Indirect and direct energy gaps in the Kondo semiconductor YbB12

Optical conductivity [$\sigma(\omega)$] of the Kondo semiconductor YbB$_{12}$ has been measured over wide ranges of temperature ($T$=8$-$690 K) and photon energy ($\hbar \omega \geq$ 1.3 meV). The $\sigma(\omega)$ data reveal the entire crossover of YbB$_{12}$ from a metallic electronic structure at high $T$ into a semiconducting one at low $T$. Associated with the gap development in $\sigma(\omega)$, a clear onset is newly found at $\hbar\omega$=15 meV for $T \leq$ 20 K. The onset energy is identified as the gap width of YbB$_{12}$ appearing in $\sigma(\omega)$. This gap in \sigma(\omega)$is interpreted as the indirect gap, which has been predicted in the band model of Kondo semiconductor. On the other hand, the strong mid-infrared (mIR) peak observed in$\sigma(\omega)$ is interpreted as arising from the direct gap. The absorption coefficient around the onset and the mIR peak indeed show characteristic energy dependences expected for indirect and direct optical transitions in conventional semiconductors.Comment: 4 pages, 3 figures, submitted to J. Phys. Soc. Jp

Carbon cycling and budget in a forested basin of southwestern Hokkaido, northern Japan

Quantification of annual carbon sequestration is very important in order to assess the function of forest ecosystems in combatting global climate change and the ecosystem responses to those changes. Annual cycling and budget of carbon in a forested basin was investigated to quantify the carbon sequestration of a cool-temperate deciduous forest ecosystem in the Horonai stream basin, Tomakomai Experimental Forest, northern Japan. Net ecosystem exchange, soil respiration, biomass increment, litterfall, soil-solution chemistry, and stream export were observed in the basin from 1999–2001 as a part of IGBP-TEMA project. We found that 258 g C m–2 year–1 was sequestered annually as net ecosystem exchange (NEE) in the forested basin. Discharge of carbon to the stream was 4 g C m–2 year–1 (about 2% of NEE) and consisted mainly of dissolved inorganic carbon (DIC). About 43% of net ecosystem productivity (NEP) was retained in the vegetation, while about 57% of NEP was sequestered in soil, suggesting that the movement of sequestered carbon from aboveground to belowground vegetation was an important process for net carbon accumulation in soil. The derived organic carbon from aboveground vegetation that moved to the soil mainly accumulated in the solid phase of the soil, with the result that the export of dissolved organic carbon to the stream was smaller than that of dissolved inorganic carbon. Our results indicated that the aboveground and belowground interaction of carbon fluxes was an important process for determining the rate and retention time of the carbon sequestration in a cool-temperate deciduous forest ecosystem in the southwestern part of Hokkaido, northern Japan

Nuclear Alpha-Particle Condensates

The $\alpha$-particle condensate in nuclei is a novel state described by a product state of $\alpha$'s, all with their c.o.m. in the lowest 0S orbit. We demonstrate that a typical $\alpha$-particle condensate is the Hoyle state ($E_{x}=7.65$ MeV, $0^+_2$ state in $^{12}$C), which plays a crucial role for the synthesis of $^{12}$C in the universe. The influence of antisymmentrization in the Hoyle state on the bosonic character of the $\alpha$ particle is discussed in detail. It is shown to be weak. The bosonic aspects in the Hoyle state, therefore, are predominant. It is conjectured that $\alpha$-particle condensate states also exist in heavier $n\alpha$ nuclei, like $^{16}$O, $^{20}$Ne, etc. For instance the $0^+_6$ state of $^{16}$O at $E_{x}=15.1$ MeV is identified from a theoretical analysis as being a strong candidate of a $4\alpha$ condensate. The calculated small width (34 keV) of $0^+_6$, consistent with data, lends credit to the existence of heavier Hoyle-analogue states. In non-self-conjugated nuclei such as $^{11}$B and $^{13}$C, we discuss candidates for the product states of clusters, composed of $\alpha$'s, triton's, and neutrons etc. The relationship of $\alpha$-particle condensation in finite nuclei to quartetting in symmetric nuclear matter is investigated with the help of an in-medium modified four-nucleon equation. A nonlinear order parameter equation for quartet condensation is derived and solved for $\alpha$ particle condensation in infinite nuclear matter. The strong qualitative difference with the pairing case is pointed out.Comment: 71 pages, 41 figures, review article, to be published in "Cluster in Nuclei (Lecture Notes in Physics) - Vol.2 -", ed. by C. Beck, (Springer-Verlag, Berlin, 2011

Helium Clustering in Neutron-Rich Be Isotopes

Measurements of the helium-cluster breakup and neutron removal cross sections for neutron-rich Be isotopes A=10-12,14 are presented. These have been studied in the 30 to 42 MeV/u energy range where reaction measurements are proposed to be sensitive to the cluster content of the ground-state wave-function. These measurements provide a comprehensive survey of the decay processes of the Be isotopes by which the valence neutrons are removed revealing the underlying alpha-alpha core-cluster structure. The measurements indicate that clustering in the Be isotopes remains important up to the drip-line nucleus 14^Be and that the dominant helium-cluster structure in the neutron-rich Be isotopes corresponds to alpha-Xn-alpha.Comment: 5 pages, 2 tables and 3 figure

Combination therapy with irinotecan and cisplatin as neoadjuvant chemotherapy in locally advanced cervical cancer

To evaluate the response rate and toxicity of the combination of irinotecan (CPT-11) and cisplatin in a neoadjuvant setting, a phase II study was conducted regarding the regimen of this combination in patients with locally advanced cervical cancer. Eligibility included patients with previously untreated stage Ib2, IIb, or IIIb squamous cell carcinoma with good performance status. CPT-11 (60 mg m−2) was administered intravenously on days 1, 8 and 15, followed by cisplatin (60 mg m−2) given intravenously on day 1. Treatment was repeated every 4 weeks for a total of two or three cycles. Among 23 eligible patients (median age: 59 years), three showed complete response (13%), 15 showed partial response (65%), for an overall response rate of 78% (95% confidence interval 58–90%). Stable disease was observed in four cases (17%) and progressive disease in one (4%). The median time to failure and median survival time have not yet been reached. Of the 52 treatment cycles administered, diarrhoea and grade 3 or 4 neutropenia were observed in 10% and 75% respectively. There were no therapy-related deaths. The combination of CPT-11 with cisplatin is a promising regimen for neoadjuvant chemotherapy in locally advanced cervical cancer. The toxicities of this regimen are well tolerated. © 1999 Cancer Research Campaig

Ab-initio structural, elastic, and vibrational properties of carbon nanotubes

A study based on ab initio calculations is presented on the estructural, elastic, and vibrational properties of single-wall carbon nanotubes with different radii and chiralities. We use SIESTA, an implementation of pseudopotential-density-functional theory which allows calculations on systems with a large number of atoms per cell. Different quantities like bond distances, Young moduli, Poisson ratio and the frequencies of different phonon branches are monitored versus tube radius. The validity of expectations based on graphite is explored down to small radii, where some deviations appear related to the curvature effects. For the phonon spectra, the results are compared with the predictions of the simple zone-folding approximation. Except for the known defficiencies of this approximation in the low-frequency vibrational regions, it offers quite accurate results, even for relatively small radii.Comment: 13 pages, 7 figures, submitted to Phys. Rev. B (11 Nov. 98

Autosomal dominant polycystic kidney disease with diffuse proliferative glomerulonephritis - an unusual association: a case report and review of the literature

<p>Abstract</p> <p>Introduction</p> <p>Autosomal dominant polycystic kidney disease is an inherited disorder that is characterized by the development and growth of cysts in the kidneys and other organs. Urinary protein excretion is usually less than 1 g/24 hours in autosomal dominant polycystic kidney disease, and an association of nephrotic syndrome with this condition is considered rare. There are only anecdotal case reports of autosomal dominant polycystic kidney disease associated with nephrotic syndrome, with focal segmental glomerulosclerosis being the most commonly reported histopathological diagnosis. Nephrotic-range proteinuria in the presence of autosomal dominant polycystic kidney disease, with or without an accompanying decline in renal function, should be investigated by open renal biopsy to exclude coexisting glomerular disease. To the best of our knowledge, this is the first case of autosomal dominant polycystic kidney disease with histologically proven diffuse proliferative glomerulonephritis presenting with nephrotic-range proteinuria. No other reports of this could be found in a global electronic search of the literature.</p> <p>Case presentation</p> <p>We report the case of a 35-year-old Indo-Aryan man with autosomal dominant polycystic kidney disease associated with nephrotic syndrome and a concomitant decline in his glomerular filtration rate. Open renal biopsy revealed diffuse proliferative glomerulonephritis. An accurate diagnosis enabled us to manage him conservatively with a successful outcome, without the use of corticosteroid which is the standard treatment and the drug most commonly used to treat nephrotic syndrome empirically.</p> <p>Conclusion</p> <p>Despite the reluctance of physicians to carry out a renal biopsy on patients with autosomal dominant polycystic kidney disease, our case supports the idea that renal biopsy is needed in patients with polycystic kidney disease with nephrotic-range proteinuria to make an accurate diagnosis. It also illustrates the importance of open renal biopsy in planning appropriate treatment for patients with autosomal dominant polycystic kidney disease with nephrotic-range proteinuria. The treatment for various histological subtypes leading to nephrotic syndrome is different, and in this modern era we should practice evidence-based medicine and should avoid empirical therapy with its associated adverse effects.</p

A Genome-Wide Association Study of the Metabolic Syndrome in Indian Asian Men

We conducted a two-stage genome-wide association study to identify common genetic variation altering risk of the metabolic syndrome and related phenotypes in Indian Asian men, who have a high prevalence of these conditions. In Stage 1, approximately 317,000 single nucleotide polymorphisms were genotyped in 2700 individuals, from which 1500 SNPs were selected to be genotyped in a further 2300 individuals. Selection for inclusion in Stage 1 was based on four metabolic syndrome component traits: HDL-cholesterol, plasma glucose and Type 2 diabetes, abdominal obesity measured by waist to hip ratio, and diastolic blood pressure. Association was tested with these four traits and a composite metabolic syndrome phenotype. Four SNPs reaching significance level p<5×10−7 and with posterior probability of association >0.8 were found in genes CETP and LPL, associated with HDL-cholesterol. These associations have already been reported in Indian Asians and in Europeans. Five additional loci harboured SNPs significant at p<10−6 and posterior probability >0.5 for HDL-cholesterol, type 2 diabetes or diastolic blood pressure. Our results suggest that the primary genetic determinants of metabolic syndrome are the same in Indian Asians as in other populations, despite the higher prevalence. Further, we found little evidence of a common genetic basis for metabolic syndrome traits in our sample of Indian Asian men

Anisotropic behaviors of massless Dirac fermions in graphene under periodic potential

Charge carriers of graphene show neutrino-like linear energy dispersions as well as chiral behavior near the Dirac point. Here we report highly unusual and unexpected behaviors of these carriers in applied external periodic potentials, i.e., in graphene superlattices. The group velocity renormalizes highly anisotropically even to a degree that it is not changed at all for states with wavevector in one direction but is reduced to zero in another, implying the possibility that one can make nanoscale electronic circuits out of graphene not by cutting it but by drawing on it in a non-destructive way. Also, the type of charge carrier species (e.g. electron, hole or open orbit) and their density of states vary drastically with the Fermi energy, enabling one to tune the Fermi surface-dominant properties significantly with gate voltage. These results address the fundamental question of how chiral massless Dirac fermions propagate in periodic potentials and point to a new possible path for nanoscale electronics.Comment: 10 pages, 9 figure

Assessing the efficiency and significance of Methylated DNA Immunoprecipitation (MeDIP) assays in using in vitro methylated genomic DNA

<p>Abstract</p> <p>Background</p> <p>DNA methylation contributes to the regulation of gene expression during development and cellular differentiation. The recently developed Methylated DNA ImmunoPrecipitation (MeDIP) assay allows a comprehensive analysis of this epigenetic mark at the genomic level in normal and disease-derived cells. However, estimating the efficiency of the MeDIP technique is difficult without previous knowledge of the methylation status of a given cell population. Attempts to circumvent this problem have involved the use of <it>in vitro </it>methylated DNA in parallel to the investigated samples. Taking advantage of this stratagem, we sought to improve the sensitivity of the approach and to assess potential biases resulting from DNA amplification and hybridization procedures using MeDIP samples.</p> <p>Findings</p> <p>We performed MeDIP assays using <it>in vitro </it>methylated DNA, with or without previous DNA amplification, and hybridization to a human promoter array. We observed that CpG content at gene promoters indeed correlates strongly with the MeDIP signal obtained using <it>in vitro </it>methylated DNA, even when lowering significantly the amount of starting material. In analyzing MeDIP products that were subjected to whole genome amplification (WGA), we also revealed a strong bias against CpG-rich promoters during this amplification procedure, which may potentially affect the significance of the resulting data.</p> <p>Conclusion</p> <p>We illustrate the use of <it>in vitro </it>methylated DNA to assess the efficiency and accuracy of MeDIP procedures. We report that efficient and reproducible genome-wide data can be obtained via MeDIP experiments using relatively low amount of starting genomic DNA; and emphasize for the precaution that must be taken in data analysis when an additional DNA amplification step is required.</p