Search

The geometry of glacial overdeepenings on the Swiss Plateau close to Bern was inferred through a combination of gravity data with a 3D gravity modelling software. The target overdeepenings have depths between 155 and > 270 m and widths between 860 and 2400 m. The models show incisions characterized by U-shaped cross-sectional geometries and steep to over-steepened lateral flanks. Existing stratigraphic data reveals that the overdeepenings were formed and then filled during at least two glacial stages, which occurred during the Last Glacial Maximum (LGM) within the Marine Isotope Stage (MIS) 2, and possibly MIS 6 or before. The U-shaped cross-sectional geometries point towards glacial erosion as the main driver for the shaping of the overdeepenings. The combination of the geometries with stratigraphic data suggests that the MIS 6 (or older) glaciers deeply carved the bedrock, whereas the LGM ice sheet only widened the existing valleys but did not further deepen them. We relate this pattern to the different ice thicknesses, where a thicker MIS 6 ice was likely more powerful for wearing down the bedrock than a thinner LGM glacier. Gravity data in combination with forward modelling thus offers robust information on the development of a landscape formed through glaciers.

The D-A-CH geoid project was initiated in 2017 between the national mapping agencies of Germany (BKG), Austria (BEV) and Switzerland (swisstopo), as well as the regional authorities of the German federal states of Bavaria (LDBV) and Baden-Württemberg (LGL), with the motivation to better harmonize the basis for height determination.In these countries, the official national height reference systems that are still in use apply different definitions of the height and the zero levels refer to different tide gauges and epochs. Additionally, the treatment of the permanent tide is not fully consistent. This causes differences at the decimeter scale which also vary along the national borders. At the same time, Austria and Switzerland do compute and store also EVRS-compatible geopotential numbers that are valuable for height system unification.The ambitions of the initiative therefore mirror the situation as described above ‒ to foster and to intensify the cooperation between the partners regarding regional gravity field modeling and to provide better information about the transformations between the national height systems.It was agreed that the cooperation should first focus on a case study area around Lake Constance, with envisaged extension to the complete territories of the “D-A-CH countries” and/or, ideally, to the most of the European Alps. The following achievements have been reached for the focus area:In view of these developments, and taking into account that these challenges are not unique for this specific area, it is planned to extend this initiative to the computation of the entire European Alps (and surrounding lowland areas) and rename the project to “European Alps Geoid (EAlpG)”.We believe that this project can contribute to a better understanding of height differences across borders. Such height differences are for instance of great interest for ground water level investigations or flood protection. Other crucial applications for cross-border height unification are engineering projects such as tunnels, bridges, supply lines, etc.What is more, these activities shall be embedded in a pan-European geoid initiative within EUREF. Contributing to the upcoming EUREF Working Group “European Height Reference Surface”, the European Alps Geoid will be one of many cornerstones to build an official EVRS height reference surface.Potential cooperation partners have been contacted. Nevertheless, the initiative shall be open to interested parties. A virtual meeting is planned to be held shortly after the vEGU2021.

Studying, understanding and modelling global change require geodetic reference frames with an order of accuracy higher than the magnitude of the effects to be actually studied and with high consistency and reliability worldwide. The International Association of Geodesy, taking care of providing a precise geodetic infrastructure for monitoring the Earth system, promotes the implementation of an integrated global geodetic reference frame that provides a reliable frame for consistent analysis and modelling of global phenomena and processes affecting the Earth’s gravity field, the Earth’s surface geometry and the Earth’s rotation. The definition, realization, maintenance and wide utilization of the International Terrestrial Reference System guarantee a globally unified geometric reference frame with an accuracy at the millimetre level. An equivalent high-precision global physical reference frame that supports the reliable description of changes in the Earth’s gravity field (such as sea level variations, mass displacements, processes associated with geophysical fluids) is missing. This paper addresses the theoretical foundations supporting the implementation of such a physical reference surface in terms of an International Height Reference System and provides guidance for the coming activities required for the practical and sustainable realization of this system. Based on conceptual approaches of physical geodesy, the requirements for a unified global height reference system are derived. In accordance with the practice, its realization as the International Height Reference Frame is designed. Further steps for the implementation are also proposed.

Sao Paulo State Univ UNESP, Ctr Human Reprod Prof Franco Jr, Paulista Ctr Diag Res & Training, Dept Gynecol & Obstet,Botucatu Med Sch, Ribeirao Preto, Brazil

We report measurements of hot-carrier photoluminescence from GaAs V-groove quantum wires. CW spectra reveal distinct one-dimensional subbands: at low excitation density recombination from laterally confined nv=1 states is dominant, which shows that carriers relax efficiently to the lowest subband; nv=2 and 3 recombination becomes pronounced at higher temperature and density, which indicates inhibited relaxation, possibly due to band filling. Time-resolved photoluminescence measurements at 10 K show a rise time of approximately 100 ps, which is due to energy relaxation. At later times the intensity of the nv=1 line shows a monotonic decay at low carrier density, but there is a nv pronounced plateau at high density that extends for approximately 200 ps. These results provide clear evidence of carrier relaxation and band filling in quantum wires.

Trapping into the active region is one of the most important design considerations in quantum well lasers. This process becomes crucial for the operation of quantum wire devices since the very small active volume demands strong coupling to the external region, otherwise trapping is greatly inhibited. We report the first measurements of electron trapping from extended three-dimensional (3D) states into one-dimensional (ID) states of a semiconductor quantum wire structure. Our joint theoretical and experimental investigation shows that the trapping time is extremely fast, ~10 ps.

Note: Ecole polytech fed lausanne,dept micro & optoelectr,ch-1015 lausanne,switzerland. Ryan, JF, UNIV OXFORD,CLARENDON LAB,DEPT PHYS,PARKS RD,OXFORD OX1 3PU,ENGLAND. ISI Document Delivery No.: TZ177 Cited References: ANTHONY CJ, 1994, SEMICOND SCI TECH, V9, P36 BLOM PWM, 1992, PHYS REV B, V47, P2027 CHRISTEN J, 1992, APPL PHYS LETT, V61, P67 CHRISTEN J, 1992, SURF SCI, V267, P257 CITRIN DS, 1993, IEEE J QUANTUM ELECT, V29, P97 DEVEAUD B, 1988, APPL PHYS LETT, V52, P1886 KAPON E, 1989, PHYS REV LETT, V63, P430 MACIEL AC, 1995, APPL PHYS LETT, V66, P3039 ROTA L, 1993, P INT WORKSH COMP EL, P236 ROTA L, 1995, PHYS REV B, V52, P5183 TIWARI S, 1994, APPL PHYS LETT, V64, P3536 NR 11 TC 30 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0163-1829 Reference LOEQ-ARTICLE-1996-025doi:10.1103/PhysRevB.53.R4225View record in Web of Science Record created on 2007-08-31, modified on 2017-05-12

Epitaxial growth on nonplanar substrates is an attractive method for producing high quality quantum wire structures for applications in low-threshold lasers. However, a crucial factor in this application is the transfer of carriers between extended (3D) three-dimensional and confined (1D) one-dimensional states. In this paper we present a joint theoretical and experimental investigation of 3D-to-1D scattering in GaAs V-groove quantum wires confined either, within GaAs AlAs short-period superlattice or bulk GaAlAs barriers. The scattering rates were computed using accurate wavefunctions for both the one-dimensional and the extended three-dimensional states. The rates are in good agreement with time-resolved luminescence measurements.

Raman spectroscopy has been used to measure phonons in GaAs v-groove quantum wire structures containing (001) and (111) GaAs/AlAs superlattice barrier regions. Resonance enhancement permits the identification of modes in different regions of the structure, and the measured phonon frequencies provide structural information which shows clear evidence of GaAs migration during growth from (001) surfaces into the grooves. Confined and interface phonons with large in-(111) plane wavevectors are observed. (C) 1996 American Institute of Physics.

We report a clear evidence of bistability in the current–voltage characteristics of p‐i‐n heterostructures containing InGaAs V‐shaped quantum wires. The observed phenomenon is explained in the framework of a single carrier transport model in which the quantum wires act like traps for the vertical current. The charge trapping phenomenon is indeed demonstrated by temperature‐dependent photocurrent experiments.

STUDY QUESTION Is the steroid hormone profile in follicular fluid (FF) at the time of oocyte retrieval different in naturally matured follicles, as in natural cycle IVF (NC-IVF), compared with follicles stimulated with conventional gonadotrophin stimulated IVF (cIVF)? SUMMARY ANSWER Anti-Mullerian hormone (AMH), testosterone (T) and estradiol (E2) concentrations are ∼3-fold higher, androstenedione (A2) is ∼1.5-fold higher and luteinizing hormone (LH) is ∼14-fold higher in NC-IVF than in cIVF follicles, suggesting an alteration of the follicular metabolism in conventional gonadotrophin stimulated IVF. WHAT IS KNOWN ALREADY In conventional IVF, the implantation rate of unselected embryos appears to be lower than in NC-IVF, which is possibly due to negative effects of the stimulation regimen on follicular metabolism. In NC-IVF, the intrafollicular concentration of AMH has been shown to be positively correlated with the oocyte fertilization and implantation rates. Furthermore, androgen treatment seems to improve the ovarian response in low responders. STUDY DESIGN, SIZE, DURATION This cross-sectional study involving 36 NC-IVF and 40 cIVF cycles was performed from 2011 to 2013. Within this population, 13 women each underwent 1 NC-IVF and 1 cIVF cycle. cIVF was performed by controlled ovarian stimulation with HMG and GnRH antagonists. PARTICIPANTS/MATERIALS, SETTING, METHODS Follicular fluid was collected from the leading follicles. AMH, T, A2, dehydroepiandrosterone (DHEA), E2, FSH, LH and progesterone (P) were determined by immunoassays in 76 women. Aromatase activity in follicular fluid cells was analysed by a tritiated water release assay in 33 different women. For statistical analysis, the non-parametric Mann-Whitney U or Wilcoxon tests were used. MAIN RESULTS AND ROLE OF CHANCE In follicular fluid from NC-IVF and from cIVF, median levels were 32.8 and 10.7 pmol/l for AMH (P < 0.0001), 47.2 and 18.8 µmol/l for T (P < 0.0001), 290 and 206 nmol/l for A2 (P = 0.0035), 6.7 and 5.6 pg/ml for DHEA (n.s.), 3292 and 1225 nmol/l for E2 (P < 0.0001), 4.9 and 7.2 mU/ml for FSH (P < 0.05), 14.4 and 0.9 mU/ml for LH (P < 0.0001) and 62 940 and 54 710 nmol/l for P (n.s.), respectively. Significant differences in follicular fluid concentrations for AMH, E2 and LH were also found in the 13 patients who underwent both NC-IVF and cIVF when they were analysed separately in pairs. Hormone analysis in serum excluded any relevant impact of AMH, T, A2, and E2 serum concentration on the follicular fluid hormone concentrations. Median serum concentrations were 29.4 and 0.9 mU/ml for LH (P < 0.0001) and 2.7 and 23.5 nmol/l for P (P < 0.0001) after NC-IVF and c-IVF, respectively. Positive correlations were seen for FF-AMH with FF-T (r = 0.35, P = 0.0002), FF-T with FF-LH (r = 0.48, P < 0.0001) and FF-E2 with FF-T (r = 0.75, P < 0.0001). The analysis of aromatase activity was not different in NC-IVF and cIVF follicular cells. LIMITATION, REASONS FOR CAUTION Any association between the hormone concentrations and the implantation potential of the oocytes could not be investigated as the oocytes in cIVF were not treated individually in the IVF laboratory. Since both c-IVF and NC-IVF follicles were stimulated by hCG before retrieval, the endocrine milieu in the natural cycle does not represent the pure physiological situation. WIDER IMPLICATIONS OF THE FINDINGS The endocrine follicular milieu and the concentration of putative markers of oocyte quality, such as AMH, are significantly different in gonadotrophin-stimulated conventional IVF compared with natural cycle IVF. This could be a cause for the suggested lower oocyte quality in cIVF compared with naturally matured oocytes. The reasons for the reduced AMH concentration might be low serum and follicular fluid LH concentrations due to LH suppression, leading initially to low follicular androgen concentrations and then to low follicular AMH production. STUDY FUNDING/COMPETING INTERESTS Funding for this study was obtained from public universities (for salaries) and private industry (for consumables). Additionally, the study was supported by an unrestricted grant from MSD Merck Sharp & Dohme GmbH and IBSA Institut Biochimique SA. The authors are clinically involved in low-dose monofollicular stimulation and IVF therapies, using gonadotrophins from all gonadotrophin distributors on the Swiss market, including Institut Biochimique SA and MSD Merck Sharp & Dohme GmbH. Otherwise, the authors have no competing interests. TRIAL REGISTRATION NUMBER Not applicable.

Investigating the ternary InxGa1−xAs alloy (x ∼ 12%) by cross-sectional scanning tunneling microscopy, we find that on the UHV-cleaved (110) surface the In distribution in both the surface and the first subsurface layer can be atomically resolved in the empty- and filled-state images, respectively. This is found to be mostly a geometric effect due to the larger size of the In. We apply this method to study the incorporation of In during the growth of In0.12Ga0.88As quantum wires on nonplanar substrates. Strong In segregation in the growth direction is seen in the structure, and we compare the incorporation profiles across the quantum wire and a planar quantum well. No In clustering beyond the statistical expectation is observed.

The mechanisms of carrier transfer from barrier regions (superlattices, side-wall and vertical quantum wells) into arrays of quantum wires are investigated by time-resolved photoluminescence. The wires are grown by different techniques on V-groove substrates. The transfer times range from 25 to 900 ps, depending on the details of the whole structure. The fast carrier transfer is modeled by a diffusion equation which allows one to estimate the quantum mechanical capture time from a two-dimensional vertical QW into a one-dimensional QWR to be

Photoluminescence (PL) and electroluminescence (EL) measurement of GaAs/AlGaAs quantum wires (QWR) located in the active region of a p-i-n junction are reported. The samples are fabricated by molecular-beam epitaxial growth on V-grooved substrates. Good control of the interface, defect density and doping profile have been achieved. Homogeneous current injection into the quantum wires is achieved with efficiencies comparable to current injection into a quantum well control sample. PL with and without an applied voltage across the junction was measured at 86 K and 300 K for different excitation densities. Peaks appearing with an applied voltage correspond to the active-region QWR transitions and are also observed on the EL spectra measured at 120 K and at 300 K. Clear evidence of 1D confinement is observed in both PL and EL spectra. They show a one-dimensional splitting of about 24 meV and a saturation of the ground state at high excitation density. The polarisation of the PL and EL is in good agreement with the expected anisotropy of the 1D matrix elements.

We have determined the main parameters of the quasi-one-dimensional excitons confined in GaAs V-shaped quantum wires, namely exciton Bohr radius and binding energy, by two-photon absorption and magnetoluminescence experiments. The experimental results are in excellent agreement with our calculations, based on realistic wave functions for the actual wire geometry.

We have investigated the optical properties of excitons in GaAs quantum wires grown on nonplanar patterned substrates (V-shaped quantum wires) by photoluminescence and magnetophotoluminescence. The experimentally observed transitions are in agreement with the theoretical evaluation of the quantized energy levels based on TEM measurements. The clear evidence of the ${\mathit{n}}_{\mathit{y}}$=1 and 2 excitonic recombination in the photoluminescence spectra is exploited to directly measure the anisotropy of the optical matrix elements.

The Federal Office of Topography swisstopo is responsible for the maintenance of the coordinate reference frames in Switzerland. Beside the static reference frames, used for national surveying, the development of a kinematic model, mainly used for scientific investigations, is under development since many years. For the determination of vertical movements the analysis of more than 100 years of levelling observations showed a significant alpine uplift of maximally 1.5 mm/year relative to an arbitrarily chosen bench mark in Aarburg (at the south of the Jura mountains). For the determination of horizontal movements the various GPS-campaigns, measured since 1988, are the basis. With the Automated GNSS Network of Switzerland (AGNES), which operates permanently since 1998, valuable information can be extracted for 30 sites. The paper shows that the time series of AGNES nowadays allow statements concerning possible vertical movements. The potential of additional information sources, such as local tie surveys, are discussed. Comparisons of the results of the two independent measuring techniques GNSS and levelling are the main topic of the paper.

EUREF, the Sub-commission for the Euro-pean Reference Frame within IAG Commission 1, in cooperation with the European Geoid and Gravity Project (EGGP), is developing a homogeneous continental GPS/leveling database. EUVN_DA, the Densification Action of the EUVN (European Unified Vertical Reference Network) project is designed to support the development of the new European geoid solutions and to contribute to the realization of an accurate continental height reference surface. The cm-accuracy GPS/leveling database could also be used for the realization of the European Vertical Reference System (EVRS) and for the analysis of the national height networks.

A new photolithographic technique is developed to visualize the deformation of composite materials at high temperature. A very fine metallic grid is deposited onto the surface of the samples. The grid is deposited by the evaporation of a metal through a mask fabricated by holographic lithography. This process provides a means of obtaining grids with a separation of lines as fine as 0.1 μm. Samples of WCCo composite material were deformed at 900°C and observed by scanning electron microscopy. The displacement of the grid lines shows the decohesion of WC grains and sliding. No deformation inside the grains was observed.

This paper describes a fabrication procedure for buried GaAlAs structures with lateral feature sizes in the nm range and with a high package density (periodicity Λ=135nm). GaAs substrates are finely structured by means of deep UV (λ=257nm) holographic lithography. We greatly improved this method by the application of a negative image reversal Novolak resist and an antireflective coating. Buried GaAs filaments are fabricated by growing GaAlAs/GaAs/GaAlAs quantum well (QW) structures on nonplanar substrates by molecular beam epitaxy (MBE). A crescent profile of the GaAs wires is obtained for [011] orientation of the grating lines. This is very attractive for the growth of quantum filaments (QF). Low temperature photoluminescence measurements reveal a high quality of QF grown by MBE over finely grooved substrates. The photoluminescence yielded by QF is comparable to that of QW grown on planar substrates.

The European Gravity and Geoid Project (EGGP) is a project within IAG Commission 2, reporting to Sub-commission 2.4. The main goal of the project is to compute an improved European geoid and quasigeoid model based on new and improved data sets which have become available since the last computation in 1997 (EGG97). The improvements include better global geopotential models from the CHAMP and GRACE missions, better digital elevation models (DEMs) in some regions (e.g., new national DEMs, SRTM3, GTOPO30), updated gravity data sets for selected areas, updated ship and altimetric gravity data, improved procedures for the merging of ship and altimetric data, the use of GPS/levelling data, as well as refined computation techniques

We have investigated the electro-optic properties of strained InGaAs/GaAs quantum wires of lateral width below 20 nm by means of electroluminescence and luminescence under electric bias. A novel room temperature electroluminescence is observed in MBE grown samples. The optical spectra reveal a strong red-shift and the suppression of the luminescence with increasing polarization either under reverse or direct bias. This anomalous Stark shift is due to the combination of the internal piezoelectric field and the external field.

We report a clear evidence of bistability in the current-voltage (I-V) characteristics of p - i - n heterostructures containing InGaAs V-shaped quantum wires. The observed phenomenon is explained in the framework of a single carrier transport model in which the quantum wires act like traps for the vertical current. The charge trapping phenomenon is indeed demonstrated by capacitance-voltage (C-V) and photocurrent experiments.

We present a comprehensive discussion of the excitonic properties of V-shaped GaAs and InGaAs quantum wires grown on patterned substrates. Systematic linear and non-linear spectroscopic studies have been performed in order to clarify the impact of lateral confinement on the exciton wave function, namely: enhanced exciton binding energy, localization in magnetic field, recombination from excited states and multiphoton absorption. The careful evaluation of the electron confinement energies, based on the actual quantum wire profile obtained by TEM micrographs, including the internal piezoelectric field induced by off-diagnoal terms of strain tensor, reproduces quite well the measured one-dimensional states. Finally, application of quantum wires in a p-i-n wave guide for bistable operation is demonstrated.

Fabrication and characterization of a current-injected InGaAs-GaAs quantum-wire gain-coupled distributed feedback (DFB) laser operating at 77 K at a wavelength of 923 nm are presented. Threshold current densities in broad area lasers were measured to be as low as 160 A/cm/sup 2/. The side-mode suppression ratio at twice threshold is 35 dB. A 4-/spl mu/m rib waveguide device has a threshold of 14 mA. The patterning process for the second-order DFB grating fabricated with deep UV holography and wet-chemical etching is described.

Summary form only given. The potential of the STM (scanning tunneling microscope) technique for the characterization of quantum wire structures is demonstrated experimentally. These measurements have the unique feature of locally controlling the electron injection and of inducing luminescence within a single quantum wire. Thus local electronical information is obtained independently of the rest of the sample. This opens up a new way for wire-by-wire characterization of quantum wire arrays and may become of great help for the fabrication of high-quality samples. >

We have measured hot carrier relaxation in GaAs V-groove quantum wires using time-resolved photoluminescence. Relaxation between confined one-dimensional subbands is clearly observed on the time scale of several hundred picoseconds. A simulation of the experiment using a hybrid multisubband Monte Carlo method which includes hot phonon and degeneracy effects gives good agreement with the measurements.© 1995 American Institute of Physics.

We report on the imaging of a molecular beam epitaxially grown GaAs/(AlAs)n(GaAs)m quantum well‐wire array by means of cross‐sectional scanning tunneling microscopy (XSTM) and scanning tunneling‐induced luminescence (STL). XSTM provides atomically resolved cross‐sectional images of sets of quantum well wires with chemical sensitivity within the group III species and electrical sensitivity to single dopant atoms. This permits the precise observation of growth mechanisms and the identification of defects responsible for inhomogeneities in the growth morphology, as well as the determination of dopant incorporation throughout the structure. STL permits the relative quantum efficiency of individual quantum wires to be quantified.

Modulated reflectance spectroscopy and resonant Raman scattering have been used to study the quantized states of crescent‐shaped GaAs quantum wires. Distinct one‐dimensional excitonic transitions originating from the quantum wires together with the expected resonances from the bent quantum wells are observed. The quantum wire transition energies compare very well with those calculated using a V‐shaped potential derived from transmission electron microscopy measurements of the lateral variation of the GaAs well width. The spectroscopic techniques employed here provide alternative methods of probing the confined states in quantum wires of low luminescence efficiency.

In this paper, capillary electrophoresis in clinical and forensic analysis is reviewed on the basis of the literature of 1999, 2000 and the first papers in 2001. An overview of progress relevant examples for each major field of application, namely (i) analysis of drug seizures, explosives residues, gunshot residues and inks, (ii) monitoring of drugs, endogenous small molecules and ions in biofluids and tissues, (iii) general screening for serum proteins and analysis of specific proteins (carbohydrate deficient transferrin, alpha1-antitrypsin, lipoproteins and hemoglobins) in biological fluids, and (iv) analysis of nucleic acids and oligonucleotides in biological samples, including oligonucleotide therapeutics, are presented.

The existing old height system of Switzerland (LNO2) consists of purely levelled heights without considering gravity measurements. This causes difficulties in the application of modern techniques such as GPS for height determination in mountainous areas and in the data exchange with neighbouring countries. Therefore, a new rigorous height system LHN95, based on geopotential numbers and the corresponding geoid, is being determined at the Federal Office of Topography. LHN95 is treated as a kinematic network with respect to the Alpine uplift which reaches amounts of up to 1.5 mm/year [Gubler et al., 1981]. The corresponding relative vertical movements are determined by repeated observations of the first and second order levelling lines. For LHN95 it was decided to use orthometric heights as the official height system. This implies the use of the geoid as the reference surface. Because it has a smooth surface and can be interpolated easily even in mountainous areas, we consider it more convenient than the quasigeoid.

A GaAs surface grating (period 574 nm) is analyzed by four crystal‐six reflection x‐ray diffraction. Two‐dimensional measurements in the vicinity of the 004 GaAs reciprocal lattice point show satellites in the transverse direction related to the periodicity of the grating. A cross pattern, centered on the 004 GaAs reciprocal lattice point, is formed by these satellites. An explanation is given by a model which includes the influence of transmission through the surface pattern on the substrate diffraction.

As pituitary function depends on the integrity of the hypothalamic-pituitary axis, any defect in the development and organogenesis of this gland may account for a form of combined pituitary hormone deficiency (CPHD). A mutation in a novel, tissue-specific, paired-like homeodomain transcription factor, termed Prophet of Pit-1 (PROP1), has been identified as causing the Ames dwarf (df) mouse phenotype, and thereafter, different PROP1 gene alterations have been found in humans with CPHD. We report on the follow-up of two consanguineous families (n = 12), with five subjects affected with CPHD (three males and two females) caused by the same nucleotide C to T transition, resulting in the substitution of Arg--Cys in PROP1 at codon 120. Importantly, there is a variability of phenotype, even among patients with the same mutation. The age at diagnosis was dependent on the severity of symptoms, ranging from 9 months to 8 yr. Although in one patient TSH deficiency was the first symptom of the disorder, all patients became symptomatic by exhibiting severe growth retardation and failure to thrive, which was mainly caused by GH deficiency (n = 4). The secretion of the pituitary-derived hormones (GH, PRL, TSH, LH, and FSH) declined gradually with age, following a different pattern in each individual; therefore, the deficiencies developed over a variable period of time. All of the subjects entered puberty spontaneously, and the two females also experienced menarche and periods before a replacement therapy was necessary.

Theoretical predictions1 have shown that confined structures, quantum wires (QWR) or quantum dots (QD), should have higher gain and absorption, compared to quantum wells, owing to the discontinuity in the joint density of states. We use a non standard description of the valence band states2 to evaluate the absorption of V-shaped quantum wires close to the band edge. We choose the projection axis of the angular momentum of the valence band states along the non-confined direction of the wire. This description has two advantages: (i) the masses are isotropic along the two confined directions and (ii) the light hole (lh) and heavy hole (hh) states are decoupled at kz=0, if the kinetic energy of the confined holes is the same along both confined directions and the energy separation between the {lh,hh}i and {lh,hh}i+1 subbands is high. This description is particularly advantageous close to the band edge where transitions are mostly excitonic. Photoluminescence (PL) and photoluminescence excitation (PLE) measurements made on V-shaped quantum wires are reinterpreted: the lowest energy transition is a e1-lh1 excitonic transition and the second lowest is a e1-hh1 excitonic transition. This new interpretation is the first to explain the lower intensity of the lowest energy peak observed in PL and PLE measurements. To assess the impact of the non-uniformity of the wires, we evaluate the absorption of V-shaped QWR (V-QWR) grown by MBE deposition over a non-planar substrate3.

We investigated the relaxation of excitons and free-carriers in V-shaped GaAs and InGaAs quantum wires with distinct one-dimensional properties. Trapping of carrier in the wires and simultaneous recombination of higher index transitions are studied by spectrally and time resolved luminescence measurements performed at the relevant energies of the quantized states observed in photoluminescence excitation spectra. The effect of disorder in low-crystalline quality quantum wires (inferred by TEM studies) is also discussed.

The exciton-to-free-carrier transition in GaAs and In_xGa_{1-x}As V-shaped quantum wires is revealed by means of temperature-dependent magnetoluminescence experiments. The experimental results are in excellent agreement with the diamagnetic shift obtained from a solution of the full two-dimensional Schrodinger equation for electrons and holes including magnetic-field and excitonic effects. In the GaAs wires, the exciton-to-free-carrier transition is found to occur at temperature consistent with the exciton binding energies. In the In_xGa_{1-x}As wires the diamagnetic shift of the luminescence is found to be free-carrier-like, independent of temperature, due to the weakening of the exciton binding energy induced by the internal piezoelectric field.

Hot carrier dynamics in semiconductor quantum wires is the subject of much current interest, since unique characteristics of inter- and intra-subband carrier-carrier (CC) and carrier-phonon (CP) interactions in quasi-one-dimensional (ID) systems have been predicted [1]. Previous studies of carrier dynamics in etched rectangular GaAs/AlGaAs wires using time-resolved photoluminescence (PL) have reported that relaxation is slower than that measured in similar 2D systems [2,3]. Hot phonon reabsorption was suggested as a possible cause. In these experiments, however, both the confining barriers and the wires were strongly excited, and so the measured relaxation times are influenced by carrier capture into the wires. V-groove structures present an alternative method of realizing quantum wires, and high optical quality has been obtained, as demonstrated by their application in efficient, low-threshold lasers [4]. Here we present picosecond time-resolved PL measurements of carrier relaxation in GaAs v-groove quantum wires which were directly photoexcited at relatively low density with respect to previous experiments. We compare our measurements with the results of a hybrid Monte Carlo simulation which allows us to evaluate the important energy relaxation processes.

We present a joint theoretical and experimental investigation of GaAs v-groove quantum wires confined in GaAs/AlAs superlattice barriers. We have computed the electronic states for both the quantum wire and the barriers. The intrinsic bending of the superlattice layers, together with systematic spatial variations of their thickness, create localized states in the barriers that are separated from the wire. This effect has a strong impact on the overall luminescence efficiency of the wires. The results are in excellent agreement with photoluminescence and photoluminescence excitation spectra.© 1995 American Institute of Physics.

Carrier capture in quantum wells (QWs) has been intensively studied in the past years, especially concerning the dependence of the capture time on QW and barrier dimensions [1]. On the other hand, little is known about the carrier transfer and capture times into one-dimensional (ID) quantum wires (QWRs). In particular, in structures such as crescent-shaped QWRs grown on V-groove substrates, in which the carriers are transferred via both 3D barrier and 2D QW regions surrounding the wires, the carrier capture into the QWRs can be quite complex.

Quantum wire heterostructures, such as V- and T-shaped wires, are very promising candidates for low-threshold lasing. A crucial issue is the excitonic vs. free-carrier nature of the radiative recombination. Here, we report on magnetophotoluminescence studies of GaAs and InGaAs V-shaped wires that allow to discriminate different regimes of radiative recombination.

We report the result of a detailed spectroscopic investigation of the optical properties of excitons in rectangular (etched) and V-shaped (grown on non-planar substrates) GaAs quantum wires. High index excitonic transitions and strong polarization anisotropy of the optical spectra have been observed. The experimentally observed trasitions are in agreement with the theoretical evaluation of quantized energy levels based on the respective model potential.

Changes of the number and properties of the epidermal growth factor (EGF) receptor occur during liver regeneration and may be of importance in the maintenance of hepatocellular mass in liver cirrhosis. We therefore studied the changes in the number and distribution of EGF receptor in the development of liver cirrhosis induced by bile duct ligation. Receptor binding assays demonstrated a marked decrease in the binding capacity of crude plasma membrane fractions from 45 +/- SD 16 to 19 +/- 10 fmol/mg protein (p0.001) in control and bile duct ligated livers, respectively while the Kd increased after 3 days of bile duct ligation from 0.5 +/- 0.2 to 1.4 +/- 0.6 nmol/l. Total receptor concentration in the same membrane fractions, as assessed by Western blot analysis, was not changed. The expression of EGF receptor mRNA was reduced to about one third of control levels after 28 days of bile obstruction. Immunohistochemistry, performed using monoclonal antibodies against EGF receptor, showed a strong labeling of cytoplasm (87 +/- 3% positive) and plasma membranes (84 +/- 24%) but no labeling of nuclei in control livers. In bile duct ligated rats, in contrast, cytoplasmic staining was decreased (15 +/- 12%) already after 3 days of bile obstruction; labeling of canalicular membranes and nuclei appeared after 14 days. The shift of EGF receptor from plasma membranes to nuclei supports the notion that EGF receptor is involved in the maintenance of hepatocellular mass in this model of liver cirrhosis. This concept is supported by the finding of decreased mRNA for EGF receptor presumably representing down-regulation as seen in regenerating rat liver.