bluuebunny/crossref_metadata_2025 huggingface dataset:
ABC transporters of antimicrobial peptides in Firmicutes bacteria – phylogeny, function and regulation
Authors: Gebhard Susanne
Published: October 2012

Antimicrobial peptides (AMPs) are a group of antibiotics that mainly target the cell wall of Gram‐positive bacteria. Resistance is achieved by a variety of mechanisms including target alterations, changes in the cell's surface charge, expression of immunity peptides or by dedicated ABC transporters. The latter often provide the greatest level of protection. Apart from resistance, ABC transporters are also required for the export of peptides during biosynthesis. In this review the different AMP transporters identified to date in Firmicutes bacteria were classified into five distinct groups based on their domain architecture, two groups with a role in biosynthesis, and three involved in resistance. Comparison of the available information for each group regarding function, transport mechanism and gene regulation revealed distinguishing characteristics as well as common traits. For example, a strong correlation between transporter group and mode of gene regulation was observed, with three different types of two‐component systems as well as XRE family transcriptional regulators commonly associated with individual transporter groups. Furthermore, the presented summary of the state‐of‐the‐art on AMP transport in Firmicutes bacteria, discussed in the context of transporter phylogeny, provides insights into the mechanisms of substrate translocation and how this may result in resistance against compounds that bind extracellular targets.
Abscisic acid accumulation modulates auxin transport in the root tip to enhance proton secretion for maintaining root growth under moderate water stress
Authors: Xu Weifeng , Jia Liguo , Shi Weiming , Liang Jiansheng , Zhou Feng , Li Qianfeng , Zhang Jianhua
Published: October 2012

Maintenance of root growth is essential for plant adaptation to soil drying. Here, we tested the hypothesis that auxin transport is involved in mediating ABA's modulation by activating proton secretion in the root tip to maintain root growth under moderate water stress.

Rice and Arabidopsis plants were raised under a hydroponic system and subjected to moderate water stress (−0.47 MPa) with polyethylene glycol (PEG). ABA accumulation, auxin transport and plasma membrane H+‐ATPase activity at the root tip were monitored in addition to the primary root elongation and root hair density.

We found that moderate water stress increases ABA accumulation and auxin transport in the root apex. Additionally, ABA modulation is involved in the regulation of auxin transport in the root tip. The transported auxin activates the plasma membrane H+‐ATPase to release more protons along the root tip in its adaption to moderate water stress. The proton secretion in the root tip is essential in maintaining or promoting primary root elongation and root hair development under moderate water stress.

These results suggest that ABA accumulation modulates auxin transport in the root tip, which enhances proton secretion for maintaining root growth under moderate water stress.
A possible ovarian carcinoma metastatic in the mandible: diagnostic perspectives
Authors: McKernon S. , Triantafyllou A. , Balmer M.C.
Published: October 2012

A very rare case of metastatic carcinoma to the left mandible of an elderly female is reported. The primary growth had caused no symptoms apart from the mandibular lesion. Histopathological examination in conjunction with step‐by‐step use of immunohistochemistry suggested an ovarian origin, and the diagnostic process is discussed. The suggested origin was subsequently supported by computerised tomography scan. The case highlights problems in the diagnosis of oral metastatic disease.
Proximal Femoral Replacement and Allograft Prosthesis Composite in the Treatment of Periprosthetic Fractures with Significant Proximal Bone Loss
Authors: Rasouli Mohammad R , Porat Manny D , Hozack William J , Parvizi Javad
Published: October 2012

Femoral bone loss due to periprosthetic fracture, a challenging problem in total hip arthroplasty (THA), is increasingly encountered due to a rise in the number of revision THAs performed. Allograft prosthesis composite (APC) and proximal femoral replacement (PFR) are two available options for management of patients with difficult type‐B3 Vancouver periprosthetic fractures. The treatment algorithm for patients with these fractures has been extensively studied and is influenced by the age and activity level of the patient. APC is often preferred in young and active patients in an attempt to preserve bone stock while older and less active patients are considered candidates for PFR. In spite of the high rate of overall complications with these two procedures, reported survivorship is acceptable. Treating patients with these complicated fractures is fraught with complications and, even with successful treatment, the outcomes are not as promising as those associated with primary hip replacement. In this paper, we aimed to review available published reports about PFR and APC for treatment of periprosthetic fractures around THAs.
Does Previous Varicose Vein Surgery Alter Deep Vein Thrombosis Risk after Lower Limb Arthroplasty?
Authors: Dua Anahita , Neiva Santiago , Sutherland Alasdair
Published: October 2012

Objective

To determine the rates of deep vein thrombosis (DVT) and pulmonary embolism (PE) after total knee arthroplasty (TKA) and total hip arthroplasty (THA) in patients who have had previous varicose vein (VV) surgery.

Methods

Data on 57,364 patients who had undergone THAs and 51,859 patients who had undergone TKAs were obtained from the Scottish Arthroplasty Project and cross‐referenced with patients for whom DVT/PE events had been recorded (Scottish Morbidity Database).

Results

The THA DVT rate in patients who had previously undergone VV surgery was 0.8% (27/3478), and in those with no previous VV diagnosis or surgery was 0.8% (428/53,659). In patients with a previous VV diagnosis but no VV surgery, the THA DVT rate was 3.1% (7/227) (Pearson χ2 test, χ2 = 14.8, degrees of freedom = 2, P = 0.001). No significant difference was found for the corresponding data in the TKA cohort. The THA PE rate in patients who had previously undergone VV surgery was 0.7% (26/3478), and in those with no previous VV diagnosis or surgery 0.7% (376/53,659). No correlation was found between prior VV interventions and PE rates.

Conclusion

Untreated VVs are associated with an increased risk of DVT after THA. Therefore, patients with VVs should consider having them treated prior to undergoing orthopedic interventions.
A Comparison between “Sandwich” and Conventional Methods of Repairing Spinal Dura Rupture
Authors: Wang Hui‐ren , Cao Sheng‐sheng , Jiang Yun‐qi , Li Jun‐ning , Li Xi‐lei , Fu Yun‐gen , Zhao Ming‐dong , Dong Jian
Published: October 2012

Objective

To study the therapeutic efficacy of the “sandwich” method (medical glue + gelatin sponge + medical glue) of spinal dural repair for preventing cerebrospinal fluid (CSF) leaks during treatment of subdural tumors.

Methods

Fifty‐four patients with spinal subdural tumors treated between April 2007 and June 2011 were retrospectively investigated. The patients were divided into two groups: a conventional group (Group A) and a “sandwich” group (Group B). The Group A patients included 16 males and 7 females with an average tumor course of 11 months (range, 2–34 months). Four of their 23 tumors were in the cervical spine, eight thoracic, and eleven lumbar. The Group B patients included 19 males and 12 females with an average tumor course of 12 months (range, 3–36 months). Five of their 31 tumors were in the cervical spines, 10 thoracic, and 16 lumbar. In Group A, the dural repairs were performed with interlocking sutures and a gelatin sponge covering the dura; whereas in Group B, they were performed with interlocking sutures, painting of medical glue around the dural incision, covering this with a gelatin sponge, and finally covering of the gelatin sponge with medical glue. The total volume of drainage after operation, incidence of CSF leaks, healing of the incision, and recovery of clinical performance were recorded.

Results

Compared to Group A patients, Group B patients had a significantly smaller total volume of drainage (P < 0.05) on the day of surgery, and the first, second, and third postoperative days. The incidence of CSF leakage in Group B was also significantly less than in Group A (P < 0.05). Before discharge, three patients in Group A developd hydrops, which was successfully treated by aspiration, continuous pressure from sandbags, and the prone position. During the first 3 months of follow‐up, five patients developed deep hydrops under their incisions but required no treatment. There were no obvious abnormalities in Group B.

Conclusion

After removal of subdural spinal tumors by incising the dura mater, or in related spinal surgery, application of the “sandwich” complex to the damaged spinal dura reduces the volume of drainage postoperatively and reduces the incidence of CSF leakage.
Cerebrospinal Fluid Leakage during Anterior Approach Cervical Spine Surgery for Severe Ossification of the Posterior Longitudinal Ligament: Prevention and Treatment
Authors: Lei Tao , Shen Yong , Wang Lin‐feng , Cao Jun‐ming , Ding Wen‐yuan , Ma Qing‐hua
Published: October 2012

Objective

The prevention and treatment of the common complication of cerebrospinal fluid leakage (CSFL) during anterior approach cervical spine surgery for severe ossification of the posterior longitudinal ligament (OPLL) is documented.

Method

A retrospective analysis of 47 patients with severe cervical OPLL aged 39 to 73 years (average, 56.4 years) who underwent anterior operations was conducted. All patients were classified as local or segmental types based on the thickness of the ossified mass (>5 mm) and canal stenosis rates exceeding 50%. Fifteen cases underwent discectomy and fusion and 32 cases corpectomy and fusion. Preoperative CT images were analyzed for operation breakthrough and decompression range. During surgery, the ossified mass was excised or floated and the arachnoid reserved in order to reduce dural damage. Sutures coupled with gelatin sponge or muscle pedicle were applied to repair dural defects. After surgery, patients were confined to bed to allow for drainage or puncture.

Results

Fifteen cases of dural defects were recognized intraoperatively. Postoperatively, 5 patients developed CSFL. Partially cut dura with intact arachnoid occurred in one patient who developed a CSF pseudocyst. No cases required secondary operations or shunt placement and all exhibited good wound healing, with JOA scores increasing from 7.30 ± 1.08 to 13.70 ± 0.81 points and improvement rates of 65.98% ± 7.35%.

Conclusion

During anterior surgical treatment for severe OPLL, CSFL can be prevented and treated through careful analysis of CT images, meticulous operative technique, careful handling of the ossified mass, and intra‐operative repair of dural damage.
Children monosensitized to pine nuts have similar patterns of sensitization
Authors: Novembre Elio , Mori Francesca , Barni Simona , Ferrante Giuliana , Pucci Neri , Ballabio Cinzia , Uberti Francesca , Penas Elena , Restani Patrizia
Published: October 2012

Background

Several cases of pine nut allergies and anaphylaxis have been reported in the literature, but only few pine nut allergens have been characterized. The aim of this research is to identify through immunoelectrophoretic techniques the major pine nut allergens in a group of children monosensitized to pine nuts.

Methods

We studied five children with pine nut allergies and no other sensitization to food except to pine nuts, confirmed by in vivo (prick test, prick‐to‐prick) and in vitro tests (specific IgE determinations [CAP‐FEIA]). The protein profile of pine nuts was analyzed by Sodium Dodecyl sulfate Polyacrylamide Gel Electrophoresis (SDS‐PAGE). Immunoblotting was performed after incubation of membranes with the sera from the children included in the present study.

Results

Immunoblotting (SDS‐PAGE) demonstrated five similar bands between 6 and 47 kDa in all the subjects studied.

Conclusion

These bands should be considered the potential allergens for pine nut allergic children.
Oral food challenge: safety, adherence to guidelines and predictive value of skin prick testing
Authors: Calvani Mauro , Berti Irene , Fiocchi Alessandro , Galli Elena , Giorgio Valentina , Martelli Alberto , Miceli Sopo Stefano , Panetta Valentina
Published: October 2012

Background

The diagnostic gold standard of food allergy is the oral food challenge (OFC). Data on severe reactions and drug use during OFC are scarce. Our aims were (i) to investigate the prevalence and spectrum of reactions' severity during OFC and to assess drug use and epinephrine use in anaphylaxis due to OFC; (ii) to investigate the predictive value of the skin prick test wheal size for the outcome of OFCs.

Methods

A retrospective charts review of children undergoing OFC at three Allergy Centres between January 2007 and December 2008 was performed.

Results

A total of 544 OFCs were analysed. Most frequently involved foods were egg, milk and wheat. 254/526 (48.3%) were positive. 167 (65.7%) were defined mild reactions, 81 (31.9%) multiorgan reactions and 6 (2.4%) anaphylaxis. No patients had cardiovascular symptoms. Data on treatments were available in 98.8% OFCs. In half of them antihistamines were used vs. 10% cases in which steroids were preferred. Six children (2.4%) were treated with Epinephrine inhalation, 5 (2%) with beta‐2 inhalation, 8 (3.1%) with steroid inhalation. One child was treated with IM Epinephrine + IV fluids. Skin prick tests predictive cut‐off were 9 mm for albumen, 7 for yolk, 13 for fresh albumen, 10 for α‐lactalbumin, seven for casein, eight for β‐lactoglobulin, 20 for cow's milk and 10 for fresh cow's milk.

Conclusion

OFCs performed in controlled settings by expert Allergists are safe. Consideration needs to be given as to whether the Anaphylaxis' Guideline need to be modified when applied in treating patients undergoing OFC.
Differential immune response in mice immunized with the A, R or C domain from TcSP protein of Trypanosoma cruzi or with the coding DNAs
Authors: Salgado‐Jiménez B. , Arce‐Fonseca M. , Baylón‐Pacheco L. , Talamás‐Rohana P. , Rosales‐Encina J. L.
Published: October 2012

In a murine model of experimental Trypanosoma cruzi (H8 strain) infection, we investigated the induction of protective immunity against the domains [amino (A), repeats (R) and carboxyl (C)] of the surface protein (SP), a member of the trans‐sialidase (TS) superfamily. Recombinant proteins and plasmid DNA coding for the respective proteins were used to immunize BALB/c mice, and the humoral response and cytokine levels were analysed. Immunization with the recombinant proteins induced higher levels of anti‐TcSP antibodies than immunization with the corresponding DNAs, and analysis of serum cytokines showed that immunization with both recombinant proteins and naked DNA resulted in a Th1–Th2 mixed T‐cell response. Mice immunized with either recombinant proteins or plasmid DNA were infected with blood trypomastigotes. The recombinant protein‐immunized mice showed a variable reduction in peak parasitemia, and most died by day 60. Only the pBKTcSPR‐immunized mice exhibited a significant reduction in peak parasitemia and survived the lethal challenge. DNA‐based immunization with DNA coding for the repeats domain of TcSP is a good candidate for the development of a vaccine against experimental T. cruzi infection.
Distinct strains of Leishmania major induce different cytokine mRNA expression in draining lymph node of BALB/c mice
Authors: Asadpour A. , Riazi‐Rad F. , Khaze V. , Ajdary S. , Alimohammadian M.H.
Published: October 2012

Four genotypically distinct strains of L. major collected from persons residing in different endemic areas of cutaneous leishmaniasis in Iran were evaluated in BALB/c mice. Parasite virulence was evaluated by measuring the parasite burden in the lymph nodes. Immunogenicity of the strains was assessed by analysis of cytokines mRNA expression levels in popliteal lymph nodes of the mice in early (3, 16, 40 h) and late (week 1, W3, W5 and W8) time periods after infection. The expression of cytokines mRNA, namely Ifng, Il2,Il4,Il10 and Il12, was quantitated by real‐time PCR. The lowest and the highest parasite loads were induced by Damghan (2·15 × 107) and Shiraz (9·59 × 109) strains, respectively. Moreover, Damghan strain elicited higher expression levels of Ifng and Il2 mRNA and the highest ratio of Ifng/Il4 mRNA expression compared with the other strains at 40 h and 8 weeks post‐infection. The results indicate that the inoculation of BALB/c mice with different strains induced high diversity in parasite burden and cytokines gene expression. Amongst the four strains, Damghan strain showed the lowest parasite load and the highest tendency to induce expression of Th1 cytokines gene and might be considered as a safe and immunogenic strain.
A new aubergine disease caused by a whitefly‐borne strain of Tomato mild mottle virus (TomMMoV)
Authors: Dombrovsky A. , Sapkota R. , Lachman O. , Pearlsman M. , Antignus Y.
Published: October 2012

The aims of the present study were to further characterize the causal agent of a new viral disease of aubergines in Israel, first observed in 2003 and tentatively named eggplant mild leaf mottle virus (EMLMV) in a previous work, and to identify the vector responsible for its spread. The disease could be transmitted mechanically from infected source plants to healthy aubergines or laboratory test plants. Transmission electron microscopy (TEM) analysis of purified virus preparations indicated the presence of viral particles with a flexible filamentous morphology (approximately 720 nm long). TEM analysis of ultrathin sections prepared from infected leaf tissue revealed the presence of cytoplasmic inclusion bodies with pinwheel and crystalline structures, typical of those induced by potyviral infection. The viral coat protein subunit was shown to have a molecular weight of 37·5 kDa by SDS‐PAGE analysis. The viral particles reacted positively in western blot analysis with an antiserum against Tomato mild mottle virus (TomMMoV) from Yemen, described as a potyvirus, vectored by the aphid Myzus persicae. The current study describes some biological properties of EMLMV and presents evidence for its transmission by the whitefly Bemisia tabaci, but not by three aphid species. The taxonomic relationship between EMLMV and TomMMoV is discussed based on their biological characteristics and sequence analysis of their genomes. It is suggested that the Israeli EMLMV should be considered a distant strain of TomMMoV, designated TomMMoV‐IL, according to the present rules of Potyviridae molecular taxonomy.
Diagnosis and treatment of latent infection with Mycobacterium tuberculosis
Authors: CHEE CYNTHIA BIN‐ENG , SESTER MARTINA , ZHANG WENHONG , LANGE CHRISTOPH
Published: October 2012

In clinical practice, latent infection with Mycobacterium tuberculosis is defined by the presence of an M. tuberculosis‐specific immune response in the absence of active tuberculosis. Targeted testing of individuals from risk groups with the tuberculin skin test or an interferon‐γ release assay is currently the best method to identify those with the highest risk for progression to tuberculosis. Positive predictive values of the immunodiagnostic tests are substantially influenced by the type of test, the age of the person who is tested, the prevalence of tuberculosis in the society and the risk group to which the person belongs. As a general rule, testing should only be offered when preventive chemotherapy will be accepted in the case of a positive test result. Preventive chemotherapy can effectively protect individuals at risk from the development of tuberculosis, although at least 3 months of combination therapy or up to 9 months of monotherapy are required, and overall acceptance rate is low. Improvements of the current generation of immunodiagnostic tests could substantially lower the number of individuals that need to be treated to prevent a case of tuberculosis. If shorter treatment regimens were equally effective than those currently recommended, acceptance of preventive chemotherapy could be much improved.
The Effect of the Selective Cytopheretic Device on Acute Kidney Injury Outcomes in the Intensive Care Unit: A Multicenter Pilot Study
Authors: Tumlin James A. , Chawla Lakhmir , Tolwani Ashita J. , Mehta Ravindra , Dillon John , Finkel Kevin W. , DaSilva J. Ricardo , Astor Brad C. , Yevzlin Alexander S. , Humes H. David
Published: October 2012

Acute kidney injury (AKI) is characterized by deterioration in kidney function resulting in multisystem abnormalities. Much of the morbidity and mortality associated with AKI result from a systemic inflammatory response syndrome (SIRS). This study described herein is a prospective, single‐arm, multicenter US study designed to evaluate the safety and efficacy of the Selective Cytopheretic Device (SCD) treatment on AKI requiring continuous renal replacement therapy (CRRT) in the ICU. The study enrolled 35 subjects. The mean age was 56.3 ± 15. With regard to race, 71.4% of the subjects were Caucasian, 22.9% were Black, and 5.7% were Hispanic. Average SOFA score was 11.3 ± 3.6. Death from any cause at Day 60 was 31.4%. Renal recovery, defined as dialysis independence, was observed in all of the surviving subjects at Day 60. The results of this pilot study indicate the potential for a substantial improvement in patient outcomes over standard of care therapy, which is associated with a greater than 50% 60‐day mortality in the literature. The SCD warrants further study in scientifically sound, pivotal trial to demonstrate reasonable assurance of safety and effectiveness.
Thyroid hormone is required for growth adaptation to pressure load in the ovine fetal heart
Authors: Segar Jeffrey L. , Volk Ken A. , Lipman Michael H. B. , Scholz Thomas D.
Published: October 2012

New Findings

What is the central question of this study?

The importance of endogenous thyroid hormone in contributing to pathophysiological adaptive growth of the fetal heart is not known.

What is the main finding and its importance?

The study identifies that thyroid hormone is required for adaptive fetal cardiac growth in response to pressure overload. Understanding the pathophysiological cardiac growth process may allow for improved clinical care and new therapeutic strategies for fetuses and infants with congenital heart disease.

Thyroid hormone exerts broad effects on the adult heart, but little is known regarding the role of thyroid hormone in the regulation of cardiac growth early in development and in response to pathophysiological conditions. To address this issue, we determined the effects of fetal thyroidectomy on cardiac growth and growth‐related gene expression in control and pulmonary‐artery‐banded fetal sheep. Fetal thyroidectomy (THX) and/or placement of a restrictive pulmonary artery band (PAB) were performed at 126 ± 1 days of gestation (term, 145 days). Four groups of animals [n= 5–6 in each group; (i) control; (ii) fetal THX; (iii) fetal PAB; and (iv) fetal PAB + THX] were monitored for 1 week prior to being killed. Fetal heart rate was significantly lower in the two THX groups compared with the non‐THX groups, while mean arterial blood pressure was similar among groups. Combined left and right ventricle free wall + septum weight, expressed per kilogram of fetal weight, was significantly increased in PAB (6.27 ± 0.85 g kg−1) compared with control animals (4.72 ± 0.12 g kg−1). Thyroidectomy significantly attenuated the increase in cardiac mass associated with PAB (4.94 ± 0.13 g kg−1), while THX alone had no detectable effect on heart mass (4.95 ± 0.27 g kg−1). The percentage of binucleated cardiomyocytes was significantly decreased in THX and PAB +THX groups (∼16%) compared with the non‐THX groups (∼27%). No differences in levels of activated Akt, extracellular signal‐regulated kinase or c‐Jun N‐terminal kinase were detected among the groups. Markers of cellular proliferation but not apoptosis or expression of growth‐related genes were lower in the THX and THX+ PAB groups relative to thyroid‐intact animals. These findings suggest that in the late‐gestation fetal heart, thyroid hormone has important cellular growth functions in both physiological and pathophysiological states. Specifically, thyroid hormone is required for adaptive fetal cardiac growth in response to pressure overload.
Energy Harvesting of Thermoacoustic-Piezo Systems With a Dynamic Magnifier
Authors: Nouh M. , Aldraihem O. , Baz A.
Published: October 2012

This study presents a novel approach for enhancing the performance of one of the promising systems in the field of energy harvesting, namely the standing wave thermoacoustic engine. Currently, conventional thermoacoustic engines have been integrated with piezoelectric membranes to harness the acoustic energy associated with this class of engines. In these thermoacoustic-piezoelectric (TAP) harvesters, the acoustic to electric energy conversion efficiency vary typically from 10% to 15%. In this paper, an attempt is made to magnify the electric energy harnessed from the piezo membranes by providing the harvester with a dynamic magnifier. The proposed system will be referred to as a dynamically magnified thermoacoustic-piezo system (DMTAP). The main purpose of the dynamic magnifier, as implied by the name, is to magnify the strain experienced by the piezo-element. With proper selection of the design parameters of such a magnifier, the output power can be significantly increased. The theory as well as the equations governing the operation of the system before and after the addition of the dynamic magnification is presented. Numerical examples are provided to illustrate the performance characteristics and merits of the improved (DMTAP) system as compared with those of a conventional TAP.
Validation and Analysis of Numerical Results for a Two-Pass Trapezoidal Channel With Different Cooling Configurations of Trailing Edge
Authors: Siddique Waseem , El-Gabry Lamyaa , Shevchuk Igor V. , Fransson Torsten H.
Published: October 2012

High inlet temperatures in a gas turbine lead to an increase in the thermal efficiency of the gas turbine. This results in the requirement of cooling of gas turbine blades/vanes. Internal cooling of the gas turbine blade/vanes with the help of two-pass channels is one of the effective methods to reduce the metal temperatures. In particular, the trailing edge of a turbine vane is a critical area, where effective cooling is required. The trailing edge can be modeled as a trapezoidal channel. This paper describes the numerical validation of the heat transfer and pressure drop in a trapezoidal channel with and without orthogonal ribs at the bottom surface. A new concept of ribbed trailing edge has been introduced in this paper which presents a numerical study of several trailing edge cooling configurations based on the placement of ribs at different walls. The baseline geometries are two-pass trapezoidal channels with and without orthogonal ribs at the bottom surface of the channel. Ribs induce secondary flow which results in enhancement of heat transfer; therefore, for enhancement of heat transfer at the trailing edge, ribs are placed at the trailing edge surface in three different configurations: first without ribs at the bottom surface, then ribs at the trailing edge surface in-line with the ribs at the bottom surface, and finally staggered ribs. Heat transfer and pressure drop is calculated at Reynolds number equal to 9400 for all configurations. Different turbulent models are used for the validation of the numerical results. For the smooth channel low-Re k-ɛ model, realizable k-ɛ model, the RNG k-ω model, low-Re k-ω model, and SST k-ω models are compared, whereas for ribbed channel, low-Re k-ɛ model and SST k-ω models are compared. The results show that the low-Re k-ɛ model, which predicts the heat transfer in outlet pass of the smooth channels with difference of +7%, underpredicts the heat transfer by −17% in case of ribbed channel compared to experimental data. Using the same turbulence model shows that the height of ribs used in the study is not suitable for inducing secondary flow. Also, the orthogonal rib does not strengthen the secondary flow rotational momentum. The comparison between the new designs for trailing edge shows that if pressure drop is acceptable, staggered arrangement is suitable for the outlet pass heat transfer. For the trailing edge wall, the thermal performance for the ribbed trailing edge only was found about 8% better than other configurations.
Experimental Comparison of Two Degrees-of-Freedom Vortex-Induced Vibration on High and Low Aspect Ratio Cylinders with Small Mass Ratio
Authors: Gonçalves Rodolfo T. , Rosetti Guilherme F. , Fujarra André L. C. , Franzini Guilherme R. , Freire César M. , Meneghini Julio R.
Published: October 2012

Vortex-induced motion (VIM) is a specific way for naming the vortex-induced vibration (VIV) acting on floating units. The VIM phenomenon can occur in monocolumn production, storage and offloading system (MPSO) and spar platforms, structures presenting aspect ratio lower than 4 and unity mass ratio, i.e., structural mass equal to the displaced fluid mass. These platforms can experience motion amplitudes of approximately their characteristic diameters, and therefore, the fatigue life of mooring lines and risers can be greatly affected. Two degrees-of-freedom VIV model tests based on cylinders with low aspect ratio and small mass ratio have been carried out at the recirculating water channel facility available at NDF-EPUSP in order to better understand this hydro-elastic phenomenon. The tests have considered three circular cylinders of mass ratio equal to one and different aspect ratios, respectively L/D = 1.0, 1.7, and 2.0, as well as a fourth cylinder of mass ratio equal to 2.62 and aspect ratio of 2.0. The Reynolds number covered the range from 10 000 to 50 000, corresponding to reduced velocities from 1 to approximately 12. The results of amplitude and frequency in the transverse and in-line directions were analyzed by means of the Hilbert-Huang transform method (HHT) and then compared to those obtained from works found in the literature. The comparisons have shown similar maxima amplitudes for all aspect ratios and small mass ratio, featuring a decrease as the aspect ratio decreases. Moreover, some changes in the Strouhal number have been indirectly observed as a consequence of the decrease in the aspect ratio. In conclusion, it is shown that comparing results of small-scale platforms with those from bare cylinders, all of them presenting low aspect ratio and small mass ratio, the laboratory experiments may well be used in practical investigation, including those concerning the VIM phenomenon acting on platforms.
An Investigation Into Using Magnetically Attached Piezoelectric Elements for Vibration Control
Authors: Collinger J. C. , Messner W. C. , Wickert J. A.
Published: October 2012

A novel vibration control method utilizing magnetically mounted piezoelectric elements is described. Piezoelectric elements are bonded to permanent magnets, termed here as control mounts, which are attached to the surface of a steel beam through their magnetic attraction. The magnetic-piezoelectric control mounts are an alternative to traditional epoxy attachment methods for piezoelectric elements which allows for easy in-the-field reconfiguration. In model and laboratory measurements, the beam is driven through base excitation and the resonant shunt technique is utilized to demonstrate the attenuation characteristics of two magnetic-piezoelectric control mounts. The coupled system is discretized using a Galerkin finite element model that incorporates the tangential and vertical contact stiffnesses of the beam-magnet interface. The vibration reduction provided by the control mounts using a single magnet are compared to those designed with a magnetic array that alternates the magnetic dipoles along the length of the mount. Even though each design uses the same magnet thickness, the alternating magnetic configuration's interfacial contact stiffness is over 1.5 and 4 times larger in the tangential and vertical directions, respectively, than that of the single magnet, resulting in increased vibration reduction. Measured and simulated results show that the magnetic-piezoelectric control mounts reduced the beam's tip velocity by as much as 3.0 dB and 3.1 dB, respectively. The design tradeoffs that occur when replacing the traditional epoxy layer with a magnet are also presented along with some methods that could improve the vibration reduction performance of the control mounts. This analysis shows that the control mounts attenuate significant vibration despite having an imperfect bond with the beam, thus providing a viable and adaptable alternative to traditional piezoelectric attachment methods.
Thermal-Structural Performance of Orthotropic Pin Fin in Electronics Cooling Applications
Authors: Arif A. F. M. , Zubair Syed M. , Pashah S.
Published: October 2012

Thermally conductive composites as compared to metals have reduced density, decreased oxidation, and improved chemical resistance, as well as adjustable properties to fit a given application. However, there are several challenges that need to be addressed before they can be successfully implemented in heat sink design. The interface between the device and heat sink is an important factor in the thermal design of microelectronics cooling. Depending on the thermal interface conditions and material properties, the contact pressure and thermal stress level can attain undesirable values. In this paper, we investigate the effect of thermal interface between the fin and base plate on thermal-structural behavior of heat sinks. A coupled-field (thermal-structural) analysis using finite element method is performed to predict temperature as well as stress fields in the interface region. In addition temperature and heat flow rate predictions are supported through analytical results. effect of various interface geometrical (such as slot-depth, axial-gap, and radial-gap) and contact properties (such as air gap with surface roughness and gaps filled with interface material) on the resulting thermal-structural response is investigated with respect to four interface materials combinations, and it is found that the thermal performance is most sensitive to the slot-depth compared to any other parameter.
Cell Death of Streptococcus mutans Induced by a Quorum-Sensing Peptide Occurs via a Conserved Streptococcal Autolysin
Authors: Dufour Delphine , Lévesque Céline M.
Published: October 2012

Streptococcus mutans
, a member of the human indigenous oral microbiome, produces a quorum-sensing peptide called the competence-stimulating peptide (CSP) pheromone. We previously demonstrated that
S. mutans
expresses its CSP pheromone under specific stresses and responds to high levels of CSP by inducing cell death in a fraction of the bacterial population. Streptococci lack the classical SOS response, and the induction of the SigX regulon has been proposed to act as a general stress response in Gram-positive bacteria. We show here that inactivation of SigX abolished the CSP-induced cell death phenotype. Among SigX-regulated genes, SMU.836 (now named

lytF
Sm

), encoding a conserved streptococcal protein, is a functional peptidoglycan hydrolase involved in CSP-induced cell lysis. We also demonstrated that LytF

Sm

is most likely a self-acting autolysin, since LytF

Sm

produced by attacker cells cannot trigger CSP-induced lysis of LytF

Sm

-deficient target cells present in the same environment. Electron microscopy revealed important morphological changes accompanying autolysis of CSP-induced wild-type cultures that were absent in the LytF

Sm

-deficient mutant. The LytF

Sm

promoter was activated in the physiological context of elevated concentrations of the CSP pheromone under stress conditions, such as exposure to heat, hydrogen peroxide, and acid. In a long-term survival assay, the viability of a mutant deficient in LytF

Sm

autolysin was significantly lower than that observed for the wild-type strain. The results of this study suggest that cell death of
S. mutans
induced by its quorum-sensing CSP pheromone may represent a kind of altruistic act that provides a way for the species to survive environmental stresses at the expense of some of its cells.
The σ
E
Pathway Is Involved in Biofilm Formation by Crohn's Disease-Associated Adherent-Invasive Escherichia coli
Authors: Chassaing Benoit , Darfeuille-Michaud Arlette
Published: October 2012

Ileal lesions of patients with Crohn's disease are colonized by adherent-invasive
Escherichia coli
(AIEC) bacteria that are able to adhere to and invade intestinal epithelial cells (IEC), to replicate within macrophages, and to form biofilm. Clinical observations showed that bacterial biofilms were associated with the mucosa of inflammatory bowel disease patients. In the present study, we analyzed the relationship between AIEC colonization of the gut and the formation of biofilm, focusing on the involvement of the σ
E
pathway in the AIEC-IEC interaction. We observed that σ
E
pathway inhibition in AIEC reference strain LF82 led to an impaired ability to adhere to and invade IEC but also induced a large decrease in the abilities to colonize the intestinal mucosa and form biofilm. This indicates that targeting of the σ
E
pathway could be a very potent therapeutic strategy by which to interfere with the ability of AIEC to form biofilm on the gut mucosa of Crohn's disease patients.
A Single Missense Mutation in a Coiled-Coil Domain of Escherichia coli Ribosomal Protein S2 Confers a Thermosensitive Phenotype That Can Be Suppressed by Ribosomal Protein S1
Authors: Aseev Leonid V. , Chugunov Anton O. , Efremov Roman G. , Boni Irina V.
Published: October 2012

Ribosomal protein S2 is an essential component of translation machinery, and its viable mutated variants conferring distinct phenotypes serve as a valuable tool in studying the role of S2 in translation regulation. One of a few available
rpsB
mutants,
rpsB1
, shows thermosensitivity and ensures enhanced expression of leaderless mRNAs. In this study, we identified the nature of the
rpsB1
mutation. Sequencing of the
rpsB1
allele revealed a G-to-A transition in the part of the
rpsB
gene which encodes a coiled-coil domain of S2. The resulting E132K substitution resides in a highly conserved site, TKKE, a so-called N-terminal capping box, at the beginning of the second alpha helix. The protruding coiled-coil domain of S2 is known to provide binding with 16S rRNA in the head of the 30S subunit and, in addition, to interact with a key mRNA binding protein, S1. Molecular dynamics simulations revealed a detrimental impact of the E132K mutation on the coiled-coil structure and thereby on the interactions between S2 and 16S rRNA, providing a clue for the thermosensitivity of the
rpsB1
mutant. Using a strain producing a leaderless
lacZ
transcript from the chromosomal
lac
promoter, we demonstrated that not only the
rpsB1
mutation generating S2/S1-deficient ribosomes but also the
rpsA
::IS
10
mutation leading to partial deficiency in S1 alone increased translation efficiency of the leaderless mRNA by about 10-fold. Moderate overexpression of S1 relieved all these effects and, moreover, suppressed the thermosensitive phenotype of
rpsB1
, indicating the role of S1 as an extragenic suppressor of the E132K mutation.
Transcriptional Regulation of Aggregatibacter actinomycetemcomitans lsrACDBFG and
lsrRK
Operons and Their Role in Biofilm Formation
Authors: Torres-Escobar Ascención , Juárez-Rodríguez María Dolores , Lamont Richard J. , Demuth Donald R.
Published: October 2012

Autoinducer-2 (AI-2) is required for biofilm formation and virulence of the oral pathogen
Aggregatibacter actinomycetemcomitans
, and we previously showed that
lsrB
codes for a receptor for AI-2. The
lsrB
gene is expressed as part of the
lsrACDBFG
operon, which is divergently transcribed from an adjacent
lsrRK
operon. In
Escherichia coli
,
lsrRK
encodes a repressor and AI-2 kinase that function to regulate
lsrACDBFG
. To determine if
lsrRK
controls
lsrACDBFG
expression and influences biofilm growth of
A. actinomycetemcomitans
, we first defined the promoters for each operon. Transcriptional reporter plasmids containing the 255-bp
lsrACDBFG-lsrRK
intergenic region (IGR) fused to
lacZ
showed that essential elements of
lsrR
promoter reside 89 to 255 bp upstream from the
lsrR
start codon. Two inverted repeat sequences that represent potential binding sites for LsrR and two sequences resembling the consensus cyclic AMP receptor protein (CRP) binding site were identified in this region. Using electrophoretic mobility shift assay (EMSA), purified LsrR and CRP proteins were shown to bind probes containing these sequences. Surprisingly, the 255-bp IGR did not contain the
lsrA
promoter. Instead, a fragment encompassing nucleotides +1 to +159 of
lsrA
together with the 255-bp IGR was required to promote
lsrA
transcription. This suggests that a region within the
lsrA
coding sequence influences transcription, or alternatively that the start codon of
A. actinomycetemcomitans lsrA
has been incorrectly annotated. Transformation of Δ
lsrR
, Δ
lsrK
, Δ
lsrRK
, and Δ
crp
deletion mutants with
lacZ
reporters containing the
lsrA
or
lsrR
promoter showed that LsrR negatively regulates and CRP positively regulates both
lsrACDBFG
and
lsrRK
. However, in contrast to what occurs in
E. coli
, deletion of
lsrK
had no effect on the transcriptional activity of the
lsrA
or
lsrR
promoters, suggesting that another kinase may be capable of phosphorylating AI-2 in
A. actinomycetemcomitans
. Finally, biofilm formation of the Δ
lsrR
, Δ
lsrRK
, and Δ
crp
mutants was significantly reduced relative to that of the wild type, indicating that proper regulation of the
lsr
locus is required for optimal biofilm growth by
A. actinomycetemcomitans
.
Identification of Transport Proteins Involved in Free Fatty Acid Efflux in Escherichia coli
Authors: Lennen Rebecca M. , Politz Mark G. , Kruziki Max A. , Pfleger Brian F.
Published: October 2012

Escherichia coli
has been used as a platform host for studying the production of free fatty acids (FFA) and other energy-dense compounds useful in biofuel applications. Most of the FFA produced by
E. coli
are found extracellularly. This finding suggests that a mechanism for transport across the cell envelope exists, yet knowledge of proteins that may be responsible for export remains incomplete. Production of FFA has been shown to cause cell lysis, induce stress responses, and impair basic physiological processes. These phenotypes could potentially be diminished if efflux rates were increased. Here, a total of 15 genes and operons were deleted and screened for their impact on cell viability and titer in FFA-producing
E. coli
. Deletions of
acrAB
and
rob
and, to a lower degree of statistical confidence,
emrAB
,
mdtEF
, and
mdtABCD
reduced multiple measures of viability, while deletion of
tolC
nearly abolished FFA production. An
acrAB emrAB
deletion strain exhibited greatly reduced FFA titers approaching the
tolC
deletion phenotype. Expression of efflux pumps on multicopy plasmids did not improve endogenous FFA production in an
acrAB
+
strain, but plasmid-based expression of
acrAB
,
mdtEF
, and an
mdtEF
-
tolC
artificial operon improved the MIC of exogenously added decanoate for an
acrAB
mutant strain. The findings suggest that AcrAB-TolC is responsible for most of the FFA efflux in
E. coli
, with residual activity provided by other resistance-nodulation-cell division superfamily-type efflux pumps, including EmrAB-TolC and MdtEF-TolC. While the expression of these proteins on multicopy plasmids did not improve production over the basal level, their identification enables future engineering efforts.
The Extracytoplasmic Function Sigma Factor EcfO Protects Bacteroides fragilis against Oxidative Stress
Authors: Ndamukong Ivan C. , Gee Jason , Smith C. Jeffrey
Published: October 2012

The anaerobe
Bacteroides fragilis
is a highly aerotolerant, opportunistic pathogen that is an important component of the human intestinal microbiota. Aerotolerance has been linked to a robust oxidative stress response, which in turn is necessary for maximal virulence in a mouse intra-abdominal abscess model. During oxidative stress, there is a dynamic change in gene expression that encompasses a third of the genome, but there is a paucity of information on factors that control this response. A large number of transcription regulators, including about 14 extracytoplasmic function (ECF) sigma factors, are affected by oxidative stress, and one of these, EcfO, was used as a model of ECF sigma factor activity during stress. Genetic and biochemical experiments showed that EcfO was located in an operon with a structurally unique anti-sigma factor, Reo. Cells deleted for EcfO were impaired during exposure to oxygen or other forms of oxidative stress, whereas
reo
mutants were more resistant to stress. Protein-protein interaction experiments demonstrated that Reo directly interacts with and regulates the activity of EcfO. Expression microarray and chromatin affinity precipitation assays were used to identify target genes regulated by EcfO, and an EcfO recognition sequence was identified. The results revealed that EcfO controls a regulon of novel lipoproteins whose distribution in nature is restricted to members of the
Bacteroidetes
phylum.
Drug therapy for children with tuberculosis
Authors: Ormerod L Peter
Published: October 2012

The scientific basis of drug treatment for both active tuberculosis (TB) disease and TB infection, has been established, with treatment in children being largely extrapolated from adult active disease trials. It is essential that active TB disease is excluded before asymptomatic TB infection is diagnosed and treated. Nearly half of all children with active TB disease are found as asymptomatic tuberculin, or interferon gamma release assay (IGRA), positive contacts on screening by local TB services, usually of sputum TB microscopy positive adult relatives or other index cases, but with evidence of lung infiltrate or mediastinal lymphadenopathy on the child's chest x-ray. New drug regimens for both active disease and latent infection are in development, and also some novel drugs. However, none of these have yet been tested in children, and so again data will need to be extrapolated from adult results. In addition, there are issues regarding pharmacokinetics and dosing for current drugs, particularly isoniazid.
Secondary spontaneous pneumothorax: a rare complication of pulmonary embolism
Authors: Mathieson Philip , Reckless Ian , Ferrett Colin
Published: October 2012

An 85-year-old lady presented with a left middle cerebral artery territory infarct. Several days into her admission she became hypoxic and haemodynamically unstable. A CT pulmonary angiogram showed bilateral pulmonary emboli, right-sided parenchymal cavitation due to infarction and an associated large pneumothorax. She was treated successfully with an intercostal drain and anticoagulation. This case describes the rare phenomenon of secondary spontaneous pneumothorax due to pulmonary infarction from pulmonary embolism. The factors associated with the development of infarcts from pulmonary thromboemboli are poorly understood although a number of predisposing conditions and pathological features have been suggested. Pulmonary infarction occurs in around 10% of cases of pulmonary emboli but the complication of secondary spontaneous pneumothorax would appear to be much less common. One should consider pulmonary embolism as the cause of pneumothorax where there is significant clinical suspicion.