bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability Evaluation of Flip Chip Using Stress Intensity Factors of an Interface Crack
Authors: Kim Won-Keun , Ikeda Toru , Miyazaki Noriyuki
Published: May 2010

Anisotropic Conductive Adhesive Film (ACF) has been used for electronic assemblies such as the connection between a Liquid Crystal Display (LCD) panel and a flexible print circuit board (FPC). ACF is expected to be a key technology for flip chip packaging and chip size packaging. The goal of our work is to provide an optimum design scheme to achieve the best combination of electrical performance and mechanical reliability for electronic packages using the ACF. This study presents an evaluation technology for the delamination of the ACF connections. We utilized the stress intensity factors of an interface crack between jointed dissimilar materials. The evaluation technology presented herein was found to provide reliability of an electronic package using the ACF connection during the solder reflow process.
Thermal Characters of Mesh Structure in a Flat Heat Pipe
Authors: Chien Liang-Han , Shih Y.-C.
Published: May 2010

In this study plate type heat pipes having mesh capillaries were investigated experimentally and theoretically. A test apparatus was designed to test thermal performance of plate type copper-water heat pipe having one or two layers of #50 or #80 mesh capillary structures with 5-to-50 W heat input. The working fluid, water is charged with 25% or 33% volume of the heat pipe internal space. In addition to horizontal orientation, the heat pipes were tested with the evaporator section elevated up to 40 degree inclination angle. Temperature distribution of the heat pipe was measured, and the evaporator, adiabatic and condensation resistances of the heat pipe were calculated separated. The effects of mesh size, charge volume, and inclination angle on each thermal resistance were discussed. In general, the #80 mesh yields lower thermal resistances than the #50 mesh; inclination angle has more significant effect on condenser than evaporator. Theoretical models of evaporation and condensation in flat heat pipes were proposed to interpolate the experimental results. The present evaporation model predicts the experimental data of evaporation resistance between −20% and +30%, and the condensation model predicts most condensation resistance data within ±30%.
Educational Effects of Industry-Academia Joint Projects on the Development of Microelectronic Packaging Technologies: Recent Experiences in Japan
Authors: Nakayama Wataru , Shiratori Masaki , Miyazaki Noriyuki
Published: May 2010

Because of its rapid pace of developments and interdisciplinary nature the microelectronic packaging technology poses enormous challenges to educators and learners alike. The education in campus is only a starting point of long learning process that spans the entire professional career of engineers. For post-college education, we need some channels that facilitate continuous exchanges between industry engineers and academia. The present paper describes such channels that have been incorporated in the projects sponsored by the Japan Society of Mechanical Engineers and the Japanese government.
Optimization Study of a Silicon-Carbide Micro-Capillary Pumped Loop
Authors: Meyer Laura J. , Phinney Leslie M.
Published: May 2010

Wide bandgap semiconductors such as SiC and GaN are materials that are advantageous for high power electronic devices. High power devices generate large amounts of energy that must be removed, and traditional cooling methods are insufficient for maintaining the desired operating temperatures. Thus, thermal management methods for high power electronic devices need to be developed. A SiC micro-capillary pumped loop thermal management system is being evaluated to cool SiC high power devices. Mathematical models incorporating two-phase flow and capillary wicking have been developed to analyze capillary pumped loops or loop heat pipes. This investigation uses a model based on the methodology of Dickey and Peterson (1994). The model takes an energy balance on the condenser and evaporator regions, as well as a pressure balance across the meniscus. A parametric study has been performed on the micro-CPL to determine the best design for a p-i-n diode that is less than 1 cm square and which produces a heat flux at the junction of over 300 W/cm2. The micro-CPL will be limited to a maximum size of 6.5 cm2. The liquid and vapor line lengths, number of grooves, and groove dimensions are varied to determine optimal values. The results and trends of the optimization calculations are discussed.
A Hybrid Flow Network-CFD Method for Achieving Any Desired Flow Partitioning Through Floor Tiles of a Raised-Floor Data Center
Authors: VanGilder James W. , Lee Ted
Published: May 2010

A technique is presented which allows a data center designer or operator to achieve any desired partitioning of available airflow among the floor tiles of a raised-floor data center without resorting to trial-and-error. The output from the analysis is a tile-by-tile prescription of flow resistance characteristics (e.g., damper settings), which accomplishes the desired partitioning. The technique is derived from an electrical-circuit analogy of the airflow in the data. Each circuit branch represents one path that air may follow from the CRAC unit supply, through a particular floor tile, and ultimately back to the CRAC return. Any desired flow partitioning through tiles can be achieved by proper adjustment of tile resistances in each circuit; however, by itself, the flow network has too many unknowns to be solvable. A CFD simulation of the entire data center, in which the desired flow partitioning is specified, provides the pressure distribution above (in the room) and below (in the plenum) the floor tiles. The method is illustrated in step-by-step fashion with a simple example case.
Thermodynamic Efficiency of Porous Glass Electroosmotic Pumps
Authors: Yao Shuhuai , Zeng Shulin , Santiago Juan G.
Published: May 2010

This paper presents an analytical and experimental study of electroosmotic (EO) pumps designed to be integrated with two-phase microchannel heat exchangers with load capacities of order 100 W and greater. We have fabricated sintered glass EO pumps that provide maximum flow rates and pressure capacities 33 ml/min and 1.3 atm, respectively, at 100 V applied potentials. We have developed an analytical model to solve for electroosmotic flow rate, total pump current, and thermodynamic efficiency as a function of pump pressure load for these porous-structure EO pumps. The model uses a symmetric electrolyte approximation valid for the high zeta potential regime and numerically solves the Poisson-Boltzmann equation for charge distribution in the idealized pore geometry. The model also incorporates an approximate ionic-strength-dependent zeta potential formulation. The effects of pressure and flow rate on thermodynamic efficiency are also analyzed theoretically and compared to our measurements.
Design and Assembly Methods for Improving High Current Board-Component Connectivity
Authors: Searls Damion , Dishongh Terry , Amir Dudi , Kang Jung
Published: May 2010

Development of higher performance silicon products often leads to more stringent demands on power delivery. Higher current sustainability is often a key parameter in successful power delivery design. One potential bottleneck in the delivery of power to the component is the printed circuit board (PCB) to component interface. However in many designs, the same interconnect structure is used for both the power and signal connection even though the requirements for power and signaling can be different. For example in current art, a substantially similar solder ball and pad design is used for both power and signal connections. This results in interconnects that may not be optimized for high current power delivery, and in turn lead to unnecessarily high power loss at the interconnect. Under this design archetype, higher current generally requires more power/ground solder balls and thus larger packages. In addition, these power connections compete with much-needed IO connections on the component. This paper discusses methods for separating and optimizing the power and signal interconnect structures. Example proof-of-concept instances are given using different component/board layout patterns and surface mount technology (SMT) structures. For example, one of these instances involves increasing BGA solder density to the point where solder may gang together during board assembly reflow (a design called ganged solder). Another example involves varying the board pad and via layout pattern and depth to accompany optimized high current socket contacts. The data indicates that employing such separation and optimization techniques can lead to a substantial drop in board and interconnect resistance. In each case, voltage gradient, temperature and resistance data is collected, and relative performance trends are discussed.
Determination of Package Die Temperature in a Set-Top Box Using JEDEC Thermal Metrics
Authors: Celik Zeki
Published: May 2010

This case study shows that neither the junction-to-ambient thermal resistance nor the junction-to-case thermal resistance will predict the die temperature of a package in a set top box application with reasonable accuracy. Instead junction-to-board thermal resistance, θJB, or junction-to-board thermal parameter, ΨJB, is proposed as the proper metric to be used to estimate die temperature under steady state conditions. Packages used in this work were 352 PBGA and 272 PBGA mounted on a 2-layer PCB which was designed to simulate a generic application. Nearby components with significant power dissipation were simulated using heater strips with specified power inputs. In the study, the die size varied from 7.1 mm × 7.1 mm to 11 mm × 11 mm. Measurements were taken in a generic set top box at various power inputs to the packages via thermal die and to the PCB via heaters.
BGA Reliability in Automotive Underhood Applications
Authors: Lall Pradeep , Islam Nokibul , Suhling Jeffrey , Darveaux Robert
Published: May 2010

Fine-Pitch BGAs and underfills have been used in benign office environments and wireless applications for a number of years, however their reliability in automotive underhood environment is not well understood. In this work, the reliability of fine-pitch PBGA packages has been evaluated in the automotive underhood environment. Experimental studies indicate that the CTE as measured by TMA typically starts to change at 10–15°C lower temperature than the Tg specified by DSC potentially extending the change in CTE well into the accelerated test envelope in the neighborhood of 125°C. High Tg substrates with glass-transition temperatures much higher than the 125°C high temperature limit are therefore not subject to the effect of high coefficient of thermal expansion close to the high temperature of the accelerated test. Darveaux’s damage relationships [1992, 1995, 2000] were derived on CBGA assemblies, with predominantly SMD pads and 62Sn36Pb2Ag solder. In addition to significant differences in the crack propagation paths for the two pad constructions, SMD pads fail significantly faster than NSMD pads in thermal fatigue. The thermal mismatch on CBGA’s is much larger than PBGA assemblies. Crack propagation in CBGA’s is often observed predominantly on the package side as opposed to both package and board side for PBGAs. In the present study, crack propagation data has been acquired on assemblies with 15 mm, 17 mm, and 23 mm size plastic BGAs with NSMD pads and 63Sn37Pb on high-Tg printed circuit boards. The data has been benchmarked against Darveaux’s data on CBGA assemblies. Experimental matrix also encompasses the effect of BT substrate thickness on reliability. Damage constants have been developed and compared against existing Darveaux Constants. Prediction error has been quantified for both sets of constants.
Sub-Continuum Heat Conduction in Electronics Using the Lattice Boltzmann Method
Authors: Ghai Sartaj S. , Escobar Rodrigo A. , Jhon Myung S. , Amon Cristina H.
Published: May 2010

The lattice Boltzmann method (LBM) is used to examine multi-length scale, confined heat conduction problems in one dimension for which sub-continuum effects are important. This paper describes the implementation of the method and its application to electronic devices. A silicon-on-insulator device with internal heat generation is used as a case study to illustrate the advantages of the LBM. We compare our results with various hierarchical equations of heat transfer such as Fourier, Cattaneo, and Boltzmann transport equations, as well as with experimental and numerical data from the literature. Our results provide excellent agreement with other methodologies, at a far less computational effort.
Measurement of the Constitutive Behavior of Underfill Encapsulants
Authors: Islam M. Saiful , Suhling Jeffrey C. , Lall Pradeep
Published: May 2010

Reliable, consistent, and comprehensive material property data are needed for microelectronic encapsulants for the purpose of mechanical design, reliability assessment, and process optimization of electronic packages. In our research efforts, the mechanical responses of several different capillary flow snap cure underfill encapsulants are being characterized. A microscale tension-torsion testing machine has been used to evaluate the uniaxial tensile stress-strain behavior of underfill materials as a function of temperature, strain rate, specimen dimensions, humidity, thermal cycling exposure, etc. A critical step to achieving accurate experimental results has been the development of a sample preparation procedure that produces mechanical test specimens that reflect the properties of true underfill encapsulant layers. In the developed method, 75–125 μm (3–5 mil) thick underfill uniaxial tension specimens are dispensed and cured using production equipment and the same processing conditions as those used with actual flip chip assemblies. Although several underfills have been examined, this work features results for the mechanical response of a single typical capillary flow snap cure underfill. A three parameter hyperbolic tangent empirical model has been shown to provide accurate fits to the observed underfill nonlinear stress-strain behavior over a range of temperatures and strain rates. In addition, typical creep data are presented.
Micromirror With Multiple Digitized Angles for Free Space Optical Crossconnects
Authors: Zhang Jianglong , Lee Y. C.
Published: May 2010

To eliminate or lower the power consumption and complexity of the control electronics that limit the applications of analog optical switches, beam steering devices and other micromirrors, this paper presents micromirrors with multiple digitized angles for free space optical crossconnects. Device requirements defined by a dual-lens and dual-micromirror array system are used to guide the designs of the micromirrors. The micromirrors with multiple digitized angles are designed using MUMPs, a MEMS foundry process, and simulated by full coupled-domain FEM/BEM. The effects of the design parameters on the digitized angles are analyzed. These parameters are flexure configuration, connector beam configuration, plate configuration and bottom electrode configuration. With these effects known, a micromirror is successfully designed for the desired optical system. Such a mirror’s repeatability is expected to be about 0.06°, which is obtained by a preliminary experimental study of a similar device. The repeatability of the digital levels highly depends on the initial gap between the mirror surface and the bottom electrode, flexure configuration, connector beam configuration and material properties.
Overview: The 7th International Seminar on Seismic Isolation, Passive Energy Dissipation and Active Control of Vibrations of Structures, Assisi, Italy, October 2–5, 2001 and Foundation of the Anti-Seismic Systems International Society (ASSISi)
Authors: Martelli Alessandro , Arato Giordano-Bruno , Forni Massimo , Spadoni Bruno , Chung Howard H.
Published: May 2010

This paper deals with the 7th International Seminar on Seismic Isolation, Passive Energy Dissipation and Active Control of Vibrations of Structures, held at Assisi (Italy) on October 2 to 5, 2001, which was jointly organized by the Italian Working Group on Seismic Isolation (GLIS) of the Italian National Association for Earthquake Engineering (ANIDIS) and Task Group 5 on Seismic Isolation of Structures (TG5) of the European Association for Earthquakes Engineering (EAEE) with the cooperation of several Institutions, associations and companies of a large number of countries, including the Italian Agency for New Technology, Energy and the Environment (ENEA) and the American Society of Mechanical Engineers (ASME). The background, scope, attendance, main technical and organizational features and conclusions of the Seminar and the associated international exhibition and technical meetings and visits are summarized. Some remarks are also reported on the foundation of the new world association on the innovative anti-seismic techniques (ASSISi – Anti-Seismic Systems International Society), which was decided during the Closing Panel of the Seminar, and on the purposes, site and main features of the next event, the 8th World Seminar on Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures, to be held at Yerevan, the Capital of Armenia, in 2003: this is the first event which will be organized in the framework of those officially involving ASSISi.
Tumor Immune Evasion
Authors: Zindl Carlene L. , Chaplin David D.
Published: May 2010

Malignant cells can induce the formation of lymphoid tissue–like structures that help the tumor evade host immunity.
Will
Deepwater Horizon
Set a New Standard for Catastrophe?
Authors: Kerr Richard , Kintisch Eli , Stokstad Erik
Published: May 2010

The fiery destruction of an oil drilling platform in the Gulf of Mexico on 20 April may have triggered one of the worst environmental disasters in U.S. history.
Radiation Accident a ‘Wake-Up Call’ For India's Scientific Community
Authors: Bagla Pallava
Published: May 2010

The improper disposal of a derelict gamma-ray research device at the University of Delhi has resulted in the death of a scrap-metal worker—and drawn scrutiny of how India's academic institutions handle radioactive materials.
Disseminated Penicilliosis, Recurrent Bacteremic Nontyphoidal Salmonellosis, and Burkholderiosis Associated with Acquired Immunodeficiency Due to Autoantibody against Gamma Interferon
Authors: Tang Bone Siu-Fai , Chan Jasper Fuk-Woo , Chen Min , Tsang Owen Tak-Yin , Mok M. Y. , Lai Raymond Wai-Man , Lee Rodney , Que Tak-Lun , Tse Herman , Li Iris Wai-Sum , To Kelvin Kai-Wang , Cheng Vincent Chi-Chung , Chan Eric Yuk-Tat , Zheng Bojian , Yuen Kwok-Yung
Published: May 2010

Acquired immunodeficiency due to autoantibody against gamma interferon has recently been associated with opportunistic nontuberculous mycobacteriosis, especially among Southeast Asians. We report another 8 cases, all except one apparently immunocompetent hosts who suffered from concomitant or sequential infections by other intracellular pathogens causing penicilliosis, extraintestinal nontyphoidal salmonellosis, and burkholderiosis. The only case with an underlying immunodeficiency syndrome had systemic lupus erythematosus that was quiescent throughout the multiple infective episodes. Eight out of 10 (80.0%) patients with serological evidence of penicilliosis, 5 out of 7 (71.4%) with culture-positive extraintestinal nontyphoidal salmonellosis, 5 out of 28 (17.9%) with serological evidence of melioidosis, and 7 out of 13 (53.8%) with culture-positive nontuberculous mycobacteriosis possessed autoantibody against gamma interferon, whereas only 1 out of 100 patients with systemic lupus erythematosus did. Our study represents the first and largest case series linking this emerging immunodeficiency syndrome with these atypical infections in apparently immunocompetent hosts. Thus, we advocate that any patient with unexplained recurrent or polymicrobial infections due to these intracellular pathogens should be screened for acquired immunodeficiency due to autoantibody against gamma interferon.
Tracking Environmental Norovirus Contamination in a Pediatric Primary Immunodeficiency Unit
Authors: Xerry Jacqueline , Gallimore Chris I. , Cubitt David , Gray Jim J.
Published: May 2010

Norovirus strains were detected in two patients and in environmental swabs from a pediatric primary immunodeficiency unit in London, United Kingdom, during an infection control incident in November and December 2007. Detailed analyses of the gene encoding the P2 domain demonstrated that the majority of the strains were not related to the patients and that the environmental contamination was most likely due to secondary transfer by the hands of staff or visitors.
Evaluation of a Loop-Mediated Isothermal Amplification Method as a Tool for Diagnosis of Infection by the Zoonotic Simian Malaria ParasitePlasmodium knowlesi
Authors: Iseki Hiroshi , Kawai Satoru , Takahashi Nobuyuki , Hirai Makoto , Tanabe Kazuyuki , Yokoyama Naoaki , Igarashi Ikuo
Published: May 2010

Loop-mediated isothermal amplification (LAMP) is a novel method that rapidly amplifies target DNA with high specificity under isothermal conditions. It has been applied as a diagnostic tool for several infectious diseases, including viral, bacterial, and parasitic diseases. In the present study, we developed a LAMP method for the molecular diagnosis ofPlasmodium knowlesiinfection (PkLAMP) and evaluated its sensitivity, specificity, and clinical applicability. We designed three sets ofPkLAMP primers for the species-specific β-tubulin gene. The primer sets forPkLAMP specifically amplified the autologous DNA extracts ofP. knowlesi, and the sensitivity of the test was 100-fold that of single-PCR assay. These results indicate that ourPkLAMP method can be used to efficiently distinguish betweenP. knowlesiand other malaria parasites. To evaluate the feasibility of usingin vivomaterials, comparisons ofPkLAMP and the conventional nested PCR (nPCR) method and microscopic examination were made with blood samples from two experimentally infected monkeys. These studies showed thatP. knowlesiinfection can be identified much earlier withPkLAMP than with nPCR and microscopy. Moreover, the detection performance ofPkLAMP using whole blood as the template was identical to that ofPkLAMP when genomic DNA extracts were used. These results suggest that thePkLAMP method is a promising tool for molecular diagnosis ofP. knowlesiinfection in areas of endemicity.
Multicenter Study To Determine Disk Diffusion and Broth Microdilution Criteria for Prediction of High- and Low-Level Mupirocin Resistance in
Staphylococcus aureus
Authors: Swenson Jana M. , Wong Betty , Simor Andrew E. , Thomson Richard B. , Ferraro Mary Jane , Hardy Dwight J. , Hindler Janet , Jorgensen James , Reller L. Barth , Traczewski Maria , McDougal Linda K. , Patel Jean B.
Published: May 2010

Mupirocin susceptibility testing of
Staphylococcus aureus
has become more important as mupirocin is used more widely to suppress or eliminate
S. aureus
colonization and prevent subsequent health care- and community-associated infections. The present multicenter study evaluated two susceptibility testing screening methods to detect mupirocin high-level resistance (HLR), broth microdilution (BMD) MICs of ≥512 μg/ml, and a 6-mm zone diameter for a disk diffusion (DD) test with a 200-μg disk. Initial testing indicated that with Clinical and Laboratory Standards Institute methods for BMD and DD testing, the optimal conditions for the detection of mupirocin HLR were 24 h of incubation and reading of the DD zone diameters with transmitted light. Using the presence or absence of
mupA
as the “gold standard” for HLR, the sensitivity and specificity of a single-well 256 μg/ml BMD test were 97 and 99%, respectively, and those for the 200-μg disk test were 98 and 99%, respectively. Testing with two disks, 200 μg and 5 μg, was evaluated for its ability to distinguish HLR isolates (MICs ≥ 512 μg/ml), low-level-resistant (LLR) isolates (MICs = 8 to 256 μg/ml), and susceptible isolates (MICs ≤ 4 μg/ml). Using no zone with both disks as an indication of HLR and no zone with the 5-μg disk plus any zone with the 200-μg disk as LLR, only 3 of the 340 isolates were misclassified, with 3 susceptible isolates being classified as LLR. Use of standardized MIC or disk tests could enable the detection of emerging high- and low-level mupirocin resistance in
S. aureus
.
Vif of Feline Immunodeficiency Virus from Domestic Cats Protects against APOBEC3 Restriction Factors from Many Felids
Authors: Zielonka Jörg , Marino Daniela , Hofmann Henning , Yuhki Naoya , Löchelt Martin , Münk Carsten
Published: May 2010

To get more insight into the role of APOBEC3 (A3) cytidine deaminases in the species-specific restriction of feline immunodeficiency virus (FIV) of the domestic cat, we tested the A3 proteins present in big cats (puma, lion, tiger, and lynx). These A3 proteins were analyzed for expression and sensitivity to the Vif protein of FIV. While A3Z3s and A3Z2-Z3s inhibited Δ
vif
FIV, felid A3Z2s did not show any antiviral activity against Δ
vif
FIV or wild-type (wt) FIV. All felid A3Z3s and A3Z2-Z3s were sensitive to Vif of the domestic cat FIV. Vif also induced depletion of felid A3Z2s. Tiger A3s showed a moderate degree of resistance against the Vif-mediated counter defense. These findings may imply that the A3 restriction system does not play a major role to prevent domestic cat FIV transmission to other
Felidae
. In contrast to the sensitive felid A3s, many nonfelid A3s actively restricted wt FIV replication. To test whether Vif
FIV
can protect also the distantly related human immunodeficiency virus type 1 (HIV-1), a chimeric HIV-1.Vif
FIV
was constructed. This HIV-1.Vif
FIV
was replication competent in nonpermissive feline cells expressing human CD4/CCR5 that did not support the replication of wt HIV-1. We conclude that the replication of HIV-1 in some feline cells is inhibited only by feline A3 restriction factors and the absence of the appropriate receptor or coreceptor.
Control of HIV-1 in Elite Suppressors despite Ongoing Replication and Evolution in Plasma Virus
Authors: O'Connell Karen A. , Brennan Timothy P. , Bailey Justin R. , Ray Stuart C. , Siliciano Robert F. , Blankson Joel N.
Published: May 2010

A subset of HIV-1-infected patients known as elite controllers or suppressors (ES) control the virus naturally. We have previously demonstrated sequence discordance between proviral and plasma
gag
clones in ES, much of which can be attributed to selective pressure from the host (J. R. Bailey, T. M. Williams, R. F. Siliciano, and J. N. Blankson, J. Exp. Med. 203:1357-1369, 2006). However, it is not clear whether ongoing viral replication continues in ES once the control of viremia has been established or whether selective pressure impacts this evolution. The cytotoxic T-lymphocyte (CTL) response in ES often targets Gag and frequently is superior to that of HIV-1 progressors, partially due to the HLA class I alleles B*57/5801 and B*27, which are overrepresented in ES. We therefore examined longitudinal plasma and proviral
gag
sequences from HLA-B*57/5801 and -B*27 ES. Despite the highly conserved nature of
gag
, we observed clear evidence of evolution in the plasma virus, largely due to synonymous substitutions. In contrast, evolution was rare in proviral clones, suggesting that ongoing replication in ES does not permit the significant reseeding of the latent reservoir. Interestingly, there was little continual evolution in CTL epitopes, and we detected
de novo
CTL responses to autologous viral mutants. Thus, some ES control viremia despite ongoing replication and evolution.
Optimal Replication of Human Cytomegalovirus Correlates with Endocytosis of Glycoprotein gpUL132
Authors: Kropff Barbara , Koedel Yvonne , Britt William , Mach Michael
Published: May 2010

Envelopment of a herpesvirus particle is a complex process of which much is still to be learned. We previously identified the glycoprotein gpUL132 of human cytomegalovirus (HCMV) as an envelope component of the virion. In its carboxy-terminal portion, gpUL132 contains at least four motifs for sorting of transmembrane proteins to endosomes; among them are one dileucine-based signal and three tyrosine-based signals of the YXXØ and NPXY (where X stands for any amino acid, and Ø stands for any bulky hydrophobic amino acid) types. To investigate the role of each of these trafficking signals in intracellular localization and viral replication, we constructed a panel of expression plasmids and recombinant viruses in which the signals were rendered nonfunctional by mutagenesis. In transfected cells wild-type gpUL132 was mainly associated with the
trans-
Golgi network. Consecutive mutation of the trafficking signals resulted in increasing fractions of the protein localized at the cell surface, with gpUL132 mutated in all four trafficking motifs predominantly associated with the plasma membrane. Concomitant with increased surface expression, endocytosis of mutant gpUL132 was reduced, with a gpUL132 expressing all four motifs in mutated form being almost completely impaired in endocytosis. The replication of recombinant viruses harboring mutations in single trafficking motifs was comparable to replication of wild-type virus. In contrast, viruses containing mutations in three or four of the trafficking signals showed pronounced deficits in replication with a reduction of approximately 100-fold. Moreover, recombinant viruses expressing gpUL132 with three or four trafficking motifs mutated failed to incorporate the mutant protein into the virus particle. These results demonstrate a role of endocytosis of an HCMV envelope glycoprotein for incorporation into the virion and optimal virus replication.
Merkel Cell Polyomavirus-Infected Merkel Cell Carcinoma Cells Require Expression of Viral T Antigens
Authors: Houben Roland , Shuda Masahiro , Weinkam Rita , Schrama David , Feng Huichen , Chang Yuan , Moore Patrick S. , Becker Jürgen C.
Published: May 2010

Merkel cell carcinoma (MCC) is the most aggressive skin cancer. Recently, it was demonstrated that human Merkel cell polyomavirus (MCV) is clonally integrated in ∼80% of MCC tumors. However, direct evidence for whether oncogenic viral proteins are needed for the maintenance of MCC cells is still missing. To address this question, we knocked down MCV T-antigen (TA) expression in MCV-positive MCC cell lines using three different short hairpin RNA (shRNA)-expressing vectors targeting exon 1 of the TAs. The MCC cell lines used include three newly generated MCV-infected cell lines and one MCV-negative cell line from MCC tumors. Notably, all MCV-positive MCC cell lines underwent growth arrest and/or cell death upon TA knockdown, whereas the proliferation of MCV-negative cell lines remained unaffected. Despite an increase in the number of annexin V-positive, 7-amino-actinomycin D (7-AAD)-negative cells upon TA knockdown, activation of caspases or changes in the expression and phosphorylation of Bcl-2 family members were not consistently detected after TA suppression. Our study provides the first direct experimental evidence that TA expression is necessary for the maintenance of MCV-positive MCC and that MCV is the infectious cause of MCV-positive MCC.
Ebola Virus Glycoprotein Counteracts BST-2/Tetherin Restriction in a Sequence-Independent Manner That Does Not Require Tetherin Surface Removal
Authors: Lopez Lisa A. , Yang Su Jung , Hauser Heiko , Exline Colin M. , Haworth Kevin G. , Oldenburg Jill , Cannon Paula M.
Published: May 2010

BST-2/tetherin is an interferon-inducible protein that restricts the release of enveloped viruses from the surface of infected cells by physically linking viral and cellular membranes. It is present at both the cell surface and in a perinuclear region, and viral anti-tetherin factors including HIV-1 Vpu and HIV-2 Env have been shown to decrease the cell surface population. To map the domains of human tetherin necessary for both virus restriction and sensitivity to viral anti-tetherin factors, we constructed a series of tetherin derivatives and assayed their activity. We found that the cytoplasmic tail (CT) and transmembrane (TM) domains of tetherin alone produced its characteristic cellular distribution, while the ectodomain of the protein, which includes a glycosylphosphatidylinositol (GPI) anchor, was sufficient to restrict virus release when presented by the CT/TM regions of a different type II membrane protein. To counteract tetherin restriction and remove it from the cell surface, HIV-1 Vpu required the specific sequence present in the TM domain of human tetherin. In contrast, the HIV-2 Env required only the ectodomain of the protein and was sensitive to a point mutation in this region. Strikingly, the anti-tetherin factor, Ebola virus GP, was able to overcome restriction conferred by both tetherin and a series of functional tetherin derivatives, including a wholly artificial tetherin molecule. Moreover, GP overcame restriction without significantly removing tetherin from the cell surface. These findings suggest that Ebola virus GP uses a novel mechanism to circumvent tetherin restriction.
Evidence for DNA Hairpin Recognition by Zta at the Epstein-Barr Virus Origin of Lytic Replication
Authors: Rennekamp Andrew J. , Wang Pu , Lieberman Paul M.
Published: May 2010

The Epstein-Barr virus immediate-early protein (Zta) plays an essential role in viral lytic activation and pathogenesis. Zta is a basic zipper (b-Zip) domain-containing protein that binds multiple sites in the viral origin of lytic replication (OriLyt) and is required for lytic-cycle DNA replication. We present evidence that Zta binds to a sequence-specific, imperfect DNA hairpin formed by an inverted repeat within the upstream essential element (UEE) of OriLyt. Mutations in the OriLyt sequence that are predicted to disrupt hairpin formation also disrupt Zta binding
in vitro
. Restoration of the hairpin rescues the defect. We also show that OriLyt DNA isolated from replicating cells contains a nuclease-sensitive region that overlaps with the inverted-repeat region of the UEE. Furthermore, point mutations in Zta that disrupt specific recognition of the UEE hairpin are defective for activation of lytic replication. These data suggest that Zta acts by inducing and/or stabilizing a DNA hairpin structure during productive infection. The DNA hairpin at OriLyt with which Zta interacts resembles DNA structures formed at other herpesvirus origins and may therefore represent a common secondary structure used by all herpesvirus family members during the initiation of DNA replication.
Self-association of copolymers with various composition profiles
Authors: Kuldová Jitka , Košovan Peter , Limpouchová Zuzana , Procházka Karel , Borisov Oleg V.
Published: May 2010

In this paper, we present Monte Carlo study of the self-assembly of linear copolymers consisting of two types of segments (well soluble A and insoluble B segments) in selective solvents. We used simple lattice model: chains were represented by self-avoiding random walks and quality of solvent for both types of segments was controlled by pair interaction parameters. We analyzed how the association behavior depends on the composition profile, i.e., on the sequence of segments A and B along the chain. The size and structure of associates formed by chains with different composition profiles were compared with those of diblock copolymers with the same content of A and B segments. It was shown that even small changes in the sequence of segments within the chains lead to significant differences in the association behavior. In addition to composition profiles, we also shown how the association behavior depends on the quality of solvent and copolymer concentration.
Pain assessment and management in medical wards: an area of unmet need
Authors: Chang S H , Maney K M , Mehta V , Langford R M
Published: May 2010

Background

Acute Pain Services (APS) were introduced primarily to improve postoperative pain management. Although pain is similar in prevalence and severity in medical and surgical wards, its assessment and management in non-surgical patients often receives less attention and resources.

Objective

To investigate the extent of APS involvement on medical wards and obtain perceptions of deficiencies.

Method

A questionnaire was mailed to APS leads in 287 UK NHS hospitals; 229 questionnaires were returned (79.8% response).

Results

Only 36 (16%) of the 225 hospitals with medical wards reported routine APS involvement. Pain scores were not recorded in 75 (33%) hospitals, 11 (5%) denied knowledge about assessments being conducted, and 185 (82.2%) respondents felt that pain management on medical wards was inadequate.

Conclusions

Perceived lack of training and awareness of healthcare staff were highly ranked contributing factors, and this was attributed to inadequate funding. This study highlights the scope for improvement of pain control in medical patients, with benefits from reduced morbidity and faster recovery.
Germ tube induction in Candida albicans
Authors: Shepherd M. G. , Yin Chiew Yoke , Ram S. P. , Sullivan P. A.
Published: May 2010

A reproducible and simple system for the production of germ tubes from yeast cells of Candida albicans using glucose and glutamine as substrates has been described.During germ tube formation there was a doubling of the dry weight but the number of cells remained constant. Although the DNA content did not change for the first 4 h of germ tube formation, the RNA content more than doubled. The DNA and RNA content of C. albicans blastospores are 4.5 × 10−15 g per cell and 48 × 10−15 g per cell respectively.Nystatin, phenethyl alcohol, 2,4-dinitrophenol, azaserine, salicylhydroxamic acid, and 5-fluorocytosine were all effective inhibitors of germ tube formation. Cysteine, potassium cyanide, and polyoxin D did not prevent germination. The incorporation of both uracil and leucine occurred rapidly during germ tube formation. The inhibitors of RNA synthesis, actinomycin D, cordycepin, and daunomycin prevented germination and inhibited uracil incorporation. The translational inhibitors, trichodermin, aurin tricarboxylic acid, puromycin, and cyloheximide were effective in inhibiting both germ tube formation and leucine incorporation.
Effect of prostaglandin E1-induced elevation of cyclic AMP on glucose repression in the lactic streptococci
Authors: Ratliff Timothy L. , Stinson Robert S. , Talburt Dwight E.
Published: May 2010

Cyclic adenosine 3′,5′-monophosphate (cAMP) activity was observed in Streptococcus lactis C2, Streptococcus cremoris C10, Streptococcus diacetlactis 18-16, and Streptococcus thermophilus C3. In vitro assays of cell-free extracts obtained from S. lactis C2 showed that the cAMP-associated enzymes adenyl cyclase and phosphodiesterase were also present. In vitro experiments showed that prostaglandin E1 (PGE) stimulation of adenyl cyclase increased cAMP concentrations approximately fivefold, and in vivo studies showed that PGE treatment of S. lactis C2 increased intracellular cAMP concentrations twofold. Furthermore, PGE-induced elevation of intracellular cAMP levels was shown to prevent the repression of β-D-phosphogalactoside galactohydrolase synthesis by glucose.
Consequences of interaction between F plasmid and a drug-resistance plasmid belonging to incompatibility group F1
Authors: Katz Leonard , Palchaudhuri Sunil
Published: May 2010

Two plasmids, pLK1 and pLK2, were derived from pIP218, an in vivo recombinant of plasmid F and the drug-resistance plasmid pIP176 (Cmr, Smr, Sur, Tcr). Of these two plasmids, pLK1 is 70 Mdaltons and carries the Tc-resistance determinant in a 7-Mdalton transposition element; pL K2 is 125 Mdaltons and carries Cm-, Sm- and Su-resistance determinants.The plasmid pLK1 resulted as a Tc-resistance segregant of pIP218 during its coexistence with another plasmid, Co1E1-araC 101, and pLK2 (125 Mdaltons) as a CmrSmrSur segregant during the conjugal transfer of pIP218. Both plasmids belong to the F1-incompatibility group, surface-exclude each other and Flac, and are derepressed for transfer. Incompatibility studies also indicated the preferential maintenance of pLK2 in hosts carrying either pLK2 and pLK1, or pLK2 and F'lac. An explanation of this phenomenon is provided. Furthermore, our data suggest the illegitimate recombination of the chromosomal lac genes with pLK1. In course of the incompatibility studies, the tet determinant was transposed from pLK1 into the chromosome, from the chromosome into the lac genes of an Flac plasmid, and from the Flac plasmid into another site on a second Flac plasmid.
Fractionation and characterization of two morphologically distinct types of cells in Rhizobium japonicum broth culture
Authors: Shantharam S. , Gow J. A. , Bal A. K.
Published: May 2010

Differential centrifugation of stationary phase broth culture of Rhizobium japonicum yielded two distinct morphological types of bacterial cells, rods, and small coccoid forms with capsulated and non-capsulated cells in each group. The rods usually had polar capsules which resulted in "star" formation. The coccoid bacteria were either free with thick capsular material surrounding the cells or held together in a common capsular sheath forming clusters and chains. 125I soybean lectin bound to the two types of cells. The binding sites were localized in the capsular material as revealed by colloidal gold- and ferritin-labelled lectin. Both fractions were capable of nodule formation in the soybean.
Composition and properties of the cell wall of Methanospirillum hungatii
Authors: Sprott G. D. , McKellar R. C.
Published: May 2010

Dithiothreitol reacted, at pH 9.0, with the isolated cell walls of Methanospirillum hungatii, to release about 23% of the cell wall dry weight as a high molecular weight fraction (> 0.5 million daltons). Untreated walls consisted of 70% amino acids, 11% lipid, and 6.6% carbohydrate. Sugars were identified as rhamnose, ribose, glucose, galactose, and mannose. The wall material that was released contained only 47% amino acids and was enriched in lipid, glucose, and phosphate. These results support data from electron micrographs, showing the localized release of cell wall material by the disulfide bond-breaking reagent at alkaline pH. In amino acid composition the untreated walls did not differ greatly from the material released by dithiothreitol, but differed considerably from the walls of another strain of M. hungatii. The ratios of the amino acids found in the cell wall proteins of several archaebacteria and of Bacillus cereus spore coats were similar.
An enzymatic release of antibiotic-containing peptidoglycan fragments from streptomycin-producing Streptomyces griseus
Authors: Barabás Gy. , Szabó I. , Ottenberger A. , Zs.-Nagy V. , Szabó G.
Published: May 2010

A cell wall bound autolytic enzyme of a streptomycin-producing strain of Streptomyces griseus was investigated. The peptidoglycan fragments released by the enzyme showed antibiotic activity. Analysis of these fragments proved that streptomycin is bound to a cell wall peptide. The peptide contained the four amino acids characteristic of Streptomyces cell wall: alanine, glycine, diaminopimelic acid, and glutamine or glutamic acid.
A function of Pseudomonas aeruginosa PAO polar pili: twitching motility
Authors: Bradley David E.
Published: May 2010

Twitching motility is a mode of flagella-independent surface translocation exhibited by Pseudomonas aeruginosa and other bacteria on solid media. All species exhibiting it carry thin pili, usually polar. This work shows that only PAO and K strains of P. aeruginosa with retractile (PSA) pili were able to move in this way, those with no pili or non-retractile pili remaining stationary. Specific agents such as anti-pilus serum, which prevents otherwise functional pili from retracting, also prevented twitching motility.
Mobilization of chromosomal determinants for the polar pili of Pseudomonas aeruginosa PAO by FP plasmids
Authors: Bradley David E.
Published: May 2010

Pseudomonas aeruginosa polar pili are determined by chromosomal genes which can be mobilized by the plasmid FP2 into a non-piliated Rec+ recipient, but not into its Rec− derivative. Matings between strains with no pili (selected by resistance to pilus-specific bacteriophages), and strains with non-retractile pili, give rise to recombinants with retractile pili.
Chemical and enzymic analyses of Pichia polymorpha cell walls
Authors: Villa Tomas G. , Notario Vicente , Villanueva Julio R.
Published: May 2010

Conventional techniques of chemical analysis have shown that the cell walls of the yeast Pichia polymorpha, at early stationary growth phase, consisted of carbohydrate (about 85%), protein (8%), and lipid (7%). Glucose and mannose were the only neutral sugars and glucosamine the sole amino sugar present among the cell wall components. Paper and gas–liquid chromatographies of acid hydrolysates of purified cell walls and cell wall fractions proved that mannan and alkali-insoluble glucans, in that order, were the major polysaccharide components, accounting for 83% of the total carbohydrate content. The isolation of an alkali-soluble glucan, non-precipitable with Fehling's solution, has been achieved. Treatments of whole cell walls and their fractions with purified cell wall lytic enzymes have shown the presence of both 1, 3- and 1, 6-β-D-linkages in all the glucan fractions. 1, 3-α-Glucan was not detected. Mannan–glucan complexes have been found containing about 50% each of mannose and glucose. All polysaccharides exhibited different turnover rates when cells were grown in the presence of D-[U-14C]glucose. The morphogenetic implications of these results are discussed.
Cellulase complex of a mesophilic Streptomyces strain
Authors: Ishaque M. , Kluepfel D.
Published: May 2010

Various cellulolytic streptomycetes were isolated from natural environments. The cellulase production of one of these mesophilic Streptomyces strains, identified as S. flavogriseus was studied. When grown as a submerged culture with 1% microcrystalline cellulose (Avicel) as substrate, the strain produced considerable amounts of β-1, 4-glucan glucanohydrolase (EC 3.2.1.4; CM cellulase) in the extracellular supernatant and exhibited good overall cellulolytic activity as measured using filter paper (FP cellulase) and cotton as substrates. The maximum enzyme yields were obtained after 72 h of incubation at 30 °C. The optimal conditions for the FP cellulase activity were found at pH 5.6 and 40 °C. All β-glucosidase and cellobiase activities were found in the mycelial fraction of the culture and could be obtained in soluble form by sonication.
A unique environmental occurrence of hydrogen sulfide positive Escherichia coli
Authors: Roberts Nell C. , Freeman Beverly O. , Bradford Jr. Henry B.
Published: May 2010

For the first time in nearly 4 decades of surveillance, H2S positive Escherichia coli have been isolated from Calcasieu Lake and River. These results are reported because of recent clinical interest in these organisms.
Cell division in Sporosarcina ureae
Authors: Beveridge T. J.
Published: May 2010

Electron microscopy of thin-sectioned and freeze-etched cells of Sporosarcina ureae demonstrated that division occurred in two or three perpendicular planes. The complex wall consisted of a 12-nm-thick amorphous layer which was adjacent to the plasma membrane (PM) and an overlying 16-nm-thick proteinaceous array (a regularly structured (RS) layer). Septation proceeded with the ingrowth of the PM and the inner layer in association with division mesosomes. The RS layer remained behind at the initiation site, and buckled and sloughed off to accommodate its continued extension. After the septal annulus had fused, perpendicular septa were initiated. As these secondary septa proceeded to form a tetrad of cells, the RS layer began a gradual peripheral ingrowth along the first division plane. Separation of the cells was incomplete until the centripetal growth of the RS layer had finished; often this was not until a packet of eight cells had been formed.