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Investigates structural and electrical properties of Al(As,Sb) dual-anion compounds grown by molecular beam epitaxy at low substrate temperature. Evidence of single-crystal growth; Details on the formation of additional donor-type defects; Analysis on the formation of precipitates upon annealing low-temperature-grown Al(As,Sb).

Investigates interface roughness scattering in indium arsenide and aluminum antimonide quantum wells. Contribution of the roughness scattering on the low-temperature mobility; Inclusion of band nonparabolicity of indium arsenide in the measurement of mobilities; Dependence of the measured mobility on electron density.

We have demonstrated the molecular beam epitaxial growth of (Al,Ga)Sb tilted superlattices (TSLs) on 2° vicinal (100) GaSb and GaAs substrates. The TSLs grown on GaSb substrates exhibit good AlSb/GaSb separation and a uniform short-range superlattice period. The TSLs grown on GaAs substrates are similar, except for the presence of threading dislocations and a decreased uniformity. The existence of TSLs proves that step-flow growth can occur in this material system, and in the presence of strain. Lateral fluctuations in the tilt angle of the superlattice are observed and are found to be caused by a nonuniform adatom distribution which is correlated with the surface step density. [ABSTRACT FROM AUTHOR]

Using atomistic pseudopotential calculations we predict the evolution of the valence-band maximum energy Eυ(x,y) and conduction-band minimum energy Ec(x,y) for a compositionally graded quaternary Ga1-yInyAsxSb1-x alloy lattice matched to GaSb or InAs as a function of (x,y) or, equivalently, as a function of distance from the substrate. We find upward-concave bowing for both Ec and Eυ, in contradiction with simple interpolative models. A transition from staggered (type II) to broken-gap (type III) lineup relative to GaSb is predicted to occur at x=0.81 and y=0.92 on a GaSb substrate, and at x=0.59 and y=0.62 on an InAs substrate. In the latter case, the quaternary alloy has a minimum gap at x=0.85 and y=0.87. [ABSTRACT FROM AUTHOR]

Presents information on a study which determined the materials quality of heavily dislocated epitaxial layers of gallium arsenide superlattices grown by molecular-beam epitaxy on silicon substrates. Insight on the presence of dislocations in semiconductors; Methodology of the study; Results and discussion.

Presents a study that determined the valence and conduction band discontinuities for the lattice matched (gallium, indium) phosphorus/gallium arsenide heterojunction using capacitance-voltage profiling. Methodology; Factors to consider in the measurement of the valence-band and conduction-band discontinuities; Information on the possible sources of errors in the study.

Examines the long-wavelength intersubband absorption under normal incidence in heavily doped binary-binary GaSb-AlSb superlattices. Observation of peak absorption per quantum well; Creation of intersubband transition under normal incident radiation; Presence of small energy difference in ellipsoidal L valleys in GaSb.

We report experimental verification of the prediction of widely bias-tunable below-gap luminescence, from lattice-matched (p) (Al,In)As/ (n) InP heterojunctions, a system that has been predicted to have staggered lineup. The diodes, grown by molecular beam epitaxy, exhibit strong luminescence at 1.4 K, with a peak energy that shifts from 0.97 to 1.04 eV as the (pulsed) current density is increased from 4.5 to 40 A/cm2. Nonshifting injection luminescence at 1.4 eV, due to hole injection into the n-InP substrate, was also present, but appreciably weaker (<25%) than the interface luminescence. The spectra indicate that the band lineup in the (Al,In)As/InP system is indeed staggered, with a residual gap at the interface close to 0.96 eV. The corresponding conduction and valence-band offsets are 0.52 and 0.40 eV. [ABSTRACT FROM AUTHOR]

Results of growth of InAs on a superconducting TlCaBaCuO (2-1-2-2) thin film are reported. The InAs was grown by molecular beam migration-enhanced epitaxy at a substrate temperature of 250 °C. The Tc(zero) of the Tl film before and after InAs deposition was 106 and 100 K, respectively. X-ray diffraction and reflection electron microscopy studies showed the InAs to be polycrystalline, having grains in the 300 Å size range. This is the first report of deposition of a III-V semiconductor on superconductor, without significant degradation of Tc. [ABSTRACT FROM AUTHOR]

Focuses on a study which investigated indium arsenide (InAs) and aluminum antimoni (AlSb) short period superlattices by grazing incidence x-ray scattering and high resolution diffractometry. Physical properties of InAs and AlSb; Methodology of the study; Results and discussion.

Presents a study which examined the influence of the interface composition of indium arsenide/ aluminum antimony superlattices on their optical and structural properties. Experimental methods; Differences in the optical and structural properties of both styles of interfaces; Results.

Presents a Raman scattering study of strained layer superlattices. Application of molecular beam epitaxy in the growth of the superlattices; Determination of structural parameters by Rutherford backscattering and x-ray diffraction; Experimental details; Result of the study.

Discusses the use of Raman scattering to study the optical phonon modes in Ga[sub1-x]In[subx]P heterostructures. Details on the stress calculated from the pressure coefficient and the observed frequency shift for the GaP-like LO phonon; Sample preparation and X-ray characterization; Discussion on Raman studies.

Focuses on superconducting YBa[sub2]Cu[sub3]O[sub7-x] (YBCO) films which were deposited in situ onto III-V superlattice substrates. Structure of the GaAs/AlAs superlattice; Data in the transmission electron microscopy cross section of YBCO on superlattice substrate.

Reports on the observation of rotational slip as a mechanism for relieving strain in III-V heterostructures grown by molecular beam epitaxy. Impact of rotational slip on the epitaxial layer; Relationship between the strain and the critical layer thickness; Description of rotational slip on planes.

Context:Risk alleles of the fat mass- and obesity-associated gene (FTO) are related not only to increased body mass index (BMI) values but also to mortality. It was speculated that cellular effects of the FTO gene affect most organs, especially their ability to maintain or regenerate proper function when afflicted by various diseases. FTO is highly expressed in the hypothalamus and also in the pituitary gland. The decrease in growth hormone (GH) secretion is known to cause a decrease in lean body mass in older subjects.Objective:We hypothesized an association of rs9926289 with insulin-like growth factor (IGF)-I.Design and setting:Cross-sectional data from the Study of Health in Pomerania, a population-based study in the northeastern part of Germany, were used.Participants:For the final analyses, 3882 subjects aged 20-79 years were available.Main outcome measures:Continuous IGF-I, low IGF-I according to clinically meaningful age- and gender-specific reference values, and BMI were used as outcome measures.Results:Over all age groups, a statistically significant relationship between FTO and IGF-I was found. In subjects younger than 55 years of age, homozygous carriers of the FTO risk allele exhibited lower serum IGF-I levels adjusted for 5-year age groups, gender and IGF-I binding protein 3 levels (linear regression, coefficient±s.e. for FTO AA genotype:−8.6±2.8; P=0.002). Further adjustments for obesity and diabetes did not suspend this association (coefficient:-7.8; P=0.005). As expected, the FTO AA genotype effect on BMI was reduced from 0.76 to 0.62 kg m−2 by including IGF-I. No relationship between FTO and IGF-I levels was found in subjects aged 55 years or older (−2.7±2.4; P=0.260 for FTO AA genotype adjusted for age, gender and IGF-I binding protein 3 levels).Conclusion:We propose that the GH-IGF-I axis is a mediator for the relationship between FTO and BMI. [ABSTRACT FROM AUTHOR]

Background and Purpose: The type-5 PDE inhibitor vardenafil reduces myocardial infarct size in situ, following ischemia/reperfusion, when applied at reperfusion in animal models. Little is known about the underlying protective signaling. Here, we test whether vardenafil is protective in rat isolated hearts and in a cell model of calcium stress.Experimental Approach: Infarct size in rat isolated hearts was measured after a 30 min regional ischemia and 120 min reperfusion. Vardenafil (1 nM-1 microM) was infused during reperfusion. HL-1 cardiomyocytes were loaded with tetramethylrhodamine ethyl ester (TMRE), a fluorescent marker of mitochondrial membrane potential (psi m).Key Results: Vardenafil at reperfusion reduced infarct size as percentage of the ischemic zone from 45.8+/-2.0% in control hearts to 26.2+/-2.7% (P<0.001) only at 10 nM, whereas higher or lower dosages failed to protect. This protective effect was blocked by co-administration of either the GC inhibitor, 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ), or the PKG inhibitor, KT-5823. HL-1 cardiomyocytes, loaded with TMRE, were treated for 80 min with the calcium ionophore, calcimycin, to induce calcium stress. This reduced the mean cell fluorescence to 63.3 +/- 3.8% of baseline values and vardenafil protected against this fall (78.6 +/- 3.6%, P<0.01). The vardenafil-induced protection of HL-1 cells was blocked by ODQ, KT-5823 or the PKG-inhibiting peptides DT-2 and DT-3, confirming a role for GC and PKG.Conclusions and Implications: These results further support the hypothesis that PDE-5 inhibitors are protective in ischemic hearts, in addition to their known clinical effects in the treatment of erectile dysfunction in men. [ABSTRACT FROM AUTHOR]

The multidrug resistance protein 4 (MRP4) is an efflux transporter involved in the transport of endogenous substrates and xenobiotics. We measured MRP4 mRNA and protein expression in human livers and found a 38- and 45-fold variability, respectively. We sequenced 2 kb of the 5′-flanking region, all exons and intron/exon boundaries of the MRP4 gene in 95 patients and identified 74 genetic variants including 10 non-synonymous variations, seven of them being located in highly conserved regions. None of the detected polymorphisms was significantly associated with changes in the MRP4 mRNA or protein expression. Immunofluorescence microscopy indicated that none of the non-synonymous variations affected the cellular localization of MRP4. However, in cholestatic patients the MRP4 mRNA and protein expression both were significantly upregulated compared to non-cholestatic livers (protein: 299±138 vs 100±60a.u., P<0.001). Taken together, human hepatic MRP4 expression is highly variable. Genetic variations were not sufficient to explain this variability. In contrast, cholestasis is one major determinant of human hepatic MRP4 expression.The Pharmacogenomics Journal (2008) 8, 42–52; doi:10.1038/sj.tpj.6500451; published online 3 April 2007 [ABSTRACT FROM AUTHOR]

Active transport across biological membranes represents a critical step in the disposition of many drugs. It is now well-established that different efflux and uptake transporters such as P-glycoprotein (P-gp), multidrug resistance-associated proteins (MRPs) or organic anion transporting polypeptides (OATPs) are involved in the overall disposition and efficacy of numerous compounds. These proteins are mainly expressed at physiological sites of drug absorption and elimination, thus leading to diminished absorption and/or increased transporter-facilitated excretion. Moreover, drug transporters are known to be of protective significance in blood-organ barriers. On the contrary, only little is known about the relevance of transporter function on drug levels within tissues and cellular compartments, i.e. the site of action for many substances. Moreover, the pharmacokinetic processing inside the cell is characterized by uptake, metabolism and elimination. It is gradually being recognized that active uptake and/or efflux transporters may modify target concentrations at the subcellular receptor sites which in turn may have an influence on drug effects. This review will summarize current knowledge about the impact of transporter proteins on drug availability within pharmacologically relevant cellular compartments and tissues as hepatocytes, enterocytes, different blood cell types, brain, and the heart with emphasis on the potential clinical significance of these transporters. [ABSTRACT FROM AUTHOR]

There is increasing evidence that polymorphisms of the adenosine 5′ triphosphate membrane transporters ABCB1 (P-glycoprotein, MDR1) may affect expression and function, whereas less information is available about the impact of ABCC2 (multidrug resistance-associated protein (MRP2)) single-nucleotide polymorphisms . Particularly, their role in human kidney for drug elimination and in the etiology of renal cell carcinoma is poorly understood. ABCB1 and ABCC2 mRNA and protein expression levels were determined by real-time polymerase chain reaction or immunohistochemistry in kidney cancer and adjacent unaffected cortex tissue of 82 nephrectomized renal cell cancer (RCC) patients (63 clear-cell RCC (CCRCC), 19 non-CCRCC). The DNA of all patients was genotyped for ABCB1 −2352G>A, −692T>C, 2677G>T/A (Ala893Ser/Thr), and 3435C>T, and ABCC2 −24C>T, 1249G>A (Val417Ile) and 3972C>T. ABCB1 and ABCC2 were less expressed in CCRCC than in normal cortex on mRNA as well as on protein level. Although the overall genotype frequency distribution did not differ between the patients and a matched control group, ABCB1 2677T/A and 3435T genotypes were associated with higher (P=0.02 and P=0.04) and ABCC2 −24 T with lower mRNA levels in normal tissues (0.03). The expression of ABCB1 and ABCC2 was not related to genetic variants in RCC tissue. In a reporter gene assay in HepG2 cells, the ABCC2 −24T construct showed an 18.7% reduced activity (P=0.003). In conclusion, ABCB1 and ABCC2 genotypes modulate the expression in the unaffected renal cortex of RCC patients, possibly contributing to inter-individual differences in drug and xenobiotics elimination. Their role in RCC cancer susceptibility or chemotherapy resistance needs further elucidation.The Pharmacogenomics Journal (2007) 7, 56–65. doi:10.1038/sj.tpj.6500403; published online 20 June 2006 [ABSTRACT FROM AUTHOR]

1. GSTM1 is present in only 50% of Caucasian individuals and deficiency of GSTM1 is associated with susceptibility to a growing number of diseases, especially cancer. Thus, a method that would allow accurate, retrospective determination of the GSTM1 phenotype in different patient populations would have many applications. 2. Developed, therefore, is a quantitative, image-analysis-based immunohistochemical technique for the analysis of GSTM1 protein in paraffin-embedded tissue samples. It was applied to the determination of the GSTM1 phenotype using liver biopsies taken from 70 patients. 3. Of the 70 cases (depending on the cut-off point), 51-54% were deficient in GSTM1. A single 27 kD band characteristic for GSTM1 was found in seven of 16 cases analysed by Western blotting using the same GSTM1 antibody as in the immunohistochemical analysis. There was a good correlation (r=0.87) between the staining intensity of the GSTM1 band and the staining intensity evaluated by immunohistochemistry. 4. It is concluded that this quantitative immunohistochemical method permits accurate determination of the GSTM1 phenotype and is well suited for retrospective analysis of GSTM1 expression in specific tissues in situ. [ABSTRACT FROM AUTHOR]

We demonstrate a lattice-matched 1.55 μm vertical-cavity surface-emitting laser operating continuous wave up to 88 °C. The laser employs AlAsSb-based mirrors, which provide high reflectivity and lattice matching to InP. The poor electrical and thermal conductivity of these mirrors is circumvented by utilizing an InP double-intracavity contacted structure. Benefits of the intracavity contacts are addressed by comparing the characteristics with the alternative contact scheme where current is injected through the Sb-based mirrors. Current and optical confinement is provided by an undercut aperture. The device shows a threshold current of 800 μA, a differential efficiency of 23%, and a maximum output power of over 1 mW at 20 °C. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

InAs quantum wells (QWs) have been used as weak links in many recent studies of novel superconductor-normal metal-superconductor junctions. The degree of coupling between the superconducting electrodes depends sensitively on both the superconductor/InAs interface and the QW material in the weak link, factors that are difficult to separate in dc transport studies. Here we used midinfrared spectroscopy to investigate the superconductor/semiconductor contact region. The remnant intersubband absorption we observe in Nb-clad InAs shows that the superconductor/InAs interface produced some confinement of electrons in the InAs. This confinement is, however, consistent with phase coherent transport in the InAs. We find no evidence for charge transfer from the superconductor to the InAs on cooling below the critical temperature of Nb. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the conduction and valence band offsets between InAs and AlAsSb semiconductors using ballistic electron emission spectroscopy (BEES). Molecular beam epitaxy samples; Room-temperature and low-temperature BEES spectra.

The growth of modulation-doped InAs/(Al,Ga)Sb quantum wells on GaAs substrates employing molecular beam epitaxy requires care in the nucleation and the use of buffer layers to achieve high quality material. Despite a 7% lattice mismatch between the substrate and the active layers, fully relaxed epitaxial growth can be accomplished, and quantum wells with electron sheet concentrations of 7×1012 cm-2 having low-temperature mobilities as high as 300 000 cm2/V s have been routinely fabricated recently in our laboratory. In the present work the combination of atomic force microscopy and van der Pauw measurements is used to investigate and explain the strong influence of the buffer layers on the morphology in the quantum well that is shown to be responsible for the great differences in the observed low-temperature mobilities. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the quality of aluminum arsenide-like and indium antimonide-like interfaces in indium arsenide/aluminum antimonide (AlAs) superlattices. Techniques used in the study; Onset of strain relaxation; Amount of arsenic located in the AlSb layers.

We have observed optical transitions between the first subbands of the conduction band and the split-off valence band in GaSb/AlSb quantum well structures. The well width dependence of the emission energies is traced to quantization in the conduction band and in the split-off band. By comparison with data for the band-edge transitions the effective Δ0 gaps is the quantum wells are determined. Contrary to previous calculations the Δ0 gap energies are almost independent of the well width. [ABSTRACT FROM AUTHOR]

Investigates the fabrication of split-gate ballistic constrictions in indium arsenide/aluminum antimonide quantum well heterostructures. Occurrence of sharp conductance steps; Implication of low effective mass for high temperature operation; Use of liquid helium dewar in measuring two-point conductance.

Examines the electrooptic modulation in polar growth axis indium gallium arsenide/gallium arsenide multiple quantum wells. Use of the x-ray diffraction and Rutherford backscattering techniques; Information on the piezoelectric properties of III-V semiconductors in the [211] structures.

Examines the far-infrared photoresponse of indium arsenide (InAs)/gallium indium antimonide (GaInSb) superlattices on gallium antimonide (GaSb) substrates. Determination of the superlattice structure; Measurement of the infrared transmission; Recovery time of the photoconductive response.

Demonstrates the realization of a high mobility two-dimensional electron gas in doped InAs/AlSb quantum wells grown on GaAs substrates by molecular beam epitaxy. Use of low-temperature electron transport measurements in the study; Results of magnetoresistance and Hall measurements.

Investigates the excitonic optical nonlinearity induced by internal field screening in (211) oriented strained-layer superlattices. Comparison of the nonlinear transmission of strained-layer superlattices grown along the (211) axis; Maximum of the nonlinear absorption index.

Superconducting YBaCuO (1-2-3) thin films have been deposited on GaAs by laser ablation, in the presence of an oxygen plasma, at a substrate temperature of 600 °C. The (100) GaAs had a thin (100 Å) Al0.3Ga0.7As cap layer, in order to prevent decomposition of the GaAs. The as-deposited YBaCuO film had a Tc (onset) of 80 K and a Tc (zero) of 20 K. Transmission electron microscopy studies showed the presence of voids in the GaAs, ∼1000 Å in length, and extending 500 Å into the GaAs. [ABSTRACT FROM AUTHOR]

An abstract of the article "Reduction of HMG-CoA-reductase leads to improved cardiac function in doxorubicin-induced cardiomyopathy in mice," by A. Riad and colleagues is presented.

Correction to: The Pharmacogenomics Journal 2006; doi.1038/sj.tpj.6500403. Advance online publication 20 June 2006In this article, published online 20.06.06, the authors have identified that there has been an error in the initial of one of the authors names.S Siegmund should have been W Siegmund.The authors would like to apologize for any confusion caused.The Pharmacogenomics Journal (2007) 7, 74. doi:10.1038/sj.tpj.6500409; published online 18 July 2006 [ABSTRACT FROM AUTHOR]

We employ an atomic force microscope to directly pattern the electron system of InAs–AlSb surface quantum wells. Sharp and sturdy electron beam deposited tips are developed to withstand the comparatively high (approx. μN) forces in the direct patterning process. By direct patterning the InAs surface quantum well we modulate the electron system without any mask. We are therefore able to directly transfer the excellent lithographic resolution of atomic force microscopy to an electron system. The magnetoresistance of such fabricated antidot arrays is discussed. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]