550 research outputs found
Polarization revival of a Bloch oscillating wave packet in conjunction with resonant Zener tunneling
No full textWe investigate the dynamics of a Bloch-oscillating wave packet in the presence of strong coupling to delocalized above barrier states (Zener tunneling), using time-resolved intraband polarization-sensitive measurements. At a threshold electric field, the resonance of localized and delocalized states causes a quantum beating which is observed as a revival in the intraband polarization. Our numerical simulation visualizes the spatial wave packet decomposition and reformation. The wave packet moves on a ps time scale over a distance of more than 100 nm and sequentially undergoes Bloch oscillations in the below- and above-barrier bands
Field-induced delocalization and Zener breakdown in semiconductor superlattices
No full textWe investigate the energy spectrum and the electron dynamics of a band in a semiconductor superlattice as a function of the electric field. Linear optical spectroscopy shows that, for high fields, the well-known localization of the Bloch states is followed by a field-induced delocalization, associated with Zener breakdown. Using time-resolved measurements, we observe Bloch oscillations in a regime where they are damped by Zener breakdown
JETP Letters V. 72, I .06
No full textJETP Letters -- September 25, 2000
Volume 72, Issue 6, pp. 279-345
FIELDS, PARTICLES, NUCLEI
New Bound to the Probability of 76Ge betabeta Decay to the 0 + 1 76Se Level
S. I. Vasil'ev, A. A. Klimenko, S. B. Osetrov, and A. A. Smol'nikov
pp. 279-281 Full Text: PDF (80 kB)
Study of the rho, omega , phi --> etagamma --> 7gamma Decays with an SND Detector on a VEPP-2M Collider
M. N. Achasov, S. E. Baru, K. I. Beloborodov, A. V. Berdyugin, A. V. Bozhenok, A. G. Bogdanchikov, D. A. Bukin, S. V. Burdin, A. V. Vasil'ev, Yu. S. Velikzhanin, T. V. Dimova, V. P. Druzhinin, M. S. Dubrovin, D. I. Ganyushin, I. A. Gaponenko, V. B. Golubev, V. N. Ivanchenko, I. A. Koop, A. A. Korol', S. V. Koshuba, G. A. Kukartsev, E. V. Pakhtusova, A. A. Sal'nikov, S. I. Serednyakov, V. V. Sharyi, Yu. M. Shatunov, V. A. Sidorov, and Z. K. Silagadze
pp. 282-285 Full Text: PDF (71 kB)
Triple Correlation in the 10B(n, alphagamma)7Li Reaction
A. M. Gagarski, G. V. Val'ski, G. A. Petrov, Yu. E. Loginov, V. E. Bunakov, I. S. Guseva, V. I. Petrova, and T. A. Zavarukhina
pp. 286-288 Full Text: PDF (36 kB)
ATOMS, SPECTRA, RADIATIONS
Atomic Recoil Effects in Slow Light Propagation
I. Carusotto, M. Artoni, and G. C. La Rocca
pp. 289-293 Full Text: PDF (73 kB)
Stabilization of Bound State Decay in an Intense Monochromatic High-Frequency Field
N. L. Manakov, M. V. Frolov, B. Borca, and A. F. Starace
pp. 294-297 Full Text: PDF (64 kB)
PLASMA, GASES
The Ion Cyclotron Resonator in the Magnetosphere
A. V. Guglielmi, A. S. Potapov, and C. T. Russell
pp. 298-300 Full Text: PDF (41 kB)
CONDENSED MATTER
Structural Transition in Liquid Cobalt
V. I. Lad'yanov, A. L. Bel'tyukov, K. G. Tronin, and L. V. Kamaeva
pp. 301-303 Full Text: PDF (46 kB)
Dimensionality of a System of Exchange-Coupled Grains and Magnetic Properties of Nanocrystalline and Amorphous Ferromagnets
R. S. Iskhakov, S. V. Komogortsev, A. D. Balaev, and L. A. Chekanova
pp. 304-307 Full Text: PDF (73 kB)
Depolarization of a Neutron Beam in Laue Diffraction by a Noncentrosymmetric Crystal
V. V. Voronin, E. G. Lapin, S. Yu. Semenikhin, and V. V. Fedorov
pp. 308-311 Full Text: PDF (72 kB)
Charge-Carrier Separation in Rolled Heterostructures
V. M. Osadchii and V. Ya. Prinz
pp. 312-315 Full Text: PDF (69 kB)
High-Pressure Phases in Nanocrystalline Co(C) Films Obtained by Pulsed Plasma Vaporization
R. S. Iskhakov, S. V. Stolyar, L. A. Chekanova, E. M. Artem'ev, and V. S. Zhigalov
pp. 316-319 Full Text: PDF (64 kB)
Long-Time Luminescence Kinetics of Localized Excitons and Conduction Band Edge Smearing in ZnSe(1 – c)Tec Solid Solutions
A. Klochikhin, S. G. Ogloblin, S. Permogorov, A. Reznitsky, C. Klingshirn, V. Lyssenko, and J. M. Hvam
pp. 320-323 Full Text: PDF (72 kB)
Screening of Excitonic States by Low-Density 2D Charge Carriers in GaAs/AlGaAs Quantum Wells
S. I. Gubarev, I. V. Kukushkin, S. V. Tovstonog, M. Yu. Akimov, J. Smet, K. von Klitzing, and W. Wegscheider
pp. 324-328 Full Text: PDF (81 kB)
Suppression of the Local Jahn–Teller Effect in Nanostructures: Self-Trapped Holes and Excitons in AgCl Nanocrystals
P. G. Baranov, V. S. Vikhnin, N. G. Romanov, and V. A. Khramtsov
pp. 329-332 Full Text: PDF (54 kB)
Tunneling Spectroscopy of Localized States near the Quantum Hall Edge
A. Alekseev, V. Cheianov, A. P. Dmitriev, and V. Yu. Kachorovskii
pp. 333-336 Full Text: PDF (51 kB)
Critical Behavior of Frustrated Systems: Monte Carlo Simulations versus Renormalization Group
D. Loison, A. I. Sokolov, B. Delamotte, S. A. Antonenko, K. D. Schotte, and H. T. Diep
pp. 337-340 Full Text: PDF (63 kB)
MISCELLANEOUS
Remarks about the Effective Conductivity of Some Three-Color Tesselations in the Plane
I. M. Khalatnikov and A. Yu. Kamenshchik
pp. 341-344 Full Text: PDF (116 kB)
ERRATA
Erratum: "High-Efficiency Zn Isotope Separation in a Photochemical Reaction Induced by Two-Photon Excitation" [JETP Lett. 71, 12, 481]
P. A. Bokhan, V. V. Buchanov, D. É. Zakrevskii, A. Yu. Stepanov, and N. V. Fateev
p. 345 Full Text: PDF (9 kB)Archived web conten
Interaction between prenatal growth and high-risk genotypes in the development of type 2 diabetes
No full textAims/hypothesis: early environmental factors and genetic variants have been reported to be involved in the pathogenesis of type 2 diabetes. The aim of this study was to investigate whether there is an interaction between birthweight and common variants in the TCF7L2, HHEX, PPARG, KCNJ11, SLC30A8, IGF2BP2, CDKAL1, CDKN2A/2B and JAZF1 genes in the risk of developing type 2 diabetes.
Methods: a total of 2,003 participants from the Helsinki Birth Cohort Study, 311 of whom were diagnosed with type 2 diabetes by an OGTT, were genotyped for the specified variants. Indices for insulin sensitivity and secretion were calculated.
Results: low birthweight was associated with type 2 diabetes (p?=?0.008) and impaired insulin secretion (p?=?0.04). Of the tested variants, the risk variant in HHEX showed a trend towards a low birthweight (p?=?0.09) and the risk variant in the CDKN2A/2B locus was associated with high birthweight (p?=?0.01). The TCF7L2 risk allele was associated with increased risk of type 2 diabetes. Pooling across all nine genes, each risk allele increased the risk of type 2 diabetes by 11%. Risk variants in the HHEX, CDKN2A/2B and JAZF1 genes interacted with birthweight, so that the risk of type 2 diabetes was highest in those with lower birthweight (p???0.05). The interaction was also present in the pooled data.
Conclusions/interpretation: low birthweight might affect the strength of the association of some common variants (HHEX, CDKN2A/2B and JAZF1) with type 2 diabetes. These findings need to be replicated in independent cohort
Early metabolic markers of the development of dysglycemia and type 2 diabetes and their physiological significance
No full textMetabolomic screening of fasting plasma from nondiabetic subjects identified α-hydroxybutyrate (α-HB) and linoleoyl-glycerophosphocholine (L-GPC) as joint markers of insulin resistance (IR) and glucose intolerance. To test the predictivity of α-HB and L-GPC for incident dysglycemia, α-HB and L-GPC measurements were obtained in two observational cohorts, comprising 1,261 nondiabetic participants from the Relationship between Insulin Sensitivity and Cardiovascular Disease (RISC) study and 2,580 from the Botnia Prospective Study, with 3-year and 9.5-year follow-up data, respectively. In both cohorts, α-HB was a positive correlate and L-GPC a negative correlate of insulin sensitivity, with α-HB reciprocally related to indices of β-cell function derived from the oral glucose tolerance test (OGTT). In follow-up, α-HB was a positive predictor (adjusted odds ratios 1.25 [95% CI 1.00-1.60] and 1.26 [1.07-1.48], respectively, for each standard deviation of predictor), and L-GPC was a negative predictor (0.64 [0.48-0.85] and 0.67 [0.54-0.84]) of dysglycemia (RISC) or type 2 diabetes (Botnia), independent of familial diabetes, sex, age, BMI, and fasting glucose. Corresponding areas under the receiver operating characteristic curve were 0.791 (RISC) and 0.783 (Botnia), similar in accuracy when substituting α-HB and L-GPC with 2-h OGTT glucose concentrations. When their activity was examined, α-HB inhibited and L-GPC stimulated glucose-induced insulin release in INS-1e cells. α-HB and L-GPC are independent predictors of worsening glucose tolerance, physiologically consistent with a joint signature of IR and β-cell dysfunction
Early metabolic markers of the development of dysglycaemia and type 2 diabetes and their physiological significance
No full textBackground and aims: Metabolomic screening of fasting plasma from nondiabetic subjects identified alpha-hydroxybutyrate (AHB) and linoleoylglycerophosphocholine (L-GPC) as joint markers of insulin resistance (IR) and glucose intolerance. We tested their predictivity for incident dysglycemia and investigated their potential physiological role.
Materials and methods: Metabolite profiling was carried out in 1,261 nondiabetic participants of the RISC study and 2,580 subjects of the Botnia cohort. Three-year (RISC) and 9.5-year (Botnia) follow-up data were analyzed.
Results: In both RISC and Botnia baseline data, AHB was a positive correlate, and L-GPC a negative correlate, of insulin sensitivity; AHB was also reciprocally related to indices of beta cell function. In a subgroup of Botnia subjects, higher AHB was associated with higher branched-chain amino acid and free fatty acid levels, and decreased glycine (constituent of glutathione). In follow-up, AHB was a positive predictor (adjusted odds ratios 1.25 [95%CI:1.00-1.60] and 1.26 [95%CI:1.07-1.48], respectively) and L-GPC a negative predictor (adj. odds ratios 0.64 [95%CI:0.48-0.85] and 0.67 [95%CI: 0.54-0.84]) of dysglycemia (RISC) or type 2 diabetes (Botnia), independent of familial diabetes, sex, age, BMI, and fasting plasma glucose, with ROC area-under-curves of 0.791 and 0.783. In morbidly obese subjects undergoing bariatric surgery, AHB halved (6.14[3.64] to 3.47[1.43] microg/ml, p<0.0001) as insulin sensitivity doubled (19.9[17.4] to 41.4[10.5] micromol.min-1.kgffm -1, p<0.0001). Consistent with their association with insulin sensitivity and secretion, in INS-1e cell cultures, AHB inhibited and L-GPC stimulated glucose/arginine-induced insulin release at physiological concentrations.
Conclusion: AHB and L-GPC are early independent predictors of worsening glucose tolerance in diverse populations. Physiologically, AHB and L-GPC appear to be signatures of IR, beta cell dysfunction, and metabolic overload
Lamellar Racemic Twinning as an Obstacle for the Resolution of Enantiomers by Crystallization: The Case of Me(All)N<sup>+</sup>(CH<sub>2</sub>Ph)Ph X<sup>-</sup> (X = Br, I) Salts
No full textAmmonium salts Me(All)N+(CH2Ph)Ph X- (X = Br, 1; X = I, 2) (Asymmetric nitrogen, communication 89,
prev. see Kostyanovsky, R. G.; Kostyanovsky, V. R.; Kadorkina, G. K.; Lyssenko, K. A. Mendeleev Commun.
2003, 111) were historically the first compounds with a chiral nitrogen center obtained in optically pure
forms via diastereoisomers. We were astonished by the fact that W. J. Pope, who first carried out the resolution
(1899), mentioned in his articles that salts have features for conglomerate formation but nowhere did he note
the registration of optical activity and manual sorting of left- and right-handed single crystals. We reinvestigated
these salts with the help of X-ray diffraction and found that the space groups of both of them are P212121.
However, despite the chiral space group, the enantiomeric composition of the majority of the crystals obtained
by crystallization from solutions of racemates was found to be near racemic. Such crystal growth behavior,
called lamellar twinning between enantiomers, represents a serious obstacle to the methods of enantiomeric
resolution by straightforward crystallization that are used in the chiral industry. The phenomenon probably
results from a high concentration in solution of heterochiral growth clusters, which promote the formation of
the intergrowth region of twins. To glance experimentally at what might possibly be the first crystal growth
units, electrospray ionization FT-ICR mass spectrometry was applied. We were able to register polyionic
clusters containing up to five chiral cations. The relative stability of the simplest dimeric clusters (two cations
linked by an anion) of 1 with homo- and heterochiral composition was estimated with a B3LYP/SDD
calculation, and heterochiral one was found to be more stable by 0.883 kcal/mol
Nonlinear transport in superlattices: Bloch oscillations and Zener breakdown
No full textSemiconductor superlattices have been intensively used as a model system for the investigation of high field transport in solids. Here, we discuss ultrafast optical experiments which allow us to monitor the electron wave packet motion in detail. First, we discuss a novel technique which directly traces the center of mass spatial motion. We use this method for the detection of a linear motion of the wave packets, which is superimposed on the harmonic Bloch oscillations. A comparison with theory shows that this coherent analog to the Shapiro effect in superconductors is associated with gain at THz frequencies. In a second part, we discuss recent results which address the Zener breakdown due to tunneling to higher bands by linear spectroscopy, which directly shows the wave function delocalization. We also trace the dynamics of the Zener tunneling by time-resolved spectroscopy and show the damping of Bloch oscillations due to Zener tunneling
A central role for GRB10 in regulation of islet function in man
No full textVariants in the growth factor receptor-bound protein 10 (GRB10) gene were in a GWAS meta-analysis associated with reduced glucose-stimulated insulin secretion and increased risk of type 2 diabetes (T2D) if inherited from the father, but inexplicably reduced fasting glucose when inherited from the mother. GRB10 is a negative regulator of insulin signaling and imprinted in a parent-of-origin fashion in different tissues. GRB10 knock-down in human pancreatic islets showed reduced insulin and glucagon secretion, which together with changes in insulin sensitivity may explain the paradoxical reduction of glucose despite a decrease in insulin secretion. Together, these findings suggest that tissue-specific methylation and possibly imprinting of GRB10 can influence glucose metabolism and contribute to T2D pathogenesis. The data also emphasize the need in genetic studies to consider whether risk alleles are inherited from the mother or the father
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