Attention deficit/hyperactivity disorder children with a 7-repeat allele of the dopamine receptor D4 gene have extreme behavior but normal performance on critical neuropsychological tests of attention

An association of the dopamine receptor D4 (DRD4) gene located on chromosome 11p15.5 and attention deficit/hyperactivity disorder (ADHD) has been demonstrated and replicated by multiple investigators. A specific allele [the 7-repeat of a 48-bp variable number of tandem repeats (VNTR) in exon 3] has been proposed as an etiological factor in attentional deficits manifested in some children diagnosed with this disorder. In the current study, we evaluated ADHD subgroups defined by the presence or absence of the 7-repeat allele of the DRD4 gene, using neuropsychological tests with reaction time measures designed to probe attentional networks with neuroanatomical foci in D4-rich brain regions. Despite the same severity of symptoms on parent and teacher ratings for the ADHD subgroups, the average reaction times of the 7-present subgroup showed normal speed and variability of response whereas the average reaction times of the 7-absent subgroup showed the expected abnormalities (slow and variable responses). This was opposite the primary prediction of the study. The 7-present subgroup seemed to be free of some of the neuropsychological abnormalities thought to characterize ADHD.

Apoptotic cells induce immunosuppression through dendritic cells: Critical roles of IFN-gamma and nitric oxide

Apoptotic cells induce immunosuppression through unknown mechanisms. To identify the underlying molecular mediators, we examined how apoptotic cells induce immunoregulation by dendritic cells (DC). We found that administration of DC exposed to apoptotic c

A critical reassessment of the role of mitochondria in tumorigenesis

Background Mitochondrial DNA (mtDNA) is being analyzed by an increasing number of laboratories in order to investigate its potential role as an active marker of tumorigenesis in various types of cancer. Here we question the conclusions drawn in most of these investigations, especially those published in high-rank cancer research journals, under the evidence that a significant number of these medical mtDNA studies are based on obviously flawed sequencing results. Methods and Findings In our analyses, we take a phylogenetic approach and employ thorough database searches, which together have proven successful for detecting erroneous sequences in the fields of human population genetics and forensics. Apart from conceptual problems concerning the interpretation of mtDNA variation in tumorigenesis, in most cases, blocks of seemingly somatic mutations clearly point to contamination or sample mix-up and, therefore, have nothing to do with tumorigenesis. Conclusion The role of mitochondria in tumorigenesis remains unclarified. Our findings of laboratory errors in many contributions would represent only the tip of the iceberg since most published studies do not provide the raw sequence data for inspection, thus hindering a posteriori evaluation of the results. There is no precedent for such a concatenation of errors and misconceptions affecting a whole subfield of medical research.

Rapid growth cost in “all-fish” growth hormone gene transgenic carp: Reduced critical swimming speed

Evidence has accumulated that there is a trade-off between benefits and costs associated with rapid growth. A trade-off between growth rates and critical. swimming speed (U-crit) had been also reported to be common in teleost fish. We hypothesize that growth acceleration in the F-3 generation of "all-fish" growth hormone gene (GH) transgenic common carp (Cyprinus carpio L.) would reduce the swimming abilities. Growth and swimming performance between transgenic fish and non-transgenic controls were) compared. The results showed that transgenic fish had a mean body weight 1.4-1.9-fold heavier, and a mean specific growth rate (SGR) value 6%-10% higher than the controls. Transgenic fish, however, had a mean absolute U-crit (cm/s) value 22% or mean relative Ucrit (BL/s) value 24% lower than the controls. It suggested that fast-growing "all-fish" GH-transgenic carp were inferior swimmers. It is also supported that there was a trade-off between growth rates and swimming performance, i.e. faster-growing individuals had lower critical swimming speed.

DTADH and quantum critical phenomena caused by anisotropy and external magnetic field for spin-1/2 Heisenberg diamond chains

Using the transfer matrix renormalization group (TMRG) method, we study the connection between the first derivative of the thermal average of driving-term Hamiltonian (DTADH) and the trace of quantum critical behaviors at finite temperatures. Connecting with the exact diagonalization method, we give the phase diagrams and analyze the properties of each phase for both the ferromagnetic and anti-ferromagnetic frustrated J(3) anisotropy diamond chain models. The finite-temperature scaling behaviors near the critical regions are also investigated. Further, we show the critical behaviors driven by external magnetic field, analyze the formation of the 1/3 magnetic plateau and the influence of different interactions on those critical points for both the ferrimagnetic and anti-ferromagnetic distorted diamond chains.

Intrinsically limited critical temperatures of highly doped Ga1-xMnxAs thin films

Ga1-xMnxAs films with exceptionally high saturation magnetizations of approximate to 100 emu/cm(3) corresponding to effective Mn concentrations of x(eff)approximate to 0.10 still have a Curie temperature T-C smaller than 195 K contradicting mean-field predictions. The analysis of the critical exponent beta of the remnant magnetization-beta = 0.407(5)-in the framework of the models for disordered/amorphous ferromagnets suggests that this limit on T-C is intrinsic and due to the short range of the ferromagnetic interactions resulting from the small mean-free path of the holes. This result questions the perspective of room-temperature ferromagnetism in highly doped GaMnAs.

Quantum critical phenomena in the XY spin chain with the Dzyaloshinski-Moriya interaction (Retracted article. See vol 80, artn 019903, 2009)

We study the effects of the Dzyaloshinski-Moriya (DM) anisotropic interaction on the ground-state properties of the Heisenberg XY spin chain by means of the fidelity susceptibility, order parameter, and entanglement entropy. Our results show that the DM interaction could influence the distribution of the regions of quantum phase transitions and cause different critical regions in the XY spin model. Meanwhile, the DM interaction has effective influence on the degree of entanglement of the system and could be used to increase the entanglement of the spin system.

Effect of critical thickness on structural and optical properties of InxGa1-xN/GaN multiple quantum wells

InGaN/GaN multiquantum-well (MQW) structures grown by metalorganic chemical-vapor deposition on n-type GaN and capped by p-type GaN were investigated by cross-sectional transmission electron microscopy, double crystal x-ray diffraction, and temperature-dependent photoluminescence. For the sample with strained-layer thicknesses greater than the critical thicknesses, a high density of pure edge type threading dislocations generated from MQW layers and extended to the cap layer was observed. These dislocations result from a relaxation of the strained layers when their thicknesses are beyond the critical thicknesses. Because of indium outdiffusion from the well layers due to the anneal effect of Mg-doped cap layer growth and defects generated from strain relaxation, the PL emission peak was almost depressed by the broad yellow band with an intensity maximum at 2.28 eV. But for the sample with strained-layer thicknesses less than the critical thicknesses, it has no such phenomenon. The measured critical thicknesses are consistent with the calculated values using the model proposed by Fischer, Kuhne, and Richter. (C) 2004 American Institute of Physics.

The formation and characteristics of Si1-xCx alloys in Si crystals by means of implantation of cions with different doses

Carbon ions with concentration of (0.6-1.5)% were implanted into silicon crystals at room temperature and Si1-xCx alloys were grown by solid phase epitaxy with high temperature annealing. The formation and characteristics of Si1-xCx alloys under different implanted carbon doses were studied. If the implanted carbon atom concentration was less than 0.6%, carbon atoms would tend to combine with the defects produced during implantation and it was difficult for Si1-xCx alloys to form during annealing at 850-950 degreesC. With the increase of implanted C concentration, almost all implanted carbon atoms would occupy substitution positions to form Si1-xCx alloys, but only part of implanted carbon atoms would occupy the substitution position to form Si1-xCx alloys as the implanted dose increased to 1.5 %. Most Si1-xCx alloy phases would vanish as the annealing temperature was increased higher.

RBS STUDIES OF THE LATTICE DAMAGE CAUSED BY 1 MEV SI+ IMPLANTATION INTO AL0.3GA0.7AS/GAAS SUPERLATTICES AT ELEVATED-TEMPERATURE

The lattice damage accumulation in GaAs and Al0.3Ga0.7As/GaAs superlattices by 1 MeV Si+ irradiation at room temperature and 350-degrees-C has been studied. For irradiations at 350-degrees-C, at lower doses the samples were almost defect-free after irradiation, while a large density of accumulated defects was induced at a higher dose. The critical dose above which the damage accumulation is more efficient is estimated to be 2 x 10(15) Si/cm2 for GaAs, and is 5 x 10(15) Si/cm2 for Al0.8Ga0.7As/GaAs superlattice for implantation with 1.0 MeV Si ions at 350-degrees-C. The damage accumulation rate for 1 MeV Si ion implantation in Al0.3Ga0.7As/GaAs superlattice is less than that in GaAs.

INVESTIGATION OF BURIED ALN LAYERS FORMED BY NITROGEN IMPLANTATION INTO AL

The composition and microstructure of buried layers of AlN formed by high energy N+ ion implantation into polycrystalline Al have been determined. Both bulk and evaporated thin films of Al have been implanted with 100 and 200 keV N+ ions to doses of up to 1.8 x 10(18)/cm2. The layers have been characterised using SIMS, XTEM, X-ray diffraction, FTIR, RBS and in terms of their microhardness. It is found that, for doses greater than the critical dose, buried, polycrystalline AlN layers are formed with preferred (100) or (002) orientations, which are sample specific. With increasing dose the nitrogen concentration saturates at the value for stoichiometric AlN although the synthesised compound is found to be rich in oxygen.

Sensitivity of Total-Dose Radiation Hardness of SIMOX Buried Oxides to Doses of Nitrogen Implantation into Buried Oxides

In order to improve the total-dose radiation hardness of the buried oxides(BOX) in the structure of separa tion-by-implanted-oxygen(SIMOX) silicon-on-insulator(SOI), nitrogen ions are implanted into the buried oxides with two different doses,2 × 1015 and 3 × 1015 cm-2 , respectively. The experimental results show that the radiation hardness of the buried oxides is very sensitive to the doses of nitrogen implantation for a lower dose of irradiation with a Co-60 source. Despite the small difference between the doses of nitrogen implantation, the nitrogen-implanted 2 × 1015 cm-2 BOX has a much higher hardness than the control sample (i. e. the buried oxide without receiving nitrogen implantation) for a total-dose irradiation of 5 × 104rad(Si), whereas the nitrogen-implanted 3 × 1015 cm-2 BOX has a lower hardness than the control sample. However,this sensitivity of radiation hardness to the doses of nitrogen implantation reduces with the increasing total-dose of irradiation (from 5 × 104 to 5 × 105 rad (Si)). The radiation hardness of BOX is characterized by MOS high-frequency (HF) capacitance-voltage (C-V) technique after the top silicon layers are removed. In addition, the abnormal HF C-V curve of the metal-silicon-BOX-silicon(MSOS) structure is observed and explained.