bluuebunny/crossref_metadata_2025 huggingface dataset:
Cellular and molecular mechanisms of liver tolerance
Authors: Crispe Ian N. , Giannandrea Matthew , Klein Ingo , John Beena , Sampson Bradford , Wuensch Sherry
Published: September 2006

Summary:  The liver exhibits a distinctive form of immune privilege, termed liver tolerance, in which orthotopic liver transplantation results in systemic donor‐specific T‐cell tolerance, while antigens introduced either into hepatocytes or via the portal vein also cause tolerance. Here we argue that the fundamental mechanism driving liver tolerance is likely to be the continuous exposure of diverse liver cell types to endotoxin, derived from the intestinal bacteria. This exposure promotes the expression of a set of cytokines, antigen‐presenting molecules, and costimulatory signals that impose T‐cell inactivation, partly via effects on liver antigen‐presenting cells. The evidence favors clonal deletion mechanisms and is consistent with a role for regulatory T cells but does not support either anergy or immune deviation as important factors in liver tolerance.
The testis in immune privilege
Authors: Fijak Monika , Meinhardt Andreas
Published: September 2006

Summary: The production, differentiation, and presence of male gametes represent inimitable challenges to the immune system, as they are unique to the body and appear long after the maturation of the immune system and formation of systemic self‐tolerance. Known to protect germ cells and foreign tissue grafts from autoimmune attack, the ‘immune privilege’ of the testis was originally, and somewhat simplistically, attributed to the existence of the blood–testis barrier. Recent research has shown a previously unknown level of complexity with a multitude of factors, both physical and immunological, necessary for the establishment and maintenance of the immunotolerance in the testis. Besides the blood–testis barrier and a diminished capability of the large testicular resident macrophage population to mount an inflammatory response, it is the constitutive expression of anti‐inflammatory cytokines in the testis by immune and particularly somatic cells, that represents an essential element for local immunosuppression. The role of androgens in testicular immune regulation has long been underestimated; yet, accumulating evidence now shows that they orchestrate the inhibition of proinflammatory cytokine expression and shift cytokine balance toward a tolerogenic environment. Furthermore, the role of the testicular dendritic cells in suppressing antigen‐specific immunity and T‐lymphocyte activation is discussed. Finally, the active role mast cells play in the induction and amplification of immune responses, both in infertile humans and in experimental models, highlights the importance of preventing mast cell activation to maintain the immune‐privileged status of the testis.
Ocular autoimmunity: the price of privilege?
Authors: Caspi Rachel R.
Published: September 2006

Summary:  The eye is the prototypic immune‐privileged organ. Its antigens were once believed to be expressed exclusively in the eye, which resides behind an efficient blood–organ barrier, and were believed to be unknown to the immune system. Self‐tolerance to ocular components was therefore believed to be based not on immune tolerance but on immune ignorance. It is now known that the relationship between the immune system and the eye is much more complex. On the one hand, immune privilege is now known to involve not only sequestration but also active mechanisms that (i) inhibit innate and adaptive immune processes within the eye and (ii) shape the response that develops systemically to antigens released from the eye. On the other hand, retinal antigens are found in the thymus and have been shown to shape the eye‐specific T‐cell repertoire. However, thymic elimination of self‐reactive T cells is incomplete, and such ‘escapee’ T cells are tolerized in the periphery as they recirculate through the body by encounter with self‐antigen in healthy tissues. Due to the relative inaccessibility of the healthy eye to the immune system, peripheral tolerance mechanisms may not operate efficiently for ocular antigens, leaving a weak link in the homeostasis of tolerance. The case shall be made that although immune privilege protects vision by keeping the immune system at bay, a potential for developing destructive anti‐retinal autoimmunity may be the price for the day‐to‐day protection afforded by immune privilege against inflammatory insults.
The tumor‐draining lymph node as an immune‐privileged site
Authors: Munn David H. , Mellor Andrew L.
Published: September 2006

Summary:  Lymph nodes that lie immediately downstream of tumors [tumor‐draining lymph nodes (TDLNs)] undergo profound alterations due to the presence of the upstream tumor. The antigen‐presenting cell population in TDLNs becomes modified such that tumor‐derived antigens are cross‐presented by host cells in a tolerizing fashion. In addition, the number and suppressor activity of regulatory T cells (Tregs) are increased in the TDLN. Emerging evidence suggests that some of these Tregs may be generated de novo against specific tumor‐derived antigens, and thus they arise as a direct consequence of antigen presentation in the TDLN. Others may represent Tregs against self‐antigens, which undergo preferential activation in the tolerogenic milieu of the TDLN. The TDLN thus becomes an anatomic context in which presentation of new antigens not only fails to elicit a protective immune response but also actively creates systemic tolerance. In this regard, the TDLN displays features analogous to classical immune privilege. Accumulating evidence thus suggests that the TDLNs, although small in size, may exert a profound tolerizing influence on the rest of the immune system. These mechanisms will need to be interrupted in order for clinical anti‐tumor immunotherapy to be successful.
Effect and mechanism of melatonin's action on the proliferation of human umbilical vein endothelial cells
Authors: Cui Peilin , Luo Zhaohua , Zhang Honggang , Su Yan , Li Ailing , Li Hongwei , Zhang Jing , Yang Zhaoxu , Xiu Ruijuan
Published: September 2006

Abstract:  Melatonin is the major secretory product of the pineal gland and is considered an important natural oncostatic agent. The anticancer activity of melatonin is due to its immunomodulatory, anti‐proliferative and antioxidative effects. At present there are no direct data available as to melatonin's possible influence on angiogenesis, which is a major biological mechanism responsible for tumor growth and dissemination. The current study investigated the influence of melatonin on angiogenesis. Human umbilical vein endothelial cells (HUVECs) were cultured, identified, and purified. Cell growth and viability, DNA fragmentation and cell cycle analyses were determined. To elucidate the mechanism of action of melatonin, Western blot analyses for P53, Bax and Bcl‐2 expression were carried out. The results demonstrate the anti‐proliferative and apoptosis‐inducing effects of melatonin; these changes were associated with cell cycle arrest, upregulation of P53 and Bax and downregulation of Bcl‐2. Taken together, our data showed that melatonin in high concentrations markedly reduces HUVECs proliferation, induces cellular apoptosis, and modulates cell cycle length. P53 and Bax/Bcl‐2 expression changes may be involved in these actions of melatonin.
Aberrant Uterine Natural Killer (NK)‐Cell Expression and Altered Placental and Serum Levels of the NK‐Cell Promoting Cytokine Interleukin‐12 in Pre‐Eclampsia
Authors: Bachmayer Nora , Rafik Hamad Rangeen , Liszka Lucie , Bremme Katarina , Sverremark‐Ekström Eva
Published: September 2006

Problem  Natural killer (NK) cells are the most abundant lymphocyte population at the maternal–fetal interface. They are suggested to be important during placentation by controlling trophoblast invasion. If placentation is suboptimal, pre‐eclampsia can occur.

Method of study  Decidual NK (dNK) cells were examined at delivery in 46 women, 22 pre‐eclamptic women and 24 healthy controls, by staining for CD56 and CD94 with immunohistochemistry (IHC). Furthermore, we investigated the placental expression and the serum levels of the NK‐cell activating cytokines interleukin(IL)‐12, IL‐15, IL‐18 and the anti‐inflammatory cytokine IL‐10 by IHC and enzyme‐linked immunosorbent assay (ELISA), respectively.

Results  Pre‐eclamptic women had higher number of CD56+ and CD94+ cells in the decidua, indicating an altered receptor expression of dNK cells. We also demonstrate for the first time that the villous trophoblasts show strong immunostaining for IL‐12 in placentae from healthy controls, while women suffering from pre‐eclampsia have significantly less IL‐12. However, pre‐eclamptic women had significantly elevated IL‐12 and IL‐15 levels in serum.

Conclusion  Results show increased numbers and altered phenotype of dNK cells in pre‐eclampsia, supporting the importance of these cells for a healthy pregnancy. The altered receptor expression of dNK cells together with diminished placental IL‐12 expression could implicate an altered NK cell‐regulation in pre‐eclampsia.
BUILDING A MULTIDISCIPLINARY, COLLABORATIVE CHILD PROTECTION SYSTEM
Authors: Mitchell David B.
Published: September 2006

The process of preparing lawyers and other professionals to work for the benefit of troubled children requires an understanding of concepts that extend far beyond the traditional course structure currently employed in American law schools. It is clear that mental health problems of children and families, compounded by substance abuse, influence behavior, resulting in children entering family and juvenile courts as victims of abuse or neglect and committing criminal acts. It is incumbent on law schools to incorporate training in fields far different from the traditional didactic experience in legal curricula if they are to address the current needs of children and familes who are ensnared in the nation's juvenile justice system. The beginning point of this process is within the legal training apparatus of America. Law schools must expand their curriculum to incorporate other disciplines to produce an advocate capable of serving the interest of children and society.
EXAMINATION OF THE IMPACT OF INCREASED COURT REVIEW ON PERMANENCY OUTCOMES FOR ABUSED AND NEGLECTED CHILDREN
Authors: Courtney Mark E. , Blakey Joan
Published: September 2006

This article provides a brief history of a federally funded court improvement program, describes the Dane County Court Improvement Project, and discusses the implications of the project evaluation's findings. As part of Wisconsin's efforts under the federally funded state court improvement program, Dane County developed and evaluated a form of accelerated review of selected juvenile court cases. The accelerated review intended to expedite permanency outcomes for abused and neglected children in out‐of‐home care. The evaluation's findings of the initiative suggest that more frequent court reviews than those mandated by law may increase the likelihood of adopting children entering out‐of‐home care with no decrease in the likelihood of family reunification. However, because many of the children whose parental rights had been terminated had yet to be placed for adoption at the time of the study's conclusion, the encouraging early findings of the initiative should be regarded with some caution.
PROTECTING CHILDREN WHO WITNESS DOMESTIC VIOLENCE
Authors: Nowling Melanie Margarida
Published: September 2006

This article argues that the Nicholson v. Williams case was decided wrongly because it does not adequately protect the interests and welfare of children who witness domestic violence. It contends that the legal system must do more to ensure the well‐being of children who witness domestic violence before permitting them to remain in the custody of their mothers who were living in violent relationships. The article does not support the notion that victims of domestic violence should be prosecuted for failure to protect or child abuse but argues that evidence reveals how detrimental witnessing domestic violence is on a child and that this necessitates the need for stricter measures to be taken to protect children from this danger.
Biochemical characterization and inhibitor discovery of shikimate dehydrogenase from Helicobacter pylori
Authors: Han Cong , Wang Lirui , Yu Kunqian , Chen Lili , Hu Lihong , Chen Kaixian , Jiang Hualiang , Shen Xu
Published: September 2006

Shikimate dehydrogenase (SDH) is the fourth enzyme involved in the shikimate pathway. It catalyzes the NADPH‐dependent reduction of 3‐dehydroshikimate to shikimate, and has been developed as a promising target for the discovery of antimicrobial agent. In this report, we identified a new aroE gene encoding SDH from Helicobacter pylori strain SS1. The recombinant H. pylori shikimate dehydrogenase (HpSDH) was cloned, expressed, and purified in Escherichia coli system. The enzymatic characterization of HpSDH demonstrates its activity with kcat of 7.7 s−1 and Km of 0.148 mm toward shikimate, kcat of 7.1 s−1 and Km of 0.182 mm toward NADP, kcat of 5.2 s−1 and Km of 2.9 mm toward NAD. The optimum pH of the enzyme activity is between 8.0 and 9.0, and the optimum temperature is around 60 °C. Using high throughput screening against our laboratory chemical library, five compounds, curcumin (1), 3‐(2‐naphthyloxy)‐4‐oxo‐2‐(trifluoromethyl)‐4H‐chromen‐7‐yl 3‐chlorobenzoate (2), butyl 2‐{[3‐(2‐naphthyloxy)‐4‐oxo‐2‐(trifluoromethyl)‐4H‐chromen‐7‐yl]oxy}propanoate (3), 2‐({2‐[(2‐{[2‐(2,3‐dimethylanilino)‐2‐oxoethyl]sulfanyl}‐1,3‐benzothiazol‐6‐yl)amino]‐2‐oxoethyl}sulfanyl)‐N‐(2‐naphthyl)acetamide (4), and maesaquinone diacetate (5) were discovered as HpSDH inhibitors with IC50 values of 15.4, 3.9, 13.4, 2.9, and 3.5 µm, respectively. Further investigation indicates that compounds 1, 2, 3, and 5 demonstrate noncompetitive inhibition pattern, and compound 4 displays competitive inhibition pattern with respect to shikimate. Compounds 1, 4, and 5 display noncompetitive inhibition mode, and compounds 2 and 3 show competitive inhibition mode with respect to NADP. Antibacterial assays demonstrate that compounds 1, 2, and 5 can inhibit the growth of H. pylori with MIC of 16, 16, and 32 µg·mL−1, respectively. This current work is expected to favor better understanding the features of SDH and provide useful information for the development of novel antibiotics to treat H. pylori‐associated infection.
Energetics of East African Pycnonotids1
Authors: Seavy Nathaniel E. , McNab Brian K.
Published: September 2006

Rate of oxygen consumption was measured in five bulbuls (Family Pycnonotidae) from western Uganda to evaluate whether this group is indeed characterized by the very low basal rates of metabolism previously reported. For three of these species, body temperature and rate of metabolism were measured as a function of ambient temperature from 10°C to 35°C. In these species body temperature was highly variable, and declined with ambient temperature in Andropadus virens. Such variation, in conjunction with behavioral adjustments, may reduce heat loss at low ambient temperatures. Body mass accounted for 98 percent of the variation in the basal rates of metabolism presented here. Basal rates in these species ranged from 81 to 90 percent of values predicted by the Aschoff–Pohl relationship for passerines, whereas previous measurements ranged from 56 to 72 percent of predicted values. This difference may reflect differences in species or measurement techniques, which, if the latter, suggests that the reduction in metabolic rate in this family may be less than originally thought. These data underline the importance of continued data collection on the metabolism of tropical birds, few of which have been measured to date.
Wide-range vibratory vacuum gauge
Authors: Thurmer Dominic J. , Price John C.
Published: September 2006

We describe a vibratory vacuum gauge in which a small force due to high-frequency compression of a gas excites a planar mechanical oscillator. Compared to vibratory viscosity gauges, this principle allows operation at lower pressures. With a prototype apparatus we demonstrate sensitivity from 105to10−4Pa for argon, nitrogen, and helium. A simple theory for the device is presented which gives an account of the pressure and molecular weight dependence of the response in the molecular flow regime.
Advanced chemical vapor deposition silicon carbide barrier technology for ultralow permeability applications
Authors: Zambov Ludmil , Weidner Ken , Shamamian Vasgen , Camilletti Robert , Pernisz Udo , Loboda Mark , Cerny Glenn , Gidley David , Peng Hua-Gen , Vallery Richard
Published: September 2006

Plasma-enhanced chemical vapor deposition (PECVD) processes have been developed to produce prototype barrier coatings for protection from detrimental gases. The strategy used is based on a combination of molecular precursor design and advanced plasma processing and represents a route to an effective, barrier solution. Silicon carbide room temperature deposition processes have been established on several reactor systems. The impact of process-operating factors on the structure and barrier performance has been analyzed and a wide range of tunability has been found. A metrology has been developed to estimate the optical, mechanical, and application-relevant barrier properties. In addition, coatings have been analyzed for subnanometer structural defects by positronium annihilation lifetime spectroscopy (PALS). None of the barriers present evidence of any mesopores or open porosity. Furthermore, the amount of nanostructural defects in layers has been found to depend on both plasma chemistry and power. Based on the PALS results, structural models of different types of barrier layers are proposed. Significant progress in barrier performance has been demonstrated in terms of water vapor transmission rate down in the range of 10−4g∕m2d.
Chemical and optical properties of thermally evaporated manganese oxide thin films
Authors: Al-Kuhaili M. F.
Published: September 2006

Manganese oxide thin films were deposited using thermal evaporation from a tungsten boat. Films were deposited under an oxygen atmosphere, and the effects of thickness, substrate temperature, and deposition rate on their properties were investigated. The chemical properties of the films were studied using x-ray photoelectron spectroscopy and x-ray fluorescence. The optical properties were determined from normal-incidence transmittance and reflectance. Based on the chemical and optical characterizations, the optimum conditions for the deposition of the films were investigated. Subsequently, the optical properties (refractive index, extinction coefficient, and band gap) of these films were determined.
X-ray photoelectron spectroscopy study of self-assembled monolayers of alkanethiols on (001) GaAs
Authors: Wieliczka David M. , Ding Ximing , Dubowski Jan J.
Published: September 2006

Self-assembled monolayers of several alkanethiol molecules, with varying chain length and terminal groups, were investigated using x-ray photoelectron spectroscopy (XPS). The chain lengths varied from 10 to 15 methylene units, and the terminal group was either hydrophilic carboxylic acid and hydroxyl or hydrophobic methyl. The alkanethiol molecules were deposited on GaAs surfaces from liquid solutions. The impact of atmospheric exposure was examined by investigating one set of samples stored under atmospheric conditions and a second set that was stored in a nitrogen atmosphere prior to analysis. Carbon, oxygen, gallium, and arsenic core level XPS spectra were obtained on all surfaces. The intensity of the gallium and arsenic core levels indicates a considerable difference in the Ga∕As ratio dependent on the terminal group of the alkanethiol. Additionally, the carbon and oxygen spectra indicate varying chemical bonding on the surface with the alkanethiol’s having a carboxylic acid terminal group showing a more complex carbon and oxygen bonding.
Effect of surface topography on reflection electron energy loss plasmon spectra of group III metals
Authors: Strawbridge B. , Singh R. K. , Beach C. , Mahajan S. , Newman N.
Published: September 2006

In situ reflection electron energy loss spectroscopy (REELS) and reflection high energy electron diffraction employing a 20keV electron beam at a 2° grazing angle were used to characterize the surface properties of molecular beam epitaxy (MBE) grown Al, Ga, and In metals on silicon and sapphire substrates. In our study we found that the surface topography strongly influences the REELS plasmon spectra. Smooth Al films with <1nm rms roughness exhibited surface plasmon peaks. Both surface and bulk plasmons are seen from an Al film with a rms roughness of 3.5nm. Aluminum surfaces with >5nm rms roughness yielded only bulk plasmon peaks. To understand the EELS spectrum for the Ga and In films, the rms roughness alone is not the relevant figure of merit as the electron beam interaction with the surface is influenced most by the shape of the tops of the surface grains and the grain size. Indium films on Si with a rms roughness of 52nm were found to excite predominantly surface plasmons as the grazing angle electron beam scattered mostly off the flat top surface of each grain and was not strongly influenced by the crevices between the grains. The rounded tops of the Ga topography with 31nm rms roughness facilitated transmission through the grains and therefore excited a combination of bulk and surface plasmons. This experimental method is very surface sensitive, as a probe depth of 0.8nm was inferred from the diminishing intensity of the substrate peak with increasing coverage of a flat metal surface. The techniques and methods discussed here can be readily applied to other thin film systems such as MBE-grown III-V semiconductors, sputtered oxides, and other vacuum deposited materials.
Previous heat treatment inducing different plasma nitriding behaviors in martensitic stainless steels
Authors: Figueroa C. A. , Alvarez F. , Mitchell D. R. G. , Collins G. A. , Short K. T.
Published: September 2006

In this work we report a study of the induced changes in structure and corrosion behavior of martensitic stainless steels nitrided by plasma immersion ion implantation (PI3) at different previous heat treatments. The samples were characterized by x-ray diffraction and glancing angle x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, and potentiodynamic measurements. Depending on the proportion of retained austenite in the unimplanted material, different phase transformations are obtained at lower and intermediate temperatures of nitrogen implantation. At higher temperatures, the great mobility of the chromium yields CrN segregations like spots in random distribution, and the α′-martensite is degraded toα-Fe (ferrite). The nitrided layer thickness follows a fairly linear relationship with the temperature and a parabolic law with the process time. The corrosion resistance depends strongly on chromium segregation from the martensitic matrix, as a result of the formation of CrN during the nitrogen implantation process and the formation of CrxC during the heat treatment process. Briefly speaking, the best results are obtained using low tempering temperature and low implantation temperature (below 375°) due to the increment of the corrosion resistance and nitrogen dissolution in the structure with not too high diffusion depths (about 5–10μm).
Angular distribution of particles sputtered from Si bottom in a CHF3 plasma
Authors: Lee Jin-Kwan , Lee Gyeo-Re , Min Jae-Ho , Moon Sang Heup
Published: September 2006

The angular distribution (AD) of particles sputtered from a Si substrate in a CHF3 plasma at bias voltages between −200 and −400V was investigated using a specially designed experimental setup for controlling the angle of incident ions on the substrate. Particles were sputtered from a primary target substrate, which was placed in a Faraday cage and on the horizontal cathode plane of a plasma etcher, by bombardment with ions incident in a direction normal to the substrate. The sputtered particles were redeposited on the surfaces of SiO2 secondary targets, which were fixed in small pieces at different positions on the convave surface of a circular sample holder, which was positioned above the primary target. A line connecting the primary and secondary targets defined the sputtering angle of the etch products. The redeposition rate was estimated from the difference in the thickness of the secondary target in two independent experiments, with and without the primary target. The redeposition rate was plotted as a function of sputtering angle and, the AD was then obtained from the plot. X-ray photoelectron spectroscopy analysis of a Si primary target subjected to etching indicated that a steady-state CFx film with a thickness of about 50Å was formed on the Si at a bias voltage of −400V. This film was thicker than the ion-energy transfer depth (30Å), and, as a result, it can be concluded that particles redeposited on the secondary target were sputtered from a steady-state CFx film that had been formed on the Si primary target. The AD of particles sputtered from the Si primary target showed an over-cosine dependence on the sputtering angle (θ), corresponding to cos3–4θ, and the power of the over-cosine dependence increased with bias voltage. The characteristic changes in the AD support the view that particles contributing to the redeposition were generated largely by physical sputtering rather than by ion-enhanced chemical etching.
High-rate plasma-deposited SiO2 films for surface passivation of crystalline silicon
Authors: Hoex B. , Peeters F. J. J. , Creatore M. , Blauw M. A. , Kessels W. M. M. , van de Sanden M. C. M.
Published: September 2006

Si O 2 films were deposited by means of the expanding thermal plasma technique at rates in the range of 0.4–1.4μm∕min using an argon∕oxygen∕octamethylcyclotetrasiloxane (OMCTS) gas mixture. The film composition was studied by means of various optical and nuclear profiling techniques. The films deposited with a low OMCTS to oxygen ratio showed no residual carbon and a low hydrogen content of ∼2% with a refractive index close to thermal oxide. For a higher OMCTS to oxygen ratio a carbon content of ∼4% was detected in the films and the refractive index increased to 1.67. The surface passivation of the SiO2 films was tested on high quality crystalline silicon. The films yielded an excellent level of surface passivation for plasma-deposited SiO2 films with an effective surface recombination velocity of 54cm∕s on 1.3Ωcm n-type float zone crystalline silicon substrates after a 15min forming gas anneal at 600°C.
Amorphous silicon layer characteristics during 70–2000eV Ar+-ion bombardment of Si(100)
Authors: Stevens A. A. E. , Kessels W. M. M. , van de Sanden M. C. M. , Beijerinck H. C. W.
Published: September 2006

Spectroscopic ellipsometry (SE) has been applied to characterize the damaged, amorphous silicon (a-Si) layer created by Ar+-ion bombardment in the ion energy range of 70–2000eV impinging at 45° angle of incidence on Si(100). The dielectric functions of a-Si during ion bombardment have been determined using the Tauc-Lorentz model for the dielectric functions ϵ1 and ϵ2. The dielectric functions resemble literature reports on a-Si-like dielectric functions. The a-Si layer thickness under ion bombardment conditions reaches values from ≈17Å at 70eV up to ≈95Å at 2000eV. These values compare reasonably well with SRIM and molecular dynamics simulations. The surface roughness, as determined with SE, is typically 5–15Å during ion bombardment, with a minimum roughness at Eion=250eV. The creation of the amorphous silicon top layer upon 70eV Ar+-ion bombardment with an ion flux of 0.07MLs−1 has been resolved using real-time spectroscopic ellipsometry. The creation of the amorphous layer shows a double exponential ion-dose dependence: a fast, initial period of a-Si creation, with 1∕e constant Δτ1=2ML, and a slower period, Δτ2=9ML, until the matrix is fully amorphous after ∼30ML of Ar+ dosing. Relaxation of the a-Si top layer has been observed after the ions are switched off and has been analyzed with a stretched-exponential decay as a function of time, which is characteristic for a defect-controlled relaxation in the bulk a-Si layer. The corresponding time constant τ is found to be ∼360s, which is typically observed for self-annealing in amorphous silicon materials.
Energy distribution and flux of fast neutrals and residual ions extracted from a neutral beam source
Authors: Ranjan Alok , Donnelly Vincent M. , Economou Demetre J.
Published: September 2006

The energy distribution and flux of the fast neutrals and residual ions extracted from a neutral beam source were measured. Positive ions generated in an inductively coupled argon plasma were extracted through a metal grid with high aspect ratio holes. Ions suffered grazing angle collisions with the inside surface of the grid holes, turning into fast neutrals. The neutral energy distribution was always shifted to lower energies compared to the corresponding residual ion energy distribution. The neutralization efficiency increased with power, decreased with boundary voltage and, for thin neutralization grids, was almost independent of plasma gas pressure. The residual ion flux decreased with increasing hole diameter and hole aspect ratio. The fast neutral flux first increased and then dropped as the hole diameter was increased. Results were explained based on plasma molding inside the grid holes.
Tailored synthesis of ZnO:Er(III) nanosystems by a hybrid rf-sputtering/sol-gel route
Authors: Armelao Lidia , Barreca Davide , Bottaro Gregorio , Gasparotto Alberto , Leonarduzzi Daniele , Maragno Cinzia , Tondello Eugenio , Sada Cinzia
Published: September 2006

The rational design of rare-earth doped materials represents one of the major goals of current research in the field of optoelectronics. In this study, ZnO:Er(III) nanosystems were synthesized by means of a hybrid rf-sputtering/sol-gel (SG) route, consisting of the erbium (guest) rf-sputtering on porous zinc oxide xerogels (host) obtained by the SG method, followed by ex situ thermal treatments in air (300–600°C, 1–5h). Particular attention was focused on tailoring the erbium content and distribution in the resulting systems by optimization of the processing conditions. The structural, morphological, and compositional characteristics and their interplay with the synthesis procedure were investigated by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, x-ray excited Auger electron spectroscopy, secondary ion mass spectrometry, UV-visible-near IR absorption spectroscopy, and atomic force microscopy. The obtained results highlight the advantages and versatility of the adopted preparation strategy in tailoring the amount and distribution of Er(III) species in high purity ZnO matrices, resulting in nanosystems endowed with compositional and morphological homogeneity at nanoscale level.
Real-time, noninvasive monitoring of ion energy and ion current at a wafer surface during plasma etching
Authors: Sobolewski Mark A.
Published: September 2006

A noninvasive, nonperturbing technique for real-time monitoring of ion energy distributions and total ion current at a wafer surface during plasma processing has been used to monitor rapid changes in CF4∕Ar etching plasmas in an inductively coupled, rf-biased plasma reactor. To mimic the effects of process recipe steps or reactor malfunctions, perturbations were made in the inductive source power, gas flow, and pressure, and the resulting effects on total ion current, sheath voltage, and ion energy were monitored. During etching of a thermal silicon dioxide film, smaller changes, which are caused by the etch process itself, were also observed. Sheath voltages determined by the noninvasive technique were in good agreement with simultaneous measurements made using a capacitive probe. In addition to providing a demonstration of the speed and accuracy of the technique, the results also provide useful information about the relative importance of different types of equipment malfunctions and suggest methods for minimizing their effects. In particular, operating at constant bias voltage, instead of constant bias power, gave more stable ion energies. The physical mechanisms that cause the observed changes in ion energy are discussed, and a comparison to other process monitoring methods is presented. No other noninvasive, nonperturbing method yields ion current or ion energies as accurately as the technique presented here.
Methods for processing tantalum films of controlled microstructures and properties
Authors: Narayan J. , Bhosle V. , Tiwari A. , Gupta A. , Kumar P. , Wu R.
Published: September 2006

The authors have fabricated thin films of alpha tantalum (α-Ta) with crystalline and amorphous structures by nonequilibrium pulsed laser deposition techniques, and compared their electrical properties and diffusion characteristics with those of polycrystalline beta tantalum (β-Ta) films produced by magnetron sputtering. The microstructure and atomic structure of these films were studied by x-ray diffraction and high-resolution electron microscopy, while elemental analysis was performed using electron energy-loss spectroscopy and x-ray dispersive analysis. The α-Ta with body-centered-cubic structure was formed only under clean, impurity-free conditions of laser molecular beam epitaxy. The resistivity measurements in the temperature range of 10–300K showed room-temperature values to be 15–30μΩcm for α-Ta, 180–200μΩcm for β-Ta, and 250–275μΩcm for amorphous tentalum (a-Ta). The temperature coefficients of resistivity (TCRs) for α-Ta and β-Ta were found to be positive with characteristic metallic behavior, while TCR for a-Ta was negative, characteristic of high-resistivity disordered metals. The authors discuss the mechanism of formation of a-Ta and show that it is stable in the temperature range of 650–700°C. Electron energy-loss spectroscopy (EELS) and Rutherford backscattering measurements showed oxygen content in a-Ta films to be less than 0.1%. The secondary ion mass spectrometry, scanning transmission electron microscope Z-contrast imaging, and EELS studies show that, after 650°C annealing for 1h, a-Ta films have less than 10nm Cu diffusion distance while polycrystalline Ta films have substantial Cu diffusion. The superior diffusion barrier properties of a-Ta for Cu metallization have been attributed to the lack of grain boundaries which usually lead to enhanced diffusion in the case of polycrystalline α-Ta and β-Ta films. Thus, superior diffusion properties of a-Ta provide an optimum solution for copper metallization in next-generation silicon microelectronic devices.
Reconstitution of Herpes Simplex Virus Type 1 Nuclear Capsid Egress In Vitro
Authors: Rémillard-Labrosse Gaudeline , Guay Ginette , Lippé Roger
Published: September 2006

Newly assembled herpesvirus capsids travel from the nucleus to the plasma
membrane by a mechanism that is poorly understood. Furthermore, the
contribution of cellular proteins to this egress has yet to be
clarified. To address these issues, an in vitro nuclear egress assay
that reproduces the exit of herpes simplex virus type 1 (HSV-1) capsids
from nuclei isolated from infected cells was established. As expected,
the assay has all the hallmarks of intracellular transport assays,
namely, a dependence on time, energy, and temperature. Surprisingly, it
is also dependent on cytosol and was slightly enhanced by infected
cytosol, suggesting an implication of both host and viral proteins in
the process. The capsids escaped these nuclei by budding through the
inner nuclear membrane, accumulated as enveloped capsids between the
two nuclear membranes, and were released in cytosol exclusively as
naked capsids, exactly as in intact cells. This is most consistent with
the view that the virus escapes by crossing the two nuclear membranes
rather than through nuclear pores. Unexpectedly, nuclei isolated at the
nonpermissive temperature from cells infected with a U
L
26
thermosensitive protease mutant (V701) supported capsid egress.
Although electron microscopy, biochemical, and PCR analyses hinted at a
likely reconstitution of capsid maturation, DNA encapsidation could not
be confirmed by a traditional SQ test. This assay should prove very
useful for identification of the molecular players involved in HSV-1
nuclear
egress.
Cryptic Properties of a Cluster of Dominant Flavivirus Cross-Reactive Antigenic Sites
Authors: Stiasny Karin , Kiermayr Stefan , Holzmann Heidemarie , Heinz Franz X.
Published: September 2006

A number of flaviviruses are important human pathogens, including yellow fever, dengue, West Nile, Japanese encephalitis, and tick-borne encephalitis (TBE) viruses. Infection with or immunization against any of these viruses induces a subset of antibodies that are broadly flavivirus cross-reactive but do not exhibit significant cross-neutralization. Nevertheless, these antibodies can efficiently bind to the major envelope protein (E), which is the main target of neutralizing and protective antibodies because of its receptor-binding and membrane fusion functions. The structural basis for this phenomenon is still unclear. In our studies with TBE virus, we have provided evidence that such cross-reactive antibodies are specific for a cluster of epitopes that are partially occluded in the cage-like assembly of E proteins at the surfaces of infectious virions and involve—but are not restricted to—amino acids of the highly conserved internal fusion peptide loop. Virus disintegration leads to increased accessibility of these epitopes, allowing the cross-reactive antibodies to bind with strongly increased avidity. The cryptic properties of these sites in the context of infectious virions can thus provide an explanation for the observed lack of efficient neutralizing activity of broadly cross-reactive antibodies, despite their specificity for a functionally important structural element in the E protein.
Receptor-Triggered but Alkylation-Arrested Env of Murine Leukemia Virus Reveals the Transmembrane Subunit in a Prehairpin Conformation
Authors: Wallin Michael , Ekström Maria , Garoff Henrik
Published: September 2006

A central feature of the prevailing model for retrovirus fusion is conversion of the transmembrane (TM) subunit from a prehairpin to a hairpin-like structure. The fusion inhibition of many retroviruses, except murine leukemia virus (MLV), with peptides corresponding to interacting regions in the hairpin supports the model. MLV fusion is controlled by isomerization of the intersubunit disulfide in Env. We show here that TM peptides bind to MLV Env that has been arrested at an intermediate stage of activation by alkylation of the isomerization-active thiol in the surface subunit. This inhibits fusion rescue by dithiothreitol-mediated reduction of the surface protein-TM disulfide.
Rapid Viral Decay in Simian Immunodeficiency Virus-Infected Macaques Receiving Quadruple Antiretroviral Therapy
Authors: Brandin Eleonor , Thorstensson Rigmor , Bonhoeffer Sebastian , Albert Jan
Published: September 2006

The viral dynamics in human immunodeficiency virus type 1 (HIV-1) infection have been studied extensively using mathematical modeling, but data from other primate lentivirus systems are scarce. This study was initiated to increase the understanding of the differences and similarities between the different primate lentiviruses. Four cynomolgus macaques were infected with SIV
mac251.
Six months after infection the monkeys received a 7-day course of subcutaneous, quadruple antiretroviral therapy with zidovudine, lamivudine, tenofovir, and ritonavir-boosted lopinavir. Plasma virus levels were determined before therapy, daily during the first 10 days of therapy, and after 14 days using a sensitive commercial reverse transcriptase assay. All four monkeys showed a rapid and uniform decline in plasma virus load between day 1 and day 4 of treatment (first-phase decay). Two mathematical models, a piecewise linear regression analysis and a nonlinear model, were used to estimate the rate of viral decay in plasma and gave similar results. The mean half-life for plasma virus was 0.47 days (range, 0.37 to 0.50) and reflects the underlying decline of virus-producing CD4
+
lymphocytes. This is the fastest primate lentivirus decay described hitherto. The rapid decay may be due to the high antiviral potency of the therapy or to intrinsic differences between simian immunodeficiency virus (SIV) infection in macaques and HIV-1 infection in humans.
Epstein-Barr Virus BNRF1 Protein Allows Efficient Transfer from the Endosomal Compartment to the Nucleus of Primary B Lymphocytes
Authors: Feederle R. , Neuhierl B. , Baldwin G. , Bannert H. , Hub B. , Mautner J. , Behrends U. , Delecluse H. J.
Published: September 2006

Epstein-Barr virus (EBV) is a tumor virus with marked B lymphotropism. After crossing the B-cell membrane, the virus enters cytoplasmic vesicles, where decapsidation takes place to allow transfer of the viral DNA to the cell nucleus. BNRF1 has been characterized as the EBV major tegument protein, but its precise function is unknown. We have constructed a viral mutant that lacks the BNRF1 gene and report here its in vitro phenotype. A recombinant virus devoid of BNRF1 (ΔBNRF1) showed efficient DNA replication and production of mature viral particles. B cells infected with the ΔBNRF1 mutant presented viral lytic antigens as efficiently as B cells infected with wild-type or BNRF1
trans
-complemented ΔBNRF1 viruses. Antigen presentation in B cells infected with either wild-type (EBV-wt) or ΔBNRF1 virus was blocked by leupeptin addition, showing that both viruses reach the endosome/lysosome compartment. These data were confirmed by direct observation of the mutant virus in endosomes of infected B cells by electron microscopy. However, we observed a 20-fold reduction in the number of B cells expressing the nuclear protein EBNA2 after infection with a ΔBNRF1 virus compared to wild-type infection. Likewise, ΔBNRF1 viruses transformed primary B cells much less efficiently than EBV-wt or BNRF1
trans
-complemented viruses. We conclude from these findings that BNRF1 plays an important role in viral transport from the endosomes to the nucleus.
Tissue-Specific Splicing of the Herpes Simplex Virus Type 1 Latency-Associated Transcript (LAT) Intron in LAT Transgenic Mice
Authors: Gussow Anne M. , Giordani Nicole V. , Tran Robert K. , Imai Yumi , Kwiatkowski Dacia L. , Rall Glenn F. , Margolis Todd P. , Bloom David C.
Published: September 2006

To study the regulation of herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) expression and processing in the absence of other
cis
and
trans
viral functions, a transgenic mouse containing the region encompassing the LAT promoter (LAP1) and the LAT 5′ exon through the 2.0-kb intron was created. LAT expression was detectable by reverse transcriptase PCR (RT-PCR) in a number of tissues, including the dorsal root ganglia (DRG), trigeminal ganglia (TG), brain, skin, liver, and kidney. However, when the accumulation of the 2.0-kb LAT intron was analyzed at the cellular level by in situ hybridization, little or no detectable accumulation was observed in the brain, spinal cord, kidney, or foot, although the 2.0-kb LAT intron was detected at high levels (over 90% of neurons) in the DRG and TG. Northern blot analysis detected the stable 2.0-kb LAT intron only in the sensory ganglia. When relative amounts of the spliced and unspliced LAT within the brain, liver, kidney, spinal cord, TG, and DRG were analyzed by real-time RT-PCR, splicing of the 2.0-kb LAT intron was significantly more efficient in the sensory ganglia than in other tissues. Finally, infection of both transgenic mice and nontransgenic littermates with HSV-1 revealed no differences in lytic replication, establishment of latency, or reactivation, suggesting that expression of the LAT transgene in
trans
has no significant effect on those functions. Taken together, these data indicate that the regulation of expression and processing of LAT RNA within the mouse is highly cell-type specific and occurs in the absence of other viral
cis
- and
trans
-acting factors.
Cidofovir Resistance in Vaccinia Virus Is Linked to Diminished Virulencein Mice
Authors: Andrei Graciela , Gammon Don B. , Fiten Pierre , De Clercq Erik , Opdenakker Ghislain , Snoeck Robert , Evans David H.
Published: September 2006

Cidofovir
[(
S
)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC)]
is recognized as a promising drug for the treatment of poxvirus
infections, but drug resistance can arise by a mechanism that is poorly
understood. We show here that in vitro selection for high
levels of resistance to HPMPC produces viruses encoding two
substitution mutations in the virus DNA polymerase (
E9L
) gene.
These mutations are located within the regions of the gene encoding the
3′-5′ exonuclease (A314T) and polymerase (A684V)
catalytic domains. These mutant viruses exhibited cross-resistance to
other nucleoside phosphonate drugs, while they remained sensitive to
other unrelated DNA polymerase inhibitors. Marker rescue experiments
were used to transfer A314T and/or A684V alleles into a vaccinia virus
Western Reserve strain. Either mutation alone could confer a drug
resistance phenotype, although the degree of resistance was
significantly lower than when virus encoded both mutations. The A684V
substitution, but not the A314T change, also conferred a spontaneous
mutator phenotype. All of the HPMPC-resistant recombinant viruses
exhibited reduced virulence in mice, demonstrating that these
E9L
mutations are inextricably linked to reduced fitness in
vivo. HPMPC, at a dose of 50 mg/kg of body weight/day for 5 days, still
protected mice against intranasal challenge with the drug-resistant
virus with A314T and A684V mutations. Our studies show that proposed
drug therapies offer a reasonable likelihood of controlling
orthopoxvirus infections, even if the viruses encode drug resistance
markers.
An Antiviral Peptide Inhibitor That Is Active against Picornavirus 2A Proteinases but Not Cellular Caspases
Authors: Deszcz Luiza , Cencic Regina , Sousa Carla , Kuechler Ernst , Skern Tim
Published: September 2006

The replication of many viruses is absolutely dependent on proteolytic cleavage. Infected cells also use this biological mechanism to induce programmed cell death in response to viral infection. Specific inhibitors for both viral and cellular proteases are therefore of vital importance. We have recently shown that the general caspase inhibitor zVAD.fmk inhibits not only caspases, but also the 2A

pro

of human rhinoviruses (HRVs) (L. Deszcz, J. Seipelt, E. Vassilieva, A. Roetzer, and E. Kuechler, FEBS Lett.
560:
51-55, 2004). Here, we describe a derivative of zVAD.fmk that inhibits HRV2 2A

pro

but that has no effect on caspase 9. This gain in specificity was achieved by replacing the aspartic acid of zVAD.fmk with methionine to generate zVAM.fmk. Methionine was chosen because an oligopeptide with methionine at the P1 position was a much better substrate than an oligopeptide with an alanine residue, which is found at the P1 position of the wild-type HRV2 2A

pro

cleavage site. zVAM.fmk inhibits the replication of HRV type 2 (HRV2), HRV14, and HRV16. In contrast to zVAD.fmk, however, zVAM.fmk did not inhibit apoptosis induced by puromycin in HeLa cells. zVAM.fmk inhibited in vitro the intermolecular cleavage of eukaryotic initiation factor 4GI (eIF4GI) by HRV2 2A

pro

at nanomolar concentrations. However, much higher concentrations of zVAM.fmk were required to inhibit HRV14 2A

pro

cleavage of eIF4GI. In contrast, intramolecular self-processing of HRV14 2A

pro

was much more susceptible to inhibition by zVAM.fmk than that of HRV2 2A

pro

, suggesting that zVAM.fmk inhibits HRV2 and HRV14 replication by targeting different reactions of the same proteinase.