bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutation Analysis of Slc26a4 in Mainland Chinese Patients with Enlarged Vestibular Aqueduct
Authors: Reyes Samuel , Wang Guojian , Ouyang Xiaomei , Han Bing , Du Li Lin , Yuan Hui Jun , Yan Denise , Dai Pu , Liu Xue‐Zhong
Published: September 2009

OBJECTIVE

We have characterized the spectrum of SLC26A4 mutations and clinical features in a population of mainland Chinese patients with nonsyndromic sensorineural hearing loss (SNHL) and enlarged vestibular aqueduct (EVA).

STUDY DESIGN

Cross‐sectional clinical genetic study.

SETTING

Tertiary care outpatient otolaryngology clinic.

METHODS

A total of 32 subjects identified with bilateral EVA using high‐resolution CT were screened for mutations in SLC26A4 by denaturing high‐performance liquid chromatography and direct sequencing methods.

RESULTS

A total of 13 different mutations were identified in the SLC26A4 gene, five of which are novel. A total of 88 percent of the patients harbored biallelic mutations, 11 patients were homozygotes, and 17 were compound heterozygotes. Four patients were found to carry a single SLC26A4 mutation. The IVS7‐2A>G mutation was the most frequent, accounting for 60 percent of the mutant alleles. We have not found any correlations between the type of SLC26A4 mutations and the type, degree, and progression of hearing loss. There are significant proportions of patients with asymmetric (26%), progressive (32%), or fluctuating hearing loss (21%).

CONCLUSION

Our data confirm the high prevalence of SLC26A4 mutations in Chinese patients with SNHL and EVA. We could not establish any relationship between genotype and pheno‐type. However, the high incidence of asymmetric, progressive, and fluctuating hearing loss found in the current study indicates that patients with those features should be routinely screened for SLC26A4 mutation in addition to diagnosis of EVA using CT or MRI.
Increased Microsatellite Instability and Epigenetic Inactivation of the Hmlh1 Gene in Head and Neck Squamous Cell Carcinoma
Authors: Zuo Chunlai , Zhang Haihong , Spencer Horace J. , Vural Emre , Suen James Y. , Schichman Steven A. , Smoller Bruce R. , Kokoska Mimi S. , Fan Chun‐Yang
Published: September 2009

OBJECTIVE

The study is designed to elucidate the relationship between epigenetic silencing of the hMLH1 (human MutL homologue 1) gene and microsatellite instability (MSI) and the prognostic values of hMLH1 promoter methylation and MSI in head and neck squamous cell carcinoma (HNSCC).

STUDY DESIGN

Cross‐sectional study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

A total of 120 cases of HNSCC were analyzed for hMLH1 promoter hypermethylation, protein expression, and MSI by using methylation‐specific polymerase chain reaction, immunohistochemical staining, and polymerase chain reaction amplification with the use of 16 fluorescent‐labeled microsatellite markers, followed by fragment analysis.

RESULTS

Of 120 HNSCCs, hMLH1 promoter hypermethylation and decreased hMLH1 protein expression were shown in 39 (32.5%) and 22 (18.3%), respectively. hMLH1 promoter hypermethylation was detected in 13 of 52 (25%) normal‐appearing squamous mucosa adjacent to invasive carcinoma. MSI was detected in 21 (17.5%) tumors at two or more markers and in 99 (82.5%) tumors with no evidence of MSI or at only one marker. Hypermethylation of the hMLH1 gene is significantly associated with decreased hMLH1 protein expression (P < 0.001). High‐frequency MSI was significantly associated with promoter hypermethylation (P = 0.01) but not with decreased protein expression (P = 0.069) of hMLH1 gene. hMLH1 promoter hypermethylation is significantly associated with decreased cause‐specific survival for HNSCC patients (P = 0.03).

CONCLUSIONS

Promoter hypermethylation of the hMLH1 gene could be detected early in head and neck squamous carcinogenesis and may be associated with increased MSI and poor survival in HNSCC.
Nonasthmatic Nasal Polyposis Patients with Allergy Exhibit Greater Epithelial MMP Positivity
Authors: Shin Hyun‐Woo , Han Doo Hee , Lim Yune Sung , Kim Hye Jung , Kim Dong‐Young , Lee Chul Hee , Min Yang‐Gi , Rhee Chae‐Seo
Published: September 2009

OBJECTIVE

To determine the influence of allergic rhinitis (AR) on the expression of matrix metalloproteinase (MMP)‐9, MMP‐2, and tissue inhibitor‐1 of metalloproteinase (TIMP‐1) in nasal polyposis.

STUDY DESIGN

A case‐control study.

SETTING

A tertiary referral center.

SUBJECTS AND METHODS

The expression of MMP‐9, MMP‐2, and TIMP‐1 was investigated in the nasal polyp tissue (NP) and maxillary sinus mucosa (MM) samples from 20 AR patients and 20 nonallergic patients undergoing endoscopic sinus surgery. Trichrome, periodic acid‐Schiff, and hematoxylin‐eosin staining were also performed and those expression levels were compared.

RESULTS

Infiltration of eosinophils was shown more intensely in NP rather than in MM, especially in the presence of AR. In the NP of AR patients, increased expression of MMP‐9, MMP‐2, and TIMP‐1 was observed more prominently than in that of the control group. In case of MM, however, there was no significant difference between AR patients and the control group.

CONCLUSION

The presence of AR may enhance the expression of MMP‐9, MMP‐2, and TIMP‐1 associated with airway remodeling in nasal polyposis.
Extracts From The Cochrane Library: Erythropoietin as an Adjuvant Treatment with (Chemo) Radiation Therapy for Head and Neck Cancer
Authors: Burton Martin J. , Deschler Daniel G. , Rosenfeld Richard M.
Published: September 2009

The “Cochrane Corner” is a quarterly section in the Journal that highlights systematic reviews relevant to otolaryngology‐ head and neck surgery, with invited commentary to aid clinical decision making. This installment features a Cochrane Review entitled “Erythropoietin as an adjuvant treatment with (chemo) radiation therapy for head and neck cancer,” which concludes that erythropoietin should not be administered as an addition to radiation therapy outside the experimental setting.
Dietary vitamin D and risk of non-Hodgkin lymphoma: the multiethnic cohort
Authors: Erber Eva , Maskarinec Gertraud , Lim Unhee , Kolonel Laurence N.
Published: September 2009

The present study explored the association between dietary vitamin D and non-Hodgkin's lymphoma (NHL) risk. The multiethnic cohort (MEC) includes more than 215 000 Caucasians, African Americans, Native Hawaiians, Japanese Americans and Latinos, aged 45–75. After 10 years of follow-up, 939 incident NHL cases were identified. Risk was estimated using proportional hazards' models adjusted for possible confounders. Vitamin D intake was not associated with NHL risk in the entire cohort (Ptrend = 0·72 for men and Ptrend = 0·83 for women), but significantly lowered disease risk in African American women (hazard ratio (HR) = 0·50, 95 % CI: 0·28, 0·90, Ptrend = 0·03) and was borderline protective in African American men (HR = 0·68; 95 % CI: 0·39, 1·19; Ptrend = 0·31) when the highest to the lowest tertile was compared. In NHL subtype analyses, a 19, 36 and 32 % lowered risk, although not significant, was observed for diffuse large B-cell lymphoma, follicular lymphoma and small lymphocytic lymphoma/chronic lymphocytic leukemia in women, respectively. High dietary intake of vitamin D did not show a protective effect against NHL within the MEC except among African Americans, possibly because vitamin D production due to sun exposure is limited in this population.
Concentration of penicillin G in mammary tissue and secretion of end-term dairy heifers following systemic prepartum administration of penethamate hydriodide
Authors: Passchyn Pieter , Piepers Sofie , Schmitt-Van de Leemput Ellen , Guidarini Christian , De Vliegher Sarne
Published: September 2009

The aim of this study was to assess the concentration of penicillin G in mammary tissue and secretion of dry heifers following systemic administration of penethamate hydriodide. Six dairy heifers in late gestation received a single intramuscular injection of 10 g penethamate hydriodide and were sacrificed 24, 48 or 144 h after treatment. Penicillin G concentrations were measured in mammary tissue and secretion samples using HPLC. Penicillin G was detected in the udder of two animals euthanized at 24 h (mammary tissue and secretion) and at 48 h post treatment (mammary secretion only) after administration at concentrations still close to or above MIC90values reported for the pathogens associated with heifer mastitis. Antibiotic concentration shortly after administration will have been substantially higher indicating a potential for systemic treatment with penethamate hydriodide to control prepartum intramammary infections in heifers without the disadvantages of local therapy such as teat contamination or risk of trauma for the administrator.
Asymptotic and numerical study of variable-density premixed flame propagation in a narrow channel
Authors: SHORT MARK , KESSLER DAVID A.
Published: September 2009

The influence of thermal expansion on the dynamics of thick to moderately thick premixed flames (flame thickness less than or comparable to the channel height) for a variable-density flow in a narrow, rectangular channel is explored. The study is conducted within the framework of the zero-Mach-number, variable-density Navier–Stokes equations. Both adiabatic and non-adiabatic channel walls are considered. A small Péclet number asymptotic solution is developed for steady, variable-density flame propagation in the narrow channel. The dynamics of channel flames are also examined numerically for O(1) Péclet numbers in configurations which include flame propagation in a semi-closed channel from the closed to the open end of the channel, flame propagation in a semi-closed channel towards the closed end of the channel and flame propagation in an open channel in which a Poiseuille flow (flame assisting or flame opposing) is imposed at the channel inlet. Comparisons of the finite-Péclet-number dynamics are made with the behaviour of the small-Péclet-number solutions. We also compare how thermal expansion modifies the flow dynamics from those determined by a constant-density model. The small-Péclet-number variable-density solution for a flame propagating in a circular pipe is given in the Appendix.
Commensurability classes of arithmetic Fuchsian surface groups of genus 2
Authors: MACLACHLAN C. , ROSENBERGER G.
Published: September 2009

Here we determine the arithmetic data i.e. the totally real number field and the set of ramified places of the defining quaternion algebra, of all those commensurability classes of arithmetic Fuchsian groups which contain a surface group of genus 2, i.e. a group of signature (2;– –).
Galois theory of Salem polynomials
Authors: CHRISTOPOULOS CHRISTOS , MCKEE JAMES
Published: September 2009

Let f(x) ∈ [x] be a monic irreducible reciprocal polynomial of degree 2d with roots r1, 1/r1, r2, 1/r2, . . ., rd, 1/rd. The corresponding trace polynomial g(x) of degree d is the polynomial whose roots are r1 + 1/r1, . . ., rd + 1/rd. If the Galois groups of f and g are Gf and Gg respectively, then Gg ≅ Gf/N, where N is isomorphic to a subgroup of C2d. In a naive sense, the generic case is Gf ≅ C2d ⋊ Sd, with N ≅ C2d and Gg ≅ Sd. When f(x) has extra structure this may be reflected in the Galois group, and it is not always true even that Gf ≅ N ⋊ Gg. For example, for cyclotomic polynomials f(x) = Φn(x) it is known that Gf ≅ N ⋊ Gg if and only if n is divisible either by 4 or by some prime congruent to 3 modulo 4.

In this paper we deal with irreducible reciprocal monic polynomials f(x) ∈ [x] that are ‘close’ to being cyclotomic, in that there is one pair of real positive reciprocal roots and all other roots lie on the unit circle. With the further restriction that f(x) has degree at least 4, this means that f(x) is the minimal polynomial of a Salem number. We show that in this case one always has Gf ≅ N ⋊ Gg, and moreover that N ≅ C2d or C2d−1, with the latter only possible if d is odd.
Geste de pointage enfantin et développement du lexique du stade du premier mot au stade de l'énoncé à deux mots
Authors: HUNKELER HERVÉ
Published: September 2009

Cette étude porte sur le rôle du geste enfantin dans le développement du lexique précoce chez des enfants jumeaux (garçon et fille) en interaction avec leur mère entre 15 et 26 mois en situation de livres d'images. Il ressort de ce travail que ces deux enfants produisent des combinaisons geste/mot(s), contenant le plus souvent un mot référentiel. Nous remarquons aussi que toutes ces combinaisons contiennent des informations identiques. Celles-ci semblent faciliter l'accroissement des combinaisons « pointage+énoncés à 2 mots » constaté chez nos deux sujets entre 24 et 26 mois. Ce résultat nouveau lié à la situation de livres d'images rompt avec les travaux cités dans la littérature.
Accent et syllabe dans les vers français: une synthèse possible?
Authors: PENSOM ROGER
Published: September 2009

RESUME

Selon certains critiques influents, l'équivalence métrique repose uniquement sur des équivalences en nombre syllabique, la division en unités rythmiques et la disposition interne des accents restant ‘libres’, c'est -à-dire indifférentes au mètre. A l'encontre de cette vue, depuis 1800, bon nombre d'amateurs et poètes ont discerné dans les vers français l'opération d'un principe formel fondé sur la répartition des accents au sein du vers. Suite à des travaux récents qui constatent la présence d'une occurrence statistiquement significative de répartitions d'accents régulières dans un vaste corpus d'alexandrins classiques, l'article présent cherche à démontrer une interdépendance fonctionnelle entre le décompte syllabique récurrent et la répartition des accents internes. La question de l'accent de vers étant actuellement le lieu d'âpres débats, tout comme celle de l'accent dans la langue, la réalité de l'accent de mot est affirmé au moyen d'une analyse distributionnelle de syntagmes nominaux dans un texte de Racine. Une analyse comparative prose/vers démontre que, dans les vers, la distribution des accents internes, ainsi que celle des voyelles atones, est sujette à contrainte; cette analyse fournit aussi des indications sur le statut linguistique du contre-accent en français. Un examen critique de Cornulier (1982, 1995) met en doute l'idée que l'isosyllabisme est la condition suffisante et nécessaire du vers français, et propose à sa place une conception dynamique où l'agencement formel du rythme accentuel joue un rôle indispensable à notre perception de la métrique du vers.
Optimal waist:height ratio cut-off point for cardiometabolic risk factors in Turkish adults
Authors: Selçuk Can Ahmet , Akal Yıldız Emine , Samur Gülhan , Rakıcıoğlu Neslişah , Pekcan Gülden , Özbayrakçı Sinan , Palaoğlu K Erhan , Gönen Mithat , Bersot Thomas P
Published: September 2009

Objective

To identify the optimal waist:height ratio (WHtR) cut-off point that discriminates cardiometabolic risk factors in Turkish adults.

Design

Cross-sectional study. Hypertension, dyslipidaemia, diabetes, metabolic syndrome score ≥2 (presence of two or more metabolic syndrome components except for waist circumference) and at least one risk factor (diabetes, hypertension or dyslipidaemia) were categorical outcome variables. Receiver-operating characteristic (ROC) curves were prepared by plotting 1 − specificity on thex-axis and sensitivity on they-axis. The WHtR value that had the highest Youden index was selected as the optimal cut-off point for each cardiometabolic risk factor (Youden index = sensitivity + specificity − 1).

Setting

Turkey, 2003.

Subjects

Adults (1121 women and 571 men) aged 18 years and over were examined.

Results

Analysis of ROC coordinate tables showed that the optimal cut-off value ranged between 0·55 and 0·60 and was almost equal between men and women. The sensitivities of the identified cut-offs were between 0·63 and 0·81, the specificities were between 0·42 and 0·71 and the accuracies were between 0·65 and 0·73, for men and women. The cut-off point of 0·59 was the most frequently identified value for discrimination of the studied cardiometabolic risk factors. Subjects classified as having WHtR ≥ 0·59 had significantly higher age and sociodemographic multivariable-adjusted odds ratios for cardiometabolic risk factors than subjects with WHtR < 0·59, except for diabetes in men.

Conclusions

We show that the optimal WHtR cut-off point to discriminate cardiometabolic risk factors is 0·59 in Turkish adults.
Bidirectional signaling of ErbB and Eph receptors at synapses
Authors: Chen Yu , Fu Amy K.Y. , Ip Nancy Y.
Published: September 2009

Synapse development and remodeling are regulated by a plethora of molecules such as receptor tyrosine kinases (RTKs), a family of cell surface receptors that play critical roles in neural development. Two families of RTKs implicated in synaptic functions, ErbBs and Ephs, share similar characteristics in terms of exhibiting forward and reverse signaling. In this review, we will discuss the latest advances in the functions of ErbBs and Ephs at the synapse, including dendritic spine morphogenesis, synapse formation and maturation, and synaptic transmission and plasticity. In addition to signaling at interneuronal synapses, communication between neuron and glia is increasingly implicated in the control of synaptic functions. Studies on RTKs and their cognate ligands in glial cells enhance our understanding on the nature of ‘tripartite synapse’. Implications of these signaling events in human diseases will be discussed.
Slow slip predictions based on granite and gabbro friction data compared to GPS measurements in northern Cascadia
Authors: Liu Yajing , Rice James R.
Published: September 2009

For episodic slow slip transients in subduction zones, a large uncertainty in comparing surface deformations predicted by forward modeling based on rate and state friction to GPS measurements lies in our limited knowledge of the frictional properties and fluid pore pressure along shallow subduction faults. In this study, we apply the laboratory rate and state friction data of granite and gabbro gouges under hydrothermal conditions to a Cascadia‐like 2‐D model to produce spontaneous aseismic transients, and we compare the resulting intertransient and transient surface deformations to GPS observations along the northern Cascadia margin. An inferred region along dip of elevated fluid pressure is constrained by seismological observations where available and by thermal and petrological models for the Cascadia and SW Japan subduction zones. For the assumed friction parameters a and a − b profiles, we search the model parameter space, by varying the level of effective normal stress , characteristic slip distance L in the source areas of transients, and the fault width under , to identify simulation cases that produce transients of total aseismic slip and recurrence interval similar to the observed 20–30 mm and 1–2 years, respectively, in northern Cascadia. Using a simple planar fault geometry and extrapolating the 2‐D fault slip to a 3‐D distribution, we find that the friction data for gabbro gouge, a better representation of the seafloor, fit GPS observations of transient deformation in northern Cascadia much better than do the granite data, which, for lack of a suitable alternative, have been the basis for most previous modeling.
Imaging of atmospheric gravity waves in the stratosphere and upper mesosphere using satellite and ground‐based observations over Australia during the TWPICE campaign
Authors: Hecht J. H. , Alexander M. J. , Walterscheid R. L. , Gelinas L. J. , Vincent R. A. , MacKinnon A. D. , Woithe J. M. , May P. T. , Skinner W. R. , Mlynczak M. G. , Russell J. M.
Published: September 2009

During the Tropical Warm Pool International Cloud Experiment (TWPICE) an intense tropical low was situated between Darwin and Alice Springs, Australia. Observations made on 31 January 2006 by the Atmospheric Infrared Sounder instrument on the NASA Aqua satellite imaged the presence of atmospheric gravity waves (AGWs), at approximately 40 km altitude, with horizontal wavelengths between 200 and 400 km that were originating from the region of the storm. Airglow images obtained from Alice Springs (about 600 km from the center of the low) showed the presence of similar waves with observed periods of 1 to 2 h. The images also revealed the presence of 30‐ to 45‐km‐horizontal‐wavelength AGWs with shorter observed periods of near 15 to 25 min. Ray tracing calculations show that (1) some of the long wavelength waves traveled on rays, without ducting, to the altitudes where the observations were obtained, and (2) shorter‐period waves rapidly reached 85 km altitude at a horizontal distance close to the storm, thus occurring over Alice Springs only if they were trapped or ducted. The mesospheric inversion layer seen in the measured temperature data almost forms such a trapped region. The winds therefore critically control the formation of the trapped region. Wind profiles deduced from the available data show the plausibility for the formation of such a trapped region. Variations in the wind, however, would make ideal trapped region conditions short‐lived, and this may account for the sporadic nature of the short‐period wave observations.
Exner equation: A continuum approximation of a discrete granular system
Authors: Coleman S. E. , Nikora V. I.
Published: September 2009

In contrast to using a standard control volume approach, general statements of sediment mass balance are derived herein from spatial averaging of the sub‐particle‐scale differential equation of solid mass conservation. The general form of the Exner equation for sediment continuity that is obtained enables analyses in terms of size fractions and also in terms of individual or successive layers, where layer interfaces (e.g., for the bed surface and for bed and suspended loads) are defined on the basis of isosurfaces of sediment concentration (volume fraction) or other sediment properties (e.g., densities or transport rates) within regions of constant concentration. The presented expressions highlight the averaged nature of variables and also the effects of the scales of consideration on definition and interpretation of the macroscopic (mixture‐scale) sediment and layer properties (e.g., averaged densities, volume concentrations or fractions, velocities, transport modes and rates, interfaces, and bed layers). For appropriate simplifications, the general form of the Exner equation is shown to reduce to give more specific conventional expressions, revealing the assumptions implicit in these equations.
Photoluminescence properties of Jahn–Teller transition-metal ions
Authors: Sanz-Ortiz Marta N. , Rodríguez Fernando
Published: September 2009

This work investigates the influence of electron-phonon coupling associated with E⊗e and T⊗e Jahn–Teller (JT) effect in different transition-metal (TM) ions on de-excitation phenomena through nonradiative multiphonon relaxation, i.e., photoluminescence (PL) quenching. We developed a configurational curve model which is able to predict from the absorption spectrum whether a given JT-TM ion is PL or quenched. The prediction is made on the basis of an adapted Dexter–Klick–Russell parameter for JT systems, defined in terms of spectroscopic parameters through ΛJT=αΔeabs/Eabs, where Δeabs refers to the splitting of the parent octahedral Eg states by the JT distortion in E⊗e (α=3/4) or T⊗e (α=1/4), and Eabs is the energy of the first absorption band involving electronic transition between Eg and T2g. We show that PL in any JT-TM ion occurs whenever ΛJT<0.1 or is quenched if ΛJT>0.2. This result is noteworthy since it allows us to establish structural requirements for the JT-TM ion and the host crystal to be PL. Although PL properties of materials containing TM ions depend on a variety of structural factors such as the electronic configuration, the site symmetry, and the crystal field produced by neighboring atoms, the present model achieves this goal through a simple spectroscopic parameter: ΛJT. In this work we correlated the PL properties of different sixfold-coordinated JT systems such as Ti3+, Cu2+, Mn3+, Cr2+, Fe2+, Co3+, and Ni3+ in halides and oxides with ΛJT obtained from their respective absorption spectra. From this analysis we conclude that depending on the nature of the JT coupling and its strength, PL is either strongly favored or quenched in T⊗e while it is mostly quenched in E⊗e systems due to the larger JT distortion.
Extension of the Bissell–Johnson plasma-sheath model for application to fusion-relevant and general plasmas
Authors: Kos L. , Jelić N. , Kuhn S. , Duhovnik J.
Published: September 2009

This article presents an approach to solving a special Fredholm-type integral equation of the first kind with a particular kernel containing a modified Bessel function for applications in plasma physics. From the physical point of view, the problem was defined by Bissell and Johnson (B&J) [Phys. Fluids 30, 779 (1987)] as a task to find the potential profile and the ion velocity distribution function in a plane-parallel discharge with a Maxwellian ion source. The B&J model is a generalization of the well-known Tonks–Langmuir (T&L) [Phys. Rev. 34, 876 (1929)] discharge model characterized by a “cold” ion source. Unlike the T&L model, which can be readily solved analytically, attempts to solve the B&J model with a “warm” ion source have been done only numerically. However, the validity of numerical solutions up to date remains constrained to a rather limited range of a crucial independent parameter of the B&J integral equation, which mathematically is the width of a Gaussian distribution and physically represents the ion temperature. It was solved only for moderately warm ion sources. This paper presents the exact numerical solution of the B&J model, which is valid without any restriction regarding the above-mentioned parameter. It is shown that the ion temperature is very different from the temperature of the ion source. The new results with high-temperature ion sources are not only of particular importance for understanding and describing the plasma-sheath boundary in fusion plasmas, but are of considerable interest for discharge problems in general. The eigenvalue of the problem, found analytically by Harrison and Thompson [Proc. Phys. Soc. 74, 145 (1959)] for the particular case of a cold ion source, is here extended to arbitrary ion-source temperatures.
Diode breakdown related to recombination active defects in block-cast multicrystalline silicon solar cells
Authors: Kwapil Wolfram , Kasemann Martin , Gundel Paul , Schubert Martin C. , Warta Wilhelm , Bronsveld Paula , Coletti Gianluca
Published: September 2009

Solar cells in modules are reverse biased when they are shaded. This can lead to diode breakdown and eventually to the occurrence of hot spots, which may, in the extreme case, destroy the module by thermal degradation. We observed at least three different types of diode breakdown in multicrystalline silicon solar cells. One of them is found to be related to the recombination activity of defects. This type is indicated by a slow increase in the reverse current with reverse bias and a relatively low breakdown voltage around −10 V. The local breakdown voltage depends significantly on the level of contamination of the material. When the solar cell is reverse biased, the breakdown sites emit bright light which shows a broad spectral distribution in the visible range with a maximum at 700 nm.
High near-infrared transparency and carrier mobility of Mo doped In2O3 thin films for optoelectronics applications
Authors: Parthiban S. , Elangovan E. , Ramamurthi K. , Martins R. , Fortunato E.
Published: September 2009

Molybdenum (0–1 at. %) doped indium oxide thin films with high near-infrared (NIR) transparency and high carrier mobility were deposited on Corning-1737 glass substrates at 400 °C by a spray pyrolysis experimental technique. X-ray diffraction (XRD) analysis confirmed the cubic bixbyite structure of indium oxide. The preferred growth orientation along the (222) plane for the low Mo doping level (≤0.5 at. %) shifts to (400) for higher Mo doping levels (>0.6 at. %). The crystallite size extracted from the XRD data corroborates the changes in full width at half maximum due to the variation in Mo doping. A scanning electron microscopy study illustrated the evolution in the surface microstructure as a function of Mo doping. The negative sign of the Hall coefficient confirmed the n-type conductivity. A high carrier mobility of ∼122.4 cm2/V s, a carrier concentration of ∼9.5×1019 cm−3, a resistivity of ∼5.3×10−4 Ω cm, and a high figure of merit of ∼4.2×10−2 Ω−1 are observed for the films deposited with 0.5 at. % Mo. The obtained high average transparency of ∼83% in the wavelengths ranging from 400 to 2500 nm confirmed the extension of transmittance well into the NIR region.
Selecting a single orientation for millimeter sized graphene sheets
Authors: van Gastel R. , N’Diaye A. T. , Wall D. , Coraux J. , Busse C. , Buckanie N. M. , Meyer zu Heringdorf F.-J. , Horn von Hoegen M. , Michely T. , Poelsema B.
Published: September 2009

We have used low energy electron microscopy and photo emission electron microscopy to study and improve the quality of graphene films grown on Ir(111) using chemical vapor deposition (CVD). CVD at elevated temperature already yields graphene sheets that are uniform and of monatomic thickness. Besides domains that are aligned with respect to the substrate, other rotational variants grow. Cyclic growth exploiting the faster growth and etch rates of the rotational variants, yields films that are 99% composed of aligned domains. Precovering the substrate with a high density of graphene nuclei prior to CVD yields pure films of aligned domains extending over millimeters. Such films can be used to prepare cluster-graphene hybrid materials for catalysis or nanomagnetism and can potentially be combined with lift-off techniques to yield high-quality, graphene based, electronic devices.
Magnetoelectric effect in BaTiO3/Ni particulate nanocomposites at microwave frequencies
Authors: Castel V. , Brosseau C. , Ben Youssef J.
Published: September 2009

We present a comprehensive study of the magnetic and microwave properties of piezoelectric BaTiO3/magnetostrictive Ni nanocomposites (NCs), fabricated under uniaxial compression, at room temperature. In the current work, we investigated samples in the compositional range between 0≤fNi≤33.5 vol % and from 0.1 to 6 GHz using broadband microwave spectroscopy in combination with atomic and magnetic force microscopy (MFM), x-ray diffraction (XRD), electron transport, and broadband (6–28 GHz) ferromagnetic resonance (FMR) experiments in the microwave regime to correlate magnetization dynamics, electromagnetic materials parameters, and microstructural information. The static magnetic response is consistent with a model of a composite medium with an unmodified Ni phase in a nonmagnetic matrix. We provide the experimental evidence for a magnetoelectric (ME) effect, i.e., the effective permittivity at microwave frequencies can be controlled by an external magnetic field, which makes these nanostructures ready for microwave tunable devices, sensors, and transducers. We show in the analysis that this magnetic field dependence is inconsistent with expectations from magnetoresistance and magnetocapacitance effects, and propose as an alternative an explanation based on the striction across the interfaces between the magnetic and piezoelectric phases. By varying the Ni content and frequency, room temperature broadband FMR was performed in order to investigate the different contributions, e.g., inhomogeneous broadening, to the effective linewidth and microwave damping. The line broadening and asymmetry of the FMR features are not intrinsic properties of the metallic nanophase but reflects the local nonmagnetic environment in which they are embedded. The increase in the effective Gilbert damping coefficient as function of the Ni content is related to the strong increase in the damping experienced by the precessing magnetization in the Ni phase. One of the characteristic features of the present results is the significant correlation between the internal field probed by FMR and the ME coupling coefficient evaluated by microwave spectroscopy which was not observed in our previous study of ZnO/Ni NCs. The present results highlight the strong influence of interfaces of the composite constituent play a crucial role in the analysis of the ME coupling. In addition MFM has been successfully used to detect the strong magnetic contrast between the phases of these nanostructures which indicates local changes in composition and structure.
Local etching of nanoholes and quantum rings with InxGa1−x droplets
Authors: Stemmann A. , Köppen T. , Grave M. , Wildfang S. , Mendach S. , Hansen W. , Heyn Ch.
Published: September 2009

We study the formation of nanoholes and quantum rings in GaAs and AlGaAs surfaces by local droplet etching with InxGa1−x. The rings are crystallized from droplet material and surround the nanohole openings. In particular, the influence of the In content x on density, diameter, and depth of the nanoholes is investigated. Our data establish an exponential dependence of these quantities on x, which is quantitatively reproduced by a model that considers different surface diffusion energy barriers for Ga and In. By etching with pure In, hole densities as low as 5×106 cm−2 have been achieved. In addition, for low In content incompletely removed initial droplets are visible on the surface. These droplets are not visible on samples with x>0.5 which indicates a higher desorption rate of In compared to Ga. As a consequence, even in the case of etching with InGa the quantum rings consist of nearly pure GaAs. This is confirmed by photoluminescence experiments of quantum rings overgrown with AlGaAs barrier material.
The jump phenomenon in the angular dependence of exchange bias for ferromagnetic/antiferromagnetic bilayers
Authors: Bai Yuhao , Yun Guohong , Bai Narsu
Published: September 2009

Based on the principle of minimal energy, the angular dependence of exchange bias for ferromagnetic/antiferromagnetic bilayers has been investigated in detail. The competition between unidirectional and uniaxial anisotropies divides the initial magnetization state of the bilayer into monostable state and bistable state, which determine the angular dependence of exchange bias directly. When the bilayer is in the bistable state, the exchange bias field and the coercivity will display a jump phenomenon at the orientation angles of the intrinsic hard axes. The jump phenomenon in the angular dependence of exchange bias has been explained by analyzing the magnetization reversal processes. It is found that both the exchange bias field and the coercivity are larger in the magnitude at the points of the jumps. This jump phenomenon is an intrinsic property of the bilayers which is dependent on the interfacial exchange-coupling constant, the thickness, and the uniaxial anisotropy constant of the ferromagnetic layer.
Phase effects in the enhanced transmission through compound subwavelength rectangular hole arrays
Authors: Liu Zhifeng , Jin Guojun
Published: September 2009

We study the enhanced transmission through compound subwavelength rectangular hole arrays in perfect electronically conductive films. It is shown that phase effects become important in the enhanced transmission when extra rectangular holes are added per period. There are two types of resonance mechanisms due to the phase effects: one is the localized waveguide mode phase resonance and the other is the surface mode phase resonance. The localized waveguide mode phase resonances, which are related to the number of holes per period and their relative positions, split the waveguide resonance peak into several peaks. The surface mode phase resonances, which appear evidently only for some special arrangements of holes in a unit cell, lead to the suppression of some surface mode resonance peaks. Our approach is advantageous to modulate the enhanced transmission in metallic hole arrays in the terahertz or microwave frequency regime.
Variation in the statistical and formative time lags of high power microwave surface flashover utilizing a superimposed dc electric field
Authors: Foster Jonathan , Thomas Mark , Neuber Andreas A.
Published: September 2009

In an effort to investigate the physics involved in the initiation of high power microwave surface flashover, a strong direct current (dc) electric field was introduced to the flashover region. The primary objective of this study is to demonstrate that an external electric field can have a significant impact on the delay time for surface flashover. It has been observed experimentally that the statistical and formative delay times for surface flashover can be varied depending on the polarity of the applied dc field. This external electric field may sweep possible breakdown initiating electrons away from the flashover region prior to the application of the high power microwave pulse. A distinct increase in the average statistical delay was observed primarily with a superimposed dc field in a positive polarity geometry as well as a decrease in the formative delay for either polarity in 167 mbar of nitrogen.
Theoretical design of GaN/ferroelectric heterostructure: Toward a strained semiconductor on ferroelectrics
Authors: Zhang Jihua , Yang Chuanren , Wu Song , Liu Ying , Chen Hongwei , Zhang Wanli , Li Yanrong
Published: September 2009

Ferroelectric/semiconductor heterostructures are of great interest for future electronic devices. This letter examined the material parameters and carrier distributions of an AlGaN(0001)/GaN(0001)/BaTiO3(111) double heterostructure by combining first principles and charge control model. Results show that in the optimized case, there will appear two channels in GaN layer, and the sheet electron density will be doubled compared to conventional AlGaN/GaN heterojunction. A possible device structure was proposed to make the channel become switchable and reduce the source/drain resistance. This strained semiconductor on ferroelectric structure may be promising for high speed power devices.
Vortex sheet motion in incompressible Richtmyer–Meshkov and Rayleigh–Taylor instabilities with surface tension
Authors: Matsuoka Chihiro
Published: September 2009

Motion of a planar interface in incompressible Richtmyer–Meshkov (RM) and Rayleigh–Taylor (RT) instabilities with surface tension is investigated numerically by using the boundary integral method. It is shown that when the Atwood number is small, an interface rolls up without regularization of the interfacial velocity. A phenomenon known as “pinching” in the physics of drops is observed in the final stage of calculations at various Atwood numbers and surface tension coefficients, and it is shown that this phenomenon is caused by a vortex dipole induced on the interface. It is also shown that when the surface tension coefficient is large, finite amplitude standing wave solutions exist for the RM instability. This standing wave solution is investigated in detail by nonlinear stability analysis. When gravity is taken into account (RT instability), linearly stable but nonlinearly unstable motion can occur under a critical condition that the frequency of the linear dispersion relation in the system is equal to zero. Further, it is shown that the growth rate of bubbles and spikes under this critical motion is neither of the exponential type nor of the power law type at both the linear stage and the asymptotic stage.
Transmission interference tuned by an external static magnetic field in a two-slit structure
Authors: Hu Bin , Gu Ben-Yuan , Zhang Yan , Liu Ming
Published: September 2009

We present a near-field analysis of transmitted field interference tuned by an external static magnetic field on an n-doped semiconductor film drilled by two slits at terahertz frequency. It is found that the peak magnetic field intensity of the interference pattern between the two slits can be strengthened twice as against that of zero external static magnetic field. The physical origin comes from the interaction between surface plasmon polaritons (SPPs) and radiative evanescent field components launched by each slit on the transmitted surface, and also from the considerable alteration of the SPPs, caused by the external static magnetic field.
Conductive atomic force microscopy study of InAs growth kinetics on vicinal GaAs (110)
Authors: Tejedor Paloma , Díez-Merino Laura , Beinik Igor , Teichert Christian
Published: September 2009

Conductive atomic force microscopy has been used to investigate the effect of atomic hydrogen and step orientation on the growth behavior of InAs on GaAs (110) misoriented substrates. Samples grown by conventional molecular beam epitaxy exhibit higher conductivity on [11¯0]-multiatomic step edges, where preferential nucleation of InAs nanowires takes place by step decoration. On H-terminated substrates with triangular terraces bounded by [11¯5]-type steps, three-dimensional InAs clusters grow selectively at the terrace apices as a result of a kinetically driven enhancement in upward mass transport via AsHx intermediate species and a reduction in the surface free energy.
Room-temperature ferromagnetism observed in Mo-doped indium oxide films
Authors: Park Chang-Yup , Yoon Soon-Gil , Jo Young-Hun , Shin Sung-Chul
Published: September 2009

We have investigated the magnetic properties of molybdenum-doped (0–5 wt %) indium oxide films deposited on (100) MgO substrates using pulsed-laser deposition technique. Interestingly these films were found to reveal room-temperature ferromagnetism, where the magnetization increases with Mo doping. The maximum saturation magnetization of ∼6.6 emu/cc was found for ∼5 wt % Mo doping, providing approximately five times enhancement in comparison to the undoped film. We believe that this enhancement is ascribed to the magnetic moments of Mo ions occupied in the In sites.
Wave energy converter with enhanced amplitude response at frequencies coinciding with Swedish west coast sea states by use of a supplementary submerged body
Authors: Engström J. , Eriksson M. , Isberg J. , Leijon M.
Published: September 2009

The full-scale direct-driven wave energy converter developed at Uppsala University has been in offshore operation at the Swedish west coast since 2006. Earlier simulations have now been validated by full-scale experiment with good agreement. Based on that, a theoretical model for a passive system having optimum amplitude response at frequencies coinciding with Swedish west coast conditions has been developed. The amplitude response is increased by adding supplementary inertia by use of the additional mass from a submerged body. A sphere with neutral buoyancy is chosen as the submerged body and modeled as being below the motion of the waves. The model is based on potential linear wave theory and the power capture ratio is studied for real ocean wave data collected at the research test site. It is found that the power capture ratio for the two body system can be increased from 30% to 60% compared to a single body system. Increased velocity in the system also decreases the value for optimal load damping from the generator, opening up the possibility to design smaller units.
Measuring the cantilever-position-sensitive detector distance and cantilever curvature for cantilever sensor applications
Authors: Xu Meng , Tian Ye , Coates M. L. , Beaulieu L. Y.
Published: September 2009

Measuring cantilever sensor deflections using an optical beam deflection system is more complicated than often assumed. The direction of the reflected beam is dependent on the surface normal of the cantilever, which in turn is dependent on the state of the cantilever. It is often assumed that the cantilever is both straight and perfectly level before the onset of sensing experiments although this assumption, especially the former, is rarely true. Failure to characterize the initial state of the cantilever can lead to irreproducibility in cantilever sensor measurements. We have developed three new methods for characterizing the initial state of the cantilever. In the first case we show how to define the initial angle of inclination β of the chip on which the cantilever is attached. This method was tested using an aluminum block with a known angle of inclination. A new method for determining the initial distance Lo between the cantilever and the position-sensitive detector (PSD) is also presented. This parameter which behaves as an amplification factor of the PSD signal is critical for obtaining precise cantilever sensor data. Lastly, we present a method for determining the initial curvature of the cantilever which often results from depositing the sensing platform on the lever. Experiments conducted using deflected cantilevers showed the model to be accurate. The characterization methods presented in this work are simple to use, easy to implement, and can be incorporated into most cantilever sensor setups.
Evidence for existence of deep acceptor levels in SiGe-on-insulator substrate fabricated using Ge condensation technique
Authors: Yang Haigui , Wang Dong , Nakashima Hiroshi
Published: September 2009

By back-gate metal-oxide-semiconductor field-effect transistor method, we examined acceptor concentration (NA) in nondoped SiGe-on-insulator (SGOI) substrates fabricated using Ge condensation. We found NA’s were much higher than the hole concentration (p) measured by Hall effect for low-Ge% SGOI, while NA’s were almost the same as p for high-Ge% SGOI. Such different behaviors between NA and p as a function of Ge% are closely related to the existence of deep acceptor levels (ETA) in SGOI and ETA energy shift toward valence band with increasing in Ge%, which was confirmed from the temperature dependence of p.
Facet formation during solid phase epitaxy regrowth: A lattice kinetic Monte Carlo model
Authors: Martin-Bragado Ignacio , Moroz Victor
Published: September 2009

An atomistic model to account for the formation of facets during solid phase epitaxy regrowth (SPER) is shown. This model relies on a lattice kinetic Monte Carlo approach. The lattice atoms produce different crystalline planes growing with different planar velocities. In particular, the model explains the arrow tip formation during SPER of thin silicon fins typical for fin field effect transistors and the formation of trenches in rectangular-shaped amorphized regions in (001) and (011) silicon, caused by the distortion of the lattice by shear strain and propagated by (111) facets.
Room-temperature lasing of electrically pumped red-emitting InP/(Al0.20Ga0.80)0.51In0.49P quantum dots embedded in a vertical microcavity
Authors: Eichfelder Marcus , Schulz Wolfgang-Michael , Reischle Matthias , Wiesner Michael , Roßbach Robert , Jetter Michael , Michler Peter
Published: September 2009

We demonstrate electrically pumped laser light emission in the visible (red) spectral range using self-assembled InP quantum dots embedded in a microcavity mesa realized by monolithically grown high-reflectivity AlGaAs distributed Bragg reflectors. We used common semiconductor laser processing steps to fabricate stand-alone index-guided vertical-cavity surface-emitting lasers with oxide apertures for optical wave-guiding and electrical current constriction. Ultra-low threshold of around 10 A/cm2 and room temperature lasing were demonstrated. Additionally, the temperature independence of the threshold current, which was predicted in theory for quantum dot lasers, is displayed.