A tunable topological insulator in the spin helical Dirac transport regime

Helical Dirac fermions-charge carriers that behave as massless relativistic particles with an intrinsic angular momentum (spin) locked to its translational momentum-are proposed to be the key to realizing fundamentally new phenomena in condensed matter physics. Prominent examples include the anomalous quantization of magneto-electric coupling, half-fermion states that are their own antiparticle, and charge fractionalization in a Bose-Einstein condensate, all of which are not possible with conventional Dirac fermions of the graphene variety. Helical Dirac fermions have so far remained elusive owing to the lack of necessary spin-sensitive measurements and because such fermions are forbidden to exist in conventional materials harbouring relativistic electrons, such as graphene or bismuth. It has recently been proposed that helical Dirac fermions may exist at the edges of certain types of topologically ordered insulators-materials with a bulk insulating gap of spin-orbit origin and surface states protected against scattering by time-reversal symmetry-and that their peculiar properties may be accessed provided the insulator is tuned into the so-called topological transport regime. However, helical Dirac fermions have not been observed in existing topological insulators. Here we report the realization and characterization of a tunable topological insulator in a bismuth-based class of material by combining spin-imaging and momentum-resolved spectroscopies, bulk charge compensation, Hall transport measurements and surface quantum control. Our results reveal a spin-momentum locked Dirac cone carrying a non-trivial Berry's phase that is nearly 100 per cent spin-polarized, which exhibits a tunable topological fermion density in the vicinity of the Kramers point and can be driven to the long-sought topological spin transport regime. The observed topological nodal state is shown to be protected even up to 300 K. Our demonstration of room-temperature topological order and non-trivial spin-texture in stoichiometric Bi(2)Se(3).M(x) (M(x) indicates surface doping or gating control) paves the way for future graphene-like studies of topological insulators, and applications of the observed spin-polarized edge channels in spintronic and computing technologies possibly at room temperature.

Corticosterone administration induces oxidative injury in skeletal muscle of broiler chickens

The present study had been conducted to explore the effect of corticosterone (CORT) on the induction of lipid peroxidation in skeletal muscle. The experimental chickens were subjected to 1 single s.c. injection of CORT (4 mg/kg of BW). Blood samples were obtained at the beginning and end of a 3-h experimental period. Muscle samples were obtained from musculus pectoralis major and musculus biceps femoris (BF) before and immediately after slaughter, and at 24- and 48-h time points postmortem. The result showed that plasma level of TBA reacting substances (TBARS) was significantly increased, whereas the activity of super-oxide dismutase was decreased after CORT injection. Plasma level of total antioxidant power, as reflected by the ferric reducing-antioxidant power, was increased by CORT administration. The preslaughter level of TBARS could be increased by CORT administration in pectoralis major. In contrast, although the preslaughter level of TBARS was not significantly changed by CORT administration in BF, the augmented TBARS level was detected at 48 h postmortem in BF of CORT chickens. During the period of storage, the concentrations of TBARS increased, whereas ferric reducing-antioxidant power level decreased over time regardless of treatment. In conclusion, the data suggest that elevated CORT due to preslaughter stress would affect the redox balance in skeletal muscle. The result suggested that the oxidative stability during storage of meat is associated with the alteration in muscle physiology induced by CORT administration.

Association between human papillomavirus (HPV) status with serum cytokine and angiogenic factor (CAF) profile after induction chemotherapy in head and neck squamous cell carcinoma (HNSCC)

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Background: Human papillomavirus has been implicated in the development of head and neck squamous cell carcinoma and is associated with a more favorable clinical outcome. Previously, we identified a serum hypoxia signature associated with HNSCC progression (Byers et al, Proc ASCO. 2008). We investigated the association between HPV status, serum biomarkers, and clinical outcome in patients treated with induction chemotherapy. Methods: 47 previously untreated patients with locally advanced nodal disease (T0–4, N2b/c/3, M0) received 6 weekly cycles of paclitaxel (135 mg/m2), carboplatin (AUC 2), and cetuximab (400 mg/m2 week 1; 250 mg/m2 weeks 2–6) followed by definitive local therapy. 46 (98%) patients had a complete or partial response to induction chemotherapy (Kies et al, Proc ASCO. 2006), and 6 have had tumor progression (PD) after a minimum follow-up of two years. Formalin fixed biopsies were available for HPV testing by in situ hybridization with non-radioisotopic chromogen for 25 patients (including 5/6 with PD). 38 CAFs were measured by multiplex bead assay before and during treatment. Results: 12/25 patients were HPV-positive, all male and six were never smokers; of the 13 HPV-negative patients, four were male and three were never smokers. Among those with available data, all 5 patients with PD were HPV-negative (p = 0.02). There were four study deaths, all in the HPV-negative group. Overall survival was superior in HPV-positive patients (p = 0.04). There was no significant association between HPV status and serum CAF markers. However, among HPV-negative patients, PD was associated with the CAF hypoxia signature (5/8 patients with the hypoxia signature progressed versus 0/5 signature-negative). Of the individual CAFs, osteopontin was significantly elevated in all HPV-negative patients with PD. Conclusions: HPV positivity was associated with a longer progression-free survival and overall survival. Among HPV-negative patients, only those with a serum hypoxia signature had disease progression. These data suggest that the combination of HPV status and CAF profiling may identify patients at risk for relapse after sequential therapy.

No significant financial relationships to disclose.

The importance of myocardial amino acids during ischemia and reperfusion in dilated left ventricle of patients with degenerative mitral valve disease

Taurine, glutamine, glutamate, aspartate, and alanine are the most abundant intracellular free amino acids in human heart. The myocardial concentration of these amino acids changes during ischemia and reperfusion due to alterations in metabolic and ionic homeostasis. We hypothesized that dilated left ventricle secondary to mitral valve disease has different levels of amino acids compared to the right ventricle and that such differences determine the extent of amino acids' changes during ischemia and reperfusion. Myocardial concentration of amino acids was measured in biopsies collected from left and right ventricles before cardioplegic arrest (Custodiol HTK) and 10 min after reperfusion in patients undergoing mitral valve surgery. The dilated left ventricle had markedly higher (P < 0.05) concentrations (nmol/mg wet weight) of taurine (17.0 +/- 1.5 vs. 10.9 +/- 1.5), glutamine (20.5 +/- 2.4 vs. 12.1 +/- 1.2), and glutamate (18.3 +/- 2.2 vs. 11.4 +/- 1.5) when compared to right ventricle. There were no differences in the basal levels of alanine or aspartate. Upon reperfusion, a significant (P < 0.05) fall in taurine and glutamine was seen only in the left ventricle. These changes are likely to be due to transport (taurine) and/or metabolism (glutamine). There was a marked increase in the alanine to glutamate ratio in both ventricles indicative of ischemic stress which was confirmed by global release of lactate during reperfusion. This study shows that in contrast to the right ventricle, the dilated left ventricle had remodeled to accumulate amino acids which are used during ischemia and reperfusion. Whether these changes reflect differences in degree of cardioplegic protection between the two ventricles remain to be investigated.

Corticosterone suppresses insulin- and NO-stimulated muscle glucose uptake in broiler chickens (Gallus gallus domesticus)

We evaluated the effects of stress as mimicked by corticosterone (CORT) administration on the uptake of glucose by skeletal muscles (M. fibularis longus) in broiler chickens (Gallus gallus domesticus). The results showed that both chronic (7 d) and short-term (3 h) CORT administration resulted in hyperglycemia and hyperinsulinemia. Plasma level of nitric oxide (NO) and the activity of NO synthase (NOS) were both suppressed by either chronic or acute stress. In vivo CORT treatment could stimulate the in vitro uptake of 2-deoxy-D-[1,2-3H]-glucose (2-DG). Sodium nitroprusside (SNP) administration improved the in vitro uptake of 2-DG in both CORT and control groups. In CORT treatment, however, the stimulating effect of NO on 2-DG uptake was relatively lower compared to control group, whereas it was restored by insulin. Insulin stimulated muscle in vitro 2-DG uptake in either control or CORT group, with the improvement being significantly higher in control chickens. The results indicated that the reduced circulating and muscle level of NO level via the suppression of NOS by corticosterone treatment was involved in the stress-induced insulin resistance. It appears that CORT could suppress the insulin stimulated glucose uptake in skeletal muscle, inducing insulin resistance in broiler chickens. We conclude that NO could stimulate glucose transport in chicken skeletal muscle and that the reduced circulating and muscle level of NO is involved in the insulin resistance induced by corticosterone treatment.

All-sky LIGO search for periodic gravitational waves in the early fifth-science-run data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10{-24} are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10{-6}, the search is sensitive to distances as great as 500 pc.

All-sky LIGO search for periodic gravitational waves in the early fifth-science-run data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10{-24} are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10{-6}, the search is sensitive to distances as great as 500 pc.

All-sky LIGO search for periodic gravitational waves in the early fifth-science-run data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10{-24} are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10{-6}, the search is sensitive to distances as great as 500 pc.

All-sky LIGO search for periodic gravitational waves in the early fifth-science-run data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10{-24} are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10{-6}, the search is sensitive to distances as great as 500 pc.

A novel epigenetic mechanism in Drosophila somatic cells mediated by Piwi and piRNAs

Small noncoding RNAs have emerged as key players in epigenetic regulation. Recently, a novel class of small RNAs that interact with Piwi proteins has been discovered in the mammalian and Drosophila germ line. These Piwi-interacting RNAs (piRNAs) represent a distinct small RNA pathway that is widely thought to function only in the germ line. In this chapter, we review our recent work with our collaborators on the epigenetic function of the Drosophila Piwi protein and its associated piRNAs in somatic cells. This work has revealed a novel epigenetic mechanism mediated by Piwi and its associated piRNAs in somatic cells that might also be applicable to the germ line. On the basis of these results, we propose a "Piwi-piRNA guidance hypothesis" for Piwi/piRNA-mediated epigenetic programming, in which the Piwi-piRNA complex serves as sequence-recognition machinery that recruits epigenetic effectors such as heterochromatin protein 1a (HP1a) to specific sites in the genome to execute epigenetic regulation.

Corticosterone administration and dietary glucose supplementation enhance fat accumulation in broiler chickens

1. The effects of exogenous corticosterone administration and glucose supplementation on energy intake, lipid metabolism and fat deposition of broiler chickens were investigated. 2. A total of 144 three-d-old male chickens were randomly assigned to one of the following 4 treatments for 7 d: a low energy diet (10.9 MJ ME/kg, 200 g/kg CP) with or without corticosterone (30 mg/kg diet) and drinking water supplemented with glucose (80 g/l) or saccharine (2 g/l, control). 3. Body weight (BW) gain and breast and thigh muscle yields (% body mass) were all significantly decreased by corticosterone treatment. The relative cumulative feed intake (RCFI) and relative ME intake (RMEI), rather than the feed (FI) or ME intake (MEI) were increased by corticosterone administration. Both feed efficiency (FE) and caloric efficiency (CE) were decreased by corticosterone administration. Corticosterone administration had no obvious effect on water consumption. 4. Glucose supplementation had no influence on BW gain and breast and thigh muscle yield (as % of body mass). FI or RCFI was decreased while MEI or RMEI was increased by glucose supplementation. FE was improved by glucose treatment, whereas CE was reduced. 5. Liver weight and abdominal, cervical and thigh fat deposits were all significantly increased by either corticosterone or glucose treatment. 6. Plasma concentrations of glucose, urate, triglyceride, non-esterified fatty acids (NEFA), very low density lipoprotein and insulin were all significantly increased by corticosterone treatment. Glucose supplementation had no obvious influence on any of the measured plasma parameters except for NEFA, which were significantly increased. 7. Lipoprotein lipase activities in either cervical or abdominal adipose tissues, rather than in thigh fat tissue, were significantly elevated by either glucose or corticosterone treatment.

Fluorescence investigation of Ho3+ in Yb3+ sensitized mixed-alkali bismuth gallate glasses

Efficient 2.0 microm infrared and visible upconversion emissions have been observed in Ho3+/Yb3+ co-doped mixed-alkali bismuth gallate (LKBBG) glasses having a maximum-phonon energy of 673 cm(-1). The Judd-Ofelt parameters Omega2, Omega4 and Omega6 of Ho3+ indicate that there is a high asymmetry and strong covalent environment in LKBBG glasses. The large absorption and emission cross-sections of Yb3+ confirm that it is a suitable sensitizer for capturing and transferring pump energy to Ho3+. The emission cross-section profile for the 5I7-->5I8 transition is derived using the reciprocity method and the peak value is 5.54 x 10(-21)cm2, which is much larger than the value in fluorozircoaluminate glasses. LKBBG glasses exhibit low maximum-phonon energy and large refractive index, and it is possible to achieve an effective 1.66 microm U-band emission of Ho3+ under 900 nm laser radiation.

Legionella pollution in cooling tower water of air-conditioning systems in Shanghai, China

AIMS

To determine Legionella pollution prevalence, describe the amount of Legionellae with respect to temperature in Shanghai cooling tower water (CTWs) in various types of public sites.

METHODS AND RESULTS

Six urban districts were selected as the study fields, adopting multiple-phase sampling methods. Routine culture was used to identify Legionellae. Of the samples, 58.9% (189/321) were observed to be positive, 19.9% were isolated over 100 CFU ml(-1). Legionella pneumophila serogroup 1 was the most frequently isolated species (155/189, 82.0%), followed by Leg. micdadei that was at the second place (44/189, 23.3%). The mean CFU ml(-1) of Legionellae in CTWs reached its peak from July to September. Over all 15.4% of the samples exceeding 100 CFU ml(-1) were observed in a hospital setting.

CONCLUSIONS

The prevalence of Legionella pollution in CTWs, especially in CTWs of subway stations and hospitals, is worrying, and the positive rate and CFU ml(-1) of Legionellae in CTWs have a close relationship with air temperature.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study demonstrates pollution prevalence rates in different types of sites and various seasons, and provides a proportion of different serogroups of Legionellae. It illuminates an urgent need for dealing with the potential risk of legionellosis in Shanghai, through improved control and prevention strategies.

Search for gravitational-wave bursts from soft gamma repeaters

We present a LIGO search for short-duration gravitational waves (GWs) associated with soft gamma ray repeater (SGR) bursts. This is the first search sensitive to neutron star f modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 2004 giant flare from SGR 1806-20 and 190 lesser events from SGR 1806-20 and SGR 1900+14. The unprecedented sensitivity of the detectors allows us to set the most stringent limits on transient GW amplitudes published to date. We find upper limit estimates on the model-dependent isotropic GW emission energies (at a nominal distance of 10 kpc) between 3x10;{45} and 9x10;{52} erg depending on waveform type, detector antenna factors and noise characteristics at the time of the burst. These upper limits are within the theoretically predicted range of some SGR models.

Corticosterone administration and high-energy feed results in enhanced fat accumulation and insulin resistance in broiler chickens

1. Two experiments were conducted to investigate the effects of exogenous corticosterone administration (30 mg/kg diet) and dietary energy level on feed or energy intake and fat deposition in broiler chickens of 1 and 4 weeks of age. 2. Corticosterone treatment significantly suppressed body weight (BW) gain and reduced feed and caloric efficiencies. The retarded growth may conceal the stimulatory effect of corticosterone on feed consumption or metabolisable energy (ME) intake. A high-energy diet may increase energy intake and partially alleviate the suppressing effect of corticosterone on growth of broilers. 3. Corticosterone administration promoted the conservation of energy stores as fat at both abdominal and subcutaneous sites and this process occurred regardless of dietary energy level in ad libitum feeding status. A high-energy diet increased fat accumulation and showed no significant interaction with corticosterone treatment. 4. The suppressed development of breast and thigh muscles by corticosterone treatment was observed only in 1-week-old chickens fed on the low-energy diet. In contrast, the yield of breast muscle but not thigh muscle was significantly decreased by corticosterone in 4-week-old chickens, suggesting that the tissue specificity to corticosterone challenge is age dependent. 5. Plasma concentrations of glucose, insulin, triglyceride, non-esterified fatty acids (NEFA) and very low density lipoprotein were increased by corticosterone treatment regardless of diet treatment. A high-energy diet increased plasma levels of NEFA and resulted in hyperinsulinism in 4-week-old chickens but not in 1-week-old chickens. 6. Lipoprotein lipase (LPL) activities in adipose tissues may have been up-regulated by corticosterone treatment and showed tissue specificity. The increased LPL activities at ad libitum feeding status were not necessarily linked with the increased fat accumulation in corticosterone challenged chickens. 7. Corticosterone resulted in augmented energy consumption and altered energy redistribution toward lipid deposition. The induced insulin resistance and enhanced hepatic de novo lipogenesis by corticosterone are likely to be responsible for the increased fat deposition.