141 research outputs found
Negative quantum capacitance in graphene nanoribbons with lateral gates
We present numerical simulations of the capacitive coupling between graphene
nanoribbons of various widths and gate electrodes in different configurations.
We compare the influence of lateral metallic or graphene side gate structures
on the overall back gate capacitive coupling. Most interestingly, we find a
complex interplay between quantum capacitance effects in the graphene
nanoribbon and the lateral graphene side gates, giving rise to an
unconventional negative quantum capacitance. The emerging non-linear capacitive
couplings are investigated in detail. The experimentally relevant relative
lever arm, the ratio between the coupling of the different gate structures, is
discussed.Comment: 8 pages, 6 figure
Controlled Stark shifts in Er-doped crystalline and amorphous waveguides for quantum state storage
We present measurements of the linear Stark effect on the I I transition in an Er-doped proton-exchanged
LiNbO crystalline waveguide and an Er-doped silicate fiber. The
measurements were made using spectral hole burning techniques at temperatures
below 4 K. We measured an effective Stark coefficient
kHz/Vcm in the crystalline waveguide and
kHz/Vcm in the silicate fiber.
These results confirm the potential of Erbium doped waveguides for quantum
state storage based on controlled reversible inhomogeneous broadening.Comment: 4 pages, 2 figures v2. typo in formula correcte
Nonequilibrium wetting
When a nonequilibrium growing interface in the presence of a wall is
considered a nonequilibrium wetting transition may take place. This transition
can be studied trough Langevin equations or discrete growth models. In the
first case, the Kardar-Parisi-Zhang equation, which defines a very robust
universality class for nonequilibrium moving interfaces, with a soft-wall
potential is considered. While in the second, microscopic models, in the
corresponding universality class, with evaporation and deposition of particles
in the presence of hard-wall are studied. Equilibrium wetting is related to a
particular case of the problem, it corresponds to the Edwards-Wilkinson
equation with a potential in the continuum approach or to the fulfillment of
detailed balance in the microscopic models. In this review we present the
analytical and numerical methods used to investigate the problem and the very
rich behavior that is observed with them.Comment: Review, 36 pages, 16 figure
Evaluation of equity in informal land development systems in two Nigerian cities
The informal land development system in Sub-Saharan Africa (SSA) is perceived to promote equity and could be leveraged to support sustainable urban development and management. However, scanty empirical evidence exists on the extent of the system’s provision of equity to support policy formulation and practice in the region. Based on stakeholder workshops, focus group discussions and questionnaire surveys, this study analyses the system’s provision of equity in Nigeria. The study finds all categories of people undertake informal developments. Consistent with literature, this finding reflects wide patronage of the informal land development system and its relevance. Nevertheless, contrary to the existing perception, the system’s provision of equity is low. The study recommends for the institution of pro-poor and gender sensitive land development and management policies and programmes to increase the levels of equity to support the achievement of the country’s sustainable urban development and management agenda
HIF1-alpha overexpression indicates a good prognosis in early stage squamous cell carcinomas of the oral floor
BACKGROUND: Hypoxia-inducible factor 1 (HIF-1) is a transcription factor, which plays a central role in biologic processes under hypoxic conditions, especially concerning tumour angiogenesis. HIF-1α is the relevant, oxygen-dependent subunit and its overexpression has been associated with a poor prognosis in a variety of malignant tumours. Therefore, HIF-1α expression in early stage oral carcinomas was evaluated in relation to established clinico-pathological features in order to determine its value as a prognostic marker. METHODS: 85 patients with histologically proven surgically treated T1/2 squamous cell carcinoma (SCC) of the oral floor were eligible for the study. Tumor specimens were investigated by means of tissue micro arrays (TMAs) and immunohistochemistry for the expression of HIF-1. Correlations between clinical features and the expression of HIF-1 were evaluated by Kaplan-Meier curves, log-rank tests and multivariate Cox regression analysis. RESULTS: HIF-1α was frequently overexpressed in a probably non-hypoxia related fashion. The expression of HIF-1α was related with a significantly improved 5-year survival rate (p < 0.01) and a significantly increased disease free period (p = 0.01) independent from nodal status and tumour size. In primary node negative T1/T2 SCC of the oral floor, absence of HIF-1α expression specified a subgroup of high-risk patients (p < 0.05). CONCLUSION: HIF-1α overexpression is an indicator of favourable prognosis in T1 and T2 SCC of the oral floor. Node negative patients lacking HIF-1α expression may therefore be considered for adjuvant radiotherapy
Experimental probing of the interplay between ferromagnetism and localisation in (Ga,Mn)As
The question whether the Anderson-Mott localisation enhances or reduces
magnetic correlations is central to the physics of magnetic alloys.
Particularly intriguing is the case of (Ga,Mn)As and related magnetic
semiconductors, for which diverging theoretical scenarios have been proposed.
Here, by direct magnetisation measurements we demonstrate how magnetism evolves
when the density of carriers mediating the spin-spin coupling is diminished by
the gate electric field in metal/insulator/semiconductor structures of
(Ga,Mn)As. Our findings show that the channel depletion results in a monotonic
decrease of the Curie temperature, with no evidence for the maximum expected
within the impurity-band models. We find that the transition from the
ferromagnetic to the paramagnetic state proceeds via the emergence of a
superparamagnetic-like spin arrangement. This implies that carrier localisation
leads to a phase separation into ferromagnetic and nonmagnetic regions, which
we attribute to critical fluctuations in the local density of states, specific
to the Anderson-Mott quantum transition.Comment: 8 pages, 3 figure
Establishment of canine hemangiosarcoma xenograft models expressing endothelial growth factors, their receptors, and angiogenesis-associated homeobox genes
<p>Abstract</p> <p>Background</p> <p>Human hemangiosarcoma (HSA) tends to have a poor prognosis; its tumorigenesis has not been elucidated, as there is a dearth of HSA clinical specimens and no experimental model for HSA. However, the incidence of spontaneous HSA is relatively high in canines; therefore, canine HSA has been useful in the study of human HSA. Recently, the production of angiogenic growth factors and their receptors in human and canine HSA has been reported. Moreover, the growth-factor environment of HSA is very similar to that of pathophysiological angiogenesis, which some homeobox genes regulate in the transcription of angiogenic molecules. In the present study, we established 6 xenograft canine HSA tumors and detected the expression of growth factors, their receptors, and angiogenic homeobox genes.</p> <p>Methods</p> <p>Six primary canine HSAs were xenografted to nude mice subcutaneously and serially transplanted. Subsequently, the expressions of vascular endothelial growth factor (VEGF)-A, basic fibroblast growth factors (bFGF), flt-1 and flk-1 (receptors of VEGF-A), FGFR-1, and angiogenic homeobox genes HoxA9, HoxB3, HoxB7, HoxD3, Pbx1, and Meis1 were investigated in original and xenograft tumors by histopathology, immunostaining, and reverse transcription polymerase chain reaction (RT-PCR), using canine-specific primer sets.</p> <p>Results</p> <p>Histopathologically, xenograft tumors comprised a proliferation of neoplastic cells that were varied in shape, from spindle-shaped and polygonal to ovoid; some vascular-like structures and vascular clefts of channels were observed, similar to those in the original tumors. The expression of endothelial markers (CD31 and vWF) was detected in xenograft tumors by immunohistochemistry and RT-PCR. Moreover, the expression of VEGF-A, bFGF, flt-1, flk-1, FGFR-1, HoxA9, HoxB3, HoxB7, HoxD3, Pbx1, and Meis1 was detected in xenograft tumors. Interestingly, expressions of bFGF tended to be higher in 3 of the xenograft HSA tumors than in the other tumors.</p> <p>Conclusion</p> <p>We established 6 xenograft canine HSA tumors in nude mice and found that the expressions of angiogenic growth factors and their receptors in xenograft HSAs were similar to those in spontaneous HSA. Furthermore, we detected the expression of angiogenic homeobox genes; therefore, xenograft models may be useful in analyzing malignant growth in HSA.</p
The 3D conductive thermal field of the North Alpine Foreland Basin: influence of the deep structure and the adjacent European Alps
First international consensus on the methodology of lymphangiogenesis quantification in solid human tumours
The lymphatic system is the primary pathway of metastasis for most human cancers. Recent research efforts in studying lymphangiogenesis have suggested the existence of a relationship between lymphatic vessel density and patient survival. However, current methodology of lymphangiogenesis quantification is still characterised by high intra- and interobserver variability. For the amount of lymphatic vessels in a tumour to be a clinically useful parameter, a reliable quantification technique needs to be developed. With this consensus report, we therefore would like to initiate discussion on the standardisation of the immunohistochemical method for lymphangiogenesis assessment
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