bluuebunny/crossref_metadata_2025 huggingface dataset:
Sexual dysfunction and sympathetic skin response recorded from the genital region in women with multiple sclerosis
Authors: Seçıl Yaprak , Yetımalar Yeşim , Gedizlioğlu Muhteşem , Arpaci Esra , Tokuçoğlu Figen , İnceoğlu Kendir Ayşen , Başoğlu Mustafa , Ertekin Cumhur
Published: February 2007

Multiple Sclerosis is known to cause autonomic and sexual dysfunction. However, genitourinary and sexual problems in female multiple sclerosis patients are difficult to analyse. Therefore, it is an understudied field. As an attempt to fill this gap, we evaluated genital region autonomic dysfunction of female multiple sclerosis patients by using genital sympathetic skin response. Forty female patients with definite multiple sclerosis and twenty healthy female controls were included in the study. We examined hand, foot and genital sympathetic skin responses. Some genitourinary parameters were questioned by and results were compared with genital sympathetic skin response results. Among multiple sclerosis patients 42.5% of them had genitourinary and 75% had sexual problems clinically. Sympathetic skin response pathologies were distributed as following: 22.5% in hand, 20% in the foot, and 50% in genital region in the patient group. A statistically significant correlation between sexual dysfunction and genital sympathetic skin response could not been found. It is found that patients with multiple sclerosis have higher genital sympathetic skin response abnormalities than foot and hand sympathetic skin response abnormalities. This might be the early sign of autonomic dysfuntion in multiple sclerosis patients. Genital sympathetic skin response may be an easy and objective method to apply and helpful to evaluate genitourinary dysfunction in women in conjunction with female sexual dysfuntion index. Multiple Sclerosis 2007; 13: 742-748. http://msj.sagepub.com
Novel synthesis of semiconductor nanocrystalline ZnS
Authors: Han J. , Yang Y.-Z. , Wang S.-Y. , Luo C.-H. , Xia C.-B.
Published: February 2007

Nanocrystalline ZnS has been successfully prepared through a hydrothermal method by the reaction of anhydrous ZnCl2 and NH4SCN at above 160°C. X-ray powder diffraction (XRD) analysis indicates that the product was cubic ZnS phase (sphalerite). Transmission electron microscopy (TEM) shows that the average particle size is ∼30 nm.
Post-weld heat treatment cracking in autogenous GTA welded cast Inconel 738LC superalloy
Authors: Sidhu R. K. , Richards N. L. , Chaturvedi M. C.
Published: February 2007

The post-weld heat treatment (PWHT) cracking in autogenous gas tungsten arc (GTA) welded Inconel 738LC superalloy, which was given two different preweld heat treatments, was studied. One of the preweld heat treatments, designated as SHT, consisted of solution heat treatment at 1120°C for 2 h in vacuum followed by argon quenching. The second preweld heat treatment, designated as UMT, consisted of solution treatment at 1120°C for 2 h followed by air cooling and then aging at 1025°C for 16 h followed by water quenching. The welded specimens were given the same conventional PWHT, which consisted of SHT at 1120°C for 2 h in vacuum followed by argon quenching and subsequent aging at 845°C for 24 h in vacuum. Microstructural examination of the welded SHT and UMT treated material showed that intergranular microfissuring occurred during welding only in the heat affected zone (HAZ) with some cracks extending into the adjoining base metal (BM), whereas after the PWHT microfissures were observed in the fusion zone (FZ), HAZ and the BM far removed from the HAZ. The crack width ranged from 5 to 10 μm in the PWHT specimens as compared with 1–2 μm in the as welded sections. Although similar type of cracks was observed in samples given the two preweld heat treatments, the UMT preweld heat treatment was found to result in a significant reduction in average total crack length and average crack length, both during welding and during the subsequent PWHT. After PWHT, SHT samples had ∼43% more cracking than the UMT samples. It is suggested that a larger particle size of γ′ precipitates in the HAZ and a smaller size of HAZ in the as welded samples, combined with a softer BM of the UMT material (hardness 280 ± 12 HV10, as compared with 380 ± 10 HV10 of the SHT material) resulted in an improved capability of the material to absorb the strain–aging stresses, and hence a reduced incidence of cracking during PWHT.
Diffusion bonding between high chromium white iron and low carbon steel
Authors: Eroglu M. , Kurt B.
Published: February 2007

In the present study, a high chromium white iron was diffusion bonded to a low carbon steel. The effects of bonding temperature and holding time at the reached temperature on microstructural developments across the joint region were investigated. After diffusion bonding, microstructural analysis including metallographical examination, energy dispersive X-ray (EDX), wavelength dispersive X-ray (WDX), microhardness measurements and shear strength tests were performed. The results showed that bonding temperature with holding time was effective on the width of the diffusion zone that affected the shear strength of the bonds. As a result, from the microstructural observations, EDX and WDX analysis, microhardness measurements and shear strength tests, it was concluded that a high temperature with a long holding time must be used in the diffusion bonding of high chromium white cast irons to low carbon steels.
Improvement of wear resistance of hot working tool steel by hardfacing Part 1 – Effect of microstructure and hardness
Authors: Kashani H. , Amadeh A. , Farhani M.
Published: February 2007

Hardfacing is one of the most useful and economical ways to improve the performance of components subjected to severe wear conditions. The aim of the present work was to investigate the influence of hardfacing on the hardness and wear resistance of a hot working tool steel. Two cobalt based and one nickel based superalloys were used as hardfacing materials. Stellite 6 and 21 were deposited on H11 steel via tungsten inert gas (TIG) and shielded metal arc welding and Inconel 625 was deposited by TIG welding techniques. The pin on disc high temperature wear tests were carried out on hardfaced materials. The worn surfaces were also characterised using SEM and X-ray diffraction methods. The results showed that TIG hardfacings process having a low dilution, owing to the refined solidification structure and high capacity of work hardening enhances better wear resistance.
Microstructure, texture and mechanical properties of continuous cast AA 5083 aluminium alloy
Authors: Li J. , Zeng Q. , Wen X. Y. , Zhai T.
Published: February 2007

Continuous cast AA 5083 aluminium alloy hot band with and without prior heat treatment at 510°C for 3 h was cold rolled to a reduction of 70% and annealed at 399°C for 3 h. It was found that the alloy without the prior heat treatment showed a strong {113}〈110〉 texture component after the thermal mechanical treatment, while with the prior heat treatment its recrystallisation texture was almost random. The alloy with the prior heat treatment exhibited a fine equiaxed grain structure after annealing, in contrast to a coarse elongated one in the alloy without the prior heat treatment. The tensile properties and their isotropy of the alloy were greatly improved by the prior heat treatment. The concurrent precipitation effect was likely to be responsible for the formation of the new texture and inferior mechanical properties of the alloy. Precipitates of 20 nm in size were observed interacting with dislocations in this alloy.
Dwell time effect on fatigue crack growth of RR1000 superalloy
Authors: Turan D. , Hunt D. , Knowles D. M.
Published: February 2007

The requirement for improved understanding of the behaviour of turbine disc alloys at elevated temperatures has led to an increased interest in the contribution of time dependant mechanisms to high temperature fatigue crack growth. A study has been conducted on a new powder alloy to investigate the contribution of such mechanisms when the applied waveform is varied in terms of hold periods and the influence of limited thermal exposure is included. Variable waveform tests performed in air at 725°C have indicated that the addition of a hold time at maximum load in a fatigue cycle tends to increase the crack growth rate per cycle in the as heat treated material. Crack growth in thermally exposed material is retarded by up to a 10 s hold time and then accelerated as the hold time increases further. Rapid near crack tip stress relaxation induced by γ′ coarsening is proposed to have a beneficial effect on the severity of this type of damage which causes the crack growth rate reduction for short hold times.
Preliminary investigation on solid solution softening effects on NiAl based alloys induced by minor Ru alloying addition
Authors: Li H. T. , Guo J. T. , Huai K. W. , Ye H. Q.
Published: February 2007

The effects of micro-Ru alloying addition on NiAl alloys were investigated by optical microscopy, SEM, X-ray diffraction and powder X-ray diffraction. The mechanical properties were characterised by Vickers microhardness measurement and compression tests at room temperature and various elevated temperatures. Micro-Ru alloying addition does not modify the crystal structure of NiAl alloys. However, local electronic structure may be modified owing to the specific site occupancy preference of Ru, smaller size difference between Ru and Al and different electronic nature of Ru and Ni. This is partially verified by the decrease of the long range order degree accurately measured via powder X-ray diffraction. As a result, a maximum softening effect occurs at 0·5 at.-%Ru addition indicated by Vickers microhardness measurement and compression testing results.
Synthesis of hydrated CeO2 nanowires and nanoneedles
Authors: Bugayeva N. , Robinson J.
Published: February 2007

Hydrated CeO2 nanowires as thin as 5 nm in diameter and nanoneedles with various aspect ratios were obtained via a chemical precipitation technique in the presence of ammonium acetate. It was possible to control the particle size, shape and agglomeration by tuning the ammonium acetate concentration in the experimental solutions. The effect of ammonium acetate on the particle morphological parameters is discussed and a possible mechanism is suggested.
Influence of counter gravity mould filling on the reproducibility of mechanical properties of a low alloy steel
Authors: Griffiths W. D. , Cox M. , Campbell J. , Scholl G.
Published: February 2007

An evaluation of the effect of counter gravity filling of investment castings on the reproducibility of mechanical properties has been carried out for a low alloy steel. Two types of gravity filled moulds, (reflecting ‘bad’ running system design practice and ‘good’ practice), and four types of counter gravity filled moulds were cast and their mechanical properties assessed by tensile testing. The Weibull moduli of the results were determined as a measure of reproducibility of the mechanical properties associated with the different casting processes. The results showed that the counter gravity filling method produced higher values of the Weibull modulus than gravity filled methods, even with well designed running systems. This clearly demonstrated the value of a mould filling approach that avoided entrainment of the surface of the cast steel. The highest value of the Weibull modulus (>186), was associated with the ‘ C3 process’, in which the mould was rotated during solidification.
High strain rate mechanical properties of austenitic manganese steel
Authors: Lee W. S. , Wang B. K.
Published: February 2007

This study uses the split Hopkinson pressure bar to investigate the high strain rate deformation and fracture behaviour of austenitic manganese steel at strain rates ranging from 2·0 × 103 to 8·0 × 103 s−1 at room temperature. Optical and scanning electron microscopy techniques are employed to analyse the fracture and microstructure characteristics of the deformed specimens in order to establish the relationships between the mechanical and microstructural properties of the tested steel. The experimental results indicate that strain rate exerts a significant influence on the flow stress of austenitic manganese steel. With increasing strain rate, the compression flow stress, work hardening rate and strain rate sensitivity increase, while the activation volume decreases. The variations of strain rate sensitivity and activation volume are closely related to the work hardening stress. It is shown that the observed flow behaviour is accurately described by the Zerilli–Armstrong constitutive equation. Fractographic analysis reveals that specimen fracture is dominated by the formation of adiabatic shear bands. Furthermore, dimple characteristics and cleavage facets are observed on the fracture surface, indicating a relatively ductile fracture mode. It is found that cleavage fracture is associated with increasing strain rate, which gives rise to a loss of deformability.
Fatigue behaviour of hot rolled reinforcing bars of austenitic and duplex stainless steels
Authors: Rodríguez C. , Real E. , Belzunce F. J. , Canteli A. F. , Aenlle M. L.
Published: February 2007

An experimental programme to determine the fatigue behaviour of hot rolled reinforced bars of two austenitic (AISI 304LN and AISI 316LN grades) and one duplex (AISI 2205 grade) stainless steels was conducted. The statistical model applied to define the S– N curves (Castillo et al.) of these products is also described. Finally, fractographic and microstructural analysis of the specimens allowed us to ascertain the parameters that have the greatest influence on the fatigue life of these structural components.
Growth of single crystal silver thin film induced by incident ion beam bombardment
Authors: Gu Y. , Zeng F. , Pan F.
Published: February 2007

The single crystal silver thin film was fabricated on NaCl single crystal substrate by low energy ion beam assisted deposition technology. It was found that the microstructure of the silver thin film was sensitive to the incident ion beam bombardment parameters. Among the various experimental conditions studied, the single crystal silver thin film was only obtained at impinging angle of 45°, ion beam energy of 500 eV and current density of 6 μA cm−2. The growth mechanism of the single crystal thin film was discussed based on channeling effects and lattice matching between silver films and the substrates.
High strength Al2O3p/6061 Al composites: Effect of particles, subgrains and precipitates
Authors: Luan B.-F. , Wu G.-H. , Hansen N. , Godfrey A. , Lei T.-Q.
Published: February 2007

Composites of 6061 Al reinforced by Al2O3 particles have been produced by squeeze casting followed by hot extrusion and a T4 precipitation hardening treatment. The tensile properties at room temperature have been determined and analysed based on microstructural parameters. The strength contributions from the matrix, particles, subgrains and precipitates have been estimated individually, and then based on an assumption of linear additivity, the yield stress values of the composites under the extruded and heat treated conditions have been calculated. Good agreement between the calculated and experimental values has been found, illustrating the suitability of the process for the manufacture of strong composites, with a maximum yield stress of 524 MPa obtained for a composite containing 60 vol.-%Al2O3.
Strontium titanate surfaces
Authors: Deak D. S.
Published: February 2007

Strontium titanate (SrTiO3) is a perovskite material with a variety of useful yet complex surface structures. Recent studies of SrTiO3 have revealed how surface treatment can give rise to multi-functional surfaces, with attributes ranging from blue-light emission and high electrical conductivity to photocatalytic activity and nanostructure self-assembly. Research encompassing the surface science of strontium titanate is reviewed which includes studies that utilise scanning tunnelling microscopy, atomic force microscopy, electron diffraction, surface spectroscopy and theoretical modelling techniques. A series of investigations that characterise the structural and chemical environment of SrTiO3 surfaces are outlined and discussed. Various issues regarding SrTiO3 surfaces are examined, including near-surface chemistry, surface terminations and surface structure. Emphasis is put on the link between surface processing methods and properties. A rich variety of surface reconstructions and structures have been observed but few are well characterised. Future advances in understanding these surfaces will be accompanied by studies that apply these surfaces for engineering new systems on the nanoscale.
Study on copper precipitation during continuous heating and cooling of HSLA steels using electrical resistivity
Authors: Bhagat A. N. , Pabi S. K. , Ranganathan S. , Mohanty O. N.
Published: February 2007

Electrical resistivity technique was used to study the phase transformation and copper precipitation during continuous heating and cooling of three Cu bearing high strength low alloy (HSLA) steels. Dilatation measurements were performed to compare the results with the resistivity. During heating, the dilatation plot revealed Ac1 and Ac3 temperature, while resistivity measurements indicated precipitation of copper in the range of 370–550°C. A method was demonstrated to estimate the amount of copper precipitation during continuous heating. During continuous cooling, the austenite transformation temperatures could be derived from resistivity, which compare well with dilatometry. A hysteresis between heating and cooling curve was noted possibly owing to formation of bainite during cooling. Non-isothermal kinetic analysis of dilatation data during continuous cooling yields an activation energy of 62 kJ mol−1, which could be related to the formation of bainite, whereas higher activation energy of 237 kJ mol−1 obtained from resistivity data may correspond to the diffusion of Cu in iron, associated with the copper precipitation during austenite transformation.
Optimising of strain sensitivity and electric characteristics of Ni–Cr thin film fabricated by magnetron sputtering
Authors: Yan J. W. , Zhou J. C.
Published: February 2007

By controlling the sputtering power, rotational speed of substrate and sputtering time, Ni–Cr thin films with appropriate composition were fabricated by double target magnetron cosputtering techniques. The homogeneity and oxidation of Ni–Cr film has been studied by Auger electron spectroscopy. The structures of films were determined by an X-ray diffractometer and a transmission electron microscope respectively. Gauge factor (GF) has been determined by the cantilever method. The relations between GF, temperature coefficient of resistance and compositions of films were discussed. The dependence of resistivity and Cr concentration in Ni–Cr thin film follows an exponential function. The optimal resistance stability of nanoscale Ni–Cr thin film is achieved by a rapid thermal process combined with a conventional thermal annealing technique. As a strain sensitive material, Ni–Cr thin films with optimal composition, desire GF and reliable electrical properties have been attained.
Effect of aging on fatigue crack growth behaviour of Cu bearing HSLA-100 steel
Authors: Das S. K. , Narasaiah N. , Sivaprasad S. , Chatterjee S. , Tarafder S.
Published: February 2007

The effect of aging on fatigue crack growth rate (FCGR) of Cu bearing HSLA-100 steel has been studied. The steel was solution treated, water quenched and aged at various temperatures in the range of 350–700°C. The fatigue crack growth resistance of the steel decreased for the initial stages of aging from 350–500°C. Further aging up to 650°C resulted in an improvement in the crack growth resistance. Beyond 650°C, once again an inferior crack growth resistance was observed. This nature of variation of FCGR behaviour was similar to the trend portrayed by the strength properties with aging treatment. The results are related to the changes in the microstructural constituents owing to the aging treatment.
Interface study of short mullite fibre reinforced Al–Cu–Mg alloy composites
Authors: Li W. , Liao N. M. , Jiang Y. D. , Shen B. L.
Published: February 2007

Short mullite fibre reinforced Al–Cu–Mg alloy composites were produced by squeeze casting. The interfacial microstructure and microchemistry of the testing composites were studied by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and energy disperse spectroscope (EDS) equipped with TEM respectively. It is shown that chopped mullite fibres in the composites are polycrystalline in structure composed of many fine mullite crystal particles which are orthorhombic in structure with lattice constants of a=0·749, b=0·927 and c=0·581 nm based on electron diffraction (ED) analysis and high resolution transmission electron microscope (HRTEM). There are highly densified dislocations in the vicinity of mullite fibre/matrix interface after solution treatment and quenching in ice water immediately. Interfacial reaction between mullite fibre and Al–Cu–Mg base alloy was observed, resulting in the formation of MgAl2O4 spinels in the testing composites.
Influence of tilt filling on Weibull modulus of 2L99 aluminium investment castings
Authors: Cox M. , Harding R. A.
Published: February 2007

A detailed investigation has been made of the tilt pouring of investment castings in order to reduce oxide film entrainment and hence improve their reliability. A computer controlled tilt casting machine has been developed to fill moulds using single and multi stage cycles. Metal flow during mould filling has been simulated using Flow 3D software and confirmed using real time X-ray radiography of moulds. Large numbers of test bars have been tilt poured in 2L99 (Al–7Si–0·4Mg) alloy. Castings have also been produced using top and bottom gated gravity filled moulds for comparison. The scatter in the breaking stresses has been analysed using the Weibull statistical technique to give the Weibull modulus λ. Top gated gravity filling gave relatively unreliable castings ( λ=23), but this was significantly improved by bottom gating ( λ=49). Fast single stage tilt filling gave λ in the range 30–45 depending on the rotation speed and an optimised multi stage tilting cycle increased λ to 55.
Preparation and characterisation of ball-like MoS2 nanoparticles
Authors: Hu K. H. , Wang Y. R. , Hu X. G. , Wo H. Z.
Published: February 2007

Molybdenum sulphide (MoSx) particles were prepared from Na2MoO4 and CH3CSNH2 by the quick homogenous precipitation method within 5 min in alcohol–water solution at 82°C and normal pressure. The prepared MoSx particles were studied by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results showed that the as prepared product was ball-like amorphous MoSx ( x=3·20) nanoparticles. The resultant amorphous ball-like MoSx nanoparticles were then calcined under hydrogen flow at a selected temperature for 50 min. The results of XRD, TEM and HRTEM confirmed that the ball-like MoS2 nanoparticles with fullerene structure were prepared by calcining the amorphous MoSx nanoparticles at 780°C. The resultant ball-like nano-MoS2 particles were transformed into polyhedron like nano-MoS2 particles as the calcining temperature was increased to 960°C.
Socio-cultural insights and lymphatic filariasis control – lessons from the Pacific
Authors: Wynd Shona , Durrheim David N , Carron Jaime , Selve Billy , Chaine JP , Leggat Peter A , Melrose Wayne
Published: February 2007

Background

Sustainable and equitable health programmes require a grounded understanding of the context in which they are being implemented. This socio-cultural understanding is pivotal for effective delivery of elimination programmes. Standardised valid methods are needed for gathering authentic socio-cultural insights. The currently recommended protocol for collecting Lymphatic Filariasis (LF) related socio-cultural data, while moving in the right direction, is inadequate. To collect data which provides an understanding of local health beliefs and practices, and communities' understanding of LF, techniques must be developed that are both valid and time efficient. An approach developed in the Pacific provides a basic snapshot of socio-cultural insights which are crucial to the development of relevant and sustainable health education and elimination programmes.

The increasing interest in socio-cultural LF research presents a unique opportunity for coupling socio-cultural and bio-medical understandings of LF. To address the backlog in the socio-cultural sphere will require investment of time and effort to integrate valid qualitative approaches into current data collection methodologies.
A dynamic model of gene expression in monocytes reveals differences in immediate/early response genes between adult and neonatal cells
Authors: Lawrence Shelley , Tang Yuhong , Frank M Barton , Dozmorov Igor , Jiang Kaiyu , Chen Yanmin , Cadwell Craig , Turner Sean , Centola Michael , Jarvis James N
Published: February 2007

Neonatal monocytes display immaturity of numerous functions compared with adult cells. Gene expression arrays provide a promising tool for elucidating mechanisms underlying neonatal immune function. We used a well-established microarray to analyze differences between LPS-stimulated human cord blood and adult monocytes to create dynamic models for interactions to elucidate observed deficiencies in neonatal immune responses.

We identified 168 genes that were differentially expressed between adult and cord monocytes after 45 min incubation with LPS. Of these genes, 95% (159 of 167) were over-expressed in adult relative to cord monocytes. Differentially expressed genes could be sorted into nine groups according to their kinetics of activation. Functional modelling suggested differences between adult and cord blood in the regulation of apoptosis, a finding confirmed using annexin binding assays. We conclude that kinetic studies of gene expression reveal potentially important differences in gene expression dynamics that may provide insight into neonatal innate immunity.
Phenotypic differences between Th1 and Th17 cells and negative regulation of Th1 cell differentiation by IL-17
Authors: Nakae Susumu , Iwakura Yoichiro , Suto Hajime , Galli Stephen J
Published: February 2007

Recent evidence fromseveral groups indicates that IL-17-producing Th17 cells, rather than, as once was thought, IFN-γ-producing Th1 cells, can represent the key effector cells in the induction/development of several autoimmune and allergic disorders. Although Th17 cells exhibit certain phenotypic and developmental differences from Th1 cells, the extent of the differences between these two T cell subsets is still not fully understood. We found that the expression profile of cell surface molecules on Th17 cells has more similarities to that of Th1 cells than Th2 cells. However, although certain Th1-lineage markers [i.e., IL-18 receptor α, CXCR3, and T cell Ig domain, mucin-like domain-3 (TIM-3)], but not Th2-lineage markers (i.e., T1/ST2, TIM-1, and TIM-2), were expressed on Th17 cells, the intensity of expression was different between Th17 and Th1 cells. Moreover, the expression of CTLA-1, ICOS, programmed death ligand 1, CD153, Fas, and TNF-related activation-induced cytokine was greater on Th17 cells than on Th1 cells. We found that IL-23 or IL-17 can suppress Th1 cell differentiation in the presence of exogenous IL-12 in vitro. We also confirmed that IL-12 or IFN-γ can negatively regulate Th17 cell differentiation. However, these cytokines could not modulate such effects on T cell differentiation in the absence of APC.
Mycobacteria-induced Gr-1+ subsets from distinct myeloid lineages have opposite effects on T cell expansion
Authors: Dietlin Therese A , Hofman Florence M , Lund Brett T , Gilmore Wendy , Stohlman Stephen A , Van der Veen Roel C
Published: February 2007

Similar to the regulation of vasodilation, the balance between NO and superoxide (O2–) regulates expansion of activated T cells in mice. Reduction of suppressive NO levels by O2– is essential for T cell expansion and development of autoimmunity. In mice primed with heat-killed Mycobacterium, a splenocyte population positive for Gr-1 (Ly-6G/C) is the exclusive source of both immunoregulatory free radicals. Distinct Gr-1+ cell subpopulations were separated according to Ly-6G expression. In culture with activated T cells, predominantly monocytic Ly-6G− Gr-1+ cells produced T cell-inhibitory NO but no O2–. However, mostly granulocytic Ly-6G+ cells produced O2– simultaneously but had no measurable effect on proliferation. Recombination of the two purified Gr-1+ subpopulations restored controlled regulation of T cell proliferation through NO and O2– interaction. Coculture of p47phox−/− and inducible NO synthase−/− Gr-1+ cells confirmed this intercellular interaction. These data suggest that bacterial products induce development of distinct Gr-1+ myeloid lineages, which upon stimulation by activated T cells, interact via their respective free radical products to modulate T cell expansion.
Characterization of the structure, function, and mechanism of B2 RNA, an ncRNA repressor of RNA polymerase II transcription
Authors: Espinoza Celso A. , Goodrich James A. , Kugel Jennifer F.
Published: February 2007

We previously found that the SINE-encoded mouse B2 RNA binds RNA polymerase II and represses mRNA transcription during the cellular heat-shock response. In vitro B2 RNA assembles into preinitiation complexes on promoter DNA via its interaction with the polymerase, thus rendering the complexes inactive. With the goal of understanding which regions of B2 RNA are important for high-affinity binding to RNA polymerase II and repression of transcription, we performed a structural and deletion analysis of a 178 nucleotide (nt) B2 RNA. We describe an experimentally derived secondary structure model for B2 RNA, and show that RNA polymerase II protects a specific region from RNase digestion. Deletion studies revealed that a 51-nt region of B2 RNA is sufficient for high-affinity binding to RNA polymerase II, association with preinitiation complexes, and repression of transcription in vitro, the latter of which involves a large predominately single-stranded region within the RNA. In addition, this piece of B2 RNA blocked the polymerase from properly associating with template DNA during the assembly of elongation complexes. Further deletion revealed that a 33-nt piece of B2 RNA binds RNA polymerase II, associates with preinitiation complexes, but cannot repress transcription. These results support a model in which RNA polymerase II contains a high-affinity ncRNA docking site to which a distinct region of B2 RNA binds, thereby allowing another region of the RNA to repress transcription. Moreover, the mechanism of transcriptional repression by B2 RNA likely involves disrupting critical contacts between RNA polymerase II and the promoter DNA.
Microtubule disruption stimulates P-body formation
Authors: Sweet Thomas J. , Boyer Brooke , Hu Wenqian , Baker Kristian E. , Coller Jeff
Published: February 2007

Processing bodies (P-bodies) are subcellular ribonucleoprotein (RNP) granules that have been hypothesized to be sites of mRNA degradation, mRNA translational control, and/or mRNA storage. Importantly, P-bodies are conserved from yeast to mammals and contain a common set of evolutionarily conserved protein constituents. P-bodies are dynamic structures and their formation appears to fluctuate in correlation with alterations in mRNA metabolism. Despite these observations, little is understood about how P-body structures are formed within the cell. In this study, we demonstrate a relationship between P-bodies and microtubules in the budding yeast,Saccharomyces cerevisiae. First, we demonstrate that disruption of microtubules by treatment with the drug benomyl leads to aggregation of P-body components. Consistent with this finding, we also demonstrate that disruption of microtubules by a temperature-sensitive allele of the major α tubulin,TUB1(tub1–724) stimulates P-body formation. Second, we find that the α-tubulin protein Tub1 colocalizes with P-bodies upon microtubule destabilization. Third, we determine that a putative tubulin tyrosine ligase, encoded byYBR094W, is a protein component of P-bodies, providing additional evidence for a physical connection between P-bodies and microtubules. Finally, we establish that P-bodies formed by microtubule destabilization fail to correlate with global changes in the stability of mRNA or in general mRNA translation. These findings demonstrate that the aggregation of P-body components is linked to the intracellular microtubule network, and, further, that P-bodies formed by disruption of microtubules aggregate independent of broad alterations in either mRNA decay or mRNA translation.
Ligand binding and gene control characteristics of tandem riboswitches in Bacillus anthracis
Authors: Welz Rüdiger , Breaker Ronald R.
Published: February 2007

Most riboswitches are composed of a single metabolite-binding aptamer and a single expression platform that function together to regulate genes in response to changing metabolite concentrations. In rare instances, two aptamers or sometimes two complete riboswitches reside adjacent to each other in untranslated regions (UTRs) of mRNAs. We have examined an example of a tandem riboswitch in the Gram-positive bacterium Bacillus anthracis that includes two complete riboswitches for thiamine pyrophosphate (TPP). Unlike other complex riboswitch systems described recently, tandem TPP riboswitches do not exhibit cooperative ligand binding and do not detect two different types of metabolites. In contrast, both riboswitches respond independently to TPP and are predicted to function in concert to mimic the more “digital” gene control outcome observed when two aptamers bind ligands cooperatively. Our findings further demonstrate that simple gene control elements made only of RNA can be assembled in different architectures to yield more complex gene control outcomes.
Global analysis of alternative splicing during T-cell activation
Authors: Ip Joanna Y. , Tong Alan , Pan Qun , Topp Justin D. , Blencowe Benjamin J. , Lynch Kristen W.
Published: February 2007

The role of alternative splicing (AS) in eliciting immune responses is poorly understood. We used quantitative AS microarray profiling to survey changes in AS during activation of Jurkat cells, a leukemia-derived T-cell line. Our results indicate that ∼10%–15% of the profiled alternative exons undergo a >10% change in inclusion level during activation. The majority of the genes displaying differential AS levels are distinct from the set of genes displaying differential transcript levels. These two gene sets also have overlapping yet distinct functional roles. For example, genes that show differential AS patterns during T-cell activation are often closely associated with cell-cycle regulation, whereas genes with differential transcript levels are highly enriched in functions associated more directly with immune defense and cytoskeletal architecture. Previously unknown AS events were detected in genes that have important roles in T-cell activation, and these AS level changes were also observed during the activation of normal human peripheral CD4+ and CD8+ lymphocytes. In summary, by using AS microarray profiling, we have discovered many new AS changes associated with T-cell activation. Our results suggest an extensive role for AS in the regulation of the mammalian immune response.
Paradigm Change in Operations Research: Thirty Years of Debate
Authors: Kirby Maurice W.
Published: February 2007

From the 1970s onwards, the OR community in Britain engaged in ongoing debate on the future of the discipline, the product of an emerging “crisis of confidence” engendered in part by the end of the “golden age of western economic growth” and the associated downsizing, or abolition, of practitioner groups in the corporate industrial sector. In addition, reservations were expressed concerning the increasing “mathematization” of academic OR in the context of the established “hard” or “classical” paradigm. In this respect, British operations researchers, aided and abetted by a number of American colleagues (notably Ackoff, Churchman, and Miser), engaged in a fundamental reappraisal of the OR methodological repertoire and its client base. Thus, in Britain, a new phase in the history of OR was inaugurated whereby the “positivist/scientist” approach bequeathed by the wartime pioneers was subject to challenge and qualification. Whilst some elements in the American OR community empathized with the emergent British critique, the response (notwithstanding Ackoff et al.) was, on the whole, relatively muted. This conservative American response provides one part of the rationale for this paper. The key issue here is to compare and contrast the tone and content of the Anglo-American debate on the future of OR after 1970: In simple terms, why did British OR practitioners and academics (especially the latter) respond so vigorously to the post-1970 OR critique in marked contrast to their American counterparts? In explaining the differential response, the paper will emphasize the interplay among an array of political, intellectual, and economic factors.
Variable Disaggregation in Network Flow Problems with Piecewise Linear Costs
Authors: Croxton Keely L. , Gendron Bernard , Magnanti Thomas L.
Published: February 2007

We study mixed-integer programming formulations, based upon variable disaggregation, for generic multicommodity network flow problems with nonconvex piecewise linear costs, a problem class that arises frequently in many application domains in telecommunications, transportation, and logistics. We present several structural results for these formulations, and we analyze the results of extensive experiments on a large set of instances with various characteristics. In particular, we show that the linear programming relaxation of an extended disaggregated model approximates the objective function by its lower convex envelope in the space of commodity flows. Together, the theoretical and computational results allow us to suggest which formulation might be the most appropriate, depending on the characteristics of the problem instances.
Maximin Latin Hypercube Designs in Two Dimensions
Authors: van Dam Edwin R. , Husslage Bart , den Hertog Dick , Melissen Hans
Published: February 2007

The problem of finding a maximin Latin hypercube design in two dimensions can be described as positioning n nonattacking rooks on an n × n chessboard such that the minimal distance between pairs of rooks is maximized. Maximin Latin hypercube designs are important for the approximation and optimization of black-box functions. In this paper, general formulas are derived for maximin Latin hypercube designs for general n, when the distance measure is l∞ or l1. Furthermore, for the distance measure l2, we obtain maximin Latin hypercube designs for n ⩽ 70 and approximate maximin Latin hypercube designs for other values of n. All these maximin Latin hypercube designs can be downloaded from the website http://www.spacefillingdesigns.nl. We show that the reduction in the maximin distance caused by imposing the Latin hypercube design structure is small. This justifies the use of maximin Latin hypercube designs instead of unrestricted designs.
Satiation in Discounted Utility
Authors: Baucells Manel , Sarin Rakesh K.
Published: February 2007

In this paper, we propose a model of intertemporal choice that explicitly incorporates satiation due to previous consumption in the evaluation of the utility of current consumption. In the discounted utility (DU) model, the utility of consumption is evaluated afresh in each time period. In our model, the utility of current consumption represents an incremental utility from the past level. When the time interval between consumption periods is large, and there are, therefore, no carryover effects, our model coincides with the DU model. For short time intervals between consumption periods, the satiation due to previous consumption lowers the utility of current consumption. Several implications of our model are examined, and comparisons with the DU model and the habituation model are made.
Determining the Acceptance of Cadaveric Livers Using an Implicit Model of the Waiting List
Authors: Alagoz Oguzhan , Maillart Lisa M. , Schaefer Andrew J. , Roberts Mark S.
Published: February 2007

The only available therapy for patients with end-stage liver disease is organ transplantation. In the United States, patients with end-stage liver disease are placed on a waiting list and offered livers based on location and waiting time, as well as current and past health. Although there is a shortage of cadaveric livers, 45% of all cadaveric liver offers are declined by the first transplant surgeon and/or patient to whom they are offered. We consider the decision problem faced by these patients: Should an offered organ of a given quality be accepted or declined? We formulate a Markov decision process model in which the state of the process is described by patient state and organ quality. We use a detailed model of patient health to estimate the parameters of our decision model and implicitly consider the effects of the waiting list through our patient-state-dependent definition of the organ arrival probabilities. We derive structural properties of the model, including a set of intuitive conditions that ensure the existence of control-limit optimal policies. We use clinical data in our computational experiments, which confirm that the optimal policy is typically of control-limit type.
Competition in Service Industries
Authors: Allon Gad , Federgruen Awi
Published: February 2007

We analyze a general market for an industry of competing service facilities. Firms differentiate themselves by their price levels and the waiting time their customers experience, as well as different attributes not determined directly through competition. Our model therefore assumes that the expected demand experienced by a given firm may depend on all of the industry’s price levels as well as a (steady-state) waiting-time standard, which each of the firms announces and commits itself to by proper adjustment of its capacity level. We focus primarily on a separable specification, which in addition is linear in the prices. (Alternative nonseparable or nonlinear specifications are discussed in the concluding section.) We define a firm’s service level as the difference between an upper-bound benchmark for the waiting-time standard (w̅) and the firm’s actual waiting-time standard.

Different types of competition and the resulting equilibrium behavior may arise, depending on the industry dynamics through which the firms select their strategic choices. In one case, firms may initially select their waiting-time standards, followed by a selection of their prices in a second stage (service-level first). Alternatively, the sequence of strategic choices may be reversed (price first) or, as a third alternative, the firms may make their choices simultaneously (simultaneous competition). We model each of the service facilities as a single-server M/M/1 queueing facility, which receives a given firm-specific price for each customer served. Each firm incurs a given cost per customer served as well as cost per unit of time proportional to its adopted capacity level.
Reliable Due-Date Setting in a Capacitated MTO System with Two Customer Classes
Authors: Kapuscinski Roman , Tayur Sridhar
Published: February 2007

We study a finite-horizon discrete-time model of due-date setting (equivalently, reserving capacity) in a make-to-order setting, where demands arrive from two different classes of customers. Demands in each period are stochastic. The two customer classes penalize with different margins the lead times quoted to them, which (once quoted) are to be satisfied reliably. We first derive the optimal policy for reserving capacity that maps to quoted due dates. We use the insights from its structure to develop a novel approximation that provides near-optimal solutions quickly. Currently available heuristics are tested and are found to be considerably less effective than the above approximation.
An OR Missionary’s Visits to the Criminal Justice System
Authors: Blumstein Alfred
Published: February 2007

One of the historic roles of operations research (OR) people in the problem domains they enter is that of missionary, bringing their OR techniques of quantitative modeling, system perspective, and planning to the fields where those approaches have not yet taken hold. One of the most primitive of social systems in that regard is the criminal justice system responsible for society’s response to crime. Over the past 40 years, I and a number of colleagues have been involved in this missionary function. The issues addressed have involved modeling of criminal careers as a stochastic process, bringing those analyses to the assessment of incapacitation effects of incarceration, review of trends in incarceration and factors contributing to those trends, and an examination of the interaction of incarceration and drug markets, with an analysis of some of the unintended counterproductive effects of that incarceration response to the drug problem.
Lexicographically Minimum and Maximum Load Linear Programming Problems
Authors: Nace Dritan , Orlin James B.
Published: February 2007

In this paper, we introduce the lexicographically minimum load linear programming problem, and we provide a polynomial approach followed by the proof of correctness. This problem has applications in numerous areas where it is desirable to achieve an equitable distribution or sharing of resources. We consider the application of our technique to the problem of lexicographically minimum load in capacitated multicommodity networks and discuss a special nonlinear case, the so-called Kleinrock load function. We next define the lexicographically maximum load linear programming problem and deduce a similar approach. An application in the lexicographically maximum concurrent flow problem is depicted followed by a discussion on the minimum balance problem as a special case of the lexicographically maximum load problem.
Nash-Cournot Equilibria in Electric Power Markets with Piecewise Linear Demand Functions and Joint Constraints
Authors: Hobbs Benjamin F. , Pang J. S.
Published: February 2007

Most previous Nash-Cournot models of competition among electricity generators have assumed smooth demand (price) functions, facilitating computation and proofs of existence and uniqueness. However, nonsmooth demand functions are an important feature of real power markets due, for example, to price caps and generator recognition of transmission constraints that limit exports. A more general model of Nash-Cournot competition on networks is proposed that accounts for these features by including (1) concave piecewise-linear demand curves and (2) joint constraints that include variables from other generating companies within the profit maximization problems for individual generators. The piecewise demand curves imply, in general, a nonmonotone multivalued variational inequality problem. Thus, for instance, imposition of a price cap can destroy the uniqueness properties found in previous models, so that distinct solutions can yield different sets of profits for market participants. The joint constraints turn the equilibrium problem into a quasi-variational inequality, which also can yield multiple solutions. The formulation poses computational challenges that can cause Lemke’s algorithm to fail; a restricted formulation is proposed that can be solved by that algorithm.