bluuebunny/crossref_metadata_2025 huggingface dataset:
Adhesion of Immature and Mature T Cells Induces inHuman Thymic Epithelial Cells (TEC) Activation of IL‐6Gene Trascription Factors (NF‐κB And NF‐IL6) and IL‐6Gene Expression: Role of αtβ1 and α6β4 Integrins
Authors: Fiorini Emma , Marchisio Pier Carlo , Scupoli Maria Teresa , Poffe Ornella , Tagliabue Elda , Brentegani Monica , Colombatti Marco , Santini Franscesco , Tridente Giuseppe , Ramarli Dunia
Published: June 2008

T cell precursors homed to thymus develop in close contact with stromal cells. Among them,
thymic epithelial cells (TEC) are known to exert dominant roles in their survival and functional
shaping. Key molecules mediating TEC/thymocytes interactions include cytokines and
growth factors secreted by the two cell types and adhesion receptors mediating cell contact.
Signaling events triggered in thymocytes by adhesion to epithelial cells have been extensively
investigated, whereas little is known on the opposite phenomenon. We have previously investigated
this issue in a co‐culture system composed of TEC cultures derived from human normal
thymus and heterologous thymocytes. We demonstrated that thymocytes adhere to TEC
involving β1 and β4 integrins and induce the clustering of (α3β1 and α6β4 heterodimers at the
TEC surface. In addition thymocyte adhesion was followed by activation of NF‐κB and
NF‐IL6 gene transciption factors and enhanced IL‐6 production. The two latter phenomena
were reproduced by the cross‐linking of the α3, α6, β1 and β4 integrins, thus implying that
the α3β1 and α6β4 heterodimers can signal during thymocyte adhesion. We have extended
our previous work investigating in the same experimental setting the inducing activity of non
stimulated or activated policlonal or clonal mature T cells as representative of the more
mature thymocyte subset. We found that adhesion of unstimulated T cell i) involved β1, but
not β4 integrin functions at the surface ii) induced the clustering of α3β1 , but not α2β1 heterodimers
at the TEC surface and iii) up‐regulated the nuclear binding activity of NF‐κB transcription
factor and the IL‐6 secretion. We propose that α3β1 and α6β4 heterodimers are
induced to cluster at the TEC surface recognizing yet unknown cellular ligands differentially
expressed during T cell development.
Expression of T‐Cell Receptor β‐Chain mRNA and Proteinin γ/δ T‐Cells from Euthymic and Athymic Rats:Implications for T‐Cell Lineage Divergence
Authors: Bischof Astrid , Park Jung-Hyun , Hünig Thomas
Published: June 2008

The relationship between α/β and γ/δ T‐cell lineages was studied in rats using RT‐PCR analysis
of TCRβ transcripts in γ/δ T‐cell hybridomas and an intracellular staining technique to
detect TCRβ protein in primary γ/δ T‐cells. We report the presence of functional TCRβ transcripts
in 2/9 γ/δ T‐cell hybridomas. About 15 % of peripheral γ/δ T‐cells and thymocytes also
express TCRβ protein, giving a minimum estimate for successful Tcrb rearrangement based
on exvivo single cell analysis. In athymic rats, γ/δ T‐cells expressing intracellular β protein
are present but at a lower frequency than in euthymic controls, suggesting that in the thymus,
more γ/δ T‐cell precursors pass through a stage where functional β rearrangement has
occurred than in extrathymic sites. Analysis of TCR expression in purified transitory immature
CD4-8+ (iCD8SP) thymocytes and their spontaneously developing CD4+8+ (DP) progeny
showed that TCRγ mRNA is expressed in iCD8SP cells but not in their immediate DP
progeny that reinitiate RAG‐1 transcription and commence α/βTCR expression. We conclude
that rat γ/δ T cells can separate from the α/β lineage after TCRβ expression, but not after
entry into the DP compartment.
Modulation of Leukocyte Behavior by an InflamedExtracellular Matrix
Authors: Schor Hagai , Vaday Gayle G. , Lider Ofer
Published: June 2008

Inflammation is a response of the immune system to foreign insult or physical damage. Various
cellular and humoral components of the immune system are recruited from the vascular
system and are translocated through endothelium, and into extracellular matrix (ECM) compartments
of inflamed tissues. This translocation is orchestrated by various types of accessory
signals, in the form of soluble or complexed molecules, which evoke remarkable transitions
in leukocyte activities. Recruited inflammatory cells give rise to mechanisms of migration,
including the secretion of enzymes and other pro‐inflammatory mediators and the alteration
of their adhesive contacts with the ECM. Hence, migrating cells secrete enzymes, chemokines,
and cytokines which interact with the ECM, and thereby, provide the cells with intrinsic
signals for coordinating their responses. Resultant products of enzymatic modifications to the
ECM microenvironment, such as cytokine‐ and ECM‐derived molecules, may be also part of
a cell‐signaling mechanism that provides leukocytes with information about the nature of
their inflammatory activity; such a mechanism may give the immune system data that can be
cognitively interpreted for consequential activities. This article reviews the findings that support
this notion and describe the dynamic interactions between participants of the inflammatory
processes.
Maturation of Lymphocyte Immunophenotypes and Memory T Helper Cell Differentiation During Development in Mice
Authors: Fagoaga Omar R. , Yellon Steven. M. , Nehlsen-Cannarella Sandra. L.
Published: June 2008

The goal of this study was to systematically investigate the ontogeny of lymphoid populations
throughout postnatal development. In CD‐1 mice, peak lymphocyte numbers occurred in
blood on postnatal day 10 (dl0) including those for natural killers (NK1.1), B cells (CD19), T
helper (CD3CD4), naïve T helper (CD4CD62LposCD44low), memory T helper
(CD4CD62LnegCD44high), and T cytotoxic (CD3CD8) cells. As percent of total lymphocytes,
peaks were achieved by d10 for all T helper subtypes but not B cells which declined
to a nadir. In spleen, lymphocyte numbers increased exponentially after d10. Proportionately,
NK and T cells peaked on d10, declined by d20, and increased 2–3‐fold by d45. Naive T cells
constituted the majority of lymphocytes during development while memory cells gained to
2.2% (blood) and 12 % (spleen) by d20. C57BL/6 mice had similar profiles except that the B
cell nadir and T cell subset peaks were at d5. Peripheralization of critical numbers of lymphocytes
by d10, and importantly, development of a repertoire of memory cells by d20, may
define immune response capabilities that close the period of immaturity for the neonate.
T Cell Migration in Three‐dimensional ExtracellularMatrix: Guidance by Polarity and Sensations
Authors: Friedl Peter , Bröker Eva-Bettina
Published: June 2008

The locomotion of T lymphocytes within 3‐D extracellular matrix (ECM) is a highly dynamic
and flexible process following the principles of ameboid movement. Ameboid motility is
characterized by a polarized yet simple cell shape allowing high speed, rapid directional
oscillations, and low affinity interactions to the substrate that are coupled to a low degree of
cytoskeletal organization lacking discrete focal contacts. At the onset of T cell migration, a
default program, here described as migration‐associated polarization, is initiated, resulting in
the polar redistribution of cell surface receptors and cytoskeletal elements. Polarization
involves protein cycling either to the leading edge (i.e. LFA‐1, CD45RO, chemokine receptors,
focal adhesion kinase), to a central polarizing compartment (MTOC, PKC, MARCKS),
or into the uropod (CD44, CD43, ICAM‐ and –3, β1 integrins). The function of such compartment
formation may be important in chemotactic response, scanning of encountered cells,
and a flexible and adaptive interaction with the ECM itself. Due to the simple shape and a diffusely
organized cytoskeleton, the interactions to the surrounding extracellular matrix are
rapid and reversible and appear to allow a broad spectrum of molecular migration strategies.
These range from (1) adhesive and haptokinetic following i.e. chemokine‐induced motility
across 2‐D surfaces to (2) largely integrin‐independent migration predominantly guided by
shape change and morphological flexibility, as seen in 3‐D type I collagen matrices. Their
prominent capacity to rapidly adapt to a given structural environment coupled to contact
guidance mechanisms set T cell locomotion apart from slow, focal contact‐dependent and
more adhesive migration strategies established by fibroblast‐like cells and cell clusters. It is
therefore likely that, within the tissues, besides chemotactic or haptotactic gradients, the preformed
matrix structure has an important impact on T cell trafficking and positioning in
health and disease.
Cell Polarization: A Comparative Cell Biologyand Immunological View
Authors: Vicente-Manzanares Miguel , Sánchez-Madrid Francisco
Published: June 2008

Cell polarization and the establishment of functionally specialized domains play a pivotal role
in many cellular processes such as vectorial transport of molecules, cell division and differentiation,
directional movement of the cells in a chemotactic gradient and activation of the
immune response. Cell polarization is a complex phenomenon, in which the interplay among
cell cytoskeletal components, extra‐ and intracellular signals and organelle and membrane
reorganization is crucial to achieve a correct cell shape change. The intracellular machinery
needed for cell polarization has been elucidated in several well‐established models, including
yeast, epithelial, neuronal and germ‐line cells. Cells of the immune system also polarize in
response to extracellular cues, but many of the intracellular signals that control cell polarization
and the role of genes with a well‐defined function in other polarization processes are still
unknown. In this review, recent advances in the study of leukocyte polarization are examined
highlighting the similarities and differences with other models of cell polarization. The extracellular
signals which direct cell polarization, the signal transduction pathways involved as
well as the role of cell polarization in the development of the immune response are discussed.
Cell Migration in the Immune System: the EvolvingInter‐Related Roles of Adhesion Molecules andProteinases
Authors: Madri Joseph A. , Graesser Donnasue
Published: June 2008

Leukocyte extravasation into perivascular tissue during inflammation and lymphocyte homing
to lymphoid organs involve transient adhesion to the vessel endothelium, followed by transmigration
through the endothelial cell (EC) layer and establishment of residency at the tissue site
for a period of time. In these processes, leukocytes undergo multiple attachments to, and detachments
from, the vessel‐lining endothelial cells, prior to transendothelial cell migration. Transmigrating
leukocytes must traverse a subendothelial basement membrane en route to perivascular
tissues and utilize enzymes known as matrix metalloproteinases to make selective clips in the
extracellular matrix components of the basement membrane. This review will focus on the evidence
for a link between adhesion of leukocytes to endothelial cells, the induction of matrix
metalloproteinases mediated by engagement of adhesion receptors on leukocytes, and the ability
to utilize these matrix metalloproteinases to facilitate leukocyte invasion of tissues. Leukocytes
with invasive phenotypes express high levels of MMPs, and expression of MMPs
enhances the migratory and invasive properties of these cells. Furthermore, MMPs may be used
by lymphocytes to proteolytically cleave molecules such as adhesion receptors and membrane
bound cytokines, increasing their efficiency in the immune response. Engagement of leukocyte
adhesion receptors may modulate adhesive (modulation of integrin affinities and expression),
synthetic (proteinase induction and activation), and surface organization (clustering of proteolyric
complexes) behaviors of invasive leukocytes. Elucidation of these pathways will lead to
better understanding of controlling mechanisms in order to develop rational therapeutic
approaches in the areas of inflammation and autoimmunity.
Aberrant Development of Thymocytesin Mice Lacking Laminin‐2
Authors: Magner William J. , Chang Andrew C. , Owens Jennie , Hong M-J. P. , Brooks Andrew , Coligan John E.
Published: June 2008

In previous in vitro studies, we proposed a role for the extracellular matrix component, laminin‐
2, and its integrin receptor, VLA‐6, in thymocyte development. The characterization of
two dystrophic mouse strains with different defects in laminin‐2 allowed us to examine this
proposal in vivo. Mice deficient in laminin‐2, dy/dy, show a significant reduction in thymus
size and number of thymocytes compared to normal littermates. These mice also exhibited
apparent alterations of thymic architecture. Examination of the CD4/CD8 populations in dy/dy
thymi showed large relative increases in the DN (CD4-CD8-) and SP (CD4+CD8-,
CD4-CD8+) populations and a significant decrease in the DP (CD4+CD8+) population. Further
examination of the DN population for CD44 and CD25 expression showed a remarkable
decrease in the more mature pre‐T cell populations. Analysis of apoptosis in situ, and by flow
cytometry, in dy/dy thymi revealed a significant increase in apoptotic DN thymocytes in the
capsule and subcapsular regions. Interestingly, thymocyte development appeared to proceed
normally in dystrophic mice expressing a mutant form of laminin‐2, dy2J, as well as, in fetal
and neonatal dy/dy mice. We propose that laminin‐2 plays an active role in thymocyte development
by delivering cell survival and differentiation signals at specific stages of development
in young adult mice.
Impact of the Stress on the Sub‐Micron N‐Metal Oxide Semiconductor Field Effect Transistor Characteristics
Authors: Marrakh R. , Bouhdada A.
Published: June 2008

In this paper, we present a drain current model for stressed short‐channel MOSFET′s.
Stress conditions are chosen so that the interface states generated by hot‐carriers are
dominant. The defects generated during stress time are simulated by a spatio‐temporal
gaussian distribution. The parasitic source and drain resistances are included. We also
investigate the impact of the interface charge density, generated during stress, on the
transconductance. Simulation results show a significant degradation of the drain
current versus stress time.
The Effect of Antigen Stimulation on the Migrationof Mature T Cells from the Peripheral Lymphoid Tissuesto the Thymus
Authors: Hardy Charles L. , Godfrey Dale I. , Scollay Roland
Published: June 2008

Although the maturation and export of T cells from the thymus has been extensively studied,
the movement of cells in the opposite direction has been less well documented. In particular,
the question of whether T cells which have been activated by antigen in the periphery are
more likely to return to the thymus had been raised but not clearly answered. We examined
this issue by activating T cells present in the periphery with their cognate antigen, and assessing migration to the thymus. TCR‐transgenic cells from OT‐I mice (Thy1.2+), which recognise the ovalbumin peptide OVA257–264 in the context of H‐2Kb, were transferred into otherwise unmanipulated Thy1.1+ C57BL/6 mice. Recipient mice were injected i.v. with 5 μg
peptide (SIINFEKL) approximately 24 hours later. The numbers of donor‐derived (Thy1.2+)
cells in the thymus and peripheral lymphoid tissue were determined. The results clearly show
increased numbers of transgenic cells in the thymus 3 days after antigenic stimulation. However,
since numbers of transgenic cells increased in the spleen and LN in about the same proportion,
the data do not support the notion that there is highly increased selective migration of
activated T cells to the thymus. Rather, they suggest that a sample of peripheral cells enters
the thymus each day, and that the mature immigrants detected in the thymus merely reflect the
contents of the peripheral T cell pool.
A Simple Binary Run‐Length Compression Technique for Non‐Binary SourcesBased on Source Mapping
Authors: Jaradat Abdel-Rahman , Irshid Mansour I.
Published: June 2008

In this paper, we propose a very simple and efficient binary run‐length compression
technique for non‐binary sources. The technique is based on mapping the non‐binary
information source into an equivalent binary source using a new fixed‐length code
instead of the ASCII code. The codes are chosen such that the probability of one of
the two binary symbols; say zero, at the output of the mapper is made as small as
possible. Moreover, the “all ones” code is excluded from the code assignments table
to ensure the presence of at least one “zero” in each of the output codewords.
Compression is achieved by encoding the number of “ones” between two consecutive
“zeros” using either a fixed‐length code or a variable‐length code. When applying this
simple encoding technique to English text files, we achieve a compression of
5.44bits/character and 4.6bits/character for the fixed‐length code and the variablelength
(Huffman) code, respectively.
Active‐Only Sinusoidal Oscillator with Electronically‐TunableFully‐Uncoupled Frequency and Condition of Oscillation
Authors: Abuelmaatti Muhammad Taher
Published: June 2008

A new active‐only sinusoidal oscillator is presented. The oscillator circuit uses two
internally compensated operational amplifiers, two plus‐type second‐generation
current conveyors and three operational transconductance amplifiers. The proposed
circuit enjoys the attractive features of totally uncoupled frequency and condition of
oscillation, low sensitivities, electronic tunability and integratability.
Role of Bruton′s Tyrosine Kinase in B Cell Development
Authors: Maas Alex , Hendriks Rudolf W.
Published: June 2008

X‐linked agammaglobulinemia (XLA) is one of the most frequent inherited immunodeficiency
diseases in man and is characterized by an almost complete arrest of B cell differentiation
at the pre‐B cell stage. The gene defective in XLA encodes the cytoplasmic signaling
molecule Bruton′s tyrosine kinase (Btk). Next to the CBA/N strain of mice, carrying a single
amino acid substitution mutation in the Btk gene, which results in the X‐linked immunodeficiency
(xid) phenotype, additional mouse models have been developed to study the role of
Btk invivo. This review discusses the analyses of Btk null‐mutants, obtained by gene targeting
in embryonic stem cells, and transgenic mice that express wild‐type or mutated forms of
the Btk gene. These studies provided information on the function of Btk at several important
checkpoints throughout B cell development. Analyses of the mouse models indicated that Btk
is not essential for pre‐B cell receptor signaling in the mouse. By contrast, Btk‐mediated B
cell receptor signaling appears to be required for the survival of immature B cells in the bone
marrow, that have performed a successful immunoglobulin (Ig) L chain locus rearrangement,
resultirig in the expression of a non‐autoreactive Ig on the membrane. Btk is also shown to be
involved in signaling pathways that govern the development of peripheral B cells, including
follicular entry, follicular maturation and plasma cell differentiation.
Close Vicinity of PrP Expressing Cells (FDC) withNoradrenergic Fibers in Healthy Sheep Spleen
Authors: Bencsik A. , Lezmi S. , Hunsmann G. , Baron T.
Published: June 2008

In naturally and experimentally occurring scrapie in sheep, prions invade the immune system
and replicate in lymphoid organs. Here we analysed immunohistochemically, in seven spleens
of 6‐month‐old healthy sheep, the nature of the cells expressing prion protein (PrP) potentially
supporting prion replication, as well as their relationship with autonomic innervation.
PrP was identified using either RB1 rabbit antiserum or 4F2 monoclonal antibody directed
against AA 108–123 portion of the bovine and AA 79–92 of human prion protein respectively.
Using double labelling analysis, we demonstrated that PrPc is expressed by follicular
dendritic cells using a specific monoclonal antibody (CNA42). We also showed the close
vicinity of these PrP expressing cells with noradrenergic fibers, using a polyclonal tyrosine
hydroxylase antibody. Our results may help the study of the cellular requirements for the possible
neuroinvasion from the spleen.
A Monte‐Carlo Approach for the Estimation of Average Transition Probabilitiesin Sequential Logic Circuits
Authors: Stamoulis Georgios I.
Published: June 2008

This paper presents an efficient and accurate Monte‐Carlo approach to the problem of
estimating average node switching probabilities in sequential circuits, which are used in
average power estimation and reliability analysis of these circuits. Specific error bounds
for the proposed estimation method are given at a certain level of confidence. This
method is based on the analysis of paths in the State Transition Graph (STG) of the
circuit and is validated by both theoretical analysis as well as experimental results.
Influence of Asymmetric Pulses in Spread Spectrum Systems
Authors: Papavasileiou A. P. , Capsalis C. N.
Published: June 2008

This paper examines the impact of asymmetric pulses in NRZ waveforms generated by
maximum‐length sequences and used in spread spectrum systems. The data asymmetry
phenomenon is produced by differential propagation delays through logic circuits in the
payloads. A model of three elementary pulse shapes is employed to characterize the
signal source and the occurrence probabilities for each is calculated. The autocorrelation
function of the waveform is eventually obtained taking into account the asymmetry, and
some numerical evaluations are finally presented to show the deviation from the
theoretic case where no asymmetry is considered.
Evidence for Distinct Mechanisms in the Shapingof the CD4 T Cell Repertoire in Histologically DistinctMyasthenia Gravis – Associated Thymomas
Authors: Ströbel P. , Helmreich M. , Kalbacher H. , Müller-Hermelink H. K. , Marx A.
Published: June 2008

The major histocompatibility complex (MHC) class II is involved both in thymocyte maturation
and peptide presentation and might thus play a key role in the pathogenesis of paraneoplastic
myasthenia gravis (MG) in thymomas. To further investigate this issue, we analyzed
and scored the expression of epithelial class II expression in 35 thymomas (medullary, MDT;
mixed, MXT; cortical and well differentiated thymic carcinoma, CT / WDTC) and correlated
it with the histological tumor subtype, prevalence of MG and thymocyte maturation, which
was analyzed by flow cytometry and RT‐PCR. Our results show that both MHC class II
expression and thymocyte maturation are highly dependent on the histological tumor subtype.
CT / WDTC retain features of the normal outer thymic cortex, namely substantial MHC class
II expression together with normal early thymocyte maturation until late phases of positive
selection, but disturbed terminal thymopoiesis. By contrast, MDT and MXT retain features of
the normal inner cortex and the medulla with low to absent class II expression and highly
abnormal early thymocyte maturation including impaired positive selection, while terminal T
cell maturation in MXT appeared undisturbed. There was no correlation between MHC class
II expression and MG status for a given tumor subtype. In conclusion, our results provide evidence
for a different histogenesis of cortical thymomas and well differentiated carcinomas on
the one hand and mixed and medullary thymomas on the other.

Decreased expression levels of MHC class II, although of crucial importance for abnormal
intratumorous maturation, are not sufficient to explain the emergence of paraneoplastic MG.
An Accurate Method for Extracting the Critical Field in Short Channel NMOS Devices
Authors: Amhouche Y. , El Abbassi A. , Raïs K. , Rmaily R.
Published: June 2008

In this letter, an accurate method for extracting the critical field Ec in short channel
MOSFET′s is presented. The principle of this method is based on the comparison
between two models which give drain saturation voltage evolution against gate
voltage Vdsat(Vg) continuously. The results obtained by this technique have shown
better agreement with measurements data and have allow in the same time to
determine the validity domain of Sodini′s law [1].
Degradation of Junction Parameters of an ElectricallyStressed NPN Bipolar Transistor
Authors: Toufik N. , Pélanchon F. , Mialhe P.
Published: June 2008

The effect of an electrical ageing on npn bipolar transistor has been studied. The current
gain decreases substantially and the electrical properties are discussed. The emitter‐base
junction parameters are degraded during the electrical stress experiments. Both the
amplitude and the rate of this degradation depend on the stress duration. The
evaluation of these parameters allows to discuss hot carrier degradation process, to
estimate the stress magnitude and to control the device.
Characterization of Defect Traps in SiO2 Thin Films
Authors: Rosaye Jean-Yves , Mialhe Pierre , Charles Jean-Pierre , Sakashita Mitsuo , Ikeda Hiroya , Sakai Akira , Zaima Shigeaki , Yasuda Yukio
Published: June 2008

In order to understand the degradation of the electrical operations of metal‐oxide‐semiconductor
(MOS) devices, this work is concerned by the defects generation processes in the non‐stoichiometric SiOx, area and at the SiO2 interface. For this purpose, a new measurement technique to study slow‐state traps and their relationship with fast‐state traps is developed. This method considers capacitance‐voltage
measurements and temperature effects during the hysteresis cycle.
Utilization of the Thermoelectric Sensor to Realize a New Fluid Level Detector
Authors: Hachami K. , Moussaid D. , Rahmoun M. , Bendada E.
Published: June 2008

This paper describes a prototype thermoelectric sensor system which makes use of the
thermoelectrical effects. The sensor includes two printed circuits, the first is
constituted of a resistive constantan track, the second is a planar thermoelectric
circuit constituted of many plated differential thermocouples. The first circuit is placed
at the top of the second circuit so that the resistive tack is placed on the top of the
even thermocouple junctions. The measuring method consists to passing an electrical
current through the constantan track in order to generate temperature gradients
between the junction points of the second circuit. Then the resulting temperature
differences between the junction points is directly converted into a proportional
Seebeck voltage. As an application, the sensor is placed into a reservoir and adapted
in order to realize a fluid level detector.
Downregulated Expression of Ly‐6‐ThB on DevelopingT Cells Marks CD4+CD8+ Subset Undergoing Selectionin the Thymus
Authors: Reese Justin T. , Mehta Hitesh , Chappell Clay H. , Bamezai Anil.
Published: June 2008

Interaction of TCRs on CD4+CD8+ immature T cell with MHC‐peptide complexes on stromal
cells is required for positive and negative selection in the thymus. Identification and characterization
of a subpopulation of CD4+CD8+ thymocytes undergoing selection in the thymus
will aid in understanding the mechanisms underlying lineage commitment and thymic selection.
Herein, we describe the expression of Ly‐6 ThB on developing thymocytes. The majority
of CD4+CD8+ thymocytes express Ly‐6 ThB at high levels. Its expression is
downregulated in a subset of CD4+CD8+ thymocytes as well as in mature CD4+CD8- and
CD4-CD8+ T cells. More importantly, interaction of TCR/coreceptor with the self‐MHC‐peptide
contributes to the downregulation of ThB expression on developing thymocytes. These
findings indicate that downregulation of ThB on CD4+CD8+ thymocytes identifies a unique subset (CD4+CD8+ThBneg–low) of thymocytes that has received the initial signals for thymic
selection but have not yet downregulated the CD4 and CD8 cell surface expression. In addition,
these results also indicate that a high frequency (Ÿ20–40%) of CD4+CD8+ immature
thymocytes receive these initial signals during thymic selection.
Analysis of Temperature and Drain Voltage Dependence of Substrate Current in Deep SubmicrometerMOSFET′S
Authors: Amhouche Y. , El Abbassi A. , Raïs K. , Rmaily R.
Published: June 2008

In this paper, a detailed experimental study of channel length, drain voltage and
temperature dependence of substrate current Isub in submicrometer MOSFET′s is presented. Impact ionization rate α is remarkably increased with decreasing channel
length L and go up from 10-7 to 6, 7  ·  10−7 when L decrease from 2 to 0.1 μm, this
behaviour found expression in a fast increase of the substrate current maximum
Isubmax⁡. Moreover it is observed that contrarily of long channels, low temperature
operation is favourable to reduce hot carrier effects in submicrometer MOSFET′s and
may represent a promising alternative for the improvement of the performances of Si
integrated circuits.
Development of Dendritic Cells from GM‐CSF-/-Mice invitro: GM‐CSF Enhances Productionand Survival of Cells
Authors: Ni Keping , O′Neill Helen C.
Published: June 2008

The production of dendritic cells (DC) from haemopoietic progenitors maintained in long
term stroma‐dependent cultures (LTC) of spleen or bone marrow (BM) occurs independently
of added granulocyte/macrophage colony stimulating factor (GM‐CSF). The possibility that
cultures depend on endogenous GM‐CSF produced in low levels was tested by attempting to
generate LTC from spleen and BM of GM‐CSF-/- mice. Multiple cultures from GM‐CSF-/-
and wild type mice were established and compared for cell production. GM‐CSF-/- LTC
developed more slowly, but by 16 weeks produced cells resembling DC in numbers comparable
to wild type cultures. LTC maintained distinct populations of small and large cells, the latter
resembling DC. Cells collected from GM‐CSF-/- LTC were capable antigen presenting
cells (APC) for T cell stimulation and morphologically resembled DC. Large cells expressed
the CD11b, CD11c, CD86, 33D1 and Dec‐205 markers of DC. Addition of GM‐CSF to
GM‐CSF-/- LTC increased the proportion of large, mature DC present in culture. Stromal cells
from GM‐CSF-/- LTC could support the differentiation of DC from early progenitors maintained
in LTC without addition of GM‐CSF. However, GM‐CSF is not a critical factor in the invitro generation of DC from progenitors. It can, however, substitute for stromal cells in
increasing the survival of mature DC.
Active‐Only Sinusoidal Oscillator Circuits
Authors: Abuelmaatti Muhammad Taher , Al-Qahtani Muhammad Ali
Published: June 2008

Two new active‐only sinusoidal oscillator circuits are proposed. The first circuit uses one
current feedback operational amplifier (CFOA) and four operational transconductance
amplifiers (OTAs). The second circuit uses only four OTAs. Without using any external
passive elements, voltage (or current) control of the frequency and condition of
oscillation, of the two circuits, can be achieved by adjusting the bias currents of the
OTAs. The proposed circuits enjoy low sensitivities.
Some Investigations on the Anisotropy of the Chemical Etching of (h k 0) and (h h l) SiliconPlates in a NaOH 35% Solution. Part II: 3D Etching Shapes, Analysis and Comparison with KOH 56%
Authors: Tellier C. R. , Hodebourg C. A. , Durand S.
Published: June 2008

This paper deals with the micromachining of various (h k 0) and (h h l) membrane–mesa
structures in a NaOH 35% solution. Final etching shapes of micromachined structures
show a marked anisotropy of type 1. Etching shapes are analysed in terms of the
kinematic and tensorial model for the anisotropic dissolution of crystals. Some of
crystallographic planes limiting membranes and mesa are identified from a
stereographic analysis of top contours. Conclusions of this study are in close
agreement with a previous work.
Characterization of Series Resistances and Mobility Attenuation Phenomena in Short Channel MOS Transistors
Authors: El Abbassi A. , Amhouche Y. , Bendada E. , Rmaily R. , Raïs K.
Published: June 2008

As the scaling proceeds, the transverse electric field increase, and a mobility attenuation
phenomenon becomes of primordial interest. Indeed, the high transverse electric field is
generally ascribed [1] to surface roughness scattering in the channel and consequently
reduce effective mobility of carriers. In short channel MOSFET, the Source‐Drain
resistance Rsd influence strongly the effective mobility.

The aim of this work is therefore to propose an original method especially conceived
for the extraction of the series resistance Rsd. Using the approach of the Surface
Roughness Scattering which enables a consistent modelling of the mobility to be
obtained from low to high electric field [2], this allow to determine all model parameters
in particular a Series Resistance from the plot of the transfer characteristic drain current
Idversus gate voltage Vg Curves.
Induction of Germinal Centers by MMTV EncodedSuperantigen on B Cells
Authors: Simmons W. J. , Simms M. , Chiarle R. , Mackay F. , Tsiagbe V. K. , Browning J. , Inghirami G. , Thorbecke G. J.
Published: June 2008

It has not been established whether an endogenous superantigen (SAg) expressed on B cells
can induce germinal centers (GCs). An interesting model is that of mammary tumor virus
encoded viral SAgs, which induce vigorous T cell proliferation and are predominantly
expressed on activated B cells. We have used this model to analyze the possibility that direct
stimulation of Mtv7+ DBA/2 B cells by vSAg‐responsive (Vβ6+) BALB/c T cells can give
rise to GCs. Injection of BALB/c SCID mice iv with 2 × 106 DBA/2 B cells, together with
LPS, followed by 2 × 106 BALB/c T cells induces numerous large splenic GCs within 3–5
days. The GCs are still large on day 7, but are very much reduced by day 10. B cell activation
with LPS is needed for this effect. These GCs form in spite of the apparent absence of follicular
dendritic cells (FDCs) as judged by staining for several FDC surface markers. Control
mice receiving either BALB/c T or DBA/2 B cells + LPS alone or DBA/2 T + B cells + LPS
fail to exhibit any GCs on days 3–7. Numerous small clusters of PNA+ cells, but few large
GCs are observed when TNF‐R(p55)‐Ig is also injected, whereas LTβR‐Ig treatment impeded
the formation of aggregations of these cells even further, leaving scattered PNA+ single cells
and very small clumps throughout the white pulp of the spleens. Anti‐TNFα had no effect.
These results suggest that endogenous vSAg mediated GC formation is independent of antigen
trapping by FDCs.
Some Investigations on the Anisotropy of the Chemical Etching of (hk0) and (hhl) Silicon Plates in a NaOH 35% Solution. Part I: 2D Etching Shapes
Authors: Hodebourg C. A. , Tellier C. R.
Published: June 2008

In this paper a study of the anisotropic dissolution of (hk0) and (hhl) silicon plates in
a NaOH 35% solution is undertaken. Effects of orientation on firstly, the geometrical
features of etched surfaces and secondly, on the cross‐sectional shape of starting circular
plates are systematically investigated. Conclusions of practical interest on the roughness
of etched (hk0) and (hhl) planes are drawn. 2D etching shapes are then analysed in terms
of the tensorial model for the anisotropic dissolution and of dissolution criteria. Finally
a comparative analysis of results related on the one hand, to 2D surface profiles and
on the other, to out‐of‐roundness profiles is made. This comparison shows that shapes
observed for profilometry traces agree with theoretical shapes as derived when we use
the resemblance in shapes between out‐of‐roundness profiles and polar diagrams of the
dissolution slowness.
Computation of Conductance and Capacitance for IC Interconnects on a GeneralLossy Multilayer Substrate
Authors: Ymeri H. , Nauwelaers B. , Maex Karen
Published: June 2008

In this paper a simple method for analysis and modelling of transmission interconnect lines
on general lossy multilayer substrates at high bit rates is presented. The analysis is based
on semi‐analytical Green′s function approach and recurrence relation between the
coefficients of potential in n and n + 1 layers, respectively. The electromagnetic concept of
free charge density is applied. It allows us to obtain integral equations between electric
scalar potential and charge density distributions. These equations are solved by the
Galerkin procedure of the Method of Moments. New approach is especially adequate to
model 2‐D layered structures with planar boundaries for frequencies up to 20GHz
(quasistationary field approach). The transmission line parameters (capacitance and
conductance per unit length) for the given interconnect multilayer geometry are computed.
A discussion of the calculated line admittance in terms of technological and geometrical
parameters of the structure is given. A comparison of the numerical results from the
new procedure with the techniques presented in the previous publications are provided,
too.
Characterization of the Rapid Proteolytic Shedding of Murine L‐Selectin
Authors: Zhao Li-Chao , Edgar John B. , Dailey Morris O.
Published: June 2008

The structural requirements for L‐selectin shedding were studied in murine leukocytes. Upon
activation, L‐selectin on both lymphocytes and neutrophils undergoes cleavage by a membrane
metalloprotease, resulting in the generation of a soluble ectodomain and a membrane‐
retained 6 kD fragment. Radiochemical sequencing demonstrated a cleavage site in the
membrane‐proximal region (MPR) between R321 and S322, which is homologous to the
human site. Although intact neutrophil L‐selectin is larger, it is cleaved at the same, or very
close, site. Analysis of several transfectants expressing L‐selectin point mutations and chimeric
constructs suggest that, like human shedding, the proteolytic process has relatively
loose sequence specificity for the substrate site. In addition, some constructs are susceptible
to slow constitutive cleavage, but their shedding does not increase upon PMA stimulation,
showing that basal and activated shedding are separable processes. Insertion of the 15 amino
acid MPR into murine B7.2 conferred upon this molecule susceptibility to constitutive shedding.
PMA stimulation results in little or no acceleration of down regulation of this molecule.
These results suggest that recognition of both the membrane‐proximal cleavage site and of a
site distant from the MPR are required for maximal induction of L‐selectin shedding.
New Method for Determination of Drain Saturation Voltage in Short Channel MOS DevicesBetween Liquid Helium to Room Temperature
Authors: Amhouche Y. , El Abbassi A. , Raïs K. , Bendada E. , Rmaily R.
Published: June 2008

A new method for drain saturation voltage extraction in submicron MOSFETs is
presented. It is based on measurements of the partial derivative of the impact ionization
rate. The method has been tested using main of channel length MOSFET devices and
compared with others methods.
Studies on Prion Replication in Spleen
Authors: Raeber Alex J. , Montrasio Fabio , Hegyi Ivan , Frigg Rico , Klein Michael A. , Aguzzi Adriano , Weissmann Charles
Published: June 2008

Some of the early events following scrapie infection take place in the lymphoreticular system
(LRS) and result in significant replication of prions in lymphoid organs. The identity of the
cells in the LRS that produce prions and their role in neuroinvasion are still unknown. We
find that in the spleen of scrapie‐infected mice, prions are associated with T and B cells and to
a somewhat lesser degree with the stroma, which contains the follicular dendritic cells
(FDC′s); curiously, no infectivity was found in lymphocytes from blood of the same mice.
Thus, splenic lymphocytes either replicate prions or acquire them from another source. Studies
on PrP knockout mice with ectopic expression of PrP restricted to only B or T lymphocytes
suggest that neither of these by themselves are competent for prion replication. To
determine whether B and T cells are able to pick up prions from other sources, irradiated
wild‐type mice were reconstituted with PrP‐deficient lymphohaematopoietic stem cells. Following
intraperitoneal inoculation of these mice, no infectivity was found on splenic lymphocytes
whereas the stroma (comprising the radiation‐resistant, PrP‐expressing FDC′s)
contained prions. These results imply that splenic lymphocytes can acquire prions, possibly
from FDC′s, but only if they express PrP.
Molecular Field Calculation of Magnetization on NdRh2Ge2 Single Crystal
Authors: Himori A. , Hattori K. , Shigeoka T.
Published: June 2008

Calculation of magnetization of the ternary single crystal compound NdRh2Ge2 has been carried out by using the wave‐like molecular field model to explain the complex magnetic behavior. The field‐induced magnetic structures having the propagation vectors, Q2 = (0, 0, 39/40), Q3 = (0, 0, 35/40), Q4 = (0, 0, 31/40), and Q5 = (0, 0, 0/40) (= the field‐induced ferromagnetic phase) were proposed. Calculation on the basis of these structures and the antiferromagnetic phase with Q1 = (0, 0, 1) well reproduces the experimental magnetization processes and H‐T magnetic phase diagram.
Accident Management in VVER-1000
Authors: D'Auria F. , Suslov A. , Muellner N. , Petrangeli G. , Cherubini M.
Published: June 2008

The present paper deals with the investigation study on accident management in VVER-1000 reactor type conducted in the framework of a European Commission funded project. The mentioned study involved both experimental and computational fields. The purpose of this paper is to summarize the main findings from the execution of a wide-range analysis focused on AM in VVER-1000 with main regard to the qualification of computational tools and the proposal for an optimal AM strategy for this kind of NPP.
Performance Analysis of Trench Power MOSFETs in High-Frequency Synchronous Buck Converter Applications
Authors: Xiong Yali , Cheng Xu , Wang Xiangcheng , Kumar Pavan , Guo Lina , Shen Z. John
Published: June 2008

This paper investigates the performance perspectives and theoretical limitations of trench power MOSFETs in synchronous rectifier buck converters operating in the MHz frequency range. Several trench MOSFET technologies are studied using a mixed-mode device/circuit modeling approach. Individual power loss contributions from the control and synchronous MOSFETs, and their dependence on switching frequency between 500 kHz and 5 MHz are discussed in detail. It is observed that the conduction loss contribution decreases from 40% to 4% while the switching loss contribution increases from 60% to 96% as the switching frequency increases from 500 KHz to 5 MHz. Beyond 1 MHz frequency there is no obvious benefit to increase the die size of either SyncFET or CtrlFET. The RDS(ON)×QG figure of merit (FOM) still correlates well to the overall converter efficiency in the MHz frequency range. The efficiency of the hard switching buck topology is limited to 80% at 2 MHz and 65% at 5 MHz even with the most advanced trench MOSFET technologies.
PECVD‐ONO: A New Deposited Firing Stable Rear Surface Passivation Layer System for Crystalline Silicon Solar Cells
Authors: Hofmann M. , Kambor S. , Schmidt C. , Grambole D. , Rentsch J. , Glunz S. W. , Preu R.
Published: June 2008

A novel plasma‐enhanced chemical vapour deposited (PECVD) stack layer system consisting of a‐SiOx:H, a‐SiNx:H, and a‐SiOx:H is presented for silicon solar cell rear side passivation. Surface recombination velocities below 60 cm/s (after firing) and below 30 cm/s (after forming gas anneal) were achieved. Solar cell precursors without front and rear metallisation showed implied open‐circuit voltages Voc values extracted from quasi‐steady‐state photoconductance (QSSPC) measurements above 680 mV. Fully finished solar cells with up to 20.0% energy conversion efficiency are presented. A fit of the cell′s internal quantum efficiency using software tool PC1D and a comparison to a full‐area aluminium‐back surface field (Al‐BSF) and thermal SiO2 is shown. PECVD‐ONO was found to be clearly superior to Al‐BSF. A separation of recombination at the metallised and the passivated area at the solar cell′s rear is presented using the equations of Fischer and Kray. Nuclear reaction analysis (NRA) has been used to evaluate the hydrogen depth profile of the passivation layer system at different
stages.
Large Area Silicon Carbide Vertical JFETs for 1200 V Cascode Switch Operation
Authors: Veliadis Victor , McNutt Ty , Snook Megan , Hearne Harold , Potyraj Paul , Junghans Jeremy , Scozzie Charles
Published: June 2008

SiC VJFETs are excellent candidates for reliable high-power/temperature switching as they only usepnjunctions in the active device area where the high-electric fields occur. VJFETs do not suffer from forward voltage degradation, exhibit excellent short-circuit performance, and operate at300°C. 0.19 cm21200 V normally-on and 0.15 cm2low-voltage normally-off VJFETs were fabricated. The 1200-V VJFET outputs 53 A with a forward drain voltage drop of 2 V and a specific onstate resistance of 5.4 mΩ cm2. The low-voltage VJFET outputs 28 A with a forward drain voltage drop of 3.3 V and a specific onstate resistance of 15 mΩ cm2. The 1200-V SiC VJFET was connected in the cascode configuration with two Si MOSFETs and with a low-voltage SiC VJFET to form normally-off power switches. At a forward drain voltage drop of 2.2 V, the SiC/MOSFETs cascode switch outputs 33 A. The all-SiC cascode switch outputs 24 A at a voltage drop of 4.7 V.
The Roles of Dietary PPARγ Ligands for Metastasis in Colorectal Cancer
Authors: Kuniyasu Hiroki
Published: June 2008

Dietary peroxisome proliferator‐activated receptor (PPAR)γ ligands, linoleic acid (LA) and conjugated linoleic acid (CLA), showed anticancer effects in colorectal carcinoma cells. LA is metabolized by two pathways. Cyclooxygenase (COX)‐2 produces procarcinogenic prostaglandin E2, whereas 15‐lipoxygenase (LOX)‐1 produces PPARγ ligands. The 15LOX‐1 pathway, which is dominant in colorectal adenomas, was downregulated and inversely COX‐2 was upregulated in colorectal cancer. LA and CLA inhibited peritoneal metastasis of colorectal cancer cells in nude mice. The inhibitory effect was abrogated by PPARγ antisense treatment. A continuous LA treatment provided cancer cells quiescence. These quiescent cells formed dormant nests in nude mice administrated LA. The quiescent and dormant cells showed downregulated PPARγ and upregulated nucleostemin. Thus, short‐term exposure to dietary PPARγ ligands inhibits cancer metastasis, whereas consistent exposure to LA provides quiescent/dormant status with possible induction of cancer stem and/or progenitor phenotype. The complicated roles of dietary PPARγ ligands are needed to examine further.
Application of Association Mapping to Understanding the Genetic Diversity of Plant Germplasm Resources
Authors: Abdurakhmonov Ibrokhim Y. , Abdukarimov Abdusattor
Published: June 2008

Compared to the conventional linkage mapping, linkage disequilibrium (LD)-mapping, using the nonrandom associations of loci in haplotypes, is a powerful high-resolution mapping tool for complex quantitative traits. The recent advances in the development of unbiased association mapping approaches for plant population with their successful applications in dissecting a number of simple to complex traits in many crop species demonstrate a flourish of the approach as a “powerful gene tagging” tool for crops in the plant genomics era of 21st century. The goal of this review is to provide nonexpert readers of crop breeding community with (1) the basic concept, merits, and simple description of existing methodologies for an association mapping with the recent improvements for plant populations, and (2) the details of some of pioneer and recent studies on association mapping in various crop species to demonstrate the feasibility, success, problems, and future perspectives of the efforts in plants. This should be helpful for interested readers of international plant research community as a guideline for the basic understanding, choosing the appropriate methods, and its application.