
Authors: Chen Liang , Chavda Kalyan D. , Mediavilla José R. , Zhao Yanan , Fraimow Henry S. , Jenkins Stephen G. , Levi Michael H. , Hong Tao , Rojtman Albert D. , Ginocchio Christine C. , Bonomo Robert A. , Kreiswirth Barry N.
Published: March 2012

We describe a multiplex real-time PCR assay capable of identifying both the epidemic
Klebsiella pneumoniae
ST258 clone and
bla
KPC
carbapenemase genes in a single reaction. The assay displayed excellent sensitivity (100%) and specificity (100%) for identification of ST258 clone and
bla
KPC
in a collection of 75
K. pneumoniae
isolates comprising 41 sequence types. Our results suggest that this assay is an effective tool for surveillance of this clone among carbapenem-resistant
K. pneumoniae
clinical isolates.
Meropenem-Clavulanic Acid Shows Activity against Mycobacterium tuberculosis In Vivo
Authors: England Kathleen , Boshoff Helena I. M. , Arora Kriti , Weiner Danielle , Dayao Emmanuel , Schimel Daniel , Via Laura E. , Barry Clifton E.
Published: March 2012

The carbapenems imipenem and meropenem in combination with clavulanic acid reduced the bacterial burden in
Mycobacterium tuberculosis
-infected macrophages by 2 logs over 6 days. Despite poor stability in solution and a short half-life in rodents, treatment of chronically infected mice revealed significant reductions of bacterial burden in the lungs and spleens. Our results show that meropenem has activity in two
in vivo
systems, but stability and pharmacokinetics of long-term administration will offer significant challenges to clinical evaluation.