bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative morphological analysis of the root developmental groove with the palato‐gingival groove
Authors: Ennes JP , Lara VS
Published: November 2004

The palato‐gingival groove is an anomaly of shape that modifies dental tissues organization while the developmental root groove is described within normal root anatomy. The morphology of dental tissues in relation to the presence of the developmental root groove has not been properly described. This study analyzed microscopically the morphology of dental tissues related to the root developmental groove comparing it with that presented on teeth affected by palato‐gingival groove. Many similarities were observed such as the increased cementum thickness, decreased dentin thickness, pulp compartment surface alteration, irregularity of the dentin–cementum junction and of the cementum surface. These results suggest a common determining factor to this structure organization pattern. It is possible that the palato‐gingival groove could be the result of an alteration of genetic mechanisms, rather than a dental germ folding, determined by privation of space, as previously hypothesized.
Molecular evaluation of residual endodontic microorganisms after instrumentation, irrigation and medication with either calcium hydroxide or Septomixine
Authors: Tang G , Samaranayake LP , Yip H‐K
Published: November 2004

Background and objective:  The correct choice of antimicrobial agents as inter‐appointment medicaments is as important as the instrumentation and irrigation to remove pathogens from infected root canals. Calcium hydroxide [Ca(OH)2] and framycetin sulfate (Septomixine) are common endodontic medicaments. Therefore, we evaluated the efficacy of either calcium hydroxide or Septomixine in eliminating residual intra‐canal bacteria, particularly Actinomyces spp., during inter‐appointment interval in endodontic therapy using molecular methods.

Methods:  A total of 31 single‐rooted teeth with primary root canal infections were studied immediately after opening the canals and subsequently after instrumentation, irrigation with sterile saline and 1‐week medication with either Ca(OH)2 (n = 25) or Septomixine (n = 6). Whole bacterial genomic DNA was isolated directly from samples and PCR with universal primers performed to detect total intra‐canal bacteria. The variable regions of 16S rDNA of bacteria were amplified and labeled with digoxigenin for further hybridization to detect Actinomyces spp. A total of seven oligonucleotide probes specific for A. bovis, A. gerencseriae, A. israelii, A. meyeri, catalase‐negative A. naeslundii (genospecies 1 and 2), catalase‐positive A. naeslundii genospecies 2 and A. odontolyticus were used to detect Actinomyces spp. in 22 of 31 medicated root canals [Ca(OH)2: n = 17; Septomixine: n = 5].

Results:  The PCR results showed that 25 of 31 examined canals were positively detected with residual microorganisms after instrumentation, irrigation with sterile saline and 1‐week medication with either Ca(OH)2 (n = 20) or Septomixine (n = 5). Thus, only six canals [Ca(OH)2: n = 5, Septomixine: n = 1] were aseptic after treatment. Hybridization results showed higher detection frequency of both A. odontolyticus and A. gerencseriae after treatment. Significant correlation was found between exposed pulp before treatment and positive detection of Actinomyces spp., particularly A. odontolyticus on the second visit (P < 0.05).

Conclusion:  The conventional, 1‐week medication of either Ca(OH)2 or Septomixine in endodontic therapy may not effectively inhibit residual bacterial growth in all root canals during inter‐appointment intervals. Further investigations using, for instance quantitative real‐time PCR analyses, are required to substantiate the present findings.
Adverse oral reactions associated with the COX‐2 inhibitor rofecoxib
Authors: Bagán JV , Thongprasom K , Scully C
Published: November 2004

Rofecoxib is an inhibitor of the enzyme cyclo‐oxygenase 2 (COX‐2) used as an analgesic and anti‐inflammatory agent especially in rheumatoid arthritis and osteoarthritis. The adverse effects are generally less than with other anti‐inflammatory drugs (NSAIDs), and no oral adverse reactions have been reported in the literature.

We present three cases of oral lesions caused by rofecoxib. Extensive erosions appeared, which in all cases resolved on withdrawal of the drug.
The prevalence of oral leukoplakia in 138 patients with oral squamous cell carcinoma
Authors: Haya‐Fernández MªC , Bagán JV , Murillo‐Cortés J , Poveda‐Roda R , Calabuig C
Published: November 2004

Objectives:  To determine the relationship between oral leukoplakia (OL) and oral squamous cell carcinoma (OSCC), and to evaluate possible differences between those carcinomas with and without associated leukoplakia.

Material and methods:  A total of 138 patients were studied at the Stomatology Service of the University General Hospital, Valencia, Spain. These patients were divided into two groups: group 1, patients with oral cancer and leukoplakia, and group 2, patients with OSCC but with no associated premalignant lesions. The relationship between this precancerous lesion and the OSCC was evaluated, as well as the possible clinical and histological differences between the tumours of the two groups.

Results:  Leukoplakia was detected in 27 (19.56%) patients with OSCC. No differences were found between the two groups regarding age and tumour location. However, statistically significant differences were observed with respect to the form, tumour stage and the presence of adenopathies in the cancers with and without leukoplakia; in that the tumours associated with leukoplakia were diagnosed as being at a more initial stage.

Conclusions:  Those patients with OL associated with oral cancer presented with tumours at a less advanced stage than those where no associated leukoplakia existed.
T102C polymorphism of the 5‐HT2A receptor gene may be associated with temporomandibular dysfunction
Authors: Mutlu N , Erdal ME , Herken H , Oz G , Bayazıt YA
Published: November 2004

Objective:  To assess whether a relationship existed between the T102C polymorphism of 5‐HT2A receptor gene and temporomandibular dysfunction.

Methods:  Sixty‐three patients with temporomandibular dysfunction, and 54 healthy volunteer controls were included in the study. Molecular analysis of the T102C polymorphism of the 5‐HT2A receptor gene was performed using PCR technique.

Results:  The C/C genotype was over represented in the patients whereas T/T genotype was over represented in the controls (P < 0.05). The genotype distribution of the patients who had temporomandibular dysfunction was not different than those who did not have temporomandibular dysfunction (P > 0.05).

Conclusion:  The T102C polymorphism may be involved in the etiology of temporomandibular dysfunction. The overrepresentation of the C/C variant of 5‐HT2A receptor gene in temporomandibular dysfunction suggests a possible role of the serotonergic system in this disease, particularly at the receptor level.
Matrix metalloproteinases (MMPs) in oral diseases
Authors: Sorsa T , Tjäderhane L , Salo T
Published: November 2004

Matrix metalloproteinases (MMPs) are a group of enzymes that in concert are responsible for the degradation of most extracellular matrix proteins during organogenesis, growth and normal tissue turnover. The expression and activity of MMPs in adult tissues is normally quite low, but increases significantly in various pathological conditions that may lead into unwanted tissue destruction, such as inflammatory diseases, tumour growth and metastasis. MMPs have a marked role also in tissue destructive oral diseases. The role of collagenases, especially MMP‐8, in periodontitis and peri‐implantitis is the best‐known example of the unwanted tissue destruction related to increased presence and activity of MMPs at the site of disease, but evidence has been brought forward to indicate that MMPs may be involved also in other oral diseases, such as dental caries and oral cancer. This brief review describes some of the history, the current status and the future aspects of the work mainly of our research groups looking at the presence and activity of various MMPs in different oral diseases, as well as some of the MMP‐related aspects that may facilitate the development of new means of diagnosis and treatment of oral diseases.
Enfuvirtide: a new class of antiretroviral therapy for HIV infection
Authors: Leao JC , Frezzini C , Porter S
Published: November 2004

Enfuvirtide is the first of a new class of antiretroviral agents recently approved for the treatment of human immunodeficiency virus (HIV)‐1 infection. Present available data suggest that enfuvirtide may be a promising agent for the control of HIV infection in patients who have previously received reverse transcriptase inhibitor and protease inhibitor regimens and who are either intolerant to such drugs and/or who have gone into virological failure. Perhaps the greater limitation to the clinical use of enfuvirtide is the cost, limiting its use in the developing world.
MMP‐2 activation by Actinobacillus actinomycetemcomitans supernatant in human PDL cells was corresponded with reduction of TIMP‐2
Authors: Tiranathanagul S , Pattamapun K , Yongchaitrakul T , Pavasant P
Published: November 2004

Objective:  Matrix metalloproteinase 2 (MMP‐2) has been implicated to play a role in pathogenesis of periodontal disease. We recently reported that Porphyromonas gingivalis supernatant could activate MMP‐2 in human periodontal ligament (HPDL) cells. In this study, activation of MMP‐2 by Actinobacillus actinomycetemcomitans supernatant and the mechanism was investigated.

Methods:  HPDL cells were treated with either A. actinomycetemcomitans or P. gingivalis supernatant for 48 h. To verify the mechanism, pretreated inhibitors were used. Gelatin zymography, RT‐PCR and Western blot analysis were used to detect the activation of MMP‐2, expression of MT1‐MMP and TIMP‐2 mRNA and the proteins, respectively.

Results:  The supernatant from A. actinomycetemcomitans could activate MMP‐2 in HPDL cells similar to that from P. gingivalis but by a different mechanism. Activation by A. actinomycetemcomitans supernatant was correlated with a reduction of TIMP‐2 secretion without any alteration of MT1‐MMP, while activation by P. gingivalis increased MT1‐MMP but no change of TIMP‐2 was found.

Conclusion:  The supernatant from A. actinomycetemcomitans and P. gingivalis could induce the activation of MMP‐2 possibly through the imbalance of MT1‐MMP and TIMP‐2 in HPDL cells but by different mechanisms. The imbalance of MT1‐MMP and TIMP‐2 may be another factor that is involved in the severity of periodontal disease.
Neuronal mechanisms mediating the variability of somatosensory evoked potentials during sleep oscillations in cats
Authors: Rosanova Mario , Timofeev Igor
Published: November 2004

The slow oscillation (SO) generated within the corticothalamic system is composed of active and silent states. The studies of response variability during active versus silent network states within thalamocortical system of human and animals provided inconsistent results. To investigate this inconsistency, we used electrophysiological recordings from the main structures of the somatosensory system in anaesthetized cats. Stimulation of the median nerve (MN) elicited cortical responses during all phases of SO. Cortical responses to stimulation of the medial lemniscus (ML) were virtually absent during silent periods. At the ventral‐posterior lateral (VPL) level, ML stimuli elicited either EPSPs in isolation or EPSPs crowned by spikes, as a function of membrane potential. Response to MN stimuli elicited compound synaptic responses and spiked at any physiological level of membrane potential. The responses of dorsal column nuclei neurones to MN stimuli were of similar latency, but the latencies of antidromic responses to ML stimuli were variable. Thus, the variable conductance velocity of ascending prethalamic axons was the most likely cause of the barrages of synaptic events in VPL neurones mediating their firing at different level of the membrane potential. We conclude that the preserved ability of the somatosensory system to transmit the peripheral stimuli to the cerebral cortex during all the phases of sleep slow oscillation is based on the functional properties of the medial lemniscus and on the intrinsic properties of the thalamocortical cells. However the reduced firing ability of the cortical neurones during the silent state may contribute to impair sensory processing during sleep.
Recruitment of motor neuronal persistent inward currents shapes withdrawal reflexes in the frog
Authors: Perrier Jean‐François , Tresch Matthew C.
Published: November 2004

The details of behaviour are determined by the interplay of synaptic connectivity within neuronal circuitry and the intrinsic membrane properties of individual neurones. One particularly dramatic intrinsic property displayed by neurones in many regions of the nervous system is membrane potential bistability, in which transient excitation of a neurone results in a persistent depolarization outlasting the initial excitation. Here we characterize the contribution of such intrinsic bistability, also referred to as plateau properties and mediated by persistent inward currents (PICs), in spinal motor neurones to the production of withdrawal behaviours in the frog. We performed experiments on the isolated frog spinal cord with attached hindlimb. This preparation allowed the simultaneous monitoring of muscle activations during motor behaviour and intracellular neuronal recordings. We found that PICs, following their potentiation by serotonin (5‐HT), are recruited and contribute to the production of withdrawal behaviours. These properties conferred a voltage‐dependent prolongation to the duration of motor neuronal activity. Consistent with this potentiation of motor neuronal PICs, 5‐HT also increased the duration of evoked muscle activations. This behavioural potentiation, as well as the expression of PICs in individual neurones, was reduced following antagonism of L‐type Ca2+ channels. These results demonstrate that PICs in motor neurones can be recruited during the production of behaviour and play a role in specifying the temporal details of motor output.
Localization and function of the Kv3.1b subunit in the rat medulla oblongata: focus on the nucleus tractus solitarii
Authors: Dallas Mark L. , Atkinson Lucy , Milligan Carol J. , Morris Neil P. , Lewis David I. , Deuchars Susan A. , Deuchars Jim
Published: November 2004

The voltage‐gated potassium channel subunit Kv3.1 confers fast firing characteristics to neurones. Kv3.1b subunit immunoreactivity (Kv3.1b‐IR) was widespread throughout the medulla oblongata, with labelled neurones in the gracile, cuneate and spinal trigeminal nuclei. In the nucleus of the solitary tract (NTS), Kv3.1b‐IR neurones were predominantly located close to the tractus solitarius (TS) and could be GABAergic or glutamatergic. Ultrastructurally, Kv3.1b‐IR was detected in NTS terminals, some of which were vagal afferents. Whole‐cell current‐clamp recordings from neurones near the TS revealed electrophysiological characteristics consistent with the presence of Kv3.1b subunits: short duration action potentials (4.2 ± 1.4 ms) and high firing frequencies (68.9 ± 5.3 Hz), both sensitive to application of TEA (0.5 mm) and 4‐aminopyridine (4‐AP; 30 μm). Intracellular dialysis of an anti‐Kv3.1b antibody mimicked and occluded the effects of TEA and 4‐AP in NTS and dorsal column nuclei neurones, but not in dorsal vagal nucleus or cerebellar Purkinje cells (which express other Kv3 subunits, but not Kv3.1b). Voltage‐clamp recordings from outside‐out patches from NTS neurones revealed an outward K+ current with the basic characteristics of that carried by Kv3 channels. In NTS neurones, electrical stimulation of the TS evoked EPSPs and IPSPs, and TEA and 4‐AP increased the average amplitude and decreased the paired pulse ratio, consistent with a presynaptic site of action. Synaptic inputs evoked by stimulation of a region lacking Kv3.1b‐IR neurones were not affected, correlating the presence of Kv3.1b in the TS with the pharmacological effects.
Voltage‐controlled Ca2+ release and entry flux in isolated adult muscle fibres of the mouse
Authors: Ursu D. , Schuhmeier R. P. , Melzer W.
Published: November 2004

The voltage‐activated fluxes of Ca2+ from the sarcoplasmic reticulum (SR) and from the extracellular space were studied in skeletal muscle fibres of adult mice. Single fibres of the interosseus muscle were enzymatically isolated and voltage clamped using a two‐electrode technique. The fibres were perfused from the current‐passing micropipette with a solution containing 15 mm EGTA and 0.2 mm of either fura‐2 or the faster, lower affinity indicator fura‐FF. Electrical recordings in parallel with the fluorescence measurements allowed the estimation of intramembrane gating charge movements and transmembrane Ca2+ inward current exhibiting half‐maximal activation at −7.60 ± 1.29 and 3.0 ± 1.44 mV, respectively. The rate of Ca2+ release from the SR was calculated after fitting the relaxation phases of fluorescence ratio signals with a kinetic model to quantify overall Ca2+ removal. Results obtained with the two indicators were similar. Ca2+ release was 2–3 orders of magnitude larger than the flux carried by the L‐type Ca2+ current. At maximal depolarization (+50 mV), release flux peaked at about 3 ms after the onset of the voltage pulse and then decayed in two distinct phases. The slower phase, most likely resulting from SR depletion, indicated a decrease in lumenal Ca2+ content by about 80% within 100 ms. Unlike in frog fibres, the kinetics of the rapid phase of decay showed no dependence on the filling state of the SR and the results provide little evidence for a substantial increase of SR permeability on depletion. The approach described here promises insight into excitation–contraction coupling in future studies of genetically altered mice.
Autogenic modulation of mechanoreceptor excitability by glutamate release from synaptic‐like vesicles: evidence from the rat muscle spindle primary sensory ending
Authors: Bewick Guy S. , Reid Brian , Richardson Christine , Banks Robert W.
Published: November 2004

Fifty‐nanometre diameter, clear, synaptic‐like vesicles (SLVs) are found in primary mechanosensory nerve terminals of vertebrate and invertebrate animals. We have investigated their role in mechanosensory function using the muscle spindle primary endings of rat Ia afferents as a model. Uptake and release of the synaptic vesicle marker FM1‐43 indicated that SLVs recycle like synaptic vesicles and do so in a Ca2+‐sensitive manner. Mechanical stimulation increased SLV recycling, increasing both dye uptake and release. Immunogold/electronmicroscopy showed that, like the central synaptic endings, Ia peripheral endings are enriched with glutamate. Moreover, exogenous glutamate enhanced stretch‐induced Ia excitability. Enhanced excitability persisted in the presence of antagonists to the commonest ionotropic and metabotropic glutamate receptors (kynurenate, MCPG, CPPG and MAP4). However, excitation by glutamate was abolished by (R,S)‐3,5‐dihydroxyphenylglycine (DHPG), and rather more effectively by (2R,1′‐S,2′‐R,3′‐S)‐2‐(2′‐carboxy‐3′‐phenylcyclopropyl) glycine (PCCG‐13). PCCG‐13 also significantly reduced stretch‐activated excitability in the absence of exogenous glutamate. These data indicate that SLVs recycle at rest, releasing glutamate, and that mechanical activity increases this process. The blockade with DHPG and PCCG‐13 suggests that endogenous glutamate release acts, at least in part, through the recently described phospholipase D‐linked metabotropic Glu receptor to maintain the excitability of the sensory endings.
Imaging transcription in vivo: distinct regulatory effects of fast and slow activity patterns on promoter elements from vertebrate troponin I isoform genes
Authors: Rana Zaheer A. , Gundersen Kristian , Buonanno Andres , Vullhorst Detlef
Published: November 2004

Firing patterns typical of slow motor units activate genes for slow isoforms of contractile proteins, but it remains unclear if there is a distinct pathway for fast isoforms or if their expression simply occurs in the absence of slow activity. Here we first show that denervation in adult soleus and EDL muscles reverses the postnatal increase in expression of troponin I (TnI) isoforms, suggesting that high‐level transcription of  both genes in mature muscles is under neural control. We then use a combination of in vivo transfection, live muscle imaging and fluorescence quantification to investigate the role of patterned electrical activity in the transcriptional control of troponin I slow (TnIs) and fast (TnIf) regulatory sequences by directly stimulating denervated muscles with pattern that mimic fast and slow motor units. Rat soleus muscles were electroporated with green fluorescent protein (GFP) reporter constructs harbouring 2.7 and 2.1 kb of TnIs and TnIf regulatory sequences, respectively. One week later, electrodes were implanted and muscles stimulated for 12 days. The change in GFP fluorescence of individual muscle fibres before and after the stimulation was used as a measure for transcriptional responses to different patterns of action potentials. Our results indicate that the response of TnI promoter sequences to electrical stimulation is consistent with the regulation of the endogenous genes. The TnIf and TnIs enhancers were activated by matching fast and slow activity patterns, respectively. Removal of nerve‐evoked activity by denervation, or stimulation with a mismatching pattern reduced transcriptional activity of both enhancers. These results strongly suggest that distinct signalling pathways couple both fast and slow patterns of activity to enhancers that regulate transcription from the fast and slow troponin I isoforms.
Role of voltage‐dependent calcium channels in stimulus–secretion coupling in rabbit carotid body chemoreceptor cells
Authors: Rocher Asunción , Geijo‐Barrientos Emilio , Cáceres Ana Isabel , Rigual Ricardo , González Constancio , Almaraz Laura
Published: November 2004

We have defined Ca2+ channel subtypes expressed in rabbit carotid body (CB) chemoreceptor cells and their participation in the stimulus‐evoked catecholamine (CA) release. Ca2+ currents (ICa) activated at –30 mV, peaked at +10 mV and were fully blocked by 200 μm Cd2+. L‐type channels (sensitive to 2 μm nisoldipine) activated at –30 mV and carried 21 ± 2% of total ICa. Non‐L‐type channels activated at potentials positive to –10 mV and carried: N channels (sensitive to 1 μmω‐conotoxin‐GVIA) 16 ± 1% of total ICa, P/Q channels (sensitive to 3 μmω‐conotoxin‐MVIIC after nisoldipine plus GVIA) 23 ± 3% of total ICa and R channels (resistant to all blockers combined) 40 ± 3% of total ICa. CA release induced by hypoxia, hypercapnic acidosis, dinitrophenol (DNP) and high K+o in the intact CB was inhibited by 79–98% by 200 μm Cd2+. Hypoxia, hypercapnic acidosis and DNP, depolarized chemoreceptor cells and eventually generated repetitive action potential discharge. Nisoldipine plus MVIIC nearly abolished the release of CAs induced by hypoxia and hypercapnic acidosis and reduced by 74% that induced by DNP. All these secretory responses were insensitive to GVIA. 30 and 100 mm K+o brought resting membrane potential (Em) of chemoreceptor cells (–48.1 ± 1.2 mV) to –22.5 and +7.2 mV, respectively. Thirty millimolar K+o‐evoked release was abolished by nisoldipine but that induced by 100 mm K+o was mediated by activation of L, N, and P/Q channels. Data show that tested stimuli depolarize rabbit CB chemoreceptor cells and elicit CA release through Ca2+ entry via voltage‐activated channels. Only L and P/Q channels are tightly coupled to the secretion of CA.
Cholinergic modulation of hippocampal cells and circuits
Authors: Cobb Stuart R. , Davies Ceri H.
Published: November 2004

Septo‐hippocampal cholinergic fibres ramify extensively throughout the hippocampal formation to release acetylcholine upon a diverse range of muscarinic and nicotinic acetylcholine receptors that are differentially expressed by distinct populations of neurones. The resultant modulation of cellular excitability and synaptic transmission within hippocampal circuits underlies the ability of acetylcholine to influence the dynamic properties of the hippocampal network and results in the emergence of a range of stable oscillatory network states. Recent findings suggest a multitude of actions contribute to the oscillogenic properties of acetylcholine which are principally induced by activation of muscarinic receptors but also regulated through activation of nicotinic receptor subtypes.
Real-time wetting dynamics and interfacial chemistry in low-melting 57Bi–42Sn–1Ag solder paste on Ni–Au
Authors: Bozack M. J.
Published: November 2004

We report the observation of real-time, in situ, wetting and spreading dynamics for 57Bi–42Sn–1Ag solder paste on Ni–Au surfaces during melting in a scanning electron microscope. The 57Bi–42Sn–1Ag is a low melting (139°C) Pb-free eutectic alloy currently under consideration by automobile manufacturers for use in instrument displays. We find that, while there is excellent wetting of 57Bi–42Sn–1Ag solder paste on Ni–Au, there is almost no spreading. A large amount of Bi segregates to the surface of 57Bi–42Sn–1Ag solder balls during the sintering process. At melting, excessive flux outgassing and pooling are observed, several melted solder balls float on top of the flux, and substantial elemental segregation occurs during the first minutes of wetting. Neither Ni nor Au fully intermixes throughout the alloy at the interface within seconds of wetting. Bi does not move outward with the expanding alloy front. This combination of detrimental effects forms voids in the solder paste, contributes to low reliability of solder joints, and complicates the materials science at the solder-substrate interface as shown by Auger electron spectroscopy. Reliability work in progress (3000 cycles) shows that 57Bi–42Sn–1Ag on Ni–Au is less reliable than eutectic Sn–37Pb on Ni–Au for 2512 chip resistors cycled from −40to125°C.
Reactions of ultrathin hard amorphous carbon (a-C) films under microbeam laser processing
Authors: Zhang Li Hong , Gong Hao , Li Yuan Qing , Wang Jian Ping
Published: November 2004

The decomposition mechanism of hard a-C films under irradiation using a microbeam laser (514.5nm) was studied. The films were magnetron sputtered at different pressures to achieve different degrees of sp3∕sp2 bonding ratio. Under laser irradiation, they showed graphitization and decomposition. The graphitization saturated at early exposure of ∼4min, while the decomposition progressed exponentially with the exposure time, following a first-order reaction mechanism. The decomposition of a-C films under laser irradiation can be modeled using a two-step process with the establishment of a quasi steady-state intermediate. The relative energy barrier and rate constant for film decomposition were calculated. With increasing sp3∕sp2 bonding ratio, the films showed increasing resistance against the irradiation-induced changes. This is shown by the decreasing rate constant and increasing energy barrier during the decomposition.
Bulk and interface charge in low temperature silicon nitride for thin film transistors on plastic substrates
Authors: Park Kie Jin , Parsons Gregory N.
Published: November 2004

We report bulk and interface charge densities in silicon nitride thin films deposited by plasma chemical vapor deposition from NH3–N2–SiH4 mixtures, at temperatures compatible with flexible plastic substrates. Bulk and interface charges are independently determined from measurements of flat band potential as a function of film thickness for a range of substrate temperatures and gas compositions. Increasing NH–SiH bond ratio in the deposited films (determined from infrared absorption) leads to a more positive interface charge and more negative bulk charge, and the trend in interface charge is consistent with a relation between charge and stress at the Si–SiNx interface. As substrate temperature is decreased from 250to50°C, the leakage is observed to decrease, the interface charge decreases, and the bulk charge changes from negative to net positive.
Silicide formation at HfO2–Si and ZrO2–Si interfaces induced by Ar+ ion bombardment
Authors: Lebedinskii Yuri , Zenkevich Andrei
Published: November 2004

The effect of ion bombardment with Ar+ at several keV energy ranges resulting in silicide formation at HfO2–Si and ZrO2–Si interfaces has been investigated in situ with x-ray photoelectron spectroscopy. The set of spectra recorded during the growth of thin HfO2 and ZrO2 layers on Si(100) was compared to those obtained during subsequent sputtering with an Ar+ beam. It is shown that the Ar+ ion beam affects the MeO2–Si (Me=Hf,Zr) interface at thickness ⩽3nm, inducing the formation of a silicide layer ∼2nm in thickness. The proposed mechanism of silicide formation including the depletion of the interface in oxygen due to its preferential sputtering and subsequent Hf–Si intermixing is corroborated by computer simulations.
Smoothing of (111) oriented Cu films by post-deposition in situ 20–100eV Ar ion bombardment
Authors: Kools J. C. S. , Devasahayam A. J.
Published: November 2004

We have studied the effect of low energy (20–100eV) Ar bombardment on the surface roughness of (111) oriented Cu films both experimentally and by molecular-dynamics simulations. We found, in good agreement between the experiments and the simulations, that a significant reduction of the surface roughness can be induced at all energies in this range. However, the angle of incidence for optimal smoothing depends strongly on the ion energy, whereby the lower energies used are more efficient at near normal incidence, and the higher energies are more efficient for off-normal angles (e.g., >45degrees).
Monte Carlo sensitivity analysis of CF2 and CF radical densities in a c-C4F8 plasma
Authors: Bose Deepak , Rauf Shahid , Hash D. B. , Govindan T. R. , Meyyappan M.
Published: November 2004

A Monte Carlo sensitivity analysis is used to build a plasma chemistry model for octacyclofluorobutane (c-C4F8) which is commonly used in dielectric etch. Experimental data are used both quantitatively and qualitatively to analyze the gas phase and gas surface reactions for neutral radical chemistry. The sensitivity data of the resulting model identifies a few critical gas phase and surface aided reactions that account for most of the uncertainty in the CF2 and CF radical densities. Electron impact dissociation of small radicals (CF2 and CF) and their surface recombination reactions are found to be the rate-limiting steps in the neutral radical chemistry. The relative rates for these electron impact dissociation and surface recombination reactions are also suggested. The resulting mechanism is able to explain the measurements of CF2 and CF densities available in the literature and also their hollow spatial density profiles.
Measurements of desorbed products by plasma beam irradiation on SiO2
Authors: Kurihara Kazuaki , Yamaoka Yoshikazu , Karahashi Kazuhiro , Sekine Makoto
Published: November 2004

A plasma beam irradiation apparatus with a controllable plasma source was constructed to investigate the plasma-surface interactions for reactive etching processes. The apparatus can control the plasma parameters, such as ion energy, radical∕ion composition, and the ratio of neutral to ion flux. The desorbed products of SiFx (x=1–3) were observed separately from COFx (x=1–3) by using a C13F4–Ar gas mixture plasma beam. The major desorbed product was not SiF4. Unsaturated fluorinated silicons [SiFx(x=1–3)] were major desorbed products under ion-rich fluorocarbon plasma etching condition. It was found that the composition of silicon containing desorbed products does not depend on the incident ion energy in the ion energy range of 300–700eV.
Detection of quasimolecular ion of Cu(hfac)(tmvs) by ion attachment mass spectrometry
Authors: Nakamura Megumi , Shiokawa Yoshiro , Fujii Toshihiro , Takayanagi Masao , Nakata Munetaka
Published: November 2004

A molecular ion of (trimethylvinylsilane)(1,1,1,5,5,5-hexafluoroacetyl-acetonato)Cu(I) [Cu(hfac)(tmvs)], which could not be detected by mass spectrometry with conventional ionization techniques such as electron impact ionization because of weak coordination bonds, has been successfully detected as a quasimolecular ion, Cu(hfac)(tmvs)Li+, for the first time by recently developed ion-attachment mass spectrometry (IAMS). Cu(hfac)(tmvs) is a material widely used in the metal organic chemical vapor deposition (MOCVD) process. In the thermal decomposition of Cu(hfac)(tmvs), trimethylvinylsilane (tmvs) and hexafluoroacetylacetone (Hhfac) were observed by IAMS as the reaction products. We also evaluated the dependence of the decomposition process on temperature. We found IAMS to be an effective tool in monitoring and clarifying MOCVD processes.
Electron trapping in metal-insulator-semiconductor structures on n-GaN with SiO2 and Si3N4 dielectrics
Authors: Bae Choelhwyi , Krug Cristiano , Lucovsky Gerald
Published: November 2004

Electron trapping in Al-gate n-GaN∕nitrided-thin-Ga2O3∕SiO2 and n-GaN∕Si3N4 MIS capacitors was evaluated by capacitance-voltage (C–V) measurements. Significant positive flatband voltage shift (ΔVfb) was observed with increasing starting dc bias in the C–V measurements. For similar equivalent oxide thickness and under the same C–V measurement conditions, ΔVfb in the nitride was 3–10 times larger than in the oxide samples. It is suggested that flatband voltage shifts are due to border traps in SiO2 and to interface and bulk traps in Si3N4 samples.
Novel rubidium atomic beam with an alkali dispenser source
Authors: Roach Timothy M. , Henclewood Dwayne
Published: November 2004

We describe a novel atomic beam apparatus with a resistively heated alkali dispenser source and a cold-pumped intermediate chamber. Using laser fluorescence spectroscopy we have measured the atomic density to be 3×1011atoms∕m3 and the total flux to be 5×108atoms∕s in a 0.3cm diameter beam. We have also characterized the velocity distribution of the source based on the Doppler-shifted fluorescence spectrum. The compact geometry, flexibility, and simplicity of the beam may make it useful as an optical frequency reference or for experiments on atom-cooling.
Growth and surface characterization of V2O5 thin films made by pulsed-laser deposition
Authors: Ramana C. V. , Smith R. J. , Hussain O. M. , Julien C. M.
Published: November 2004

V 2 O 5 thin films were produced by pulsed laser deposition (PLD) over a wide temperature range, 30–500 °C. The effects of temperature and structural characteristics of the substrate on the growth, surface morphology, and local atomic structure of V2O5 films were probed with atomic force microscopy (AFM) and Raman spectroscopy (RS). The growth mode and microstructure evolution were strongly dependent on the substrate temperature. The onset of crystallization occurred at 200 °C with an activation energy of 0.43–0.55 eV. Polycrystalline PLD V2O5 films with layered structure exhibited the same local structural symmetry found in crystalline orthorhombic bulk V2O5.
Structure and electrical properties of MgTiO3 thin films deposited by rf magnetron sputtering
Authors: Huang Cheng-Liang , Pan Chung-Long
Published: November 2004

Bulk MgTiO3 ceramics have shown excellent dielectric properties at microwave frequencies; however, the high sintering temperature of the bulk materials is major obstacle in their use as dielectric resonators to miniaturize microwave circuits. In this article, MgTiO3 thin films were fabricated on n-type Si(100) substrates by rf magnetron sputtering by using MgTiO3 target which was synthesized in the experiment. It was possible to obtain highly oriented MgTiO3(110) thin film at a rf power density of 7.7W∕cm2 and a substrate temperature of 400°C, which is much lower than the bulk sintering temperature. These films were studied by choosing different rf power densities and substrate temperature. The microstructure and surface morphology of the MgTiO3 films deposited on Si(100) was determined by x-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy. The XRD showed that the deposited films exhibited a polycrystalline microstructure. The grain size of the film increased with an increase in the rf power density and substrate temperature. The electrical properties were measured using C-V and current-voltage I-V measurements on metal-insulator-semiconductor capacitor structures. As rf power density of 7.7W∕cm2 and substrate temperature of 400°C, a dielectric constant of 14.9 (f=10MHz) and a dissipation factor of 0.031 were obtained.
Formation and analysis of disk-shaped grains by Ni-mediated crystallization of amorphous silicon
Authors: Kim Kyung Ho , Oh Jae Hwan , Kim Eun Hyun , Jang Jin
Published: November 2004

Disk- and needle-shaped grains can be seen in polycrystalline silicon (poly-Si) made by Ni-mediated crystallization of amorphous silicon (a-Si). A major parameter to give the difference of grain structure is the Ni area density on a-Si. However, there are many other parameters such as heating rate and structure of a-Si to affect the grain structure. The use of Ni density of ∼1013cm−2 on a-Si for the crystallization gives the disk-shaped grains. There is no amorphous phase in the disk-shaped grains which are composed of well-aligned needles. On the other hand, the poly-Si has some amorphous phase inside when it was crystallized into needlelike rods. It is found that the width of needles in the disk-shaped grains is smaller than that of needlelike crystallites. The Ni atoms are at the grain boundaries formed by the collisions of neighboring grains.
Y Chromosome of
D. pseudoobscura
Is Not Homologous to the Ancestral
Drosophila
Y
Authors: Carvalho Antonio Bernardo , Clark Andrew G.
Published: November 2004

We report a genome-wide search of Y-linked genes in
Drosophila pseudoobscura
. All six identifiable orthologs of the
D. melanogaster
Y-linked genes have autosomal inheritance in
D. pseudoobscura
. Four orthologs were investigated in detail and proved to be Y-linked in
D. guanche
and
D. bifasciata
, which shows that less than 18 million years ago the ancestral
Drosophila
Y chromosome was translocated to an autosome in the
D. pseudoobscura
lineage. We found 15 genes and pseudogenes in the current Y of
D. pseudoobscura
, and none are shared with the
D. melanogaster
Y. Hence, the Y chromosome in the
D. pseudoobscura
lineage appears to have arisen de novo and is not homologous to the
D. melanogaster
Y.
Hemoxygenase-2 Is an Oxygen Sensor for a Calcium-Sensitive Potassium Channel
Authors: Williams Sandile E. J. , Wootton Phillippa , Mason Helen S. , Bould Jonathan , Iles David E. , Riccardi Daniela , Peers Chris , Kemp Paul J.
Published: November 2004

Modulation of calcium-sensitive potassium (BK) channels by oxygen is important in several mammalian tissues, and in the carotid body it is crucial to respiratory control. However, the identity of the oxygen sensor remains unknown. We demonstrate that hemoxygenase-2 (HO-2) is part of the BK channel complex and enhances channel activity in normoxia. Knockdown of HO-2 expression reduced channel activity, and carbon monoxide, a product of HO-2 activity, rescued this loss of function. Inhibition of BK channels by hypoxia was dependent on HO-2 expression and was augmented by HO-2 stimulation. Furthermore, carotid body cells demonstrated HO-2–dependent hypoxic BK channel inhibition, which indicates that HO-2 is an oxygen sensor that controls channel activity during oxygen deprivation.
Microsatellite Mapping of
Mycobacterium leprae
Populations in Infected Humans
Authors: Young Saroj K. , Taylor G. Michael , Jain Suman , Suneetha Lavanya M. , Suneetha Sujai , Lockwood Diana N. J. , Young Douglas B.
Published: November 2004

To investigate genetic diversity in a bacterial population, we measured the copy numbers of simple sequence repeats, or microsatellites, in
Mycobacterium leprae
from patients living in and around Hyderabad, India. Three microsatellite loci containing trinucleotide or dinucleotide repeats were amplified from infected tissues, and the copy numbers were established by sequence analysis. Extensive diversity was observed in a cross-sectional survey of 33 patients, but closely related profiles were found for members of a multicase family likely to share a common transmission source. Sampling of multiple tissues from single individuals demonstrated identical microsatellite profiles in the skin, nasal cavity, and bloodstream but revealed differences at one or more loci for
M. leprae
present in nerves. Microsatellite mapping of
M. leprae
represents a useful tool for tracking short transmission chains. Comparison of skin and nerve lesions suggests that the evolution of disease within an individual involves the expansion of multiple distinct subpopulations of
M. leprae
.
New Quadriplex PCR Assay for Detection of Methicillin and Mupirocin Resistance and Simultaneous Discrimination ofStaphylococcus aureusfrom Coagulase-Negative Staphylococci
Authors: Zhang Kunyan , Sparling Jennifer , Chow Barbara L. , Elsayed Sameer , Hussain Zafar , Church Deirdre L. , Gregson Daniel B. , Louie Thomas , Conly John M.
Published: November 2004

Major challenges in diagnostic molecular microbiology are to develop a simple assay to distinguishStaphylococcus aureusfrom the less virulent but clinically important coagulase-negative staphylococci (CoNS) and to simultaneously determine their antibiotic resistance profiles. Multiplex PCR assays have been developed for the detection of methicillin- and mupirocin-resistantS. aureusand CoNS but not for the simultaneous discrimination ofS. aureusfrom CoNS. We designed a new set ofStaphylococcusgenus-specific primers and developed a novel quadriplex PCR assay targeting the 16S rRNA (Staphylococcusgenus specific),nuc(S. aureusspecies specific),mecA(a determinant of methicillin resistance), andmupA(a determinant of mupirocin resistance) genes to identify most staphylococci, to discriminateS. aureusfrom CoNS and other bacteria, and to simultaneously detect methicillin and mupirocin resistance. Validation of the assay with 96 ATCC control strains and 323 previously characterized clinical isolates, including methicillin- and mupirocin-sensitive and -resistantS. aureusand CoNS isolates and other bacteria, demonstrated 100% sensitivity, specificity, and accuracy. This assay represents a simple, rapid, accurate, and reliable approach for the detection of methicillin- and mupirocin-resistant staphylococci and offers the hope of preventing their widespread dissemination through early and reliable detection.
Characterization of Spotted Fever Group Rickettsiae in Flea and Tick Specimens from Northern Peru
Authors: Blair Patrick J. , Jiang Ju , Schoeler George B. , Moron Cecilia , Anaya Elizabeth , Cespedes Manuel , Cruz Christopher , Felices Vidal , Guevara Carolina , Mendoza Leonardo , Villaseca Pablo , Sumner John W. , Richards Allen L. , Olson James G.
Published: November 2004

Evidence of spotted fever group (SFG) rickettsiae was obtained from flea pools and individual ticks collected at three sites in northwestern Peru within the focus of an outbreak of febrile disease in humans attributed, in part, to SFG rickettsia infections. Molecular identification of the etiologic agents from these samples was determined after partial sequencing of the 17-kDa common antigen gene (
htrA
) as well as pairwise nucleotide sequence homology with one or more of the following genes:
gltA
,
ompA
, and
ompB
. Amplification and sequencing of portions of the
htrA
and
ompA
genes in pooled samples (2 of 59) taken from fleas identified the pathogen
Rickettsia felis
. Four tick samples yielded molecular evidence of SFG rickettsiae. Fragments of the
ompA
(540-bp) and
ompB
(2,484-bp) genes were amplified from a single
Amblyomma maculatum
tick (tick 124) and an
Ixodes boliviensis
tick (tick 163). The phylogenetic relationships between the rickettsiae in these samples and other rickettsiae were determined after comparison of their
ompB
sequences by the neighbor-joining method. The dendrograms generated showed that the isolates exhibited close homology (97%) to
R. aeschlimannii
and
R. rhipicephali
. Significant bootstrap values supported clustering adjacent to this nodule of the SFG rickettsiae. While the agents identified in the flea and tick samples have not been linked to human cases in the area, these results demonstrate for the first time that at least two SFG rickettsia agents were circulating in northern Peru at the time of the outbreak. Furthermore, molecular analysis of sequences derived from the two separate species of hard ticks identified a possibly novel member of the SFG rickettsiae.
Development and Evaluation of a Quality-Controlled Ribosomal Sequence Database for 16S Ribosomal DNA-Based Identification of
Staphylococcus
Species
Authors: Becker Karsten , Harmsen Dag , Mellmann Alexander , Meier Christian , Schumann Peter , Peters Georg , von Eiff Christof
Published: November 2004

To establish an improved ribosomal gene sequence database as part of the Ribosomal Differentiation of Microorganisms (RIDOM) project and to overcome the drawbacks of phenotypic identification systems and publicly accessible sequence databases, both strands of the 5′ end of the 16S ribosomal DNA (rDNA) of 81 type and reference strains comprising all validly described staphylococcal (sub)species were sequenced. Assuming a normal distribution for pairwise distances of all unique staphylococcal sequences and choosing a reporting criterion of ≥98.7% similarity for a “distinct species,” a statistical error probability of 1.0% was calculated. To evaluate this database, a 16S rDNA fragment (corresponding to
Escherichia coli
positions 54 to 510) of 55 clinical
Staphylococcus
isolates (including those of the small-colony variant phenotype) were sequenced and analyzed by the RIDOM approach. Of these isolates, 54 (98.2%) had a similarity score above the proposed threshold using RIDOM; 48 (87.3%) of the sequences gave a perfect match, whereas 83.6% were found by searching National Center for Biotechnology Information (NCBI) database entries. In contrast to RIDOM, which showed four ambiguities at the species level (mainly concerning
Staphylococcus intermedius
versus
Staphylococcus delphini
), the NCBI database search yielded 18 taxon-related ambiguities and showed numerous matches exhibiting redundant or unspecified entries. Comparing molecular results with those of biochemical procedures, ID 32 Staph (bioMérieux, Marcy I'Etoile, France) and VITEK 2 (bioMérieux) failed to identify 13 (23.6%) and 19 (34.5%) isolates, respectively, due to incorrect identification and/or categorization below acceptable values. In contrast to phenotypic methods and the NCBI database, the novel high-quality RIDOM sequence database provides excellent identification of staphylococci, including rarely isolated species and phenotypic variants.