bluuebunny/crossref_metadata_2025 huggingface dataset:
Emerging Microsporidian Infections in Russian HIV-Infected Patients
Authors: Sokolova Olga I. , Demyanov Anton V. , Bowers Lisa C. , Didier Elizabeth S. , Yakovlev Alexei V. , Skarlato Sergei O. , Sokolova Yuliya Y.
Published: March 2011

Microsporidia were identified in stool specimens by histochemistry and PCR of 30 (18.9%) of 159 HIV-infected patients presenting to the S. P. Botkin Memorial Clinical Hospital of Infectious Diseases, St. Petersburg, Russia. The higher prevalence ofEncephalitozoon intestinalis, in 21 (12.8%) patients, than ofEnterocytozoon bieneusi, in 2 patients (1.2%), was unexpected.Encephalitozoon cuniculiwas detected in three patients: one with strain I and two with strain II.Encephalitozoon hellemwas detected in one patient, and two patients were identified as being infected byMicrosporidiumspecies. One patient was infected with bothE. intestinalisandE. cuniculi. In two patients, the microsporidian species were not identifiable. No statistically significant differences in gender, age, and stage of AIDS were observed between the microsporidian-positive and -negative HIV-infected patients. HIV-infected patients diagnosed with microsporidian infection, however, were significantly more likely to exhibit ≤100 CD4+T cells/μl blood (20/30 patients [67%]; odds ratio [OR], 3.150; 95% confidence interval [CI95], 1.280 to 7.750;P= 0.0116) and weight loss of >10% of the baseline (19/30 patients [63%]; odds ratio, 2.995; CI95, 1.100 to 8.158;P= 0.0352) than HIV-infected patients not diagnosed with microsporidian infection. In summary, this is the first report describing the diagnosis of microsporidian infection of HIV-infected patients in Russia and the first detection ofE. cuniculistrain II in a human.
Baculovirus VP80 Protein and the F-Actin Cytoskeleton Interact and Connect the Viral Replication Factory with the Nuclear Periphery
Authors: Marek Martin , Merten Otto-Wilhelm , Galibert Lionel , Vlak Just M. , van Oers Monique M.
Published: March 2011

Recently, we showed that the
Autographa californica
multicapsid nucleopolyhedrovirus (AcMNPV) VP80 protein is essential for the formation of both virion types, budded virus (BV) and occlusion-derived virus (ODV). Deletion of the
vp80
gene did not affect assembly of nucleocapsids. However, these nucleocapsids were not able to migrate from the virogenic stroma to the nuclear periphery. In the current paper, we constructed a baculovirus recombinant with enhanced-green fluorescent protein (EGFP)-tagged VP80, allowing visualization of the VP80 distribution pattern during infection. In baculovirus-infected cells, the EGFP-VP80 protein is entirely localized in nuclei, adjacent to the virus-triggered F-actin scaffold that forms a highly organized three-dimensional network connecting the virogenic stroma physically with the nuclear envelope. Interaction between VP80 and host actin was confirmed by coimmunoprecipitation. We further showed that VP80 is associated with the nucleocapsid fraction of both BVs and ODVs, typically at one end of the nucleocapsids. In addition, the presence of sequence motifs with homology to invertebrate paramyosin proteins strongly supports a role for VP80 in the polar transport of nucleocapsids to the periphery of the nucleus on their way to the plasma membrane to form BVs and for assembly in the nuclear periphery to form ODVs for embedding in viral occlusion bodies.
Identification of a Golgi Complex-Targeting Signal in the Cytoplasmic Tail of the Severe Acute Respiratory Syndrome Coronavirus Envelope Protein
Authors: Cohen Jennifer R. , Lin Lisa D. , Machamer Carolyn E.
Published: March 2011

The 2003 global outbreak of progressive respiratory failure was caused by a newly emerged virus, severe acute respiratory syndrome coronavirus (SARS-CoV). In contrast to many well-studied enveloped viruses that assemble and bud at the plasma membrane, coronaviruses assemble by budding into the lumen of the endoplasmic reticulum-Golgi intermediate compartment and are released from the cell by exocytosis. For this to occur, the viral envelope proteins must be efficiently targeted to the Golgi region of the secretory pathway. Although the envelope protein (E) makes up only a small percentage of the viral envelope, it plays an important, as-yet-undefined role in virus production. To dissect the targeting of the SARS-CoV E protein to the Golgi region, we exogenously expressed the protein and various mutants from cDNA and determined their localization using immunofluorescence microscopy and biochemical assays. We show that the cytoplasmic tail of the SARS-CoV E protein is sufficient to redirect a plasma membrane protein to the Golgi region. Through site-directed mutagenesis, we demonstrate that a predicted beta-hairpin structural motif in the tail is sufficient for Golgi complex localization of a reporter protein. This motif is conserved in E proteins of beta and gamma coronaviruses (formerly referred to as group 2 and 3 coronaviruses), where it also functions as a Golgi complex-targeting signal. Dissecting the mechanism of targeting of the SARS-CoV E protein will lead to a better understanding of its role in the assembly and release of virions.
The Checkpoints of Viral Gene Expression in Productive and Latent Infection: the Role of the HDAC/CoREST/LSD1/REST Repressor Complex
Authors: Roizman Bernard
Published: March 2011

At the portal of entry into the body, herpes simplex viruses (HSV) vigorously multiply and spread until curtailed by the adaptive immune response. At the same time, HSV invades nerve ending-abutting infected cells and is transported in a retrograde manner to the neuronal nucleus, where it establishes a latent (silent) infection. At intervals, as a consequence of physical or metabolic stress, the virus is activated and transported in an anterograde manner to the body surface. The progression of infection is regulated at four checkpoints. In cell culture or at the portal of entry into the body, HSV uses components of the HDAC1- or HDAC2/CoREST/LSD1/REST repressor complex to activate α genes (checkpoint 1) and then uses an α protein, ICP0, to suppress the same repressor complex from silencing post-α gene expression (checkpoint 2). In neurons destined to harbor latent virus (checkpoint 3), HSV hijacks the same repressor complex to silence itself as a first step in the establishment of the latent state. Suppression of histone deacetylases (HDACs) plays a key role in the reactivation from latency (checkpoint 4). HSV has evolved a strategy of using the same host repressor complex to meet its diverse lifestyle needs.
Interactions of Human Complement with Virus Particles Containing the Nipah Virus Glycoproteins
Authors: Johnson John B. , Aguilar Hector C. , Lee Benhur , Parks Griffith D.
Published: March 2011

Complement is an innate immune response system that most animal viruses encounter during natural infections. We have tested the role of human complement in the neutralization of virus particles harboring the Nipah virus (NiV) glycoproteins. A luciferase-expressing vesicular stomatitis virus (VSV) pseudotype that contained the NiV fusion (F) and attachment (G) glycoproteins (NiVpp) showed dose- and time-dependent activation of human complement through the alternative pathway. In contrast to our findings with other paramyxoviruses, normal human serum (NHS) alone did not neutralize NiVpp infectivityin vitro, and electron microscopy demonstrated no significant deposition of complement component C3 on particles. This lack of NiVpp neutralization by NHS was not due to a global inhibition of complement pathways, since complement was found to significantly enhance neutralization by antibodies specific for the NiV F and G glycoproteins. Complement components C4 and C1q were necessary but not sufficient by themselves for the enhancement of antibody neutralization. Human complement also enhanced NiVpp neutralization by a soluble version of the NiV receptor EphrinB2, and this depended on components in the classical pathway. The ability of complement to enhance neutralization fell into one of two profiles: (i) anti-F monoclonal antibodies showed enhancement only at high and not low antibody concentrations, and (ii) anti-G monoclonal antibodies and EphrinB2 showed enhancement at both high and very low levels of antibody (e.g., 3.1 ng) or EphrinB2 (e.g., 2.5 ng). Together, these data establish the importance of human complement in the neutralization of particles containing the NiV glycoproteins and will help guide the design of more effective therapeutics that harness the potency of complement pathways.
Measles Virus Glycoprotein-Pseudotyped Lentiviral Vector-Mediated Gene Transfer into Quiescent Lymphocytes Requires Binding to both SLAM and CD46 Entry Receptors
Authors: Frecha Cecilia , Lévy Camille , Costa Caroline , Nègre Didier , Amirache Fouzia , Buckland Robin , Russell Steven J. , Cosset François-Loïc , Verhoeyen Els
Published: March 2011

Gene transfer into quiescent T and B cells is of importance for gene therapy and immunotherapy approaches to correct hematopoietic disorders. Previously, we generated lentiviral vectors (LVs) pseudotyped with the Edmonston measles virus (MV) hemagglutinin and fusion glycoproteins (Hgps and Fgps) (H/F-LVs), which, for the first time, allowed efficient transduction of quiescent human B and T cells. These target cells express both MV entry receptors used by the vaccinal Edmonston strain, CD46 and signaling lymphocyte activation molecule (SLAM). Interestingly, LVs pseudotyped with an MV Hgp, blind for the CD46 binding site, were completely inefficient for resting-lymphocyte transduction. Similarly, SLAM-blind H mutants that recognize only CD46 as the entry receptor did not allow stable LV transduction of resting T cells. The CD46-tropic LVs accomplished vector-cell binding, fusion, entry, and reverse transcription at levels similar to those achieved by the H/F-LVs, but efficient proviral integration did not occur. Our results indicate that both CD46 and SLAM binding sites need to be present in
cis
in the Hgp to allow successful stable transduction of quiescent lymphocytes. Moreover, the entry mechanism utilized appears to be crucial: efficient transduction was observed only when CD46 and SLAM were correctly engaged and an entry mechanism that strongly resembles macropinocytosis was triggered. Taken together, our results suggest that although vector entry can occur through the CD46 receptor, SLAM binding and subsequent signaling are also required for efficient LV transduction of quiescent lymphocytes to occur.
Species-Specific Variation in RELA Underlies Differences in NF-κB Activity: a Potential Role in African Swine Fever Pathogenesis
Authors: Palgrave Christopher J. , Gilmour Linzi , Lowden C. Stewart , Lillico Simon G. , Mellencamp Martha A. , Whitelaw C. Bruce A.
Published: March 2011

African swine fever virus (ASFV) is a highly infectious disease of domestic pigs, with virulent isolates causing a rapidly fatal hemorrhagic fever. In contrast, the porcine species endogenous to Africa tolerate infection. The ability of the virus to persist in one host while killing another genetically related host implies that disease severity may be, in part, modulated by host genetic variation. To complement transcription profiling approaches to identify the underlying genetic variation in the host response to ASFV, we have taken a candidate gene approach based on known signaling pathways that interact with the virus-encoded immunomodulatory protein A238L. We report the sequencing of these genes from different pig species and the identification and initial
in vitro
characterization of polymorphic variation in RELA (p65; v-rel reticuloendotheliosis viral oncogene homolog A), the major component of the NF-κB transcription factor. Warthog RELA and domestic pig RELA differ at three amino acids. Transient cell transfection assays indicate that this variation is reflected in reduced NF-κB activity
in vitro
for warthog RELA but not for domestic pig RELA. Induction assays indicate that warthog RELA and domestic pig RELA are elevated essentially to the same extent. Finally, mutational studies indicate that the S531P site conveys the majority of the functional variation between warthog RELA and domestic pig RELA. We propose that the variation in RELA identified between the warthog and domestic pig has the potential to underlie the difference between tolerance and rapid death upon ASFV infection.
A Conserved Amphipathic Helix in the N-Terminal Regulatory Region of the Papillomavirus E1 Helicase Is Required for Efficient Viral DNA Replication
Authors: Morin Geneviève , Fradet-Turcotte Amélie , Di Lello Paola , Bergeron-Labrecque Fanny , Omichinski James G. , Archambault Jacques
Published: March 2011

The papillomavirus E1 helicase, with the help of E2, assembles at the viral origin into a double hexamer that orchestrates replication of the viral genome. The N-terminal region (NTR) of E1 is essential for DNA replication
in vivo
but dispensable
in vitro
, suggesting that it has a regulatory function. By deletion analysis, we identified a conserved region of the E1 NTR needed for efficient replication of viral DNA. This region is predicted to form an amphipathic α-helix (AH) and shows sequence similarity to portions of the p53 and herpes simplex virus (HSV) VP16 transactivation domains known as transactivation domain 2 (TAD2) and VP16C, which fold into α-helices upon binding their target proteins, including the Tfb1/p62 (
Saccharomyces cerevisiae
/human) subunit of general transcription factor TFIIH. By nuclear magnetic resonance (NMR) spectroscopy and isothermal titration calorimetry (ITC), we found that a peptide spanning the E1 AH binds Tfb1 on the same surface as TAD2/VP16C and with a comparable affinity, suggesting that it does bind as an α-helix. Furthermore, the E1 NTRs from several human papillomavirus (HPV) types could activate transcription in yeast, and to a lesser extent in mammalian cells, when fused to a heterologous DNA-binding domain. Mutation of the three conserved hydrophobic residues in the E1 AH, analogous to those in TAD2/VP16C that directly contact their target proteins, decreased transactivation activity and, importantly, also reduced by 50% the ability of E1 to support transient replication of DNA in C33A cells, at a step following assembly of the E1-E2-ori preinitiation complex. These results demonstrate the existence of a conserved TAD2/VP16C-like AH in E1 that is required for efficient replication of viral DNA.
What Does Virus Evolution Tell Us about Virus Origins?
Authors: Holmes Edward C.
Published: March 2011

Despite recent advances in our understanding of diverse aspects of virus evolution, particularly on the epidemiological scale, revealing the ultimate origins of viruses has proven to be a more intractable problem. Herein, I review some current ideas on the evolutionary origins of viruses and assess how well these theories accord with what we know about the evolution of contemporary viruses. I note the growing evidence for the theory that viruses arose before the last universal cellular ancestor (LUCA). This ancient origin theory is supported by the presence of capsid architectures that are conserved among diverse RNA and DNA viruses and by the strongly inverse relationship between genome size and mutation rate across all replication systems, such that pre-LUCA genomes were probably both small and highly error prone and hence RNA virus-like. I also highlight the advances that are needed to come to a better understanding of virus origins, most notably the ability to accurately infer deep evolutionary history from the phylogenetic analysis of conserved protein structures.
Inhibition of 2′,5′-Oligoadenylate Synthetase Expression and Function by the Human Cytomegalovirus ORF94 Gene Product
Authors: Tan Joanne C. G. , Avdic Selmir , Cao John Z. , Mocarski Edward S. , White Kirsten L. , Abendroth Allison , Slobedman Barry
Published: March 2011

The human cytomegalovirus (HCMV) ORF94 gene product has been reported to be expressed during both productive and latent phases of infection, although its function is unknown. We report that expression of pORF94 leads to decreased 2′,5′-oligoadenylate synthetase (OAS) expression in transfected cells with and without interferon stimulation. Furthermore, the functional activity of OAS was inhibited by pORF94. Finally, we present evidence of OAS modulation by pORF94 during productive HCMV infection of human fibroblasts. This study provides the first identification of a function for pORF94 and identifies an additional means by which HCMV may limit a critical host cell antiviral response.
Pseudotyping Vesicular Stomatitis Virus with Lymphocytic Choriomeningitis Virus Glycoproteins Enhances Infectivity for Glioma Cells and Minimizes Neurotropism
Authors: Muik Alexander , Kneiske Inna , Werbizki Marina , Wilflingseder Doris , Giroglou Tsanan , Ebert Oliver , Kraft Anna , Dietrich Ursula , Zimmer Gert , Momma Stefan , von Laer Dorothee
Published: March 2011

Vesicular stomatitis virus (VSV)-based oncolytic virotherapy has the potential to significantly improve the prognosis of aggressive malignancies such as brain cancer. However, VSV's inherent neurotoxicity has hindered clinical development so far. Given that this neurotropism is attributed to the glycoprotein VSV-G, VSV was pseudotyped with the nonneurotropic envelope glycoprotein of the lymphocytic choriomeningitis virus (LCMV-GP→VSV-GP). Compared to VSV, VSV-GP showed enhanced infectivity for brain cancer cells
in vitro
while sparing primary human and rat neurons
in vitro
and
in vivo
, respectively. In conclusion, VSV-GP has a much wider therapeutic window than VSV and is thus more suitable for clinical applications, especially in the brain.
Characterization of Empty Adenovirus Particles Assembled in the Absence of a Functional Adenovirus IVa2 Protein
Authors: Ostapchuk Philomena , Almond Matthew , Hearing Patrick
Published: March 2011

The molecular mechanism for packaging of the adenovirus (Ad) genome into the capsid is likely similar to that of DNA bacteriophages and herpesviruses—the insertion of viral DNA through a portal structure into a preformed prohead driven by an ATP-hydrolyzing molecular machine. It is speculated that the IVa2 protein of adenovirus is the ATPase providing the power stroke of the packaging machinery. Purified IVa2 binds ATP
in vitro
and, along with a second Ad protein, the L4 22-kilodalton protein (L4-22K), binds specifically to sequences in the Ad genome that are essential for packaging. The efficiency of binding of these proteins
in vitro
was correlated with the efficiency of packaging
in vivo
. By utilizing a virus unable to express IVa2,
pm
8002, it was reported that IVa2 plays a role in assembly of the empty virion. We wanted to address the question of whether the ATP binding, and hence the putative ATPase activity, of IVa2 was required for its role in virus assembly. Our results show that ATPase activity was not required for the assembly of empty virus particles. In addition, we present evidence that particles were assembled in the absence of IVa2 by using two viruses null for IVa2—a deletion mutant virus, ΔIVa2, and the previously described mutant virus,
pm
8002. Empty virus particles produced by these IVa2 mutant viruses did not contain detectable viral DNA. We conclude that the major role of IVa2 is in viral DNA packaging. A characterization of the empty particles obtained from the IVa2 mutant viruses compared to wild-type empty particles is presented.
Rift Valley Fever: Recent Insights into Pathogenesis and Prevention
Authors: Boshra Hani , Lorenzo Gema , Busquets Núria , Brun Alejandro
Published: March 2011

Rift Valley fever virus (RVFV) is a zoonotic pathogen that primarily affects ruminants but can also be lethal in humans. A negative-stranded RNA virus of the familyBunyaviridae, this pathogen is transmitted mainly via mosquito vectors. RVFV has shown the ability to inflict significant damage to livestock and is also a threat to public health. While outbreaks have traditionally occurred in sub-Saharan Africa, recent outbreaks in the Middle East have raised awareness of the potential of this virus to spread to Europe, Asia, and the Americas. Although the virus was initially characterized almost 80 years ago, the only vaccine approved for widespread veterinary use is an attenuated strain that has been associated with significant pathogenic side effects. However, increased understanding of the molecular biology of the virus over the last few years has led to recent advances in vaccine design and has enabled the development of more-potent prophylactic measures to combat infection. In this review, we discuss several aspects of RVFV, with particular emphasis on the molecular components of the virus and their respective roles in pathogenesis and an overview of current vaccine candidates. Progress in understanding the epidemiology of Rift Valley fever has also enabled prediction of potential outbreaks well in advance, thus providing another tool to combat the physical and economic impact of this disease.
Mother-to-Infant Transmission of Simian Immunodeficiency Virus Is Rare in Sooty Mangabeys and Is Associated with Low Viremia
Authors: Chahroudi Ann , Meeker Tracy , Lawson Benton , Ratcliffe Sarah , Else James , Silvestri Guido
Published: March 2011

Mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1) occurs
in utero
, intrapartum, and through breastfeeding, with a cumulative rate of transmission of 35 to 40%. As a result, ∼400,000 children become infected each year. Little is known about mother-to-infant transmission (MTIT) during natural simian immunodeficiency virus (SIV) infection of sooty mangabeys (SMs) that typically is nonpathogenic despite high viral loads. In this study, we retrospectively investigated the rates of MTIT in a large colony of naturally SIV-infected SMs using serological (anti-SIV antibody by enzyme-linked immunosorbent assay [ELISA] and Western blot analysis) and virological (SIV
smm
real-time reverse transcription-PCR) methods. We examined 161 SM infants born to SIV-infected mothers and found that 150 (93.2%) were infected by non-MTIT (
n
= 120) or remained uninfected (
n
= 30). The remaining 11 SM infants (6.8%) were defined as acquiring SIV by presumptive MTIT based on (i) the presence of anti-SIV antibodies without seroreversion and (ii) a viral load of >500 copies/ml of serum in the first year of life. SM infants infected with SIV by presumptive MTIT did not show any increased morbidity or mortality, indicating that the infection is nonpathogenic even when acquired early in life. Interestingly, viral loads of SIV-infected SM infants with presumptive MTIT were 2-log lower than those of SIV-infected adult SMs living in the same colony (i.e., ∼1,000 and 100,000 copies/ml, respectively). These results indicate that MTIT is substantially less frequent in naturally SIV-infected SMs than in HIV-1-infected humans and results in nonpathogenic infection associated with low SIV viremia. Evolutionary pressure to reduce MTIT may have contributed to the restriction of SIV pathogenesis in natural hosts.
Mutations in the Fusion Protein Cleavage Site of Avian Paramyxovirus Serotype 2 Increase Cleavability and Syncytium Formation but Do Not Increase Viral Virulence in Chickens
Authors: Subbiah Madhuri , Khattar Sunil K. , Collins Peter L. , Samal Siba K.
Published: March 2011

Avian paramyxovirus serotype 2 (APMV-2) is one of the nine serotypes of APMV, which infect a wide variety of avian species around the world. In this study, we constructed a reverse genetics system for recovery of infectious recombinant APMV-2 strain Yucaipa (APMV-2/Yuc) from cloned cDNA. The rescued recombinant virus (rAPMV-2) resembled the biological virus in growth properties
in vitro
and in pathogenicity
in vivo
. The reverse genetics system was used to analyze the role of the cleavage site of the fusion (F) protein in viral replication and pathogenesis. The cleavage site of APMV-2/Yuc (
K
PAS
R
↓F) contains only a single basic residue (position −1) that matches the preferred furin cleavage site [
R
X(
K/R
)
R
↓]. (Underlining indicates the basic amino acids at the F protein cleavage site, and the arrow indicates the site of cleavage.) Contrary to what would be expected for this cleavage sequence, APMV-2 does not require, and is not augmented by, exogenous protease supplementation for growth in cell culture. However, it does not form syncytia, and the virus is avirulent in chickens. A total of 12 APMV-2 mutants with F protein cleavage site sequences derived from APMV serotypes 1 to 9 were generated. These sites contain from 1 to 5 basic residues. Whereas a number of these cleavage sites are associated with protease dependence and lack of syncytium formation in their respective native viruses, when transferred into the APMV-2 backbone, all of them conferred protease independence, syncytium formation, and increased replication in cell culture. Examination of selected mutants during a pulse-chase experiment demonstrated an increase in F protein cleavage compared to that for wild-type APMV-2. Despite the gains in cleavability, replication, and syncytium formation, analysis of viral pathogenicity in 9-day-old embryonated chicken eggs, 1-day-old chicks, and 2-week-old chickens showed that the F protein cleavage site mutants did not exhibit increased pathogenicity and remained avirulent. These results imply that structural features in addition to the cleavage site play a major role in the cleavability of the F protein and the activity of the cleaved protein. Furthermore, cleavage of the F protein is not a determinant of APMV-2 pathogenicity in chickens.
Pitfalls in the use of multicolour flow cytometry in haematology
Authors: Johansson Ulrika , Macey Marion
Published: March 2011

Multicolour flow cytometry in haematology has developed considerably in recent years. The ability to analyse eight or more colours of fluorescence on millions of cells in a matter of minutes has enabled the provision of rapid and reliable measures of minimal residual disease for clinicians. The use of multicolour analysis has also enabled more specific characterisation of presenting leukaemias and lymphomas. However, there has not been a concomitant increase in the knowledge and experience of the flow cytometrists to deal with certain problems associated with this more complex analysis.
Views of contraceptive service delivery to young people in the UK: a systematic review and thematic synthesis
Authors: Baxter Susan , Blank Lindsay , Guillaume Louise , Squires Hazel , Payne Nick
Published: March 2011

Background and methodology

Despite widespread availability of contraceptives and increasing service provision in the UK, rates of teenage pregnancy remain a concern. It has been suggested that young people face particular obstacles in accessing services, leading to a need for specialist provision. This systematic review examined the literature reporting views of service providers and young people. Data were synthesised in order to develop key themes to inform the development of contraceptive services for this population.

Results

A total of 59 papers reporting studies carried out within the UK were included. Forty-five of these provided qualitative or mixed method data and 14 reported survey findings. Seven key themes were identified: perceptions of services; accessibility; embarrassment; anonymity and confidentiality; the clinic environment; the consultation; and service organisation.

Conclusions

This review suggests that the most significant concern for young people is the preservation of anonymity and confidentiality. There seems to be a need for young people to be given greater assurances about this, with process and environmental changes suggested. The fear of staff being critical or unfriendly also presents a considerable obstacle to some young people. Issues of service accessibility – such as convenience of location and opening hours – are also highlighted, with lifestyle factors and restrictions on where under-18s can go suggested as important aspects. The review suggests that varying preferences among young people with regard to which service to access requires choice to be preserved and, where possible, extended. This requires services to work effectively together to consider provision across a locality.
Rethinking paternalism: an exploration of responses to the Israel Patient's Rights Act 1996
Authors: Waltho Simon
Published: March 2011

Questions of patient autonomy have formed an important part of ethical debate in medicine from at least the post-war period onwards. Although initially important as a counterweight to widespread medical paternalism, recent years have seen a reaction against a widely perceived ‘triumph of autonomy’. In particular, competent patients' refusal of life-saving or clearly beneficial treatment presents complex dilemmas for both healthcare professionals and ethicists. Discussion of the mechanism provided by the Israel Patient's Rights Act of 1996 for ethics committees to override refusal of treatment by such patients has provided several examples in which it seems an obligation to benefit the patient can outweigh concerns regarding respect for their autonomy. However, such analyses as have been undertaken so far may be seen to omit important elements of the moral decision-making process that takes place even when the latter appears to ‘win out’. In addition to helping better prepare clinicians to meet such challenges in the future, a fuller appreciation of those elements that are present in justified cases of coercive treatment may enable them to arrive at a better understanding of what autonomy itself can mean in a medical context.
DIELECTRIC RELAXATION AND ELECTRICAL STUDY OF BaNb2O6 PREPARED BY SOL–GEL ROUTE
Authors: BAJPAI P. K. , SINGH K. N.
Published: March 2011

A gel was formed when an aqueous solution of BaCl 2, NbF 5 and citric acid in stoichiometric ratio is heated on a water bath at 100°C. This gel on decomposition at 700°C yielded the nano phase of BaNb 2 O 6 as confirmed by X-ray diffraction study. The crystal structure is orthorhombic with unit cell parameter a = 12.2136 Å, b = 10.2413 Å, c = 7.8831 Å. The estimated grain size is 88 nm. Dielectric studies reveal the dielectric relaxation mechanism. Conducting charges and free charges both contribute to the dielectric relaxation in this material. Electrical properties of the material were studied using impedance spectroscopy technique. Detailed analysis of impedance spectrum suggested that the electrical properties are strongly temperature-dependent. The relaxation is polydispersive and conduction is mainly through grains. AC conduction activation energies are estimated from Arrheneus plots and conduction mechanism is discussed.
Z-SCAN STUDIES OF THE NONLINEAR OPTICAL PROPERTIES OF GOLD AQUEOUS COLLOID PREPARED BY THE CHEMICAL REACTION METHOD
Authors: JIA TING-JIAN , CHENG HONG , HE TING-CHAO , CUI YU-TING , LIU CUI-MEI
Published: March 2011

Nonlinear optical properties of gold aqueous colloid obtained with chemical reaction method are investigated using Z-scan technique with 38 ps pulses. Experimental results indicate that the colloid exhibits large nonlinear refraction and nonlinear absorption under the excitation of ps 532 nm pulses, while it presents large two photon absorption under ps 1064 nm pulses excitation. Meanwhile, the fluorescence emission spectrum of gold aqueous colloid is recorded under the excitation of 350 nm, and two fluorescence peaks are observed at 454 nm and 704 nm. Moreover, the average fluorescence lifetime of colloid is estimated to be 1.33 ns.
FLUCTUATION CONDUCTIVITY IN GRANULAR Tm1-xPrxBa2Cu3O7-δ SUPERCONDUCTOR
Authors: OPATA YURI APARECIDO , DE LEITE GUSMÃO PINHEIRO LINCOLN BRUM , JURELO ALCIONE ROBERTO , RODRIGUES PEDRO
Published: March 2011

We have studied fluctuations on the electrical conductivity in granular Tm 1-x Pr x Ba 2 Cu 3 O 7-δ (0 ≤ x ≤ 0.10) superconductors. Samples were prepared by the standard solid-state reaction technique. The results are described in terms of the temperature derivative of the resistivity, dρ/dT, and of the logarithmic temperature derivative of the conductivity, d ln (Δσ)/dT. The results show clearly that the resistive transition proceeds in two stages: intragranular and intergranular. Also, it was not observed in dρ/dT, near the transition, a structure consisting of two closely separated maxima, as seen in studies with other rare earth elements. Yet, the analysis of the conductivity in the normal phase has shown contributions from critical fluctuations and they were not affected by Pr doping. Below TC, on approaching the zero resistance state, our results show a power-law behavior with critical exponent s ≅ 4.1 for x = 0.00 and s ≅ 2.8 for x = 0.05 sample, indicating a phase transition from a paracoherent to a coherent state of the granular array. This behavior was not observed for x = 0.10 sample, showing that Pr affected the coherence transition.
PYROELECTRIC AND PHASE TRANSITION PROPERTIES OF A FINITE ALTERNATING FERROELECTRIC SUPERLATTICE WITH THREE SURFACE LAYERS
Authors: KUANG FANG-GUANG , KUANG XIAO-YU , ZHENG BAO-BING
Published: March 2011

The pyroelectric and phase transition properties of a finite alternating ferroelectric superlattice with three surface layers are studied on the basis of the transverse Ising model by using the mean field approximation. The temperature-dependence of the polarization and pyroelectric coefficient of the superlattice with various inter-layer exchange interaction constants are given. The profiles of the polarization as well as the pyroelectric coefficient of the superlattice are shown. By taking into account the effects of the exchange interaction and transverse field parameters on the phase diagrams, we find that the phase transition properties of the superlattice are sensitive to the changes of transverse Ising model parameters.
A MECHANISM FOR ELECTRON PAIR FORMATION
Authors: VERHULST TOBIAS , NAUDTS JAN
Published: March 2011

We consider a lattice model in which phonons scatter with pairs of electrons carrying a net spin current. All the energy eigenvalues and eigenvectors of this model can be obtained analytically. For a suitable choice of parameters the ground state consists of a Fermi sea of non-interacting electrons, with a layer of paired electrons on top of it. The binding energy of one electron pair is partly canceled by increased kinetic energy of another pair of electrons. This results in a momentum-dependent gap in the spectrum of the electrons.
DEPENDENCE OF CAPACITANCE–VOLTAGE CHARACTERISTICS OF NOMINALLY UNDOPED AlGaN/GaN HETEROSTRUCTURES ON SEVERAL KEY PARAMETERS OF THE MATERIALS
Authors: TAN GUIYING , SU YONGBO
Published: March 2011

Nominally undoped AlGaN / GaN heterostructure samples were grown on c-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition, and their material properties, such as crystal quality, roughness of heterointerface, thickness and Al mole fraction of AlGaN barrier layer, were identified by high resolution X-ray diffraction (HRXRD). Mercury-probe capacitance–voltage (C–V) measurements were carried out to investigate the carrier distribution in the heterostructures and accurately evaluate the sheet carrier concentration of two-dimensional electron gas (2DEG) formed at AlGaN / GaN heterointerface. The dependence of C–V characteristics of these samples on some key material parameters were clearly revealed. The Al -content effect, barrier-thickness effect in AlGaN layer, and their synergy effect were specifically studied. It demonstrated that the C–V characteristics of AlGaN / GaN heterostructure could be improved by perfecting the crystal epitaxial process, and adjusting the Al -content or thickness of AlGaN barrier layer.
RESONANT SPIN POLARIZATION IN A TWO-DIMENSIONAL HOLE GAS
Authors: MA TIANXING
Published: March 2011

Within the Luttinger Hamiltonian, electric-field-induced resonant spin polarization of a two-dimensional hole gas in a perpendicular magnetic field was studied. The spin polarization arising from splitting between the light and the heavy hole bands shows a resonant peak at a certain magnetic field. Especially, the competition between the Luttinger term and the structural inversion asymmetry leads to a rich resonant peaks structure, and the required magnetic field for the resonance may be effectively reduced by enlarging the effective width of the quantum well. Furthermore, the Zeeman splitting tends to move the resonant spin polarization to a relative high magnetic field and destroy these rich resonant spin phenomena. Finally, both the height and the weight of the resonant peak increase as the temperature decreases. It is believed that such resonant spin phenomena may be verified in the sample of a two-dimensional hole gas, and it may provide an efficient way to control spin polarization by an external electric field.
THE MODEL OF DRYING SESSILE DROP OF COLLOIDAL SOLUTION
Authors: VODOLAZSKAYA I. V. , TARASEVICH YU. YU.
Published: March 2011

We have proposed and investigated a model of drying colloidal suspension drop placed onto a horizontal substrate in which the sol to gel phase transition occurs. The temporal evolution of volume fraction of the solute and the gel phase dynamics were obtained from numerical simulations. Our model takes into account the fact that some physical quantities are dependent on volume fraction of the colloidal particles.
COMPUTATIONAL STUDY OF A CNT-URACIL-CNT COMPOUND
Authors: MIRZAEI MARYAM , YOUSEFI MOHAMMAD , MIRZAEI MAHMOUD
Published: March 2011

Density functional calculations were performed to investigate the properties of a combination of two representative carbon nanotubes by assistance of the atomic sites of uracil, which is the characteristic nucleobase of RNA. The obtained parameters indicated that the resulting compound exhibit new properties with respect to the original nanotubes and uracil. The effects of the modification process were significant for the dipole moments and conductivity properties of the components as were seen by the significant changes in the new compound. The values of quadrupole coupling constants for the nitrogen and oxygen atoms of the uracil counterpart of the investigated models also indicated the effects of changes of the electronic environments of the components due to the modification process.
THE CRITICAL EFFECTS OF TIME DELAY AND NOISE CORRELATION ON STOCHASTIC RESONANCE IN AN ASYMMETRIC BISTABLE SYSTEM
Authors: JIA ZHENG-LIN , MEI DONG-CHENG
Published: March 2011

We investigate the effects of time delay and noise correlation on the stochastic resonance induced by a multiplicative signal in an asymmetric bistable system. By the two-state theory and small delay approximation, the expression of the output signal-to-noise ratio (SNR) is obtained in the adiabatic limit. The results show that SNR as a function of the multiplicative noise intensity D shows a transition from two peaks to one peak with the decreasing of cross-correlation strength λ and the increasing of delay time τ. Moreover, there are the doubly critical phenomena for SNR versus λ and τ, and SNR versus D and α (additive noise intensity).
TRANSMISSION PROPERTIES OF THE ONE-DIMENSIONAL ARRAY OF DELTA POTENTIALS
Authors: CORDOURIER-MARURI GUILLERMO , DE COSS ROMEO , GUPTA VIRENDRA
Published: March 2011

The problem of one-dimensional quantum wire along which a moving particle interacts with a linear array of N delta-function potentials is studied. Using a quantum waveguide approach, the transfer matrix is calculated to obtain the transmission probability of the particle. Results for arbitrary N and for specific regular arrays are presented. Some particular symmetries and invariances of the delta-function potential array for the N = 2 case are analyzed in detail. It is shown that perfect transmission can take place in a variety of situations.
SCALING BEHAVIOR OF SEDIMENT TRANSPORT INDUCED BY WATER DIVERSION IN RIVER NETWORKS
Authors: WANG XU-MING , HUO JIE , CAO SHI-FENG , HAO RUI
Published: March 2011

A sediment transport dynamic model, based on the consideration of streams confluence and/or diversion, is proposed to investigate the influence of water diversion on the mainstream. The simulated results accord qualitatively with the observed or experimental phenomenon in the Yellow River, that is, sedimentation will get more in the main channel as the water is diverted. Some interesting scaling laws describing the behavior of the erosion–sedimentation state in the process of sediment transport are observed, which may help us to get some understandings of sediment transport dynamics in a river network.
TRIPLE-TUNNEL JUNCTION SINGLE ELECTRON TRANSISTOR (TTJ-SET)
Authors: SHAHHOSEINI ALI , SAGHAFI KAMYAR , MORAVVEJ-FARSHI MOHAMMAD KAZEM , FAEZ RAHIM
Published: March 2011

We propose a triple-tunnel junction single electron transistor (TTJ-SET). The proposed structure consists of a metallic quantum-dot island that is capacitive coupled to a gate contact and surrounded by three tunnel junctions. To the best of our knowledge, this is the first instance of introducing this new structure that is suitable for both digital and analog applications. I–V D characteristics of the proposed TTJ-SET, simulated by a HSPICE macro model for various gate voltages, are in excellent agreement with those obtained by SIMON, which is a Monte-Carlo based simulator. We show how one can design a digital inverter by using a single TTJ-SET. We also show that, under suitable conditions, a TTJ-SET can operate as a full- or half-wave analog rectifier.
A COMMENT ON BCC CRYSTALLIZATION IN HIGHER DIMENSIONS
Authors: ELITZUR SHMUEL , KARNI BOAZ , RABINOVICI ELIEZER
Published: March 2011

The result that near the melting point three-dimensional crystals have an octahedronic structure is generalized to higher flat non-compact dimensions.
TIME EVOLUTION OF THE NONCLASSICALITY FOR THE FOCK STATES AND THEIR SUPERPOSITION STATES BY THE WIGNER FUNCTION
Authors: SI KUN , ZHU NING-LI , JIA HUAN-YU
Published: March 2011

The Wigner functions of the Fock states and their superposition states have negative value clearly. We focus on discussing the time evolution of the Fock states and their superposition states by the Wigner function under the coherent drive (pumping laser) and dissipation channels (cavity radiation). The results show that the negative region of their Wigner function gradually diminishes as the time kt or the gain coefficient g increasing. In addition, the disappearing time is related to the value of g - k. The loss of non-classical features becomes slower when g increases with the k > g; there is the "frozen zone" when k = g; then the loss of non-classical features becomes faster when g increases with k < g.
AB INITIO ELECTRONIC STRUCTURE CALCULATIONS OF HALF-METALLIC FERROMAGNETISM IN CALCIUM CHALCOGENIDES DOPED WITH B, C AND N
Authors: YOGESWARI M. , KALAPANA G.
Published: March 2011

Self-consistent ab initio calculations were carried out to study the structural, electronic and magnetic properties of nine ternary compounds Ca 4 XA 3 ( X = B , C and N ; A = S , Se and Te ). The calculations were performed by using tight-binding linear muffin tin orbital (TB-LMTO) method within the local density approximation (LDA). The calculations reveal that half-metallic ferromagnetism can be obtained for C - and N -doping with the integer magnetic moment of 2.00 μ B and 1.00 μ B per cell. However, B substitution does not induce magnetism in CaS and CaSe systems, but it produces ferromagnetism in CaTe system with magnetic moment of 2.67 μ B per cell. Moreover C - and N -doping enhance the stable ferromagnetic state in calcium chalcogenide systems. Spin-dependent electronic band structure, total and partial densities of state calculations demonstrate that localized magnetic moments substantially come from impurity atoms. Half-metallic ferromagnetism predominately originates from spin-polarization of electrons in 2p orbital states of C and N atoms. In addition, equilibrium lattice constant, bulk modulus, atomic local magnetic moments, half-metallic gap and robustness of half-metallicity have been calculated.
AN INVESTIGATION ON IMPURITY AND GRAIN BOUNDARY EFFECTS ON STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF SnO2:F THIN FILMS DEPOSITED BY SPRAY PYROLYSIS
Authors: ESHGHI HOSEIN , BIARAM ALIREZA , ADELIFARD MEHDI
Published: March 2011

We have investigated the effect of fluorine dopant concentration (0–15 F / Sn wt.%) on structural, optical and electrical properties of SnO 2 thin films grown by spray pyrolysis technique. According to the experimental evidences and data analysis, we found in these samples: (1) the polycrystalline layers, while in undoped conditions it mainly grow along (211) direction in doped ones (200) is the preferred direction with a direct band gap energy of about 3.7–3.9 eV; (2) The main cause for the relatively high absorption coefficients below Eg could be due to the presence of wide (~ 1–2 eV) band tails in the forbidden gap; (3) the highest (5.4 × 10-3 Ω-1) figure of merit belongs to the sample with 5 wt.% F / Sn concentration; (4) the grain boundary scattering is the main limiting mechanism in the electrical transport properties of the layers.
THE FORMATION AND EVOLUTION OF SINGLE-CRYSTALLINESnO2NANOBELTS
Authors: DUAN JUN-HONG , YAN CHAO , HE XING-DAO , GAO YI-QING , SHI PEI-QIN , LIU ZHI-ANG , JIANG MANG
Published: March 2011

Single-crystalline SnO2zigzag nanobelts and straight nanobelts with triangular tip were synthesized by a simple Tin–water reaction method. The product was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman scattering and micro-photoluminescence spectroscopy to obtain the structural and optical information. Why zigzag nanobelts and straight nanobelts can be formed respectively under the same experimental conditions? On the basis of TEM characterization and thermodynamic analysis, the formation mechanism of zigzag nanobelts and straight nanobelts were proposed respectively.
THE ROLE OF COMPOSITIONAL STRAIN IN THE INSTABILITY OF SOLID-FLUID THIN FILM INTERFACES
Authors: ASLE ZAEEM M. , EL KADIRI H. , HORSTEMEYER M. F. , WANG P. T. , CHERKAOUI M.
Published: March 2011

Consider a binary substitutional solid solution not in equilibrium with a fluid rich in either solid component. At the interface, depending on the chemical energy, the solid may selectively lose or gain atoms from the fluid. Any atom exchange upsets the nominal composition; thereby stresses are generated in the solid by simultaneous action of lattice dilation and interdiffusion. As stresses build up, the local changing volume tends to split up into islands in an effort to escape from stresses, while curvature tends to amalgamate the islands in an effort to minimize surface energy. This competition could lead to substantial corrugations of the solid-fluid interface. These corrugations and the thresholds for noticeable competition between stresses and curvatures had an old tradition in chemo-mechanical models of sharp interfaces beginning with Srolovitz (1989). However, stresses were generally considered as a mere cause of external loads, so a pure solid was tacitly asserted. This paper couples elasticity with a conserved-phase field model to mainly investigate the effect of compositional strain on the interface instability process between a binary solid selectively interacting with a fluid. The chemical energy barrier is considered, however, uncoupled from stress, and the mobility quadratically dependent on the gradient of composition. Under initial enforced sinusoidal perturbations, results of simulations showed that the compositional strain parameter can dramatically alter the effect of the chemical energy barrier on the critical wavelength of perturbations that trigger interface instability.