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Sample records for rockwood grade iii-v

  1. [Double Endobutto reconstituting coracoclavicular ligament combined with repairing acromioclavicular ligament at stage I for the treatment of acromioclavicular dislocation with Rockwood type III - V].

    Science.gov (United States)

    Hu, Wen-yue; Yu, Chong; Huang, Zhong-ming; Han, Lei

    2015-06-01

    To explore clinical efficacy of double Endobutto reconstituting coracoclavicular ligament combined with repairing acromioclavicular ligament in stage I in treating acromioclavicular dislocation with Rockwood type III - V . From January 2010 to September 2013, 56 patients with Rockwood type III - V acromioclavicular dislocation were treated by operation, including 20 males and 36 femlaes, aged from 32 to 52 years old with an average of 38.5 years old. Twenty-five patients were on the left side and 31 cases on the right side. The time from injury to operation was from 3 to 14 days, averaged 7 days. All patients were diagnosed as acromioclavicular dislocation with Rockwood type III - V, and double Endobutto were used to reconstituting coracoclavicular ligament, line metal anchors were applied for repairing acromioclavicular ligament. Postoperative complications were observed, Karlsson and Constant-Murley evaluation standard were used to evaluate clinical effects. All patients were followed up from 8 to 24 months with average of 11 months. According to Karlsson evaluation standard at 6 months after operation,42 cases were grade A, 13 were grade B and 1 was grade C. Constant-Murley score were improved from (42.80±5.43) before operation to (91.75±4.27) at 6 months after operation. All items at 6 months after operation were better than that of preoperative items. Forty-eight patients got excellent results, 7 were moderate and only 1 with bad result. No shoulder joint adhesion, screw loosening or breakage were occurred during following up. Double Endobutto reconstituting coracoclavicular ligament combined with repairing acromioclavicular ligament in stage I for the treatment of acromioclavicular dislocation with Rockwood type III - V could obtain early staisfied clinical effects, and benefit for early recovery of shoulder joint function.

  2. Concomitant glenohumeral pathologies in high-grade acromioclavicular separation (type III - V).

    Science.gov (United States)

    Markel, Jochen; Schwarting, Tim; Malcherczyk, Dominik; Peterlein, Christian-Dominik; Ruchholtz, Steffen; El-Zayat, Bilal Farouk

    2017-11-10

    Acromioclavicular joint (ACJ) dislocations are common injuries of the shoulder associated with physical activity. The diagnosis of concomitant injuries proves complicated due to the prominent clinical symptoms of acute ACJ dislocation. Because of increasing use of minimally invasive surgery techniques concomitant pathologies are diagnosed more often than with previous procedures. The aim of this study was to identify the incidence of concomitant intraarticular injuries in patients with high-grade acromioclavicular separation (Rockwood type III - V) as well as to reveal potential risk constellations. The concomitant pathologies were compiled during routine arthroscopically assisted treatment in altogether 163 patients (147 male; 16 female; mean age 36.8 years) with high-grade acromioclavicular separation (Rockwood type III: n = 60; Rockwood type IV: n = 6; Rockwood type V: n = 97). Acromioclavicular separation occurred less often in women than men (1:9). In patients under 35, the most common cause for ACJ dislocation was sporting activity (37.4%). Rockwood type V was observed significantly more often than the other types with 57.5% (Rockwood type III = 36.8%, Rockwood type IV 3.7%). Concomitant pathologies were diagnosed in 39.3% of the patients with that number rising to as much as 57.3% in patients above 35 years. Most common associated injuries were rotator cuff injuries (32.3%), chondral defects (30.6%) and SLAP-lesions (22.6%). Of all patients, 8.6% needed additional reconstructive surgery. Glenohumeral injuries are a much more common epiphenomenon during acromioclavicular separation than previously ascertained. High risk group for accompanying injuries are patients above 35 years with preexisting degenerative disease. The increasing use of minimally invasive techniques allows for an easier diagnosis and simultaneous treatment of the additional pathologies.

  3. FREQUENCY DEFORMITY SCOLIOSIS AND FLAT FEET IN PUPILS III, V.VII GRADE SCHOOL

    Directory of Open Access Journals (Sweden)

    Dejаn Gojković

    2013-07-01

    Full Text Available Scoliosis is a lateral deviation of the spine or the angular deviation of the normal position of one or more segmenata.Funkcional curve can be fully corrected until the internal structural scoliosis are bone disorders, muscle nerve elements that support the spine, and complete correction is impossible. Static role is reflected in the foot taking kisses body weight through the bones pop and transmission and distribution of weight on the main point of support of the foot and therefore subject to various changes in the normal foot status.Dinamic role is reflected in walking, running and jumping in different forms. Because of this, the percentage of foot disorders is particularly large in the form of lowering the testing we arche.Perform o.š.Pale Pale deformities in scoliosis and flat feet in students III, V, VII grade. Our aim was to verify the extent to which physical education classes take appropriate measures in the detection and removal of poor posture and physical deformities. For testing we used: clinical method for scoliosis, a method for flat feet -Thomson method.

  4. Intensity of adjuvant chemotherapy regimens and grade III-V toxicities among elderly stage III colon cancer patients.

    Science.gov (United States)

    van Erning, F N; Razenberg, L G E M; Lemmens, V E P P; Creemers, G J; Pruijt, J F M; Maas, H A A M; Janssen-Heijnen, M L G

    2016-07-01

    The aim of this study was to provide insight in the use, intensity and toxicity of therapy with capecitabine and oxaliplatin (CAPOX) and capecitabine monotherapy (CapMono) among elderly stage III colon cancer patients treated in everyday clinical practice. Data from the Netherlands Cancer Registry were used. All stage III colon cancer patients aged ≥70 years diagnosed in the southeastern part between 2005 and 2012 and treated with CAPOX or CapMono were included. Differences in completion of all planned cycles, cumulative dosages and toxicity between both regimens were evaluated. One hundred ninety-three patients received CAPOX and 164 patients received CapMono; 33% (n = 63) of the patients receiving CAPOX completed all planned cycles of both agents, whereas 55% (n = 90) of the patients receiving CapMono completed all planned cycles (P characteristics, CapMono was associated with a lower odds of developing grade III-V toxicity than CAPOX (odds ratio 0.54, 95% confidence interval 0.33-0.89). For patients treated with CAPOX, the most common toxicities were gastrointestinal (29%), haematological (14%), neurological (11%) and other toxicity (13%). For patients treated with CapMono, dermatological (17%), gastrointestinal (13%) and other toxicity (11%) were the most common. CAPOX is associated with significantly more grade III-V toxicities than CapMono, which had a pronounced impact on the cumulative dosage received and completion of all planned cycles. In this light, CapMono seems preferable over CAPOX. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Transarticular fixation by hook plate versus coracoclavicular stabilization by single multistrand titanium cable for acute Rockwood grade-V acromioclavicular joint dislocation: a case-control study.

    Science.gov (United States)

    Gao, You-Shui; Zhang, Yue-Lei; Ai, Zi-Sheng; Sun, Yu-Qiang; Zhang, Chang-Qing; Zhang, Wei

    2015-11-19

    Hook plate (HP) is popularly used for acute and severely displaced acromioclavicular (AC) dislocations. However, subacromial impingement and acromion osteolysis induced by transarticular fixation are notorious. The current case-control study was to compare transarticular fixation by HP to coracoclavicular (CC) stabilization by single multistrand titanium cable (MSTC). Between January 2006 and August 2009, 24 patients with acute AC dislocations were surgically treated by open reduction and transarticular fixation with HP. These patients were matched to a series of 24 patients, who were managed by CC stabilization with MSTC in the same period. All AC dislocations were graded as Rockwood type V. Implant was removed 8-12 months after the primary operation in all patients, and 12 months at least were needed to assess the maintenance of AC joint. Functional results were evaluated before implant removal as well as in the last follow-up based on Constant-Murley criteria. There were no differences of demographic data including age, dominant gender and side, injury-to-surgery interval, operation time and follow-up period. In terms of functionality, Constant score was 95.8 ± 4.1 in MSTC group, while 76.7 ± 8.0 in HP group before implant removal (P acromioclavicular joint presented in 16 patients (66.7%) in patients treated by HP, while it was found in only 3 patients (12.5%) treated by MSTC (P acromioclavicular dislocation both before and after removal of the implant. Hardware removal is of great benefits for functional improvement in patients treated by HP.

  6. III-V microelectronics

    CERN Document Server

    Nougier, JP

    1991-01-01

    As is well known, Silicon widely dominates the market of semiconductor devices and circuits, and in particular is well suited for Ultra Large Scale Integration processes. However, a number of III-V compound semiconductor devices and circuits have recently been built, and the contributions in this volume are devoted to those types of materials, which offer a number of interesting properties. Taking into account the great variety of problems encountered and of their mutual correlations when fabricating a circuit or even a device, most of the aspects of III-V microelectronics, from fundamental p

  7. Acromioclavicular joint dislocations: radiological correlation between Rockwood classification system and injury patterns in human cadaver species.

    Science.gov (United States)

    Eschler, Anica; Rösler, Klaus; Rotter, Robert; Gradl, Georg; Mittlmeier, Thomas; Gierer, Philip

    2014-09-01

    The classification system of Rockwood and Young is a commonly used classification for acromioclavicular joint separations subdividing types I-VI. This classification hypothesizes specific lesions to anatomical structures (acromioclavicular and coracoclavicular ligaments, capsule, attached muscles) leading to the injury. In recent literature, our understanding for anatomical correlates leading to the radiological-based Rockwood classification is questioned. The goal of this experimental-based investigation was to approve the correlation between the anatomical injury pattern and the Rockwood classification. In four human cadavers (seven shoulders), the acromioclavicular and coracoclavicular ligaments were transected stepwise. Radiological correlates were recorded (Zanca view) with 15-kg longitudinal tension applied at the wrist. The resulting acromio- and coracoclavicular distances were measured. Radiographs after acromioclavicular ligament transection showed joint space enlargement (8.6 ± 0.3 vs. 3.1 ± 0.5 mm, p acromioclavicular joint space width increased to 16.7 ± 2.7 vs. 8.6 ± 0.3 mm, p acromioclavicular joint lesions higher than Rockwood type I and II. The clinical consequence for reconstruction of low-grade injuries might be a solely surgical approach for the acromioclavicular ligaments or conservative treatment. High-grade injuries were always based on additional structural damage to the coracoclavicular ligaments. Rockwood type V lesions occurred while muscle attachments were intact.

  8. Semiconducting III-V compounds

    CERN Document Server

    Hilsum, C; Henisch, Heinz R

    1961-01-01

    Semiconducting III-V Compounds deals with the properties of III-V compounds as a family of semiconducting crystals and relates these compounds to the monatomic semiconductors silicon and germanium. Emphasis is placed on physical processes that are peculiar to III-V compounds, particularly those that combine boron, aluminum, gallium, and indium with phosphorus, arsenic, and antimony (for example, indium antimonide, indium arsenide, gallium antimonide, and gallium arsenide).Comprised of eight chapters, this book begins with an assessment of the crystal structure and binding of III-V compounds, f

  9. Transformational III-V Electronics

    KAUST Repository

    Nour, Maha A.

    2014-01-01

    Flexible electronics using III-V materials for nano-electronics with high electron mobility and optoelectronics with direct band gap are attractive for many applications. This thesis describes a complementary metal oxide semiconductor (CMOS

  10. ISAKOS upper extremity committee consensus statement on the need for diversification of the Rockwood classification for acromioclavicular joint injuries

    DEFF Research Database (Denmark)

    Beitzel, Knut; Mazzocca, Augustus D; Bak, Klaus

    2014-01-01

    Optimal treatment for the unstable acromioclavicular (AC) joint remains a highly debated topic in the field of orthopaedic medicine. In particular, no consensus exists regarding treatment of grade III injuries, which are classified according to the Rockwood classification by disruption of both th...

  11. Transformational III-V Electronics

    KAUST Repository

    Nour, Maha A.

    2014-04-01

    Flexible electronics using III-V materials for nano-electronics with high electron mobility and optoelectronics with direct band gap are attractive for many applications. This thesis describes a complementary metal oxide semiconductor (CMOS) compatible process for transforming traditional III-V materials based electronics into flexible one. The thesis reports releasing 200 nm of Gallium Arsenide (GaAs) from 200 nm GaAs / 300 nm Aluminum Arsenide (AlAs) stack on GaAs substrate using diluted hydrofluoric acid (HF). This process enables releasing a single top layer compared to peeling off all layers with small sizes at the same time. This is done utilizing a network of release holes that contributes to the better transparency (45 % at 724 nm wavelengths) observed. Fabrication of metal oxide semiconductor capacitor (MOSCAPs) on GaAs is followed by releasing it to have devices on flexible 200 nm GaAs. Similarly, flexible GaSb and InP fabrication process is also reported to transform traditional electronics into large-area flexible electronics.

  12. III-V semiconductor materials and devices

    CERN Document Server

    Malik, R J

    1989-01-01

    The main emphasis of this volume is on III-V semiconductor epitaxial and bulk crystal growth techniques. Chapters are also included on material characterization and ion implantation. In order to put these growth techniques into perspective a thorough review of the physics and technology of III-V devices is presented. This is the first book of its kind to discuss the theory of the various crystal growth techniques in relation to their advantages and limitations for use in III-V semiconductor devices.

  13. Hybrid III-V/silicon lasers

    Science.gov (United States)

    Kaspar, P.; Jany, C.; Le Liepvre, A.; Accard, A.; Lamponi, M.; Make, D.; Levaufre, G.; Girard, N.; Lelarge, F.; Shen, A.; Charbonnier, P.; Mallecot, F.; Duan, G.-H.; Gentner, J.-.; Fedeli, J.-M.; Olivier, S.; Descos, A.; Ben Bakir, B.; Messaoudene, S.; Bordel, D.; Malhouitre, S.; Kopp, C.; Menezo, S.

    2014-05-01

    The lack of potent integrated light emitters is one of the bottlenecks that have so far hindered the silicon photonics platform from revolutionizing the communication market. Photonic circuits with integrated light sources have the potential to address a wide range of applications from short-distance data communication to long-haul optical transmission. Notably, the integration of lasers would allow saving large assembly costs and reduce the footprint of optoelectronic products by combining photonic and microelectronic functionalities on a single chip. Since silicon and germanium-based sources are still in their infancy, hybrid approaches using III-V semiconductor materials are currently pursued by several research laboratories in academia as well as in industry. In this paper we review recent developments of hybrid III-V/silicon lasers and discuss the advantages and drawbacks of several integration schemes. The integration approach followed in our laboratory makes use of wafer-bonded III-V material on structured silicon-on-insulator substrates and is based on adiabatic mode transfers between silicon and III-V waveguides. We will highlight some of the most interesting results from devices such as wavelength-tunable lasers and AWG lasers. The good performance demonstrates that an efficient mode transfer can be achieved between III-V and silicon waveguides and encourages further research efforts in this direction.

  14. Thermal oxidation of III-V compounds

    International Nuclear Information System (INIS)

    Monteiro, O.R.; Evans, J.W.

    1988-01-01

    The thermal oxidation of two important III-V compound semiconductor materials, namely GaAs and InP, has been studied between 300 and 600 0 C. In-situ TEM, cross-sectional TEM (XTEM) and SIMS analyses were used to characterize the reaction products. The first technique allows us to access the reactions at the very moment they are occurring. XTEM provides a clearer picture of the distribution of phases in the oxidized samples. SIMS gives us information on the dopant redistribution after oxidation as well as enrichment of group V element at the oxide semiconductor interface. Based on those results, the reaction products were characterized and reaction mechanisms proposed

  15. Progress in III-V materials technology

    Science.gov (United States)

    Grant, Ian R.

    2004-12-01

    Compound semiconductors, in the form of GaAs and InP have achieved major commercial significance in areas of application such as mobile communications, displays and telecoms and offer a versatility of function beyond the capabilities of Si. III-V compounds, and in particular GaAs, have since their early development been the subject of defence related interest. Support from this sector established the basic materials technologies and nurtured development up until their commercial breakthrough into consumer products. GaAs, for example, now provides essential components for mobile phones and CD / DVD players. An overview is presented of the crystal growth and processing methods used in the manufacture of these materials. Current state of the art characteristics on crystal form and quality are discussed, together with the evolution of single crystal growth techniques. Consideration is given to how these principal compounds together with the minor materials, InSb, GaSb and InAs are employed in diverse applications over a broad spectral range, together with information on markets and future perspectives.

  16. Comparative study on the treatment of Rockwood type III acute acromioclavicular dislocation: Clinical results from the TightRope® technique vs. K-wire fixation.

    Science.gov (United States)

    Horst, K; Garving, C; Thometzki, T; Lichte, P; Knobe, M; Dienstknecht, T; Hofman, M; Pape, H-C

    2017-04-01

    The aim of this study was to address the inconsistency regarding the operative treatment of Rockwood type III acromioclavicular joint separation. We compared results after single- and double TightRope ® reduction with results after acromioclavicular transfixation via K-wires only and additional ligament augmentation in acute acromioclavicular (AC) joint separations graded Rockwood type III, and hypothesized that the TightRope ® technique leads to better clinical and radiological results. We conducted a retrospective clinical cohort study and included 42 consecutive patients (mean age 43 years [24-66]) diagnosed and operatively treated between 2004 and 2012 (mean follow-up was 54.6 months [15-118]). Specific shoulder scores as well as scores reflecting the patients' overall mental and physical health status were used. Radiological evaluation was also performed. The SF12 test revealed comparability between all subgroups. Specific shoulder tests and a visual analogue scale demonstrated comparable results. Radiographic measurements showed a significant reduction in the AC distance and CC distance after surgery in all subgroups. The early complication rate was 9.5% for all patients, while late complications occurred in 14.3% of all cases. Compared to the established methods, the operative TightRope ® procedures represent a safe alternative in Rockwood III injuries. All investigated techniques predominantly led to good and excellent clinical results in acute Rockwood type III AC joint instabilities. Avoidance of material removal and shorter hospital stays appear to speak in favour for the TightRope ® technique. IV. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  17. Position-controlled epitaxial III-V nanowires on silicon

    NARCIS (Netherlands)

    Roest, A.L.; Verheijen, M.A.; Wunnicke, O.; Serafin, S.N.; Wondergem, H.J.; Bakkers, E.P.A.M.

    2006-01-01

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the VLS mechanism with laser ablation as well as metal-organic vapour phase epitaxy. The hetero-epitaxial growth of the III-V nanowires on silicon was confirmed with x-ray diffraction

  18. Magnetooptical investigations on ferromagnetic III-V-semiconductors; Magnetooptische Untersuchungen an ferromagnetischen III-V-Halbleitern

    Energy Technology Data Exchange (ETDEWEB)

    Winter, Andreas

    2009-07-23

    Magnetooptical Kerr effect (MOKE) and Magnetic Circular Dichroism (MCD) have been used to investigate magnetic as well as bandstructure properties of diluted magnetic III-V-semiconductors containing Mn. In these ferromagnetic systems it has been found that the strength of the observed effects depends linearly on the magnetization of the samples with no influence of the external magnetic field. The magnetooptical effects allowed the recording of hysteresis loops of GaMnAs, GaMnSb, InMnAs and InMnSb samples for different temperatures and in the case of GaMnAs also for different alignments of the external magnetic field with respect to the easy axis of magnetization. The Stoner-Wohlfahrt-Model has been used to describe the resulting shapes of the loops yielding the magnetic anisotropy parameters of the samples. For magnetically saturated samples, spectra of MOKE and MCD have been recorded. Contrary to pure III-V-semiconductors, which exhibit lots of sharp resonances due to interband transitions between Landau levels, III-Mn-V-semi-conductors how only very few (or just one) considerably broad resonance(s). Their spectral position(s) do(es) neither depend upon the magnetic field as it would be the case for pure III-V-semiconductors nor the magnetization. Only the amplitude increases linearly with the magnetization. Utilizing a kp-theory it has been possible to describe the observed dependencies. Valence- and conduction-band are split into Landau levels by the external magnetic field and, in addition to the Zeeman-effect, the spin-levels are split by the exchange interaction between the localized electrons of the Mn ions and the free carriers which is proportional to the magnetization of the samples. This splitting is much bigger than the Landau level splitting. Due to an inhomogeneous distribution of the Mn ions and due to the high carrier density the Landau levels are strongly broadened and their structure is not observable. Owing to the high carrier-concentration in

  19. Position-controlled epitaxial III-V nanowires on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Roest, Aarnoud L; Verheijen, Marcel A; Wunnicke, Olaf; Serafin, Stacey; Wondergem, Harry; Bakkers, Erik P A M [Philips Research Laboratories, Professor Holstlaan 4, 5656 AA Eindhoven (Netherlands); Kavli Institute of NanoScience, Delft University of Technology, PO Box 5046, 2600 GA Delft (Netherlands)

    2006-06-14

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the VLS mechanism with laser ablation as well as metal-organic vapour phase epitaxy. The hetero-epitaxial growth of the III-V nanowires on silicon was confirmed with x-ray diffraction pole figures and cross-sectional transmission electron microscopy. We show preliminary results of two-terminal electrical measurements of III-V nanowires grown on silicon. E-beam lithography was used to predefine the position of the nanowires.

  20. Position-controlled epitaxial III-V nanowires on silicon

    International Nuclear Information System (INIS)

    Roest, Aarnoud L; Verheijen, Marcel A; Wunnicke, Olaf; Serafin, Stacey; Wondergem, Harry; Bakkers, Erik P A M

    2006-01-01

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the VLS mechanism with laser ablation as well as metal-organic vapour phase epitaxy. The hetero-epitaxial growth of the III-V nanowires on silicon was confirmed with x-ray diffraction pole figures and cross-sectional transmission electron microscopy. We show preliminary results of two-terminal electrical measurements of III-V nanowires grown on silicon. E-beam lithography was used to predefine the position of the nanowires

  1. Development of III-V/Si Multijunction Space Photovoltaics

    Data.gov (United States)

    National Aeronautics and Space Administration — High substrate costs, as well as weight, typically play a major role in the high costs of multijunction space solar cell production and deployment. III-V/Si...

  2. Hybrid III-V/SOI Resonant Cavity Photodetector

    DEFF Research Database (Denmark)

    Learkthanakhachon, Supannee; Taghizadeh, Alireza; Park, Gyeong Cheol

    2016-01-01

    A hybrid III-V/SOI resonant cavity photo detector has been demonstrated, which comprises an InP grating reflectorand a Si grating reflector. It can selectively detects an incident light with 1.54-µm wavelength and TM polarization.......A hybrid III-V/SOI resonant cavity photo detector has been demonstrated, which comprises an InP grating reflectorand a Si grating reflector. It can selectively detects an incident light with 1.54-µm wavelength and TM polarization....

  3. Surface passivation technology for III-V semiconductor nanoelectronics

    International Nuclear Information System (INIS)

    Hasegawa, Hideki; Akazawa, Masamichi

    2008-01-01

    The present status and key issues of surface passivation technology for III-V surfaces are discussed in view of applications to emerging novel III-V nanoelectronics. First, necessities of passivation and currently available surface passivation technologies for GaAs, InGaAs and AlGaAs are reviewed. Then, the principle of the Si interface control layer (ICL)-based passivation scheme by the authors' group is introduced and its basic characterization is presented. Ths Si ICL is a molecular beam epitaxy (MBE)-grown ultrathin Si layer inserted between III-V semiconductor and passivation dielectric. Finally, applications of the Si ICL method to passivation of GaAs nanowires and GaAs nanowire transistors and to realization of pinning-free high-k dielectric/GaAs MOS gate stacks are presented

  4. Research progress of III-V laser bonding to Si

    Science.gov (United States)

    Bo, Ren; Yan, Hou; Yanan, Liang

    2016-12-01

    The vigorous development of silicon photonics makes a silicon-based light source essential for optoelectronics' integration. Bonding of III-V/Si hybrid laser has developed rapidly in the last ten years. In the tireless efforts of researchers, we are privileged to see these bonding methods, such as direct bonding, medium adhesive bonding and low temperature eutectic bonding. They have been developed and applied to the research and fabrication of III-V/Si hybrid lasers. Some research groups have made remarkable progress. Tanabe Katsuaki of Tokyo University successfully implemented a silicon-based InAs/GaAs quantum dot laser with direct bonding method in 2012. They have bonded the InAs/GaAs quantum dot laser to the silicon substrate and the silicon ridge waveguide, respectively. The threshold current of the device is as low as 200 A/cm2. Stevan Stanković and Sui Shaoshuai successfully produced a variety of hybrid III-V/Si laser with the method of BCB bonding, respectively. BCB has high light transmittance and it can provide high bonding strength. Researchers of Tokyo University and Peking University have realized III-V/Si hybrid lasers with metal bonding method. We describe the progress in the fabrication of III-V/Si hybrid lasers with bonding methods by various research groups in recent years. The advantages and disadvantages of these methods are presented. We also introduce the progress of the growth of III-V epitaxial layer on silicon substrate, which is also a promising method to realize silicon-based light source. I hope that readers can have a general understanding of this field from this article and we can attract more researchers to focus on the study in this field.

  5. Epitaxial III-V nanowires on silicon for vertical devices

    NARCIS (Netherlands)

    Bakkers, E.P.A.M.; Borgström, M.T.; Einden, Van Den W.; Weert, van M.H.M.; Helman, A.; Verheijen, M.A.

    2006-01-01

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the Vapor-Liquid-Solid (VLS) mechanism with laser ablation as well as metal organic vapor phase epitaxy. The VLS growth enables the fabrication of complex axial and radial

  6. Antisites in III-V semiconductors: Density functional theory calculations

    KAUST Repository

    Chroneos, A.; Tahini, Hassan Ali; Schwingenschlö gl, Udo; Grimes, R. W.

    2014-01-01

    as a function of the Fermi level and under different growth conditions. The formation energies of group III antisites (III V q) decrease with increasing covalent radius of the group V atom though not group III radius, whereas group V antisites (V I I I

  7. Long-wavelength III-V/silicon photonic integrated circuits

    NARCIS (Netherlands)

    Roelkens, G.C.; Kuyken, B.; Leo, F.; Hattasan, N.; Ryckeboer, E.M.P.; Muneeb, M.; Hu, C.L.; Malik, A.; Hens, Z.; Baets, R.G.F.; Shimura, Y.; Gencarelli, F.; Vincent, B.; Loo, van de R.; Verheyen, P.A.; Lepage, G.; Campenhout, van J.; Cerutti, L.; Rodriquez, J.B.; Tournie, E.; Chen, X; Nedeljkovic, G.; Mashanovich, G.; Liu, X.; Green, W.S.

    2013-01-01

    We review our work in the field of short-wave infrared and mid-infrared photonic integrated circuits for applications in spectroscopic sensing systems. Passive silicon waveguide circuits, GeSn photodetectors, the integration of III-V and IV-VI semiconductors on these circuits, and silicon nonlinear

  8. III-V/Active-Silicon Integration for Low-Cost High-Performance Concentrator Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Ringel, Steven [The Ohio State Univ., Columbus, OH (United States); Carlin, John A [The Ohio State Univ., Columbus, OH (United States); Grassman, Tyler [The Ohio State Univ., Columbus, OH (United States)

    2018-04-17

    This FPACE project was motivated by the need to establish the foundational pathway to achieve concentrator solar cell efficiencies greater than 50%. At such an efficiency, DOE modeling projected that a III-V CPV module cost of $0.50/W or better could be achieved. Therefore, the goal of this project was to investigate, develop and advance a III-V/Si mulitjunction (MJ) CPV technology that can simultaneously address the primary cost barrier for III-V MJ solar cells while enabling nearly ideal MJ bandgap profiles that can yield efficiencies in excess of 50% under concentrated sunlight. The proposed methodology was based on use of our recently developed GaAsP metamorphic graded buffer as a pathway to integrate unique GaAsP and Ga-rich GaInP middle and top junctions having bandgaps that are adjustable between 1.45 – 1.65 eV and 1.9 – 2.1 eV, respectively, with an underlying, 1.1 eV active Si subcell/substrate. With this design, the Si can be an active component sub-cell due to the semi-transparent nature of the GaAsP buffer with respect to Si as well as a low-cost alternative substrate that is amenable to scaling with existing Si foundry infrastructure, providing a reduction in materials cost and a low cost path to manufacturing at scale. By backside bonding of a SiGe, a path to exceed 50% efficiency is possible. Throughout the course of this effort, an expansive range of new understanding was achieved that has stimulated worldwide efforts in III-V/Si PV R&D that spanned materials development, metamorphic device optimization, and complete III-V/Si monolithic integration. Highlights include the demonstration of the first ideal GaP/Si interfaces grown by industry-standard MOCVD processes, the first high performance metamorphic tunnel junctions designed for III-V/Si integration, record performance of specific metamorphic sub-cell designs, the first fully integrated GaInP/GaAsP/Si double (1.7 eV/1.1 eV) and triple (1.95 eV/1.5 eV/1.1 eV) junction solar cells, the first

  9. Cleavage mechanoluminescence in elemental and III-V semiconductors

    International Nuclear Information System (INIS)

    Chandra, B.P.; Patel, R.P.; Gour, Anubha S.; Chandra, V.K.; Gupta, R.K.

    2003-01-01

    The present paper reports the theory of mechanoluminescence (ML) produced during cleavage of elemental and III-V semiconductors. It seems that the formation of crack-induced localized states is responsible for the ML excitation produced during the cleavage of elemental and III-V semiconductors. According to this mechanism, as the atoms are drawn away from each other in an advancing crack tip, the decreasing wave function overlap across the crack may result in localized states which is associated with increasing electron energy. If the energy of these localized states approach that of the conduction band, transition to the conduction band via tunnelling would be possible, creating minority carriers, and consequently the electron-hole recombination may give rise to mechanoluminescence. When an elemental or III-V semiconductor is cleaved, initially the ML intensity increases with time, attains a peak value I m at the time t m corresponding to completion of the cleavage of the semiconductor, and then it decreases following power law decay. Expressions are derived for the ML intensity I m corresponding to the peak of the ML intensity versus time curve and for the total ML intensity I T . It is shown that both I m and I T should increase directly with the area of the newly created surfaces of the crystals. From the measurements of the ML intensity, the velocity of crack propagation in material can be determined by using the relation v=H/t m

  10. Antisites in III-V semiconductors: Density functional theory calculations

    KAUST Repository

    Chroneos, A.

    2014-07-14

    Density functional based simulation, corrected for finite size effects, is used to investigate systematically the formation of antisite defects in III-V semiconductors (III=Al, Ga, and In and V=P, As, and Sb). Different charge states are modelled as a function of the Fermi level and under different growth conditions. The formation energies of group III antisites (III V q) decrease with increasing covalent radius of the group V atom though not group III radius, whereas group V antisites (V I I I q) show a consistent decrease in formation energies with increase in group III and group V covalent radii. In general, III V q defects dominate under III-rich conditions and V I I I q under V-rich conditions. Comparison with equivalent vacancy formation energy simulations shows that while antisite concentrations are always dominant under stoichiometric conditions, modest variation in growth or doping conditions can lead to a significantly higher concentration of vacancies. © 2014 AIP Publishing LLC.

  11. Morphological classification of acromial spur: correlation between Rockwood tilt view and arthroscopic finding

    Directory of Open Access Journals (Sweden)

    Kongmalai Pinkawas

    2017-01-01

    Full Text Available Purpose and hypothesis: Acromion spur is the extrinsic factor for impingement syndrome and rotator cuff tear. The Rockwood tilt view can be used to evaluate prominence of the anterior acromion, however no study has shown the correlation of findings between the Rockwood tilt view and the arthroscopic finding. Methods: We developed the arthroscopic classification of acromion spur as type 1 flat spur, type 2 bump spur, type 3 heel spur, type 4 keel spur, and type 5 irregular spur. Patients with rotator cuff syndrome who underwent arthroscopic surgery were recruited. Two observers were asked to classify the type of spur from arthroscopic findings and Rockwood tilt views separately in random pattern. The prevalence of supraspinatus tendon tear was also recorded as no tear, partial-thickness tear, and full-thickness tear. Results: The keel spur (33.9% was the most common finding followed by the heel spur (27.8%. The correlation was high especially for the heel, the keel, and the irregular spur (75.47%, 74.03%, and 72.73%, respectively. These three types of spurs have a high prevalence of full thickness of supraspinatus tendon tear. Conclusion: The Rockwood tilt view can be used to evaluate the morphology of an acromion spur, especially the at-risk spur that correlates highly with the full-thickness supraspinatus tendon tear. The arthroscopic classification will also be a useful tool to improve communication between the surgeon and the guide for appropriate treatment in a rotator cuff tear patient when encountering the heel, keel, and irregular spur.

  12. Subsurface dimerization in III-V semiconductor (001) surfaces

    DEFF Research Database (Denmark)

    Kumpf, C.; Marks, L.D.; Ellis, D.

    2001-01-01

    We present the atomic structure of the c(8 X 2) reconstructions of InSb-, InAs-, and GaAs-(001) surfaces as determined by surface x-ray diffraction using direct methods. Contrary to common belief, group III dimers are not prominent on the surface, instead subsurface dimerization of group m atoms ...... takes place in the second bilayer, accompanied by a major rearrangement of the surface atoms above the dimers to form linear arrays. By varying the occupancies of four surface sites the (001)-c(8 X 2) reconstructions of III-V semiconductors can be described in a unified model....

  13. Radiation Effects in III-V Nanowire Devices

    Science.gov (United States)

    2016-09-01

    fabrication of an in-plane nanowire (NW) GaAs metal-oxide-semiconductor field- effect transistor (MOSFET) by focused -ion beam (FIB) etching and chemical...8725 John J. Kingman Road, MS 6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-16-94 Radiation Effects in III-V...5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING / MONITORING AGENCY

  14. DX centers in III-V semiconductors under hydrostatic pressure

    International Nuclear Information System (INIS)

    Wolk, J.A.

    1992-11-01

    DX centers are deep level defects found in some III-V semiconductors. They have persistent photoconductivity and large difference between thermal and optical ionization energies. Hydrostatic pressure was used to study microstructure of these defects. A new local vibrational mode (LVM) was observed in hydrostatically stressed, Si-doped GaAs. Corresponding infrared absorption peak is distinct from the Si Ga shallow donor LVM peak, which is the only other LVM peak observed in our samples, and is assigned to the Si DX center. Analysis of the relative intensities of the Si DX LVM and the Si shallow donor LVM peaks, combined with Hall effect and resistivity indicate that the Si DX center is negatively charged. Frequency of this new mode provides clues to the structure of this defect. A pressure induced deep donor level in S-doped InP was also discovered which has the properties of a DX center. Pressure at which the new defect becomes more stable than the shallow donor is 82 kbar. Optical ionization energy and energy dependence of the optical absorption cross section was measured for this new effect. Capture barrier from the conduction band into the DX state were also determined. That DX centers can be formed in InP by pressure suggests that DX states should be common in n-type III-V semiconductors. A method is suggested for predicting under what conditions these defects will be the most stable form of the donor impurity

  15. III-V nanoelectronics and related surface/interface issues

    International Nuclear Information System (INIS)

    Hasegawa, Hideki

    2003-01-01

    The conventional logic gate architecture is not suitable for high-density integration of quantum devices which are non-robust and extremely structure- and charge-sensitive. In this paper, our novel hexagonal binary-decision-diagram (BDD) quantum circuit approach for III-V nanoelectronics is reviewed and related critical surface/interface issues for high-density integration are discussed. First, the basic concept and actual implementation method of our approach are explained, giving examples of novel BDD quantum integrated circuits where nanowire networks are controlled by nanoscale Schottky wrap gates. For high-density integration, growth of embedded sub-10 nm III-V quantum wire networks by selective molecular beam epitaxy (MBE) on patterned substrates is described, including effects of atomic hydrogen irradiation and kinetic control of wire width. The key processing issue lies in understanding and control of nanostructure surfaces/interfaces. Behavior of nanoscale Schottky gates, recent scanning tunneling microscopy (STM)/scanning tunneling spectroscopy (STS) studies of surface states, and successful removal of surface states by MBE-grown silicon interface control layer are discussed

  16. Hybrid III-V-on-Si Vertical Cavity laser for Optical Interconnects

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Semenova, Elizaveta; Chung, Il-Sug

    2013-01-01

    Combining a III-V active material onto the Si platform is an attractive approach for silicon photonics light source. We have developed fabrication methods for novel III-V on Si vertical cavity lasers.......Combining a III-V active material onto the Si platform is an attractive approach for silicon photonics light source. We have developed fabrication methods for novel III-V on Si vertical cavity lasers....

  17. Fast optical in situ spectroscopy in III-V MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Kaspari, C.

    2007-09-29

    This work describes the application of optical in situ measurement techniques (reflectance anisotropy spectroscopy, RAS, and spectroscopic ellipsometry, SE) to processes that are important for the growth of III-V semiconductors like GaAs, InP, InAs and GaP in metal-organic vapour phase epitaxy (MOVPE). Special emphasis is placed on the determination of the free carrier concentration (doping level) and the study of the thermal desorption properties of III-V oxides. A large part of this work is concerned with the development and the construction of a multichannel RAS setup that allows the recording of RAS spectra within fractions of a second. On the basis of benchmark measurements it was shown that the spectral resolution is sufficiently accurate for application in epitaxy. To demonstrate the recording of spectra with high temporal resolution, RAS monolayer oscillations during growth of GaAs were studied and it was shown that the surface changes periodically between a relatively smooth morphology with adsorbed methyl groups (type III) and a stepped, gallium-rich surface (type II). Furthermore the non-reversible process of growing InAs quantum dots on GaAs was studied. It was shown that the multichannel RAS is capable of detecting the 2D-3D transition as well as the following morphological change of the surface at high temporal resolution. For the measurement of the doping level, the relationship between the doping-induced internal electric field and the anisotropy of the sample was studied. To understand the effect of the so-called doping oscillations, a theoretical model was developed. For the investigation of the thermal desorption of the III-V oxides in MOVPE, a number of test series were realised. It was also found that the formation of the reconstructed surface is finished a considerable time after the SE transient indicates stable conditions (no further reduction of the oxide layer). The activation energy for oxide desorption from InAs, GaAs and InP was

  18. Modified closed-loop double-endobutton technique for repair of rockwood type III acromioclavicular dislocation

    Science.gov (United States)

    Zhang, Lei; Zhou, Xin; Qi, Ji; Zeng, Yan; Zhang, Shaoqun; Liu, Gang; Ping, Ruiyue; Li, Yikai; Fu, Shijie

    2018-01-01

    Acromioclavicular dislocation (ACD) is a common injury. According to the Rockwood classification, ACD is classified into six types (type I–VI); however, for type III injuries, it remains controversial whether or not operative treatment should be applied. Numerous studies have advocated early surgical treatment to ensure early rehabilitation activities. Thus, the present study aimed to investigate a modified closed-loop double-endobutton technique (MCDT), that may be used to repair Rockwood type III ACD. In the current study, 61 patients with Rockwood type III ACD were enrolled during a period of 5 years at the Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University. Patients were divided into three groups according to the surgical method used, the MCDT group (n=20), the common closed-loop double-endobutton technique (CCDT) group (n=21), and the clavicular hook plate fixation (CHPF) group (n=20). Preoperative and intraoperative information were recorded. Furthermore, the functional scores of injured shoulder were evaluated prior to surgery and following surgery with a 1-year follow-up. Among the three groups, postoperative functional scores were significantly more improved compared with those prior to surgery (P0.05). Postoperative functional scores in the MCDT and CCDT groups were significantly more improved compared those in the CHPF group (P<0.05). In addition, the duration of surgery in the MCDT group was significantly shorter compared with that in the CCDT group (P<0.05). Furthermore, compared with the CHPF group, the incision length was significantly shorter with reduced hemorrhage in the MCDT group (P<0.05). In conclusion, the results of the current study suggest that MCDT is more simple, convenient and efficient compared with CCDT, and is worth popularizing. PMID:29399102

  19. Organic / IV, III-V Semiconductor Hybrid Solar Cells

    Directory of Open Access Journals (Sweden)

    Pang-Leen Ong

    2010-03-01

    Full Text Available We present a review of the emerging class of hybrid solar cells based on organic-semiconductor (Group IV, III-V, nanocomposites, which states separately from dye synthesized, polymer-metal oxides and organic-inorganic (Group II-VI nanocomposite photovoltaics. The structure of such hybrid cell comprises of an organic active material (p-type deposited by coating, printing or spraying technique on the surface of bulk or nanostructured semiconductor (n-type forming a heterojunction between the two materials. Organic components include various photosensitive monomers (e.g., phtalocyanines or porphyrines, conjugated polymers, and carbon nanotubes. Mechanisms of the charge separation at the interface and their transport are discussed. Also, perspectives on the future development of such hybrid cells and comparative analysis with other classes of photovoltaics of third generation are presented.

  20. Concomitant glenohumeral pathologies associated with acute and chronic grade III and grade V acromioclavicular joint injuries.

    Science.gov (United States)

    Jensen, Gunnar; Millett, Peter J; Tahal, Dimitri S; Al Ibadi, Mireille; Lill, Helmut; Katthagen, Jan Christoph

    2017-08-01

    The purpose of this study was to identify the risk of concomitant glenohumeral pathologies with acromioclavicular joint injuries grade III and V. Patients who underwent arthroscopically-assisted stabilization of acromioclavicular joint injuries grade III or grade V between 01/2007 and 12/2015 were identified in the patient databases of two surgical centres. Gender, age at index surgery, grade of acromioclavicular joint injury (Rockwood III or Rockwood V), and duration between injury and index surgery (classified as acute or chronic) were of interest. Concomitant glenohumeral pathologies were noted and their treatment was classified as debridement or reconstructive procedure. A total of 376 patients (336 male, 40 female) were included. Mean age at time of arthroscopic acromioclavicular joint reconstruction surgery was 42.1 ± 14.0 years. Overall, 201 patients (53%) had one or more concomitant glenohumeral pathologies. Lesions of the biceps tendon complex and rotator cuff were the most common. Forty-five patients (12.0%) had concomitant glenohumeral pathologies that required an additional repair. The remaining 156 patients (41.5%) received a debridement of their concomitant pathologies. Rockwood grade V compared to Rockwood grade III (p = 0.013; odds ratio 1.7), and chronic compared to acute injury were significantly associated with having a concomitant glenohumeral pathology (p = 0.019; odds ratio 1.7). The probability of having a concomitant glenohumeral pathology was also significantly associated with increasing age (p acromioclavicular joint injury of either grade III or V. Twenty-two percent of these patients with concomitant glenohumeral pathologies received an additional dedicated repair procedure. Although a significant difference in occurrence of concomitant glenohumeral pathologies was seen between Rockwood grades III and V, and between acute and chronic lesions, increasing age was identified as the most dominant predictor. Level IV, case series.

  1. Spectroscopic characterization of III-V semiconductor nanomaterials

    Science.gov (United States)

    Crankshaw, Shanna Marie

    III-V semiconductor materials form a broad basis for optoelectronic applications, including the broad basis of the telecom industry as well as smaller markets for high-mobility transistors. In a somewhat analogous manner as the traditional silicon logic industry has so heavily depended upon process manufacturing development, optoelectronics often relies instead on materials innovations. This thesis focuses particularly on III-V semiconductor nanomaterials, detailed characterization of which is invaluable for translating the exhibited behavior into useful applications. Specifically, the original research described in these thesis chapters is an investigation of semiconductors at a fundamental materials level, because the nanostructures in which they appear crystallize in quite atypical forms for the given semiconductors. Rather than restricting the experimental approaches to any one particular technique, many different types of optical spectroscopies are developed and applied where relevant to elucidate the connection between the crystalline structure and exhibited properties. In the first chapters, for example, a wurtzite crystalline form of the prototypical zincblende III-V binary semiconductor, GaAs, is explored through polarization-dependent Raman spectroscopy and temperature-dependent photoluminescence, as well as second-harmonic generation (SHG). The altered symmetry properties of the wurtzite crystalline structure are particularly evident in the Raman and SHG polarization dependences, all within a bulk material realm. A rather different but deeply elegant aspect of crystalline symmetry in GaAs is explored in a separate study on zincblende GaAs samples quantum-confined in one direction, i.e. quantum well structures, whose quantization direction corresponds to the (110) direction. The (110) orientation modifies the low-temperature electron spin relaxation mechanisms available compared to the usual (001) samples, leading to altered spin coherence times explored

  2. Design and Characterisation of III-V Semiconductor Nanowire Lasers

    Science.gov (United States)

    Saxena, Dhruv

    The development of small, power-efficient lasers underpins many of the technologies that we utilise today. Semiconductor nanowires are promising for miniaturising lasers to even smaller dimensions. III-V semiconductors, such as Gallium Arsenide (GaAs) and Indium Phosphide (InP), are the most widely used materials for optoelectronic devices and so the development of nanowire lasers based on these materials is expected to have technologically significant outcomes. This PhD dissertation presents a comprehensive study of the design of III-V semiconductor nanowire lasers, with bulk and quantum confined active regions. Based on the design, various III-V semiconductor nanowire lasers are demonstrated, namely, GaAs nanowire lasers, GaAs/AlGaAs multi-quantum well (MQW) nanowire lasers and InP nanowire lasers. These nanowire lasers are shown to operate at room temperature, have low thresholds, and lase from different transverse modes. The structural and optoelectronic quality of nanowire lasers are characterised via electron microscopy and photoluminescence spectroscopic techniques. Lasing is characterised in all these devices by optical pumping. The lasing characteristics are analysed by rate equation modelling and the lasing mode(s) in these devices is characterised by threshold gain modelling, polarisation measurements and Fourier plane imaging. Firstly, GaAs nanowire lasers that operate at room temperature are demonstrated. This is achieved by determining the optimal nanowire diameter to reduce threshold gain and by passivating nanowires to improve their quantum efficiency (QE). High-quality surface passivated GaAs nanowires of suitable diameters are grown. The growth procedure is tailored to improve both QE and structural uniformity of nanowires. Room-temperature lasing is demonstrated from individual nanowires and lasing is characterised to be from TM01 mode by threshold gain modelling. To lower threshold even further, nanowire lasers with GaAs/AlGaAs coaxial multi

  3. III - V semiconductor structures for biosensor and molecular electronics applications

    Energy Technology Data Exchange (ETDEWEB)

    Luber, S M

    2007-01-15

    The present work reports on the employment of III-V semiconductor structures to biosensor and molecular electronics applications. In the first part a sensor based on a surface-near two dimensional electron gas for a use in biological environment is studied. Such a two dimensional electron gas inherently forms in a molecular beam epitaxy (MBE) grown, doped aluminum gallium arsenide - gallium arsenide (AlGaAs-GaAs) heterostructure. Due to the intrinsic instability of GaAs in aqueous solutions the device is passivated by deposition of a monolayer of 4'-substituted mercaptobiphenyl molecules. The influence of these molecules which bind to the GaAs via a sulfur group is investigated by Kelvin probe measurements in air. They reveal a dependence of GaAs electron affinity on the intrinsic molecular dipole moment of the mercaptobiphenyls. Furthermore, transient surface photovoltage measurements are presented which demonstrate an additional influence of mercaptobiphenyl chemisorption on surface carrier recombination rates. As a next step, the influence of pH-value and salt concentration upon the sensor device is discussed based on the results obtained from sensor conductance measurements in physiological solutions. A dependence of the device surface potential on both parameters due to surface charging is deduced. Model calculations applying Poisson-Boltzmann theory reveal as possible surface charging mechanisms either the adsorption of OH- ions on the surface, or the dissociation of OH groups in surface oxides. A comparison between simulation settings and physical device properties indicate the OH- adsorption as the most probable mechanism. In the second part of the present study the suitability of MBE grown III-V semiconductor structures for molecular electronics applications is examined. In doing so, a method to fabricate nanometer separated, coplanar, metallic electrodes based on the cleavage of a supporting AlGaAs-GaAs heterostructure is presented. This is followed by a

  4. III - V semiconductor structures for biosensor and molecular electronics applications

    Energy Technology Data Exchange (ETDEWEB)

    Luber, S.M.

    2007-01-15

    The present work reports on the employment of III-V semiconductor structures to biosensor and molecular electronics applications. In the first part a sensor based on a surface-near two dimensional electron gas for a use in biological environment is studied. Such a two dimensional electron gas inherently forms in a molecular beam epitaxy (MBE) grown, doped aluminum gallium arsenide - gallium arsenide (AlGaAs-GaAs) heterostructure. Due to the intrinsic instability of GaAs in aqueous solutions the device is passivated by deposition of a monolayer of 4'-substituted mercaptobiphenyl molecules. The influence of these molecules which bind to the GaAs via a sulfur group is investigated by Kelvin probe measurements in air. They reveal a dependence of GaAs electron affinity on the intrinsic molecular dipole moment of the mercaptobiphenyls. Furthermore, transient surface photovoltage measurements are presented which demonstrate an additional influence of mercaptobiphenyl chemisorption on surface carrier recombination rates. As a next step, the influence of pH-value and salt concentration upon the sensor device is discussed based on the results obtained from sensor conductance measurements in physiological solutions. A dependence of the device surface potential on both parameters due to surface charging is deduced. Model calculations applying Poisson-Boltzmann theory reveal as possible surface charging mechanisms either the adsorption of OH- ions on the surface, or the dissociation of OH groups in surface oxides. A comparison between simulation settings and physical device properties indicate the OH- adsorption as the most probable mechanism. In the second part of the present study the suitability of MBE grown III-V semiconductor structures for molecular electronics applications is examined. In doing so, a method to fabricate nanometer separated, coplanar, metallic electrodes based on the cleavage of a supporting AlGaAs-GaAs heterostructure is presented. This is followed

  5. Wide bandgap collector III-V double heterojunction bipolar transistors

    International Nuclear Information System (INIS)

    Flitcroft, R.M.

    2000-10-01

    This thesis is devoted to the study and development of Heterojunction Bipolar Transistors (HBTs) designed for high voltage operation. The work concentrates on the use of wide bandgap III-V semiconductor materials as the collector material and their associated properties influencing breakdown, such as impact ionisation coefficients. The work deals with issues related to incorporating a wide bandgap collector into double heterojunction structures such as conduction band discontinuities at the base-collector junction and results are presented which detail, a number of methods designed to eliminate the effects of such discontinuities. In particular the use of AlGaAs as the base material has been successful in eliminating the conduction band spike at this interface. A method of electrically injecting electrons into the collector has been employed to investigate impact ionisation in GaAs, GaInP and AlInP which has used the intrinsic gain of the devices to extract impact ionisation coefficients over a range of electric fields beyond the scope of conventional optical injection techniques. This data has enabled the study of ''dead space'' effects in HBT collectors and have been used to develop an analytical model of impact ionisation which has been incorporated into an existing Ebers-Moll HBT simulator. This simulator has been shown to accurately reproduce current-voltage characteristics in both the devices used in this work and for external clients. (author)

  6. Treatment of Rockwood type III acromioclavicular joint dislocation using autogenous semitendinosus tendon graft and endobutton technique

    Directory of Open Access Journals (Sweden)

    Ye G

    2016-01-01

    Full Text Available Gang Ye, Chao-An Peng, Hua-Bin Sun, Jing Xiao, Kang Zhu Department of Orthopedics, the People’s Hospital of Huangpi District, Wuhan City, People’s Republic of China Background: The aim of this study was to evaluate the therapeutic effect of autogenous semitendinosus graft and endobutton technique, and compare with hook plate in treatment of Rockwood type III acromioclavicular (AC joint dislocation.Methods: From April 2012 to April 2013, we treated 46 patients with Rockwood type III AC joint dislocation. Patients were randomly divided into two groups: Group A was treated using a hook plate and Group B with autogenous semitendinosus graft and endobutton technique. All participants were followed up for 12 months. Radiographic examinations were performed every 2 months postoperatively, and clinical evaluation was performed using the Constant–Murley score at the last follow-up.Results: Results indicated that patients in Group B showed higher mean scores (90.3±5.4 than Group A (80.4±11.5 in terms of Constant–Murley score (P=0.001. Group B patients scored higher in terms of pain (P=0.002, activities (P=0.02, range of motion (P<0.001, and strength (P=0.004. In Group A, moderate pain was reported by 2 (8.7% and mild pain by 8 (34.8% patients. Mild pain was reported by 1 (4.3% patient in Group B. All patients in Group B maintained complete reduction, while 2 (8.7% patients in Group A experienced partial reduction loss. Two patients (8.7% encountered acromial osteolysis on latest radiographs, with moderate shoulder pain and limited range of motion.Conclusion: Autogenous semitendinosus graft and endobutton technique showed better results compared with the hook plate method and exhibited advantages of fewer complications such as permanent pain and acromial osteolysis. Keywords: Rockwood type III acromioclavicular joint dislocation, autogenous semitendinosus graft, endobutton, hook plate

  7. Ultrabroadband Hybrid III-V/SOI Grating Reflector for On-chip Lasers

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Taghizadeh, Alireza; Chung, Il-Sug

    2016-01-01

    We report on a new type of III-V/SOI grating reflector with a broad stopband of 350 nm. This reflector has promising prospects for applications in high-speed III-V/SOI vertical cavity lasers with an improved heat dissipation capability.......We report on a new type of III-V/SOI grating reflector with a broad stopband of 350 nm. This reflector has promising prospects for applications in high-speed III-V/SOI vertical cavity lasers with an improved heat dissipation capability....

  8. Heterogeneous Silicon III-V Mode-Locked Lasers

    Science.gov (United States)

    Davenport, Michael Loehrlein

    Mode-locked lasers are useful for a variety of applications, such as sensing, telecommunication, and surgical instruments. This work focuses on integrated-circuit mode-locked lasers: those that combine multiple optical and electronic functions and are manufactured together on a single chip. While this allows production at high volume and lower cost, the true potential of integration is to open applications for mode-locked laser diodes where solid state lasers cannot fit, either due to size and power consumption constraints, or where small optical or electrical paths are needed for high bandwidth. Unfortunately, most high power and highly stable mode-locked laser diode demonstrations in scientific literature are based on the Fabry-Perot resonator design, with cleaved mirrors, and are unsuitable for use in integrated circuits because of the difficulty of producing integrated Fabry-Perot cavities. We use silicon photonics and heterogeneous integration with III-V gain material to produce the most powerful and lowest noise fully integrated mode-locked laser diode in the 20 GHz frequency range. If low noise and high peak power are required, it is arguably the best performing fully integrated mode-locked laser ever demonstrated. We present the design methodology and experimental pathway to realize a fully integrated mode-locked laser diode. The construction of the device, beginning with the selection of an integration platform, and proceeding through the fabrication process to final optimization, is presented in detail. The dependence of mode-locked laser performance on a wide variety of design parameters is presented. Applications for integrated circuit mode-locked lasers are also discussed, as well as proposed methods for using integration to improve mode-locking performance to beyond the current state of the art.

  9. Mixing of III-V compound semiconductor superlattices

    International Nuclear Information System (INIS)

    Mei, Ping.

    1989-01-01

    In this work, the methods as well as mechanisms of III-V compound superlattice mixing are discussed, with particular attention on the AlGaAs based superlattice system. Comparative studies of ion-induced mixing showed two distinct effects resulting from ion implantation followed by a thermal anneal; i.e. collisional mixing and impurity induced mixing. It was found that Ga and As ion induced mixing are mainly due to the collisional effect, where the extent of the mixing can be estimated theoretically, with the parameters of ion mass, incident energy and the implant dose. The impurity effect was dominant for Si, Ge, Be, Zn and Te. Quantitative studies of impurity induced mixing have been conducted on samples doped with Si or Te during the growth process. It was discovered that Si induced AlGaAs superlattice mixing yielded an activation energy of approximately 4 eV for the Al diffusion coefficient with a high power law dependence of the prefactor on the Si concentration. In the Te doped AlGaAs superlattice the Al diffusion coefficient exhibited an activation energy of ∼3.0 eV, with a prefactor approximately proportional to the Te concentration. These results are of importance in examining the current diffusion models. Zn and Si induced InP/InGaAs superlattice mixing are examined. It was found that Zn predominantly induces cation interdiffusion, while Si induces comparable cation and anion interdiffusion. In addition, widely dispersed Zn rich islands form with Zn residing in the InP layers in the form of Zn 3 P 2 . With unstrained starting material, the layer bandgap disparity increases due to mixing induced strain, while in the Si diffused sample the mixed region would be expected to exhibit bandgaps intermediate between those of the original layers. Semiconductor superlattice mixing shows technological potential for optoelectronic device fabrication

  10. Relationship between type III-V radio and hard X-ray bursts

    International Nuclear Information System (INIS)

    Stewart, R.T.

    1978-01-01

    Type III-V radio bursts are found to be closely associated with impulsive hard X-ray bursts. Probably 0.1% to 1% of the fast electrons in the X-ray source region escape to heights >0.1 solar radii in the corona and excite the type III-V burst. (Auth.)

  11. Analysis of novel silicon and III-V solar cells by simulation and experiment; Analyse neuartiger Silizium- und III-V-Solarzellen mittels Simulation und Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Hermle, Martin

    2008-11-27

    This work presents various simulation studies of silicon and III-V solar cells. For standard silicon solar cells, one of the critical parameters to obtain good performance, is the rear side recombination velocity. The optical and electrical differences of the different cell structures were determined. The optical differences and the effective recombination velocity Sback of the different rear side structures for 1 Ohmcm material were extracted. Beside standard silicon solar cells, back junction silicon solar cells were investigated. Especially the influence of the front surface field and the electrical shading due to the rear side, was investigated. In the last two chapters, III-V solar cells were analysed. For the simulation of III-V multi-junction solar cells, the simulation of the tunneldiode is the basic prerequisite. In this work, the numerical calibration of an GaAs tunneldiode was achieved by using an non-local tunnel model. Using this model, it was possible to successfully simulate a III-V tandem solar cell. The last chapter deals with an optimization of the III-V 3-junction cell for space applications. Especially the influence of the GaAs middle cell was investigated. Due to structural changes, the end-of-life efficiency was drastically increased.

  12. Growth and characterization of manganese doped III-V heterostructures; Herstellung und Charakterisierung von Mangan dotierten III-V Halbleiterheterostrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Wurstbauer, Ursula

    2008-04-15

    Subject of this thesis is the growth of III-V heterostructures doped with manganese by means of molecular beam epitaxy (MBE). The characterization was done primarily by magnetotransport measurements in the temperature range from 300 K to 20 mK and fields up to 19 T. Two different kind of Mn doped materials, ferromagnetic GaMnAs layers and Mn modulation doped magnetic two dimensional hole systems were studied. The first part focuses on the enhancement of the electric and magnetic properties of ferromagnetic properties and the integration of GaMnAs layers in more sophisticated heterostructures. Therefore, the crystal quality and the influence of the buffer layer beneath the magnetic layer are crucial. The MBE-growth of ferromagnetic GaMnAs layers on (001), (311)A and (311)A was successfully achieved with present values of the Curie-temperature (TC). Additionally, the growth of ferromagnetic GaMnAs layers on nonpolar (110) substrates and on cleaved [110] edges was established. An application of the latter was the investigation of magnetic bipolar junctions. Magnetic two dimensional hole gases (M2DHG) has been realized by the use of In0.75Al0.25As/In0.75Ga0.25As/InAs quantum well (QW) structures. It is necessary to grow a buffer layer for strain relaxation due to the lattice mismatch by gradually increasing the In mole fraction. Magnetotransport measurements were carried out on Si doped two-dimensional electron gases (2DEG) and on Mn doped M2DHGs. From magnetotransport measurements on the M2DHGs we see some interesting features, in particular in the mK region. From the 2DEGs and all non inverted doped M2DEGs weak localization and weak antilocalization effects can be observed in the low field region. Whereas all M2DHGs with an inverted doping layer show strong localization effects and a metal insulator transition dependent on the applied magnetic field perpendicular to the QW. In the high field region Shubnikov-de-Haas oscillations in the longitudinal resistance and

  13. Results of Operative and Nonoperative Treatment of Rockwood Types III and V Acromioclavicular Joint Dislocation

    Science.gov (United States)

    Joukainen, Antti; Kröger, Heikki; Niemitukia, Lea; Mäkelä, E. Antero; Väätäinen, Urho

    2014-01-01

    Background: The optimal treatment of acute, complete dislocation of the acromioclavicular joint (ACJ) is still unresolved. Purpose: To determine the difference between operative and nonoperative treatment in acute Rockwood types III and V ACJ dislocation. Study Design: Randomized controlled trial; Level of evidence, 2. Methods: In the operative treatment group, the ACJ was reduced and fixed with 2 transarticular Kirschner wires and ACJ ligament suturing. The Kirschner wires were extracted after 6 weeks. Nonoperatively treated patients received a reduction splint for 4 weeks. At the 18- to 20-year follow-up, the Constant, University of California at Los Angeles Shoulder Rating Scale (UCLA), Larsen, and Simple Shoulder Test (SST) scores were obtained, and clinical and radiographic examinations of both shoulders were performed. Results: Twenty-five of 35 potential patients were examined at the 18- to 20-year follow-up. There were 11 patients with Rockwood type III and 14 with type V dislocations. Delayed surgical treatment for ACJ was used in 2 patients during follow-up: 1 in the operatively treated group and 1 in the nonoperatively treated group. Clinically, ACJs were statistically significantly less prominent or unstable in the operative group than in the nonoperative group (normal/prominent/unstable: 9/4/3 and 0/6/3, respectively; P = .02) and in the operative type III (P = .03) but not type V dislocation groups. In operatively and nonoperatively treated patients, the mean Constant scores were 83 and 85, UCLA scores 25 and 27, Larsen scores 11 and 11, and SST scores 11 and 12 at follow-up, respectively. There were no statistically significant differences in type III and type V dislocations. In the radiographic analysis, the ACJ was wider in the nonoperative than the operative group (8.3 vs 3.4 mm; P = .004), and in the type V dislocations (nonoperative vs operative: 8.5 vs 2.4 mm; P = .007). There was no statistically significant difference between study groups in

  14. Methods for enhancing P-type doping in III-V semiconductor films

    Science.gov (United States)

    Liu, Feng; Stringfellow, Gerald; Zhu, Junyi

    2017-08-01

    Methods of doping a semiconductor film are provided. The methods comprise epitaxially growing the III-V semiconductor film in the presence of a dopant, a surfactant capable of acting as an electron reservoir, and hydrogen, under conditions that promote the formation of a III-V semiconductor film doped with the p-type dopant. In some embodiments of the methods, the epitaxial growth of the doped III-V semiconductor film is initiated at a first hydrogen partial pressure which is increased to a second hydrogen partial pressure during the epitaxial growth process.

  15. High bandgap III-V alloys for high efficiency optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Alberi, Kirstin; Mascarenhas, Angelo; Wanlass, Mark

    2017-01-10

    High bandgap alloys for high efficiency optoelectronics are disclosed. An exemplary optoelectronic device may include a substrate, at least one Al.sub.1-xIn.sub.xP layer, and a step-grade buffer between the substrate and at least one Al.sub.1-xIn.sub.xP layer. The buffer may begin with a layer that is substantially lattice matched to GaAs, and may then incrementally increase the lattice constant in each sequential layer until a predetermined lattice constant of Al.sub.1-xIn.sub.xP is reached.

  16. The coupling of thermochemistry and phase diagrams for group III-V semiconductor systems. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, T.J.

    1998-07-21

    The project was directed at linking the thermochemical properties of III-V compound semiconductors systems with the reported phase diagrams. The solid-liquid phase equilibrium problem was formulated and three approaches to calculating the reduced standard state chemical potential were identified and values were calculated. In addition, thermochemical values for critical properties were measured using solid state electrochemical techniques. These values, along with the standard state chemical potentials and other available thermochemical and phase diagram data, were combined with a critical assessment of selected III-V systems. This work was culminated with a comprehensive assessment of all the III-V binary systems. A novel aspect of the experimental part of this project was the demonstration of the use of a liquid encapsulate to measure component activities by a solid state emf technique in liquid III-V systems that exhibit high vapor pressures at the measurement temperature.

  17. Interpreting Interfacial Structure in Cross-Sectional STM Images of III-V Semiconductor Heterostructures

    National Research Council Canada - National Science Library

    Nosho, B. Z; Barvosa-Carter, W; Yang, M. J; Bennett, B. R; Whitman, L. J

    2000-01-01

    ...) can be used for the study of III-V heterostructure interfaces. The interpretation of interfacial structure in XSTM images is impeded by the fact that only every other III or V plane as grown on the (001...

  18. High Efficiency Quantum Dot III-V Multijunction Solar Cell for Space Power, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — We are proposing to utilize quantum dots to develop a super high-efficiency multijunction III-V solar cell for space. In metamorphic triple junction space solar...

  19. Structure of metal-rich (001) surfaces of III-V compound semiconductors

    DEFF Research Database (Denmark)

    Kumpf, C.; Smilgies, D.; Landemark, E.

    2001-01-01

    The atomic structure of the group-III-rich surface of III-V semiconductor compounds has been under intense debate for many years, yet none of the models agrees with the experimental data available. Here we present a model for the three-dimensional structure of the (001)-c(8x2) reconstruction on In......(8 x 2) reconstructions of III-V semiconductor surfaces contain the same essential building blocks....

  20. Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

    Science.gov (United States)

    Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

    2015-01-13

    Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

  1. Progress in the development of metamorphic multi-junction III-V space solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Sinharoy, S.; Patton, M.O.; Valko, T.M.; Weizer, V.G. [Essential Research Inc., Cleveland, OH (United States)

    2002-07-01

    Theoretical calculations have shown that highest-efficiency III-V multi-junction solar cells require alloy structures that cannot be grown on a lattice-matched substrate. Ever since the first demonstration of high efficiency metamorphic single-junction 1.1 and 1.2 eV InGaAs solar cells, interest has grown in the development of multi-junction cells of this type, using graded buffer layer technology. Essential Research Incorporated (ERI) is currently developing a dual-junction 1.6 eV InGaP/1.1 eV InGaAs tandem cell (projected practical air-mass zero (AMO), one-sun efficiency of 27%, and 100-sun efficiency of 31.1%) under a Ballistic Missile Defense Command (BMDO) SBIR Phase II program. A second ongoing research effort involves the development of a 2.1 eV A1GaInP/1.6 eV InGaAsP/1.2 eV InGaAs triple-junction concentrator tandem cell (projected practical AMO efficiency 36.5% under 100 suns) under a SBIR Phase II program funded by the Air Force. We are in the process of optimizing the dual-junction cell performance. For the triple-junction cell, we have developed the bottom and the middle cell, and are in the process of developing the layer structures needed for the top cell. A progress report is presented in this paper. (author)

  2. III-V Ultra-Thin-Body InGaAs/InAs MOSFETs for Low Standby Power Logic Applications

    Science.gov (United States)

    Huang, Cheng-Ying

    BTBT leakage. With further replacement of raised InGaAs spacers by recessed, doping-graded InP spacers at high field regions, BTBT leakage can be reduced ~100:1. Using the above-mentioned techniques, record high performance InAs MOSFETs with a 2.7 nm InAs channel and a ZrO2 gate dielectric were demonstrated with Ion = 500 microA/microm at Ioff = 100 nA/microm and VDS =0.5 V, showing the highest on-state performance among all the III-V MOSFETs and comparable performance to 22 nm Si FinFETs. Record low leakage InGaAs MOSFETs with recessed InP source/drain spacers were also demonstrated with minimum I off = 60 pA/microm at 30 nm-Lg , and Ion = 150 microA/microm at I off = 1 nA/microm and VDS =0.5 V. This recessed InP source/drain spacer technique improves device scalability and enables III-V MOSFETs for low standby power logic applications. Furthermore, ultra-thin InAs channel MOSFETs were fabricated on Si substrates, exhibiting high yield and high transconductance gm ~2.0 mS/microm at 20 nm- Lg and VDS =0.5 V. With further scaling of gate lengths, a 12 nm-Lg III-V MOSFET has shown maximum Ion/Ioff ratio ~8.3x105 , confirming that III-V MOSFETs are scalable to sub-10-nm technology nodes.

  3. III-V-on-silicon solar cells reaching 33% photoconversion efficiency in two-terminal configuration

    Science.gov (United States)

    Cariou, Romain; Benick, Jan; Feldmann, Frank; Höhn, Oliver; Hauser, Hubert; Beutel, Paul; Razek, Nasser; Wimplinger, Markus; Bläsi, Benedikt; Lackner, David; Hermle, Martin; Siefer, Gerald; Glunz, Stefan W.; Bett, Andreas W.; Dimroth, Frank

    2018-04-01

    Silicon dominates the photovoltaic industry but the conversion efficiency of silicon single-junction solar cells is intrinsically constrained to 29.4%, and practically limited to around 27%. It is possible to overcome this limit by combining silicon with high-bandgap materials, such as III-V semiconductors, in a multi-junction device. Significant challenges associated with this material combination have hindered the development of highly efficient III-V/Si solar cells. Here, we demonstrate a III-V/Si cell reaching similar performances to standard III-V/Ge triple-junction solar cells. This device is fabricated using wafer bonding to permanently join a GaInP/GaAs top cell with a silicon bottom cell. The key issues of III-V/Si interface recombination and silicon's weak absorption are addressed using poly-silicon/SiOx passivating contacts and a novel rear-side diffraction grating for the silicon bottom cell. With these combined features, we demonstrate a two-terminal GaInP/GaAs//Si solar cell reaching a 1-sun AM1.5G conversion efficiency of 33.3%.

  4. Transferable tight-binding model for strained group IV and III-V materials and heterostructures

    Science.gov (United States)

    Tan, Yaohua; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy B.; Klimeck, Gerhard

    2016-07-01

    It is critical to capture the effect due to strain and material interface for device level transistor modeling. We introduce a transferable s p3d5s* tight-binding model with nearest-neighbor interactions for arbitrarily strained group IV and III-V materials. The tight-binding model is parametrized with respect to hybrid functional (HSE06) calculations for varieties of strained systems. The tight-binding calculations of ultrasmall superlattices formed by group IV and group III-V materials show good agreement with the corresponding HSE06 calculations. The application of the tight-binding model to superlattices demonstrates that the transferable tight-binding model with nearest-neighbor interactions can be obtained for group IV and III-V materials.

  5. III-V/Si wafer bonding using transparent, conductive oxide interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Tamboli, Adele C., E-mail: Adele.Tamboli@nrel.gov; Hest, Maikel F. A. M. van; Steiner, Myles A.; Essig, Stephanie; Norman, Andrew G.; Bosco, Nick; Stradins, Paul [National Center for Photovoltaics, National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401 (United States); Perl, Emmett E. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106-9560 (United States)

    2015-06-29

    We present a method for low temperature plasma-activated direct wafer bonding of III-V materials to Si using a transparent, conductive indium zinc oxide interlayer. The transparent, conductive oxide (TCO) layer provides excellent optical transmission as well as electrical conduction, suggesting suitability for Si/III-V hybrid devices including Si-based tandem solar cells. For bonding temperatures ranging from 100 °C to 350 °C, Ohmic behavior is observed in the sample stacks, with specific contact resistivity below 1 Ω cm{sup 2} for samples bonded at 200 °C. Optical absorption measurements show minimal parasitic light absorption, which is limited by the III-V interlayers necessary for Ohmic contact formation to TCOs. These results are promising for Ga{sub 0.5}In{sub 0.5}P/Si tandem solar cells operating at 1 sun or low concentration conditions.

  6. Integration, gap formation, and sharpening of III-V heterostructure nanowires by selective etching

    DEFF Research Database (Denmark)

    Kallesoe, C.; Mølhave, Kristian; Larsen, K. F.

    2010-01-01

    Epitaxial growth of heterostructure nanowires allows for the definition of narrow sections with specific semiconductor composition. The authors demonstrate how postgrowth engineering of III-V heterostructure nanowires using selective etching can form gaps, sharpening of tips, and thin sections...... lithography is used for deposition of catalyst particles on trench sidewalls and the lateral growth of III-V nanowires is achieved from such catalysts. The selectivity of a bromine-based etch on gallium arsenide segments in gallium phosphide nanowires is examined, using a hydrochloride etch to remove the III...

  7. Monte-Carlo simulation of crystallographical pore growth in III-V-semiconductors

    International Nuclear Information System (INIS)

    Leisner, Malte; Carstensen, Juergen; Foell, Helmut

    2011-01-01

    The growth of crystallographical pores in III-V-semiconductors can be understood in the framework of a simple model, which is based on the assumption that the branching of pores is proportional to the current density at the pore tips. The stochastic nature of this model allows its implementation into a three-dimensional Monte-Carlo-simulation of pore growth. The simulation is able to reproduce the experimentally observed crysto pore structures in III-V-semiconductors in full quantitative detail. The different branching probabilities for different semiconductors, as well as doping levels, can be deduced from the specific passivation behavior of the semiconductor-electrolyte-interface at the pore tips.

  8. Photoelectrochemistry of III-V epitaxial layers and nanowires for solar energy conversion

    Science.gov (United States)

    Parameshwaran, Vijay; Enck, Ryan; Chung, Roy; Kelley, Stephen; Sampath, Anand; Reed, Meredith; Xu, Xiaoqing; Clemens, Bruce

    2017-05-01

    III-V materials, which exhibit high absorption coefficients and charge carrier mobility, are ideal templates for solar energy conversion applications. This work describes the photoelectrochemistry research in several IIIV/electrolyte junctions as an enabler for device design for solar chemical reactions. By designing lattice-matched epitaxial growth of InGaP and GaP on GaAs and Si, respectively, extended depletion region electrodes achieve photovoltages which provide an additional boost to the underlying substrate photovoltage. The InGaP/GaAs and GaP/Si electrodes drive hydrogen evolution currents under aqueous conditions. By using nanowires of InN and InP under carefully controlled growth conditions, current and capacitance measurements are obtained to reveal the nature of the nanowire-electrolyte interface and how light is translated into photocurrent for InP and a photovoltage in InN. The materials system is expanded into the III-V nitride semiconductors, in which it is shown that varying the morphology of GaN on silicon yields insights to how the interface and light conversion is modulated as a basis for future designs. Current extensions of this work address growth and tuning of the III-V nitride electrodes with doping and polarization engineering for efficient coupling to solar-driven chemical reactions, and rapid-throughput methods for III-V nanomaterials synthesis in this materials space.

  9. Generic technique to grow III-V semiconductor nanowires in a closed glass vessel

    Directory of Open Access Journals (Sweden)

    Kan Li

    2016-06-01

    Full Text Available Crystalline III-V semiconductor nanowires have great potential in fabrication of nanodevices for applications in nanoelectronics and optoelectronics, and for studies of novel physical phenomena. Sophisticated epitaxy techniques with precisely controlled growth conditions are often used to prepare high quality III-V nanowires. The growth process and cost of these experiments are therefore dedicated and very high. Here, we report a simple but generic method to synthesize III-V nanowires with high crystal quality. The technique employs a closed evacuated tube vessel with a small tube carrier containing a solid source of materials and another small tube carrier containing a growth substrate inside. The growth of nanowires is achieved after heating the closed vessel in a furnace to a preset high temperature and then cooling it down naturally to room temperature. The technique has been employed to grow InAs, GaAs, and GaSb nanowires on Si/SiO2 substrates. The as-grown nanowires are analyzed by SEM, TEM and Raman spectroscopy and the results show that the nanowires are high quality zincblende single crystals. No particular condition needs to be adjusted and controlled in the experiments. This technique provides a convenient way of synthesis of III-V semiconductor nanowires with high material quality for a wide range of applications.

  10. Controlling the emission wavelength in group III-V semiconductor laser diodes

    KAUST Repository

    Ooi, Boon S.

    2016-12-29

    Methods are provided for modifying the emission wavelength of a semiconductor quantum well laser diode, e.g. by blue shifting the emission wavelength. The methods can be applied to a variety of semiconductor quantum well laser diodes, e.g. group III-V semiconductor quantum wells. The group III-V semiconductor can include AlSb, AlAs, Aln, AlP, BN, GaSb, GaAs, GaN, GaP, InSb, InAs, InN, and InP, and group III-V ternary semiconductors alloys such as AlxGai.xAs. The methods can results in a blue shifting of about 20 meV to 350 meV, which can be used for example to make group III-V semiconductor quantum well laser diodes with an emission that is orange or yellow. Methods of making semiconductor quantum well laser diodes and semiconductor quantum well laser diodes made therefrom are also provided.

  11. Cr-doped III-V nitrides: Potential candidates for spintronics

    KAUST Repository

    Amin, Bin

    2011-02-19

    Studies of Cr-doped III-V nitrides, dilute magnetic alloys in the zincblende crystal structure, are presented. The objective of the work is to investigate half-metallicity in Al 0.75Cr 0.25N, Ga 0.75Cr 0.25N, and In 0.75Cr 0.25N for their possible application in spin-based electronic devices. The calculated spin-polarized band structures, electronic properties, and magnetic properties of these compounds reveal that Al 0.75Cr 0.25N and Ga 0.75Cr 0.25N are half-metallic dilute magnetic semiconductors while In 0.75Cr 0.25N is metallic in nature. The present theoretical predictions provide evidence that some Cr-doped III-V nitrides can be used in spintronics devices. © 2011 TMS.

  12. Efficient n-type doping of zinc-blende III-V semiconductor nanowires

    Science.gov (United States)

    Besteiro, Lucas V.; Tortajada, Luis; Souto, J.; Gallego, L. J.; Chelikowsky, James R.; Alemany, M. M. G.

    2014-03-01

    We demonstrate that it is preferable to dope III-V semiconductor nanowires by n-type anion substitution as opposed to cation substitution. Specifically, we show the dopability of zinc-blende nanowires is more efficient when the dopants are placed at the anion site as quantified by formation energies and the stabilization of DX-like defect centers. The comparison with previous work on n - type III-V semiconductor nanocrystals also allows to determine the role of dimensionality and quantum confinement on doping characteristics of materials. Our results are based on first-principles calculations of InP nanowires by using the PARSEC code. Work supported by the Spanish MICINN (FIS2012-33126) and Xunta de Galicia (GPC2013-043) in conjunction with FEDER. JRC acknowledges support from DoE (DE-FG02-06ER46286 and DESC0008877). Computational support was provided in part by CESGA.

  13. Coherent-potential approximation for the lattice vibrations of mixed III-V crystals

    International Nuclear Information System (INIS)

    Kleinert, P.

    1984-01-01

    The coherent-potential approximation (CPA) is applied to the lattice dynamics of some III-V mixed crystals. The calculations are based on an eleven-parameter rigid-ion model (RIM 11). Explicit results are reported for the one-mode system In/sub 1-c/Ga/sub c/P and the two mixed-mode crystals In/sub 1-c/Ga/sub c/Sb and GaSb/sub 1-c/As/sub c/. Both, the reflectivity spectra and the composition dependence of vibrations at the GAMMA and X points are compared with existing experimental data. Force-constant changes are considered by the virtual-crystal approximation (VCA). The CPA theory is uniquely successful for III-V mixed-mode systems, which appear to switch from one-mode to two-mode behaviour. (author)

  14. III-V group compound semiconductor light-emitting element having a doped tantalum barrier layer

    International Nuclear Information System (INIS)

    Oanna, Y.; Ozawa, N.; Yamashita, M.; Yasuda, N.

    1984-01-01

    Disclosed is a III-V Group compound semiconductor light-emitting element having a III-V Group compound semiconductor body with a p-n junction and including a p-type layer involved in forming the p-n junction; and a multi-layer electrode mounted on the p-type layer of the semiconductor body. The electrode comprises a first layer of gold alloy containing a small amount of beryllium or zinc and formed in direct contact with the p-type layer of the semiconductor body and an uppermost layer formed of gold or aluminum. A tantalum layer doped with carbon, nitrogen and/or oxygen is formed between the first layer and the uppermost layer by means of vacuum vapor deposition

  15. David Adler Lectureship Award Talk: III-V Semiconductor Nanowires on Silicon for Future Devices

    Science.gov (United States)

    Riel, Heike

    Bottom-up grown nanowires are very attractive materials for direct integration of III-V semiconductors on silicon thus opening up new possibilities for the design and fabrication of nanoscale devices for electronic, optoelectronic as well as quantum information applications. Template-Assisted Selective Epitaxy (TASE) allows the well-defined and monolithic integration of complex III-V nanostructures and devices on silicon. Achieving atomically abrupt heterointerfaces, high crystal quality and control of dimension down to 1D nanowires enabled the demonstration of FETs and tunnel devices based on In(Ga)As and GaSb. Furthermore, the strong influence of strain on nanowires as well as results on quantum transport studies of InAs nanowires with well-defined geometry will be presented.

  16. Cr-doped III-V nitrides: Potential candidates for spintronics

    KAUST Repository

    Amin, Bin; Arif, Suneela K.; Ahmad, Iftikhar; Maqbool, Muhammad; Ahmad, Roshan; Goumri-Said, Souraya; Prisbrey, Keith A.

    2011-01-01

    Studies of Cr-doped III-V nitrides, dilute magnetic alloys in the zincblende crystal structure, are presented. The objective of the work is to investigate half-metallicity in Al 0.75Cr 0.25N, Ga 0.75Cr 0.25N, and In 0.75Cr 0.25N for their possible application in spin-based electronic devices. The calculated spin-polarized band structures, electronic properties, and magnetic properties of these compounds reveal that Al 0.75Cr 0.25N and Ga 0.75Cr 0.25N are half-metallic dilute magnetic semiconductors while In 0.75Cr 0.25N is metallic in nature. The present theoretical predictions provide evidence that some Cr-doped III-V nitrides can be used in spintronics devices. © 2011 TMS.

  17. Blocking of indium incorporation by antimony in III-V-Sb nanostructures

    International Nuclear Information System (INIS)

    Sanchez, A M; Beltran, A M; Ben, T; Molina, S I; Beanland, R; Gass, M H; De la Pena, F; Walls, M; Taboada, A G; Ripalda, J M

    2010-01-01

    The addition of antimony to III-V nanostructures is expected to give greater freedom in bandgap engineering for device applications. One of the main challenges to overcome is the effect of indium and antimony surface segregation. Using several very high resolution analysis techniques we clearly demonstrate blocking of indium incorporation by antimony. Furthermore, indium incorporation resumes when the antimony concentration drops below a critical level. This leads to major differences between nominal and actual structures.

  18. Low Thermal Budget Fabrication of III-V Quantum Nanostructures on Si Substrates

    International Nuclear Information System (INIS)

    Bietti, S; Somaschini, C; Sanguinetti, S; Koguchi, N; Isella, G; Chrastina, D; Fedorov, A

    2010-01-01

    We show the possibility to integrate high quality III-V quantum nanostructures tunable in shape and emission energy on Si-Ge Virtual Substrate. Strong photoemission is observed, also at room temperature, from two different kind of GaAs quantum nanostructures fabricated on Silicon substrate. Due to the low thermal budget of the procedure used for the fabrication of the active layer, Droplet Epitaxy is to be considered an excellent candidate for implementation of optoelectronic devices on CMOS circuits.

  19. Observation of electron polarization above 80% in photoemission from strained III-V compounds

    International Nuclear Information System (INIS)

    Garwin, E.L.; Maruyama, T.; Prepost, R.; Zapalac, G.H.

    1992-02-01

    Spin-polarized electron photoemission has been investigated for strained III--V compounds; (1) strained In x Ga 1-x As epitaxially grown on a GaAs substrate, and (2) strained GaAs grown on a GaAs 1-x P x buffer layer. The lattice mismatched heterostructure results in a highly strained epitaxial layer, and electron spin polarization as high as 90% has been observed

  20. Transferable tight binding model for strained group IV and III-V heterostructures

    Science.gov (United States)

    Tan, Yaohua; Povolotskyi, Micheal; Kubis, Tillmann; Boykin, Timothy; Klimeck, Gerhard

    Modern semiconductor devices have reached critical device dimensions in the range of several nanometers. For reliable prediction of device performance, it is critical to have a numerical efficient model that are transferable to material interfaces. In this work, we present an empirical tight binding (ETB) model with transferable parameters for strained IV and III-V group semiconductors. The ETB model is numerically highly efficient as it make use of an orthogonal sp3d5s* basis set with nearest neighbor inter-atomic interactions. The ETB parameters are generated from HSE06 hybrid functional calculations. Band structures of strained group IV and III-V materials by ETB model are in good agreement with corresponding HSE06 calculations. Furthermore, the ETB model is applied to strained superlattices which consist of group IV and III-V elements. The ETB model turns out to be transferable to nano-scale hetero-structure. The ETB band structures agree with the corresponding HSE06 results in the whole Brillouin zone. The ETB band gaps of superlattices with common cations or common anions have discrepancies within 0.05eV.

  1. III-V quantum light source and cavity-QED on silicon.

    Science.gov (United States)

    Luxmoore, I J; Toro, R; Del Pozo-Zamudio, O; Wasley, N A; Chekhovich, E A; Sanchez, A M; Beanland, R; Fox, A M; Skolnick, M S; Liu, H Y; Tartakovskii, A I

    2013-01-01

    Non-classical light sources offer a myriad of possibilities in both fundamental science and commercial applications. Single photons are the most robust carriers of quantum information and can be exploited for linear optics quantum information processing. Scale-up requires miniaturisation of the waveguide circuit and multiple single photon sources. Silicon photonics, driven by the incentive of optical interconnects is a highly promising platform for the passive optical components, but integrated light sources are limited by silicon's indirect band-gap. III-V semiconductor quantum-dots, on the other hand, are proven quantum emitters. Here we demonstrate single-photon emission from quantum-dots coupled to photonic crystal nanocavities fabricated from III-V material grown directly on silicon substrates. The high quality of the III-V material and photonic structures is emphasized by observation of the strong-coupling regime. This work opens-up the advantages of silicon photonics to the integration and scale-up of solid-state quantum optical systems.

  2. Implications of the Differential Toxicological Effects of III-V Ionic and Particulate Materials for Hazard Assessment of Semiconductor Slurries.

    Science.gov (United States)

    Jiang, Wen; Lin, Sijie; Chang, Chong Hyun; Ji, Zhaoxia; Sun, Bingbing; Wang, Xiang; Li, Ruibin; Pon, Nanetta; Xia, Tian; Nel, André E

    2015-12-22

    Because of tunable band gaps, high carrier mobility, and low-energy consumption rates, III-V materials are attractive for use in semiconductor wafers. However, these wafers require chemical mechanical planarization (CMP) for polishing, which leads to the generation of large quantities of hazardous waste including particulate and ionic III-V debris. Although the toxic effects of micron-sized III-V materials have been studied in vivo, no comprehensive assessment has been undertaken to elucidate the hazardous effects of submicron particulates and released III-V ionic components. Since III-V materials may contribute disproportionately to the hazard of CMP slurries, we obtained GaP, InP, GaAs, and InAs as micron- (0.2-3 μm) and nanoscale (particles for comparative studies of their cytotoxic potential in macrophage (THP-1) and lung epithelial (BEAS-2B) cell lines. We found that nanosized III-V arsenides, including GaAs and InAs, could induce significantly more cytotoxicity over a 24-72 h observation period. In contrast, GaP and InP particulates of all sizes as well as ionic GaCl3 and InCl3 were substantially less hazardous. The principal mechanism of III-V arsenide nanoparticle toxicity is dissolution and shedding of toxic As(III) and, to a lesser extent, As(V) ions. GaAs dissolves in the cell culture medium as well as in acidifying intracellular compartments, while InAs dissolves (more slowly) inside cells. Chelation of released As by 2,3-dimercapto-1-propanesulfonic acid interfered in GaAs toxicity. Collectively, these results demonstrate that III-V arsenides, GaAs and InAs nanoparticles, contribute in a major way to the toxicity of III-V materials that could appear in slurries. This finding is of importance for considering how to deal with the hazard potential of CMP slurries.

  3. Morphology of interior interfaces in dilute nitride III/V material systems; Morphologie innerer Grenzflaechen in verduennt stickstoffhaltigen III/V-Materialsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Oberhoff, S.

    2007-12-03

    This study aims to clarify structure formation processes in dilute N-containing III/V-based material systems, using highly selective etching methods and subsequent atomic force microscopy (AFM) to expose and analyse interior interfaces. In the first part of this study it was directly proved for the first time that adding Sb during growth interruption inhibits the GI-induced structural phase transition and reduces the diffusivity on GaAs and (GaIn)(NAs) surfaces. However, applying Sb during GI does not affect the driving force of the structural phase transition. Therefore a fundamental analysis about the incorporation of Sb into GaAs, Ga(NAs) and (GaIn)(NAs) was carried out in the second part of the study. Using a combination of high resolution X-ray diffraction, transmission electron microscopy and SIMS measurements, it was verified that incorporating Sb into (GaIn)(NAs) causes an increase of the In content and a decrease of the N content. In the third part of the study, novel etching methods for the GaP-based material system Ga(NAsP) are introduced which provide the opportunity to analyse structure formation processes on interior interfaces in this material system by AFM. (orig.)

  4. Hydrogen-Mediated Nitrogen Clustering in Dilute III-V Nitrides

    Science.gov (United States)

    Du, Mao-Hua; Limpijumnong, Sukit; Zhang, S. B.

    2006-08-01

    First-principles calculation reveals multi-N clusters to be the ground states for hydrogenated N in dilute III-V nitrides. While hydrogenation of a single N, forming H2*(N), can relax the large strain induced by the size-mismatched N, formation of the clusters will relax the strain even more effectively. This suppresses the formation of H2*(N), the existence of which has recently been debated. More importantly, postgrowth dehydrogenation of the N-H clusters provides an explanation to the observed metastable bare N clusters in GaAsN grown by gas-source molecular beam epitaxy or metal-organic chemical vapor deposition.

  5. General theory of the transverse dielectric constant of III-V semiconducting compounds

    Science.gov (United States)

    Kahen, K. B.; Leburton, J. P.

    1985-01-01

    A general model of the transverse dielectric constant of III-V compounds is developed using a hybrid method which combines the kp method with a nonlocal pseudopotential calculation. In this method the Brillouin zone is partitioned into three regions by expanding the energy bands and matrix elements about the F, X, and L symmetry points. The real and imaginary parts of the dielectric constant are calculated as a sum of the individual contributions of each region. By using this partition method, it is possible to get good insight into the dependence of the dielectric constant on the shape of the band structure.

  6. Ultracompact electro-optic phase modulator based on III-V-on-silicon microdisk resonator.

    Science.gov (United States)

    Lloret, J; Kumar, R; Sales, S; Ramos, F; Morthier, G; Mechet, P; Spuesens, T; Van Thourhout, D; Olivier, N; Fédéli, J-M; Capmany, J

    2012-06-15

    A novel ultracompact electro-optic phase modulator based on a single 9 μm-diameter III-V microdisk resonator heterogeneously integrated on and coupled to a nanophotonic waveguide is presented. Modulation is enabled by effective index modification through carrier injection. Proof-of-concept implementation involving binary phase shift keying modulation format is assembled. A power imbalance of ∼0.6  dB between both symbols and a modulation rate up to 1.8 Gbps are demonstrated without using any special driving technique.

  7. On the use of the plasma in III-V semiconductor processing

    Energy Technology Data Exchange (ETDEWEB)

    Bruno, G.; Capezzuto, P.; Losurdo, M. [C.N.R.-Centro di Studio per la Chimica dei Plasmi Dipartimento di Chimica-Universita di Bari via Orabona, 4-70126 Bari (Italy)

    1996-03-01

    The manufacture of usable devices based on III-V semiconductor materials is a complex process requiring epilayer growth, anisotropic etching, defect passivation, surface oxidation and substrate preparation processes. The combination of plasma based methods with metalorganic chemical vapor deposition (MOCVD) offers some real advantages: {ital in} {ital situ} production and preactivation of PH{sub 3} and sample preparation using H-atom. The detailed understanding and use of the plasma (using mass spectrometry, optical emission spectroscopy, laser reflectance interferometry and spectroscopic ellipsometry) as applied to InP material is discussed. {copyright} {ital 1996 American Institute of Physics.}

  8. Study of III-V semiconductor band structure by synchrotron photoemission

    International Nuclear Information System (INIS)

    Williams, G.P.; Cerrina, F.; Anderson, J.; Lapeyre, G.J.; Smith, R.J.; Hermanson, J.; Knapp, J.A.

    1982-01-01

    Angle-resolved synchrotron photoemission studies of six III-V semiconductors have been carried out. For emission normal to the (110) plane of these materials, peaks in the experimental spectra were identified with the bands involved in the transitions, and the critical point energies X 3 , X 5 , and Σ 1 /sup min/, were determined. The data indicate that k perpendicular is conserved in the transitions. Comparison of the data with theoretical bands permits an evaluation of k perpendicular associated with the experimentally observed transition, and from this information the bands were plotted out

  9. Pulsed laser deposition of II-VI and III-V semiconductor materials

    Energy Technology Data Exchange (ETDEWEB)

    Mele, A.; Di Palma, T.M.; Flamini, C.; Giardini Guidoni, A. [Rome, Univ. `La Sapienza` (Italy). Dep. di Chimica

    1998-12-01

    Pulsed laser irradiation of a solid target involves electronic excitation and heating, followed by expansion from the target of the elliptical gas cloud (plume) which can be eventually condensed on a suitable substrate. Pulsed laser ablation has been found to be a valuable technique to prepare II-VI and III-V thin films of semiconductor materials. Pulsed laser ablation deposition is discussed in the light of the results of an investigation on CdS, CdSe, CdTe and CdSe/CdTe multilayers and AIN, GaN and InN together with Al-Ga-In-N heterostructures. [Italiano] L`irradiazione di un target solido, mediante un fascio laser impulsato, genera una serie di processi che possono essere schematizzati come segue: riscaldamento ed eccitazione elettronica del target, da cui consegue l`espulsione di materiale sotto forma di una nube gassosa di forma ellissoidale (plume), che espande e puo` essere fatta depositare su un opportuno substrato. L`ablazione lasersi e` rivelata una tecnica valida per preparare film sottili di composti di elementi del II-VI e del III-V gruppo della tavola periodica. La deposizione via ablazione laser viene discussa alla luce dei risultati ottenuti nella preparazione di film di CdS, CdSe, CdTe e di film multistrato di CdSe/CdTe, di film di AIN, GaN, InN e di eterostrutture di Al-Ga-In-N.

  10. Mechanical properties of some binary, ternary and quaternary III-V compound semiconductor alloys

    International Nuclear Information System (INIS)

    Navamathavan, R.; Arivuoli, D.; Attolini, G.; Pelosi, C.; Choi, Chi Kyu

    2007-01-01

    Vicker's microindentation tests have been carried out on InP/InP, GaAs/InP, InGaAs/InP and InGaAsP/InP III-V compound semiconductor alloys. The detailed mechanical properties of these binary, ternary and quaternary epilayers were determined from the indentation experiments. Microindentation studies of (1 1 1) GaAs/InP both A and B faces show that the hardness value increases with load and attains a constant for further increase in load and the microhardness values were found to lie between 3.5 and 4.0 GPa. The microhardness values of InGaAs/InP epilayers with different thickness were found to lie between 3.93 and 4.312 GPa. The microhardness values of InGaAsP/InP with different elemental composition were found to lie between 5.08 and 5.73 GPa. The results show that the hardness of the quaternary alloy drastically increases, the reason may be that the increase in As concentration hardens the lattice when phosphorous concentration is less and hardness decreases when phosphorous is increased. It was interestingly observed that the hardness value increases as we proceed from binary to quaternary III-V compound semiconductor alloys

  11. Cycloadditions to Epoxides Catalyzed by GroupIII-V Transition-Metal Complexes

    KAUST Repository

    D'Elia, Valerio

    2015-05-25

    Complexes of groupIII-V transition metals are gaining increasing importance as Lewis acid catalysts for the cycloaddition of dipolarophiles to epoxides. This review examines the latest reports, including homogeneous and heterogeneous applications. The pivotal step for the cycloaddition reactions is the ring opening of the epoxide following activation by the Lewis acid. Two modes of cleavage (C-C versus C-O) have been identified depending primarily on the substitution pattern of the epoxide, with lesser influence observed from the Lewis acid employed. The widely studied cycloaddition of CO2 to epoxides to afford cyclic carbonates (C-O bond cleavage) has been scrutinized in terms of catalytic efficiency and reaction mechanism, showing that unsophisticated complexes of groupIII-V transition metals are excellent molecular catalysts. These metals have been incorporated, as well, in highly performing, recyclable heterogeneous catalysts. Cycloadditions to epoxides with other dipolarophiles (alkynes, imines, indoles) have been conducted with scandium triflate with remarkable performances (C-C bond cleavage). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Cycloadditions to Epoxides Catalyzed by GroupIII-V Transition-Metal Complexes

    KAUST Repository

    D'Elia, Valerio; Pelletier, Jeremie; Basset, Jean-Marie

    2015-01-01

    Complexes of groupIII-V transition metals are gaining increasing importance as Lewis acid catalysts for the cycloaddition of dipolarophiles to epoxides. This review examines the latest reports, including homogeneous and heterogeneous applications. The pivotal step for the cycloaddition reactions is the ring opening of the epoxide following activation by the Lewis acid. Two modes of cleavage (C-C versus C-O) have been identified depending primarily on the substitution pattern of the epoxide, with lesser influence observed from the Lewis acid employed. The widely studied cycloaddition of CO2 to epoxides to afford cyclic carbonates (C-O bond cleavage) has been scrutinized in terms of catalytic efficiency and reaction mechanism, showing that unsophisticated complexes of groupIII-V transition metals are excellent molecular catalysts. These metals have been incorporated, as well, in highly performing, recyclable heterogeneous catalysts. Cycloadditions to epoxides with other dipolarophiles (alkynes, imines, indoles) have been conducted with scandium triflate with remarkable performances (C-C bond cleavage). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Dense Plasma Focus-Based Nanofabrication of III-V Semiconductors: Unique Features and Recent Advances.

    Science.gov (United States)

    Mangla, Onkar; Roy, Savita; Ostrikov, Kostya Ken

    2015-12-29

    The hot and dense plasma formed in modified dense plasma focus (DPF) device has been used worldwide for the nanofabrication of several materials. In this paper, we summarize the fabrication of III-V semiconductor nanostructures using the high fluence material ions produced by hot, dense and extremely non-equilibrium plasma generated in a modified DPF device. In addition, we present the recent results on the fabrication of porous nano-gallium arsenide (GaAs). The details of morphological, structural and optical properties of the fabricated nano-GaAs are provided. The effect of rapid thermal annealing on the above properties of porous nano-GaAs is studied. The study reveals that it is possible to tailor the size of pores with annealing temperature. The optical properties of these porous nano-GaAs also confirm the possibility to tailor the pore sizes upon annealing. Possible applications of the fabricated and subsequently annealed porous nano-GaAs in transmission-type photo-cathodes and visible optoelectronic devices are discussed. These results suggest that the modified DPF is an effective tool for nanofabrication of continuous and porous III-V semiconductor nanomaterials. Further opportunities for using the modified DPF device for the fabrication of novel nanostructures are discussed as well.

  14. Growth of Ag-seeded III-V Nanowires and TEM Characterization

    DEFF Research Database (Denmark)

    Lindberg, Anna Helmi Caroline

    appropriate, the density and the vertical yield were obtained. The crystal structures for the grown nanowires have been investigated with TEM.We have also performed additional growths to further understand exactly how the nanowire growth proceeds as well as to understand the limitations of using Ag as a seed......This thesis deals with growth and characterization of GaAs and InAs nanowires. Today Au nanoparticle-seeding together with self-catalyzing are the dominating techniques to grow III-V nanowires with molecular beam epitaxy. In this thesis we instead investigate the possibility to use Ag as seed...... particle for growth of GaAs and InAs nanowires. The aim with the experiments performed has been to conclude whether Ag can be used to nucleate and grow nanowires on III-V substrates with molecular beam epitaxy. To investigate this we have performed growths of GaAs nanowires on GaAs(111)B and GaAs(100...

  15. Final Report: Vapor Transport Deposition for Thin Film III-V Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Boettcher, Shannon [Univ. of Oregon, Eugene, OR (United States); Greenaway, Ann [Univ. of Oregon, Eugene, OR (United States); Boucher, Jason [Univ. of Oregon, Eugene, OR (United States); Aloni, Shaul [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2016-02-10

    Silicon, the dominant photovoltaic (PV) technology, is reaching its fundamental performance limits as a single absorber/junction technology. Higher efficiency devices are needed to reduce cost further because the balance of systems account for about two-thirds of the overall cost of the solar electricity. III-V semiconductors such as GaAs are used to make the highest-efficiency photovoltaic devices, but the costs of manufacture are much too high for non-concentrated terrestrial applications. The cost of III-V’s is driven by two factors: (1) metal-organic chemical vapor deposition (MOCVD), the dominant growth technology, employs expensive, toxic and pyrophoric gas-phase precursors, and (2) the growth substrates conventionally required for high-performance devices are monocrystalline III-V wafers. The primary goal of this project was to show that close-spaced vapor transport (CSVT), using water vapor as a transport agent, is a scalable deposition technology for growing low-cost epitaxial III-V photovoltaic devices. The secondary goal was to integrate those devices on Si substrates for high-efficiency tandem applications using interface nanopatterning to address the lattice mismatch. In the first task, we developed a CSVT process that used only safe solid-source powder precursors to grow epitaxial GaAs with controlled n and p doping and mobilities/lifetimes similar to that obtainable via MOCVD. Using photoelectrochemical characterization, we showed that the best material had near unity internal quantum efficiency for carrier collection and minority carrier diffusions lengths in of ~ 8 μm, suitable for PV devices with >25% efficiency. In the second task we developed the first pn junction photovoltaics using CSVT and showed unpassivated structures with open circuit photovoltages > 915 mV and internal quantum efficiencies >0.9. We also characterized morphological and electrical defects and identified routes to reduce those defects. In task three we grew epitaxial

  16. Comparison of the Tight Rope Technique and Clavicular Hook Plate for the Treatment of Rockwood Type III Acromioclavicular Joint Dislocation.

    Science.gov (United States)

    Cai, Leyi; Wang, Te; Lu, Di; Hu, Wei; Hong, Jianjun; Chen, Hua

    2018-06-01

    Acromioclavicular joint dislocation is one of the most common shoulder problems and may lead to instability or degenerative changes. The aim of this study was to compare the clinical outcomes of the Tight Rope system and clavicular hook plate for Rockwood type III acromioclavicular joint dislocation in adults. This was a prospective, randomized study in a hospital setting. From January 2012 to December 2014, 69 patients with type III injury were reviewed. Patients were randomly divided into two groups: Group A was treated using the TightRope system and Group B with the clavicular hook plate. All participants were followed up for 12 months. Clinical outcomes, radiological results and postoperative complications were recorded. The length of incision was significantly shorter in Goup A than that in Group B. The blood loss of surgery was significantly less in the Group A. Significant difference could be found between the two groups regarding the Visual Analogue Scale scores one day after surgery, at the 3 and 12 months follow-up. There were no differences according to the improvement of the Constant-Murley score and the coracoclavicular distance between the groups. The two groups have similar clinical and radiological outcomes. Both treatments could relieve the pain of dislocation, improve the function of Acromioclavicular joint and rectify the coracoclavicular distance measured in plain films. However, the TightRope system exhibited some advantages in terms of length of incision, blood loss of surgery, the pain postoperatively and no need for a second surgery.

  17. Structural properties of III-V zinc-blende semiconductors under pressure

    International Nuclear Information System (INIS)

    Froyen, S.; Cohen, M.L.

    1983-01-01

    The pseudopotential method within the local-density approximation is used to investigate the static and structural properties of some III-V compound semiconductors. Comparisons of calculated total energies as a function of volume and structure yield information about solid-solid phase transformations. At high pressures the results indicate that several metallic structures are lower in energy than the zinc-blende structure. From our results the compounds (AlP, AlAs, GaP, and GaAs) can be divided into two classes. In the Ga compounds, we find a pressure-induced phase transformation to either rocksalt, β-Sn, or NiAs, whereas in the Al compounds rocksalt and NiAs are stabilized with respect to β-Sn. All structures except zinc blende are metallic. We discuss the electronic structure of each phase and show how it relates to structural stability

  18. New III-V cell design approaches for very high efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; Patkar, M.P.; Young, M.P. (Purdue Univ., Lafayette, IN (United States))

    1993-04-01

    This report describes to examine new solar cell desip approaches for achieving very high conversion efficiencies. The program consists of two elements. The first centers on exploring new thin-film approaches specifically designed for M-III semiconductors. Substantial efficiency gains may be possible by employing light trapping techniques to confine the incident photons, as well as the photons emitted by radiative recombination. The thin-film approach is a promising route for achieving substantial performance improvements in the already high-efficiency, single-junction, III-V cell. The second element of the research involves exploring desip approaches for achieving high conversion efficiencies without requiring extremely high-quality material. This work has applications to multiple-junction cells, for which the selection of a component cell often involves a compromise between optimum band pp and optimum material quality. It could also be a benefit manufacturing environment by making the cell's efficiency less dependent on materialquality.

  19. Hydrogen-mediated Nitrogen Clustering in Dilute III-V Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Du, M.-H.; Limpijumnong, S.; Zhang, S. B

    2006-01-01

    First-principles calculation reveals multi-N clusters to be the ground states for hydrogenated N in dilute III-V nitrides. While hydrogenation of a single N, forming H*{sub 2}(N), can relax the large strain induced by the size-mismatched N, formation of the clusters will relax the strain even more effectively. This suppresses the formation of H*{sub 2}(N), the existence of which has recently been debated. More importantly, postgrowth dehydrogenation of the N-H clusters provides an explanation to the observed metastable bare N clusters in GaAsN grown by gas-source molecular beam epitaxy or metal-organic chemical vapor deposition.

  20. Acousto-optic modulation of III-V semiconductor multiple quantum wells

    International Nuclear Information System (INIS)

    Smith, D.L.; Kogan, S.M.; Ruden, P.P.; Mailhiot, C.

    1996-01-01

    We present an analysis of the effect of surface acoustic waves (SAW close-quote s) on the optical properties of III-V semiconductor multiple quantum wells (MQW close-quote s). Modulation spectra at the fundamental and second harmonic of the SAW frequency are presented. The SAW modulates the optical properties of the MQW primarily by changing optical transition energies. The SAW generates both strains, which modulate the transition energies by deformation potential effects, and electric fields, which modulate the transition energies by the quantum confined Stark effect. We find that modulation of the transition energies by strain effects is usually more important than by electric-field effects. If large static electric fields occur in the MQW, the SAW-generated electric field can mix with the static field to give optical modulation, which is comparable in magnitude to modulation from the deformation potential effect. If there are no large static electric fields, modulation by the SAW-generated fields is negligible. A large static electric field distributes oscillator strength among the various optical transitions so that no single transition is as strong as the primary allowed transitions without a static electric field. To achieve the maximum modulation for fixed SAW parameters, it is best to modulate a strong optical transition. Thus optimum modulation occurs when there are no large static electric fields present and that modulation is primarily from deformation potential effects. We specifically consider Ga x In 1-x As/Ga x Al 1-x As MQW close-quote s grown on (100) and (111) oriented substrates, but our general conclusions apply to other type I MQW close-quote s fabricated from III-V semiconductors. copyright 1996 The American Physical Society

  1. Optical analysis of a III-V-nanowire-array-on-Si dual junction solar cell.

    Science.gov (United States)

    Chen, Yang; Höhn, Oliver; Tucher, Nico; Pistol, Mats-Erik; Anttu, Nicklas

    2017-08-07

    A tandem solar cell consisting of a III-V nanowire subcell on top of a planar Si subcell is a promising candidate for next generation photovoltaics due to the potential for high efficiency. However, for success with such applications, the geometry of the system must be optimized for absorption of sunlight. Here, we consider this absorption through optics modeling. Similarly, as for a bulk dual-junction tandem system on a silicon bottom cell, a bandgap of approximately 1.7 eV is optimum for the nanowire top cell. First, we consider a simplified system of bare, uncoated III-V nanowires on the silicon substrate and optimize the absorption in the nanowires. We find that an optimum absorption in 2000 nm long nanowires is reached for a dense array of approximately 15 nanowires per square micrometer. However, when we coat such an array with a conformal indium tin oxide (ITO) top contact layer, a substantial absorption loss occurs in the ITO. This ITO could absorb 37% of the low energy photons intended for the silicon subcell. By moving to a design with a 50 nm thick, planarized ITO top layer, we can reduce this ITO absorption to 5%. However, such a planarized design introduces additional reflection losses. We show that these reflection losses can be reduced with a 100 nm thick SiO 2 anti-reflection coating on top of the ITO layer. When we at the same time include a Si 3 N 4 layer with a thickness of 90 nm on the silicon surface between the nanowires, we can reduce the average reflection loss of the silicon cell from 17% to 4%. Finally, we show that different approximate models for the absorption in the silicon substrate can lead to a 15% variation in the estimated photocurrent density in the silicon subcell.

  2. Narrow-linewidth Si/III-V lasers: A study of laser dynamics and nonlinear effects

    Science.gov (United States)

    Vilenchik, Yaakov Yasha

    Narrow-linewidth lasers play an important role in a wide variety of applications, from sensing and spectroscopy to optical communication and on-chip clocks. Current narrow-linewidth systems are usually implemented in doped fibers and are big, expensive, and power-hungry. Semiconductor lasers compete favorably in size, cost, and power consumption, but their linewidth is historically limited to the sub-MHz regime. However, it has been recently demonstrated that a new design paradigm, in which the optical energy is stored away from the active region in a composite high-Q resonator, has the potential to dramatically improve the coherence of the laser. This work explores this design paradigm, as applied on the hybrid Si/III-V platform. It demonstrates a record sub-KHz white-noise-floor linewidth. It further shows, both theoretically and experimentally, that this strategy practically eliminates Henry's linewidth enhancement by positioning a damped relaxation resonance at frequencies as low as 70 MHz, yielding truly quantum limited devices at frequencies of interest. In addition to this empirical contribution, this work explores the limits of performance of this platform. Here, the effect of two-photon-absorption and free-carrier-absorption are analyzed, using modified rate equations and Langevin force approach. The analysis predicts that as the intra-cavity field intensity builds up in the high-Q resonator, non-linear effects cause a new domain of performance-limiting factors. Steady-state behavior, laser dynamics, and frequency noise performance are examined in the context of this unique platform, pointing at the importance of nonlinear effects. This work offers a theoretical model predicting laser performance in light of nonlinear effects, obtaining a good agreement with experimental results from fabricated high-Q Si/III-V lasers. In addition to demonstrating unprecedented semiconductor laser performance, this work establishes a first attempt to predict and demonstrate

  3. Truly anatomic coracoclavicular ligament reconstruction with 2 Endobutton devices for acute Rockwood type V acromioclavicular joint dislocations.

    Science.gov (United States)

    Xue, Cheng; Song, Li-Jun; Zhang, Hao; Tang, Guo-Long; Li, Xiang; Fang, Jia-Hu

    2018-06-01

    Truly anatomic coracoclavicular ligament reconstruction (TACCR) according to the original insertions is a creative new method for the treatment of severe acromioclavicular separation. This research analyzed the clinical and radiologic results of TACCR in 25 patients with at least 2-year follow-up. The study enrolled 25 patients with Rockwood type V acromioclavicular joint dislocations who underwent TACCR using 2 Endobutton (Smith & Nephew Inc., Andover, MA, USA) devices from May 2013 to October 2015. Patients were assessed with clinical and radiologic follow-up at 3, 6, 12, 18, and 24 months postoperatively. The clinical assessments consisted of the visual analog scale and the Constant score. The radiographic evaluations were performed by measurements of the coracoclavicular distance. The mean follow-up was 34 ± 6.8 months (range, 24-48 months). The visual analog scale and Constant scores revealed significant advancements from 5 ± 0.9 (range, 4-7) and 45 ± 5.6 (range, 30-54) scores preoperatively to 0 ± 0.5 (range, 0-2) and 95 ± 2.9 (range, 91-98) scores at 24 months postoperatively, respectively. The coracoclavicular distance significantly decreased from 23 ± 5.4 mm (range, 16-34 mm) preoperatively to 8 ± 0.9 mm (range, 7-10 mm) at the final follow-up. TACCR represents a safe, reliable and creative surgical technique that yields good to excellent clinical and radiologic outcomes in the treatment of severe acromioclavicular separation. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  4. A retrospective comparative study of arthroscopic fixation in acute Rockwood type IV acromioclavicular joint dislocation: single versus double paired Endobutton technique.

    Science.gov (United States)

    Xu, Jian; Liu, Haifeng; Lu, Wei; Li, Dingfu; Zhu, Weimin; Ouyang, Kan; Wu, Bing; Peng, Liangquan; Wang, Daping

    2018-05-24

    Rockwood type IV acromioclavicular joint (ACJ) dislocation is a trauma usually needs surgical treatment. Paired EndoButton technique (PET) is used in treating such condition. However, the effect of using different types of PET (single versus double PET) for fixation remains controversial. This study aims to evaluate and compare the efficacy of single and double PET and to provide a suitable option for the surgeons. We retrospectively reviewed the charts of patients with acute Rockwood type IV ACJ dislocation who had undergone arthroscopic fixation using single or double PET fixation between March 2009 and March 2015. Seventy-eight consecutive patients identified from chart review were picked and were divided into the single and double PET group with 39 cases in each group. The indexes of visual analog scale score (VAS) for pain, the radiographs of the affected shoulder at different time points of the follow-up, the time of return to activities and sports, the constant functional score, and the Karlsson acromioclavicular joint (ACJ) score, were assessed in a minimum of 2 years postoperation. The average coracoclavicular (CC) and acromioclavicular (AC) distances of the affected joints in the double PET group were significantly smaller than those of the single PET group 2 years postoperation (P  0.05). The mean VAS pain score was not significantly different, while significant difference was found for the number and times of cases return to activities and sports, constant functional score, and Karlsson ACJ score (P < 0.05) between the two groups. Therefore, the double PET group has better outcome than the single PET group. Complications including redislocation, button slippage, erosion, or AC joint instability occurred in the single PET group, while the complication in the double PET group was rare. Compared with the single PET, the double PET group achieved better outcome with less complications in arthroscopically treating acute Rockwood type IV ACJ

  5. High Efficiency Nanostructured III-V Photovoltaics for Solar Concentrator Application

    Energy Technology Data Exchange (ETDEWEB)

    Hubbard, Seth

    2012-09-12

    The High Efficiency Nanostructured III-V Photovoltaics for Solar Concentrators project seeks to provide new photovoltaic cells for Concentrator Photovoltaics (CPV) Systems with higher cell efficiency, more favorable temperature coefficients and less sensitivity to changes in spectral distribution. The main objective of this project is to provide high efficiency III-V solar cells that will reduce the overall cost per Watt for power generation using CPV systems.This work is focused both on a potential near term application, namely the use of indium arsenide (InAs) QDs to spectrally "tune" the middle (GaAs) cell of a SOA triple junction device to a more favorable effective bandgap, as well as the long term goal of demonstrating intermediate band solar cell effects. The QDs are confined within a high electric field i-region of a standard GaAs solar cell. The extended absorption spectrum (and thus enhanced short circuit current) of the QD solar cell results from the increase in the sub GaAs bandgap spectral response that is achievable as quantum dot layers are introduced into the i-region. We have grown InAs quantum dots by OMVPE technique and optimized the QD growth conditions. Arrays of up to 40 layers of strain balanced quantum dots have been experimentally demonstrated with good material quality, low residual stain and high PL intensity. Quantum dot enhanced solar cells were grown and tested under simulated one sun AM1.5 conditions. Concentrator solar cells have been grown and fabricated with 5-40 layers of QDs. Testing of these devices show the QD cells have improved efficiency compared to baseline devices without QDs. Device modeling and measurement of thermal properties were performed using Crosslight APSYS. Improvements in a triple junction solar cell with the insertion of QDs into the middle current limiting junction was shown to be as high as 29% under one sun illumination for a 10 layer stack QD enhanced triple junction solar cell. QD devices have strong

  6. Analytical Electron Diffraction from Iii-V and II-Vi Semiconductors

    Science.gov (United States)

    Spellward, Paul

    Available from UMI in association with The British Library. This thesis describes the development and evaluation of a number of new TEM-based techniques for the measurement of composition in ternary III-V and II-VI semiconductors. New methods of polarity determination in binary and ternary compounds are also presented. The theory of high energy electron diffraction is outlined, with particular emphasis on zone axis diffraction from well-defined strings. An account of TEM microstructural studies of Cd_{rm x}Hg _{rm 1-x}Te and CdTe epitaxial layers, which provided the impetus for developing the diffraction-based analytical techniques, is given. The wide range of TEM-based compositional determination techniques is described. The use of HOLZ deficiency lines to infer composition from a lattice parameter measurement is evaluated. In the case of Cd_{ rm x}Hg_{rm 1-x}Te, it is found to be inferior to other techniques developed. Studies of dynamical aspects of HOLZ diffraction can yield information about the dispersion surface from which a measure of composition may be obtained. This technique is evaluated for Al_{rm x}Ga_{rm 1-x} As, in which it is found to be of some use, and for Cd_{rm x}Hg _{rm 1-x}Te, in which the large Debye-Waller factor associated with mercury in discovered to render the method of little value. A number of critical voltages may be measured in medium voltage TEMs. The (111) zone axis critical voltage of Cd_{rm x}Hg _{rm 1-x}Te is found to vary significantly with x and forms the basis of an accurate technique for composition measurement in that ternary compound. Other critical voltage phenomena are investigated. In Al _{rm x}Ga_ {rm 1-x}As and other light ternaries, a non-systematic critical voltage is found to vary with x, providing a good indicator of composition. Critical voltage measurements may be made by conventional CBED or by various other techniques, which may also simultaneously yield information on the spatial variation of composition. The

  7. Positron annihilation studies of defects in molecular beam epitaxy grown III-V layers

    International Nuclear Information System (INIS)

    Umlor, M.T.; Keeble, D.J.; Cooke, P.W.

    1994-01-01

    A summary of recent positron annihilation experiments on molecular beam epitaxy (MBE) grown III-V layers is Presented. Variable energy positron beam measurements on Al 0.32 Ga 0.68 As undoped and Si doped have been completed. Positron trapping at a open volume defect in Al 0.32 Ga 0.68 :Si for temperatures from 300 to 25 K in the dark was observed. The positron trap was lost after 1.3 eV illumination at 25K. These results indicate an open volume defect is associated with the local structure of the deep donor state of the DX center. Stability of MBE GaAs to thermal annealing war, investigated over the temperature range of 230 to 700 degrees C, Proximity wafer furnace anneals in flowing argon were used, Samples grown above 450 degrees C were shown to be stable but for sample below this temperature an anneal induced vacancy related defect was produced for anneals between 400 and 500 degrees C. The nature of the defect was shown to be different for material grown at 350 and 230 degrees C. Activation energies of 2.5 eV to 2.3 eV were obtained from isochronal anneal experiments for samples grown at 350 and 230 degrees C, respectively

  8. III-V semiconductors for photoelectrochemical applications: surface preparation and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Fertig, Dominic; Schaechner, Birgit; Calvet, Wofram; Kaiser, Bernhard; Jaegermann, Wolfram [TU Darmstadt, Fachbereich Materialwissenschaft, Fachgebiet Oberflaechenforschung (Germany)

    2011-07-01

    III-V semiconductors are promising reference systems for photoelectrochemical energy conversion. Therefore we have studied the influence of different acids and acidic solutions on the etching of p-doped gallium-arsenide and gallium-phosphide single crystal surfaces. From our experiments we conclude, that etching with HCl and subsequent annealing up to 450 C gives the best results for the removal of the carbonates and the oxides without affecting the quality of the sample. By treating the surfaces with ''piranha''-solution (H{sub 2}SO{sub 4}:H{sub 2}O{sub 2}:H{sub 2}O/7:2:1), the creation of an oxide layer with well defined thickness can be achieved. For the creation of an efficient photoelectrochemical cell, Pt nanoparticles have been deposited from solution. These surfaces are then characterized by photoelectron spectroscopy and AFM. Further electrochemical measurements try to correlate the effect of the surface cleaning and the Pt deposition on the photoactivity of the GaAs- and GaP-semiconductors.

  9. Spin Relaxation in III-V Semiconductors in various systems: Contribution of Electron-Electron Interaction

    Science.gov (United States)

    Dogan, Fatih; Kesserwan, Hasan; Manchon, Aurelien

    2015-03-01

    In spintronics, most of the phenomena that we are interested happen at very fast time scales and are rich in structure in time domain. Our understanding, on the other hand, is mostly based on energy domain calculations. Many of the theoretical tools use approximations and simplifications that can be perceived as oversimplifications. We compare the structure, material, carrier density and temperature dependence of spin relaxation time in n-doped III-V semiconductors using Elliot-Yafet (EY) and D'yakanov-Perel'(DP) with real time analysis using kinetic spin Bloch equations (KSBE). The EY and DP theories fail to capture details as the system investigated is varied. KSBE, on the other hand, incorporates all relaxation sources as well as electron-electron interaction which modifies the spin relaxation time in a non-linear way. Since el-el interaction is very fast (~ fs) and spin-conserving, it is usually ignored in the analysis of spin relaxation. Our results indicate that electron-electron interaction cannot be neglected and its interplay with the other (spin and momentum) relaxation mechanisms (electron-impurity and electron-phonon scattering) dramatically alters the resulting spin dynamics. We use each interaction explicitly to investigate how, in the presence of others, each relaxation source behaves. We use GaAs and GaN for zinc-blend structure, and GaN and AlN for the wurtzite structure.

  10. Growth, structure and phase transitions of epitaxial nanowires of III-V semiconductors

    International Nuclear Information System (INIS)

    Glas, F; Patriarche, G; Harmand, J C

    2010-01-01

    We review and illustrate the impact of TEM on the study of nanowires of non-nitride III-V semiconductors, with particular emphasis on the understanding of the thermodynamics and kinetics of their formation assisted by nano-sized catalyst particles. Besides providing basic information about the morphology of the nanowires and their growth rate as a function of diameter, TEM offers insights into the peculiar crystalline structure that they adopt. We discuss the formation of the unusual wurtzite hexagonal crystalline phase and that of planar stacking defects in these nanowires and show that they are kinetically controlled. We also demonstrate the transformation of wurtzite into cubic sphalerite upon epitaxial burying of the nanowires. Nanowires are particularly interesting in that they allow the fabrication of precisely positioned quantum dots with well-defined geometries. In this respect, we discuss the formation of strained quantum-size inclusions in nanowires, their critical dimensions and the kinetic and thermodynamic factors governing the changes of the crystalline structure that sometimes occur around a hetero-interface.

  11. Long-range ordering of III-V semiconductor nanostructures by shallowly buried dislocation networks

    International Nuclear Information System (INIS)

    Coelho, J; Patriarche, G; Glas, F; Saint-Girons, G; Sagnes, I

    2004-01-01

    We account for lateral orderings of III-V nanostructures resulting from a GaAs/InAs/InGaAs/GaAs sequence grown on GaAs by metallorganic vapour phase epitaxy at two different temperatures. For both samples, the ordering is induced by the stress field of a periodic dislocation network (DN) shallowly buried and parallel to the surface. This DN is a grain boundary (GB) that forms, between a thin GaAs layer (on which growth was performed) and a GaAs substrate joined together by wafer bonding, in order to accommodate a tilt and a twist between these two crystals; both these misorientations are imposed in a controlled manner. This GB is composed of a one-dimensional network of mixed dislocations and of a one-dimensional network of screw dislocations. For both samples, the nanostructures observed by transmission electron microscopy (TEM) and atomic force microscopy are ordered by the underlying DN observed by TEM since they have same dimensions and orientations as the cells of the DN

  12. Band structure effects on resonant tunneling in III-V quantum wells versus two-dimensional vertical heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Philip M., E-mail: philip.campbell@gatech.edu [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Electronic Systems Laboratory, Georgia Tech Research Institute, Atlanta, Georgia 30332 (United States); Tarasov, Alexey; Joiner, Corey A.; Vogel, Eric M. [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Ready, W. Jud [Electronic Systems Laboratory, Georgia Tech Research Institute, Atlanta, Georgia 30332 (United States)

    2016-01-14

    Since the invention of the Esaki diode, resonant tunneling devices have been of interest for applications including multi-valued logic and communication systems. These devices are characterized by the presence of negative differential resistance in the current-voltage characteristic, resulting from lateral momentum conservation during the tunneling process. While a large amount of research has focused on III-V material systems, such as the GaAs/AlGaAs system, for resonant tunneling devices, poor device performance and device-to-device variability have limited widespread adoption. Recently, the symmetric field-effect transistor (symFET) was proposed as a resonant tunneling device incorporating symmetric 2-D materials, such as transition metal dichalcogenides (TMDs), separated by an interlayer barrier, such as hexagonal boron-nitride. The achievable peak-to-valley ratio for TMD symFETs has been predicted to be higher than has been observed for III-V resonant tunneling devices. This work examines the effect that band structure differences between III-V devices and TMDs has on device performance. It is shown that tunneling between the quantized subbands in III-V devices increases the valley current and decreases device performance, while the interlayer barrier height has a negligible impact on performance for barrier heights greater than approximately 0.5 eV.

  13. Band structure effects on resonant tunneling in III-V quantum wells versus two-dimensional vertical heterostructures

    Science.gov (United States)

    Campbell, Philip M.; Tarasov, Alexey; Joiner, Corey A.; Ready, W. Jud; Vogel, Eric M.

    2016-01-01

    Since the invention of the Esaki diode, resonant tunneling devices have been of interest for applications including multi-valued logic and communication systems. These devices are characterized by the presence of negative differential resistance in the current-voltage characteristic, resulting from lateral momentum conservation during the tunneling process. While a large amount of research has focused on III-V material systems, such as the GaAs/AlGaAs system, for resonant tunneling devices, poor device performance and device-to-device variability have limited widespread adoption. Recently, the symmetric field-effect transistor (symFET) was proposed as a resonant tunneling device incorporating symmetric 2-D materials, such as transition metal dichalcogenides (TMDs), separated by an interlayer barrier, such as hexagonal boron-nitride. The achievable peak-to-valley ratio for TMD symFETs has been predicted to be higher than has been observed for III-V resonant tunneling devices. This work examines the effect that band structure differences between III-V devices and TMDs has on device performance. It is shown that tunneling between the quantized subbands in III-V devices increases the valley current and decreases device performance, while the interlayer barrier height has a negligible impact on performance for barrier heights greater than approximately 0.5 eV.

  14. Interface formation between hydrocarbon ring molecules and III-V semiconductor surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Passmann, Regina

    2008-08-15

    In this work a systematical study to investigate the adsorption structures of small hydrocarbon ring shaped molecules on III-V semiconductor surfaces with Photo-Emission Spectroscopy (PES), Reflectance Anisotropy Spectroscopy (RAS), Scanning Tunneling Microscopy (STM) as well as Low Electron Energy Diffraction (LEED) was performed. To investigate the influence of the surface structure in detail the surface dimer configuration to the adsorption process of organic molecules GaAs(001) surfaces, the c(4 x 4), the (2 x 4) and the (4 x 2) have been investigated as well as the adsorption of cyclopentene on the InP(001)(2 x 4) reconstructed surface. In the direct comparison it is shown that cyclopentene bonds to the InP(001)(2 x 4) surface via a cycloaddition like reaction. During this adsorption the double bond splits which is in contrast to the adsorption of cyclopentene on the GaAs(001) surfaces. Therefrom it is concluded that the surface geometry has an influence on the resulting adsorption structure. In order to investigate the influence of the intra-molecular double bonds, cyclopentene (one double bond), 1,4-cyclohexadiene (two double bonds) and benzene (three double bonds) were used for the characterization of the interface formation. With the investigations on the GaAs(001) reconstructed surfaces it was shown that a dependency of the bonding configuration on the intra-molecular double bonds exists. During the adsorption of cyclopentene no evidence was found that the double bond has to be involved in the interface formation while during the adsorption of 1,4-cyclohexadiene and benzene the double bonds are involved. Furthermore it was found that a bonding to As atoms of the surface is more likely than a bonding to Ga atoms. (orig.)

  15. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Veer Dhaka

    2016-01-01

    Full Text Available Low temperature (∼200 °C grown atomic layer deposition (ALD films of AlN, TiN, Al2O3, GaN, and TiO2 were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP nanowires (NWs, and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL at low temperatures (15K, and the best passivation was achieved with a few monolayer thick (2Å film. For InP NWs, the best passivation (∼2x enhancement in room-temperature PL was achieved with a capping of 2nm thick Al2O3. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al2O3 layer increased the carrier decay time from 251 ps (as-etched nanopillars to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al2O3 provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  16. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dhaka, Veer, E-mail: veer.dhaka@aalto.fi; Perros, Alexander; Kakko, Joona-Pekko; Haggren, Tuomas; Lipsanen, Harri [Department of Micro- and Nanosciences, Micronova, Aalto University, P.O. Box 13500, FI-00076 (Finland); Naureen, Shagufta; Shahid, Naeem [Research School of Physics & Engineering, Department of Electronic Materials Engineering, Australian National University, Canberra ACT 2601 (Australia); Jiang, Hua; Kauppinen, Esko [Department of Applied Physics and Nanomicroscopy Center, Aalto University, P.O. Box 15100, FI-00076 (Finland); Srinivasan, Anand [School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, S-164 40 Kista (Sweden)

    2016-01-15

    Low temperature (∼200 °C) grown atomic layer deposition (ALD) films of AlN, TiN, Al{sub 2}O{sub 3}, GaN, and TiO{sub 2} were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP) nanowires (NWs), and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL) at low temperatures (15K), and the best passivation was achieved with a few monolayer thick (2Å) film. For InP NWs, the best passivation (∼2x enhancement in room-temperature PL) was achieved with a capping of 2nm thick Al{sub 2}O{sub 3}. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al{sub 2}O{sub 3} layer increased the carrier decay time from 251 ps (as-etched nanopillars) to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al{sub 2}O{sub 3} provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  17. A III-V nanowire channel on silicon for high-performance vertical transistors.

    Science.gov (United States)

    Tomioka, Katsuhiro; Yoshimura, Masatoshi; Fukui, Takashi

    2012-08-09

    Silicon transistors are expected to have new gate architectures, channel materials and switching mechanisms in ten years' time. The trend in transistor scaling has already led to a change in gate structure from two dimensions to three, used in fin field-effect transistors, to avoid problems inherent in miniaturization such as high off-state leakage current and the short-channel effect. At present, planar and fin architectures using III-V materials, specifically InGaAs, are being explored as alternative fast channels on silicon because of their high electron mobility and high-quality interface with gate dielectrics. The idea of surrounding-gate transistors, in which the gate is wrapped around a nanowire channel to provide the best possible electrostatic gate control, using InGaAs channels on silicon, however, has been less well investigated because of difficulties in integrating free-standing InGaAs nanostructures on silicon. Here we report the position-controlled growth of vertical InGaAs nanowires on silicon without any buffering technique and demonstrate surrounding-gate transistors using InGaAs nanowires and InGaAs/InP/InAlAs/InGaAs core-multishell nanowires as channels. Surrounding-gate transistors using core-multishell nanowire channels with a six-sided, high-electron-mobility transistor structure greatly enhance the on-state current and transconductance while keeping good gate controllability. These devices provide a route to making vertically oriented transistors for the next generation of field-effect transistors and may be useful as building blocks for wireless networks on silicon platforms.

  18. Phenomenological survey on the potential profile evolution in III-V binary compounds

    Directory of Open Access Journals (Sweden)

    Alejandro Mendoza Álvarez

    2011-01-01

    Full Text Available En este artículo se presenta el cambio en el perfil de eficacia potencial de algunos compuestos cuando el bandmixing de huecos ligeros y pesados se altera. Se obtuvieron mediante la aplicación de este teorema generalizado Shur a un problema de valores propios cuadrática obtenidos a partir de un sistema con N ecuaciones de segundo orden, junto en el contexto de la aproximación de masa efectiva multibanda. Se consideraron los valores de energía incidente que fue menor, igual y superior a la altura de la barrera de dispersión potencial de diferentes compuestos de semiconductores III-V binario. La mayoría de las propiedades estándar de los compuestos binarios en este estudio están garantizados, pero no todos los materiales que elegimos, han puesto de manifiesto la evolución que se espera en su perfil de potencial efectivo: algunos de los que constituyen los pozos cuánticos (QW en aplicaciones tecnológicas sólo convertirse en efectiva barrera (B las conductas de los agujeros de luz (LH cuando están en la energía incidente diferente (E se extiende y bandmixing diferentes presentes. Ninguno de los compuestos que constituyen barreras para las aplicaciones tecnológicas en este estudio se convierte en eficaz comportamientos QW válido tanto para la LH y HH. Sorprendentemente, todos los compuestos en este estudio que constituyen barreras estándar en las aplicaciones tecnológicas, las transiciones presente desde CS a B para la LH en el rango donde el valor de E es mayor que la altura de la barrera.

  19. Interface formation between hydrocarbon ring molecules and III-V semiconductor surfaces

    International Nuclear Information System (INIS)

    Passmann, Regina

    2008-01-01

    In this work a systematical study to investigate the adsorption structures of small hydrocarbon ring shaped molecules on III-V semiconductor surfaces with Photo-Emission Spectroscopy (PES), Reflectance Anisotropy Spectroscopy (RAS), Scanning Tunneling Microscopy (STM) as well as Low Electron Energy Diffraction (LEED) was performed. To investigate the influence of the surface structure in detail the surface dimer configuration to the adsorption process of organic molecules GaAs(001) surfaces, the c(4 x 4), the (2 x 4) and the (4 x 2) have been investigated as well as the adsorption of cyclopentene on the InP(001)(2 x 4) reconstructed surface. In the direct comparison it is shown that cyclopentene bonds to the InP(001)(2 x 4) surface via a cycloaddition like reaction. During this adsorption the double bond splits which is in contrast to the adsorption of cyclopentene on the GaAs(001) surfaces. Therefrom it is concluded that the surface geometry has an influence on the resulting adsorption structure. In order to investigate the influence of the intra-molecular double bonds, cyclopentene (one double bond), 1,4-cyclohexadiene (two double bonds) and benzene (three double bonds) were used for the characterization of the interface formation. With the investigations on the GaAs(001) reconstructed surfaces it was shown that a dependency of the bonding configuration on the intra-molecular double bonds exists. During the adsorption of cyclopentene no evidence was found that the double bond has to be involved in the interface formation while during the adsorption of 1,4-cyclohexadiene and benzene the double bonds are involved. Furthermore it was found that a bonding to As atoms of the surface is more likely than a bonding to Ga atoms. (orig.)

  20. Operative treatment of acute acromioclavicular dislocations Rockwood III and V-Comparative study between K-wires combined with FiberTape(®) vs. TightRope System(®).

    Science.gov (United States)

    Vrgoč, G; Japjec, M; Jurina, P; Gulan, G; Janković, S; Šebečić, B; Starešinić, M

    2015-11-01

    Acromioclavicular (AC) joint dislocations usually occur in a young active population as a result of a fall on the shoulder. Rockwood divided these dislocations into six types. Optimal treatment is still a matter of discussion. Many operative techniques have been developed, but the main choice is between open and minimally-invasive arthroscopic procedures. The aim of this study was to compare two different surgical methods on two groups of patients to find out which method is superior in terms of benefit to the patient. The methods were evaluated through objective and subjective scores, with a focus on complications and material costs. A retrospective two-centre study was conducted in patients with acute AC joint dislocation Rockwood types III and V. The two methods conducted were an open procedure using K-wires combined with FiberTape(®) (Arthrex, Naples, USA) (Group 1) and an arthroscopic procedure using the TightRope System(®) (Arthrex, Naples, USA) (Group 2). Groups underwent procedures during a two-year period. Diagnosis was based on the clinical and radiographic examination of both AC joints. Surgical treatment and rehabilitation were performed. Sixteen patients were included in this study: Group 1 comprised 10 patients, all male, average age 41.6 years (range 17-64 years), Rockwood type III (eight patients) and Rockwood type V (two patients); Group 2 had six patients, one female and five male, average age 37.8 years (range 18-58 years), Rockwood type III (two patients) and Rockwood type V (four patients). Time from injury to surgery was shorter and patients needed less time to return to daily activities in Group 1. Duration of the surgical procedure was shorter in Group 2 compared with Group 1. Complications of each method were noted. According to the measured scores and operative outcome between dislocation Rockwood type III and V, no significant difference was found. Implant material used in Group 2 was 4.7 times more expensive than that used in Group 1

  1. Accumulation capacitance frequency dispersion of III-V metal-insulator-semiconductor devices due to disorder induced gap states

    International Nuclear Information System (INIS)

    Galatage, R. V.; Zhernokletov, D. M.; Dong, H.; Brennan, B.; Hinkle, C. L.; Wallace, R. M.; Vogel, E. M.

    2014-01-01

    The origin of the anomalous frequency dispersion in accumulation capacitance of metal-insulator-semiconductor devices on InGaAs and InP substrates is investigated using modeling, electrical characterization, and chemical characterization. A comparison of the border trap model and the disorder induced gap state model for frequency dispersion is performed. The fitting of both models to experimental data indicate that the defects responsible for the measured dispersion are within approximately 0.8 nm of the surface of the crystalline semiconductor. The correlation between the spectroscopically detected bonding states at the dielectric/III-V interface, the interfacial defect density determined using capacitance-voltage, and modeled capacitance-voltage response strongly suggests that these defects are associated with the disruption of the III-V atomic bonding and not border traps associated with bonding defects within the high-k dielectric.

  2. Optimization of the silicon subcell for III-V on silicon multijunction solar cells: Key differences with conventional silicon technology

    Science.gov (United States)

    García-Tabarés, Elisa; Martín, Diego; García, Iván; Lelièvre, Jean François; Rey-Stolle, Ignacio

    2012-10-01

    Dual-junction solar cells formed by a GaAsP or GaInP top cell and a silicon (Si) bottom cell seem to be attractive candidates to materialize the long sought-for integration of III-V materials on Si for photovoltaic (PV) applications. Such integration would offer a cost breakthrough for PV technology, unifying the low cost of Si and the efficiency potential of III-V multijunction solar cells. The optimization of the Si solar cells properties in flat-plate PV technology is well-known; nevertheless, it has been proven that the behavior of Si substrates is different when processed in an MOVPE reactor In this study, we analyze several factors influencing the bottom subcell performance, namely, 1) the emitter formation as a result of phosphorus diffusion; 2) the passivation quality provided by the GaP nucleation layer; and 3) the process impact on the bottom subcell PV properties.

  3. Is coracoclavicular stabilisation alone sufficient for the endoscopic treatment of severe acromioclavicular joint dislocation (Rockwood types III, IV, and V)?

    Science.gov (United States)

    Barth, J; Duparc, F; Andrieu, K; Duport, M; Toussaint, B; Bertiaux, S; Clavert, P; Gastaud, O; Brassart, N; Beaudouin, E; De Mourgues, P; Berne, D; Bahurel, J; Najihi, N; Boyer, P; Faivre, B; Meyer, A; Nourissat, G; Poulain, S; Bruchou, F; Ménard, J F

    2015-12-01

    The primary objective was to evaluate correlations linking anatomical to functional outcomes after endoscopically assisted repair of acute acromioclavicular joint dislocation (ACJD). Combined acromioclavicular and coracoclavicular stabilisation improves radiological outcomes compared to coracoclavicular stabilisation alone. A prospective multicentre study was performed. Clinical outcome measures were pain intensity on a visual analogue scale (VAS), subjective functional impairment (QuickDASH score), and Constant's score. Anatomical outcomes were assessed on standard radiographs (anteroposterior view of the acromioclavicular girdle and bilateral axillary views) obtained preoperatively and postoperatively and on postoperative dynamic radiographs taken as described by Tauber et al. Of 116 patients with acute ACJD included in the study, 48% had type III, 30% type IV, and 22% type V ACJD according to the Rockwood classification. Coracoclavicular stabilisation was achieved using a double endobutton in 93% of patients, and concomitant acromioclavicular stabilisation was performed in 50% of patients. The objective functional outcome was good, with an unweighted Constant's score ≥ 85/100 and a subjective QuickDASH functional disability score ≤ 10 in 75% of patients. The radiographic analysis showed significant improvements from the preoperative to the 1-year postoperative values in the vertical plane (decrease in the coracoclavicular ratio from 214 to 128%, p=10(-6)) and in the horizontal plane (decrease in posterior displacement from 4 to 0mm, p=5×10(-5)). The anatomical outcome correlated significantly with the functional outcome (absolute R value=0.19 and p=0.045). We found no statistically significant differences across the various types of constructs used. Intra-operative control of the acromioclavicular joint did not improve the result. Implantation of a biological graft significantly improved both the anatomical outcome in the vertical plane (p=0.04) and

  4. Silicon, germanium, and III-V-based tunneling devices for low-power applications

    Science.gov (United States)

    Smith, Joshua T.

    While the scaling of transistor dimensions has kept pace with Moore's Law, the voltages applied to these devices have not scaled in tandem, giving rise to ever-increasing power/heating challenges in state-of-the-art integrated circuits. A primary reason for this scaling mismatch is due to the thermal limit---the 60 mV minimum required at room temperature to change the current through the device by one order of magnitude. This voltage scaling limitation is inherent in devices that rely on the mechanism of thermal emission of charge carriers over a gate-controlled barrier to transition between the ON- and OFF-states, such as in the case of conventional CMOS-based technologies. To overcome this voltage scaling barrier, several steep-slope device concepts have been pursued that have experimentally demonstrated sub-60-mV/decade operation since 2004, including the tunneling-field effect transistor (TFET), impact ionization metal-oxide-semiconductor (IMOS), suspended-gate FET (SG-FET), and ferroelectric FET (Fe-FET). These reports have excited strong efforts within the semiconductor research community toward the realization of a low-power device that will support continued scaling efforts, while alleviating the heating issues prevalent in modern computer chips. Literature is replete with claims of sub-60-mV/decade operation, but often with neglect to other voltage scaling factors that offset this result. Ideally, a low-power device should be able to attain sub-60-mV/decade inverse subthreshold slopes (S) employing low supply and gate voltages with a foreseeable path toward integration. This dissertation describes the experimental development and realization of CMOS-compatible processes to enhance tunneling efficiency in Si and Si/Ge nanowire (NW) TFETs for improved average S (S avg) and ON-currents (ION), and a novel, III-V-based tunneling device alternative is also proposed. After reviewing reported efforts on the TFET, IMOS, and SG-FET, the TFET is highlighted as the

  5. First principles calculation of material properties of group IV elements and III-V compounds

    Science.gov (United States)

    Malone, Brad Dean

    This thesis presents first principles calculations on the properties of group IV elements and group III-V compounds. It includes investigations into what structure a material is likely to form in, and given that structure, what are its electronic, optical, and lattice dynamical properties as well as what are the properties of defects that might be introduced into the sample. The thesis is divided as follows: • Chapter 1 contains some of the conceptual foundations used in the present work. These involve the major approximations which allow us to approach the problem of systems with huge numbers of interacting electrons and atomic cores. • Then, in Chapter 2, we discuss one of the major limitations to the DFT formalism introduced in Chapter 1, namely its inability to predict the quasiparticle spectra of materials and in particular the band gap of a semiconductor. We introduce a Green's function approach to the electron self-energy Sigma known as the GW approximation and use it to compute the quasiparticle band structures of a number of group IV and III-V semiconductors. • In Chapter 3 we present a first-principles study of a number of high-pressure metastable phases of Si with tetrahedral bonding. The phases studied include all experimentally determined phases that result from decompression from the metallic beta-Sn phase, specifically the BC8 (Si-III), hexagonal diamond (Si-IV), and R8 (Si-XII). In addition to these, we also study the hypothetical ST12 structure found upon decompression from beta-Sn in germanium. • Our attention is then turned to the first principles calculations of optical properties in Chapter 4. The Bethe-Salpeter equation is then solved to obtain the optical spectrum of this material including electron-hole interactions. The calculated optical spectrum is compared with experimental data for other forms of silicon commonly used in photovoltaic devices, namely the cubic, polycrystalline, and amorphous forms. • In Chapter 5 we present

  6. III/V nano ridge structures for optical applications on patterned 300 mm silicon substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kunert, B.; Guo, W.; Mols, Y.; Pantouvaki, M.; Van Campenhout, J.; Langer, R.; Barla, K. [imec, Kapeldreef 75, 3001 Heverlee (Belgium); Tian, B.; Wang, Z.; Shi, Y.; Van Thourhout, D. [Photonics Research Group, Ghent University, Technologiepark-Zwijnaarde 15, 9052 Gent (Belgium)

    2016-08-29

    We report on an integration approach of III/V nano ridges on patterned silicon (Si) wafers by metal organic vapor phase epitaxy (MOVPE). Trenches of different widths (≤500 nm) were processed in a silicon oxide (SiO{sub 2}) layer on top of a 300 mm (001) Si substrate. The MOVPE growth conditions were chosen in a way to guarantee an efficient defect trapping within narrow trenches and to form a box shaped ridge with increased III/V volume when growing out of the trench. Compressively strained InGaAs/GaAs multi-quantum wells with 19% indium were deposited on top of the fully relaxed GaAs ridges as an active material for optical applications. Transmission electron microcopy investigation shows that very flat quantum well (QW) interfaces were realized. A clear defect trapping inside the trenches is observed whereas the ridge material is free of threading dislocations with only a very low density of planar defects. Pronounced QW photoluminescence (PL) is detected from different ridge sizes at room temperature. The potential of these III/V nano ridges for laser integration on Si substrates is emphasized by the achieved ridge volume which could enable wave guidance and by the high crystal quality in line with the distinct PL.

  7. Electrically driven hybrid Si/III-V Fabry-Pérot lasers based on adiabatic mode transformers.

    Science.gov (United States)

    Ben Bakir, B; Descos, A; Olivier, N; Bordel, D; Grosse, P; Augendre, E; Fulbert, L; Fedeli, J M

    2011-05-23

    We report the first demonstration of an electrically driven hybrid silicon/III-V laser based on adiabatic mode transformers. The hybrid structure is formed by two vertically superimposed waveguides separated by a 100-nm-thick SiO2 layer. The top waveguide, fabricated in an InP/InGaAsP-based heterostructure, serves to provide optical gain. The bottom Si-waveguides system, which supports all optical functions, is constituted by two tapered rib-waveguides (mode transformers), two distributed Bragg reflectors (DBRs) and a surface-grating coupler. The supermodes of this hybrid structure are controlled by an appropriate design of the tapers located at the edges of the gain region. In the middle part of the device almost all the field resides in the III-V waveguide so that the optical mode experiences maximal gain, while in regions near the III-V facets, mode transformers ensure an efficient transfer of the power flow towards Si-waveguides. The investigated device operates under quasi-continuous wave regime. The room temperature threshold current is 100 mA, the side-mode suppression ratio is as high as 20 dB, and the fiber-coupled output power is ~7 mW.

  8. Acute high-grade acromioclavicular joint injuries: quality of life comparison between patients managed operatively with a hook plate versus patients managed non-operatively.

    Science.gov (United States)

    Natera Cisneros, Luis Gerardo; Sarasquete Reiriz, Juan

    2017-04-01

    Surgical indication for acromioclavicular joint (ACJ) injuries still represents a reason for shoulder and trauma debate. In high-grade injuries, surgery is advocated because some of the non-operatively managed patients may have persistent shoulder pain that could make them unable to return to their previous activity. It has been shown that many of the patients with high-grade ACJ injuries that are managed non-operatively involve the development of scapular dyskinesis, situation that may result in loss of strength and weakness. On the other side, it has been widely reported that the period while the hook plate is present involves functional limitations and pain. The purpose of this study was to compare the quality of life (QoL) of patients with acute high-grade ACJ injuries (Rockwood grade III-V), managed operatively with a hook plate versus the QoL of patients managed non-operatively, 24 months or more after shoulder injury. Patients with acute high-grade ACJ injuries managed operatively (hook plate) or non-operatively, between 2008 and 2012 were included. The QoL was evaluated by means of the Health Survey questionnaire (SF36), the Visual Analogue Scale (VAS) for pain, the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, the Constant score and the Global Satisfaction (scale from 0 to 10) assessed at the last follow-up visit. The presence of scapular dyskinesis was assessed. Comparison between groups was made. Thirty-two patients were included: 11 hook plate-group (PLATE group) (5 Rockwood III and 6 V) and 21 conservative-group (CONS group) (4 Rockwood III and 17 V). The mean age was 41 [19-55] years old for the PLATE group and 38 [19-55] for the CONS group (p = 0.513). The mean follow-up was 32.50 ± 11.64 months for the PLATE group and 34.77 ± 21.98 months for the CONS group (p = 0.762). The mean results of the questionnaires assessed at the last follow-up visit were: (1) physical SF36 score (PLATE group 53.70 ± 4.33 and CONS group

  9. Metabolomic and proteomic biomarkers for III-V semiconductors: Chemical-specific porphyrinurias and proteinurias

    International Nuclear Information System (INIS)

    Fowler, Bruce A.; Conner, Elizabeth A.; Yamauchi, Hiroshi

    2005-01-01

    A pressing need exists to develop and validate molecular biomarkers to assess the early effects of chemical agents, both individually and in mixtures. This is particularly true for new and chemically intensive industries such as the semiconductor industry. Previous studies from this laboratory and others have demonstrated element-specific alterations of the heme biosynthetic pathway for the III-V semiconductors gallium arsenide (GaAs) and indium arsenide (InAs) with attendant increased urinary excretion of specific heme precursors. These data represent an example of a metabolomic biomarker to assess chemical effects early, before clinical disease develops. Previous studies have demonstrated that the intratracheal or subcutaneous administration of GaAs and InAs particles to hamsters produces the induction of the major stress protein gene families in renal proximal tubule cells. This was monitored by 35-S methionine labeling of gene products followed by two-dimensional gel electrophoresis after exposure to InAs particles. The present studies examined whether these effects were associated with the development of compound-specific proteinuria after 10 or 30 days following subcutaneous injection of GaAs or InAs particles in hamsters. The results of these studies demonstrated the development of GaAs- and InAs-specific alterations in renal tubule cell protein expression patterns that varied at 10 and 30 days. At the 30-day point, cells in hamsters that received InAs particles showed marked attenuation of protein expression, suggesting inhibition of the stress protein response. These changes were associated with GaAs and InAs proteinuria patterns as monitored by two-dimensional gel electrophoresis and silver staining. The intensity of the protein excretion patterns increased between the 10- and 30-day points and was most pronounced for animals in the 30-day InAs treatment group. No overt morphologic signs of cell death were seen in renal tubule cells of these animals

  10. Quantitative STEM on indium containing group III-V semiconductor nanostructures

    International Nuclear Information System (INIS)

    Mehrtens, Thorsten

    2013-01-01

    In the framework of this thesis. a method for compositional analysis of semiconductor nanostructures is applied on technologically relevant group III-V alloys. It is based on a quantitative comparison between intensities of experimentally acquired High-Angle Annular Dark Field Scanning Tansmission Electron Microscopy (HAADF-STEM) images and simulated intensities from multislice calculations in the frozen lattice approach. The demonstrated method allows determination of specimen thickness and material composition on subnanometer scale. Since quantitative HAADF-STEM is still a very young technique, its applicability has only been proven for a few materials, yet. Thus, the main goal of this thesis is the simulation of suitable reference datasets for different ternary semiconducting alloys and to test their reliability by complementary analysis. A total of three different semiconducting materials are thereby analyzed (InGaN, InGaAs and InAlN) that have all in common that they contain indium. The main focus of this work lies on InGaN which is due to its bandgap particularly suitable for the fabrication of optoelectronic devices operating in the visible spectrum of the light. In the first part of the presented results, the quality of ultra-thin TEM-specimens prepared by techniques involving ion milling at high energies is optimized. This is done by an additional ion milling step where the impinging ions possess an energy of only 400 eV. It is found that the preparation induced amorphous surface layer that occurs during ion milling can be drastically reduced below 1 nm. The second part concentrates on results obtained on InGaN. Here, different simulations in the frozen lattice approach are carried out under certain conditions. These simulations either include or do not include thermal diffuse scattering and/or static atomic displacement to demonstrate their influence on the amount of intensity measured in the experiment. As the consideration of thermal diffuse scattering

  11. Understanding the vapor-liquid-solid growth and composition of ternary III-V nanowires and nanowire heterostructures

    Science.gov (United States)

    Dubrovskii, V. G.

    2017-11-01

    Based on the recent achievements in vapor-liquid-solid (VLS) synthesis, characterization and modeling of ternary III-V nanowires and axial heterostructures within such nanowires, we try to understand the major trends in their compositional evolution from a general theoretical perspective. Clearly, the VLS growth of ternary materials is much more complex than in standard vapor-solid epitaxy techniques, and even maintaining the necessary control over the composition of steady-state ternary nanowires is far from straightforward. On the other hand, VLS nanowires offer otherwise unattainable material combinations without introducing structural defects and hence are very promising for next-generation optoelectronic devices, in particular those integrated with a silicon electronic platform. In this review, we consider two main problems. First, we show how and by means of which parameters the steady-state composition of Au-catalyzed or self-catalyzed ternary III-V nanowires can be tuned to a desired value and why it is generally different from the vapor composition. Second, we present some experimental data and modeling results for the interfacial abruptness across axial nanowire heterostructures, both in Au-catalyzed and self-catalyzed VLS growth methods. Refined modeling allows us to formulate some general growth recipes for suppressing the unwanted reservoir effect in the droplet and sharpening the nanowire heterojunctions. We consider and refine two approaches developed to date, namely the regular crystallization model for a liquid alloy with a critical size of only one III-V pair at high supersaturations or classical binary nucleation theory with a macroscopic critical nucleus at modest supersaturations.

  12. Improved Electron Yield and Spin-Polarization from III-V Photocathodes via Bias Enhanced Carrier Drift: Final Report

    International Nuclear Information System (INIS)

    Mulhollan, Gregory A.

    2006-01-01

    In this DOE STTR program, Saxet Surface Science, with the Stanford Linear Accelerator Center as partner, designed, built and tested photocathode structures such that optimal drift-enhanced spin-polarization from GaAs based photoemitters was achieved with minimal bias supply requirements. The forward bias surface grid composition was optimized for maximum polarization and yield, together with other construction parameters including doping profile. This program has culminated in a cathode bias structure affording increased electron spin polarization when applied to III-V based photocathodes. The optimized bias structure has been incorporated into a cathode mounting and biasing design for use in a polarized electron gun.

  13. Factors affecting stress distribution and displacements in crystals III-V grown by Czochralski method with liquid encapsulation

    International Nuclear Information System (INIS)

    Schvezov, C.E.; Samarasekera, I.; Weinberg, F.

    1988-01-01

    A mathematical model based on the finite element method for calculating temperature and shear stress distributions in III-V crystals grown by LEC technique was developed. The calculated temperature are in good agreements with the experimental measurements. The shear stress distribution was calculated for several environmental conditions. The results showed that the magnitude and the distribution of shear stresses are highly sensitive to the crystal environment, including thickness and temperature distribution in boron oxides and the gas. The shear stress is also strongly influenced by interface curvature and cystals radius. (author) [pt

  14. 30 CFR 57.22202 - Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Main fans (I-A, I-B, I-C, II-A, III, V-A, and V... Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines). (a) Main fans shall be— (1) Installed on the... mines, provided with an automatic signal device to give an alarm when the fan stops. The signal device...

  15. Preservation of water samples for arsenic(III/V) determinations: An evaluation of the literature and new analytical results

    Science.gov (United States)

    McCleskey, R. Blaine; Nordstrom, D. Kirk; Maest, A.S.

    2004-01-01

    Published literature on preservation procedures for stabilizing aqueous inorganic As(III/V) redox species contains discrepancies. This study critically evaluates published reports on As redox preservation and explains discrepancies in the literature. Synthetic laboratory preservation experiments and time stability experiments were conducted for natural water samples from several field sites. Any field collection procedure that filters out microorganisms, adds a reagent that prevents dissolved Fe and Mn oxidation and precipitation, and isolates the sample from solar radiation will preserve the As(III/V) ratio. Reagents that prevent Fe and Mn oxidation and precipitation include HCl, H 2SO4, and EDTA, although extremely high concentrations of EDTA are necessary for some water samples high in Fe. Photo-catalyzed Fe(III) reduction causes As(III) oxidation; however, storing the sample in the dark prevents photochemical reactions. Furthermore, the presence of Fe(II) or SO 4 inhibits the oxidation of As(III) by Fe(III) because of complexation reactions and competing reactions with free radicals. Consequently, fast abiotic As(III) oxidation reactions observed in the laboratory are not observed in natural water samples for one or more of the following reasons: (1) the As redox species have already stabilized, (2) most natural waters contain very low dissolved Fe(III) concentrations, (3) the As(III) oxidation caused by Fe(III) photoreduction is inhibited by Fe(II) or SO4.

  16. Towards large size substrates for III-V co-integration made by direct wafer bonding on Si

    Directory of Open Access Journals (Sweden)

    N. Daix

    2014-08-01

    Full Text Available We report the first demonstration of 200 mm InGaAs-on-insulator (InGaAs-o-I fabricated by the direct wafer bonding technique with a donor wafer made of III-V heteroepitaxial structure grown on 200 mm silicon wafer. The measured threading dislocation density of the In0.53Ga0.47As (InGaAs active layer is equal to 3.5 × 109 cm−2, and it does not degrade after the bonding and the layer transfer steps. The surface roughness of the InGaAs layer can be improved by chemical-mechanical-polishing step, reaching values as low as 0.4 nm root-mean-square. The electron Hall mobility in 450 nm thick InGaAs-o-I layer reaches values of up to 6000 cm2/Vs, and working pseudo-MOS transistors are demonstrated with an extracted electron mobility in the range of 2000–3000 cm2/Vs. Finally, the fabrication of an InGaAs-o-I substrate with the active layer as thin as 90 nm is achieved with a Buried Oxide of 50 nm. These results open the way to very large scale production of III-V-o-I advanced substrates for future CMOS technology nodes.

  17. Towards large size substrates for III-V co-integration made by direct wafer bonding on Si

    Energy Technology Data Exchange (ETDEWEB)

    Daix, N., E-mail: dai@zurich.ibm.com; Uccelli, E.; Czornomaz, L.; Caimi, D.; Rossel, C.; Sousa, M.; Siegwart, H.; Marchiori, C.; Fompeyrine, J. [IBM Research - Zürich, Säumerstrasse 4, CH-8803 Rüschlikon (Switzerland); Hartmann, J. M. [CEA, LETI 17, rue des Martyrs, F-38054 Grenoble (France); Shiu, K.-T.; Cheng, C.-W.; Krishnan, M.; Lofaro, M.; Kobayashi, M.; Sadana, D. [IBM T. J. Watson Research Center, 1101 Kitchawan Rd., Route 134 Yorktown Heights, New York 10598 (United States)

    2014-08-01

    We report the first demonstration of 200 mm InGaAs-on-insulator (InGaAs-o-I) fabricated by the direct wafer bonding technique with a donor wafer made of III-V heteroepitaxial structure grown on 200 mm silicon wafer. The measured threading dislocation density of the In{sub 0.53}Ga{sub 0.47}As (InGaAs) active layer is equal to 3.5 × 10{sup 9} cm{sup −2}, and it does not degrade after the bonding and the layer transfer steps. The surface roughness of the InGaAs layer can be improved by chemical-mechanical-polishing step, reaching values as low as 0.4 nm root-mean-square. The electron Hall mobility in 450 nm thick InGaAs-o-I layer reaches values of up to 6000 cm{sup 2}/Vs, and working pseudo-MOS transistors are demonstrated with an extracted electron mobility in the range of 2000–3000 cm{sup 2}/Vs. Finally, the fabrication of an InGaAs-o-I substrate with the active layer as thin as 90 nm is achieved with a Buried Oxide of 50 nm. These results open the way to very large scale production of III-V-o-I advanced substrates for future CMOS technology nodes.

  18. Towards large size substrates for III-V co-integration made by direct wafer bonding on Si

    Science.gov (United States)

    Daix, N.; Uccelli, E.; Czornomaz, L.; Caimi, D.; Rossel, C.; Sousa, M.; Siegwart, H.; Marchiori, C.; Hartmann, J. M.; Shiu, K.-T.; Cheng, C.-W.; Krishnan, M.; Lofaro, M.; Kobayashi, M.; Sadana, D.; Fompeyrine, J.

    2014-08-01

    We report the first demonstration of 200 mm InGaAs-on-insulator (InGaAs-o-I) fabricated by the direct wafer bonding technique with a donor wafer made of III-V heteroepitaxial structure grown on 200 mm silicon wafer. The measured threading dislocation density of the In0.53Ga0.47As (InGaAs) active layer is equal to 3.5 × 109 cm-2, and it does not degrade after the bonding and the layer transfer steps. The surface roughness of the InGaAs layer can be improved by chemical-mechanical-polishing step, reaching values as low as 0.4 nm root-mean-square. The electron Hall mobility in 450 nm thick InGaAs-o-I layer reaches values of up to 6000 cm2/Vs, and working pseudo-MOS transistors are demonstrated with an extracted electron mobility in the range of 2000-3000 cm2/Vs. Finally, the fabrication of an InGaAs-o-I substrate with the active layer as thin as 90 nm is achieved with a Buried Oxide of 50 nm. These results open the way to very large scale production of III-V-o-I advanced substrates for future CMOS technology nodes.

  19. Preservation of water samples for arsenic(III/V) determinations: an evaluation of the literature and new analytical results

    International Nuclear Information System (INIS)

    McCleskey, R.Blaine; Nordstrom, D.Kirk; Maest, Ann S.

    2004-01-01

    Published literature on preservation procedures for stabilizing aqueous inorganic As(III/V) redox species contains discrepancies. This study critically evaluates published reports on As redox preservation and explains discrepancies in the literature. Synthetic laboratory preservation experiments and time stability experiments were conducted for natural water samples from several field sites. Any field collection procedure that filters out microorganisms, adds a reagent that prevents dissolved Fe and Mn oxidation and precipitation, and isolates the sample from solar radiation will preserve the As(III/V) ratio. Reagents that prevent Fe and Mn oxidation and precipitation include HCl, H 2 SO 4 , and EDTA, although extremely high concentrations of EDTA are necessary for some water samples high in Fe. Photo-catalyzed Fe(III) reduction causes As(III) oxidation; however, storing the sample in the dark prevents photochemical reactions. Furthermore, the presence of Fe(II) or SO 4 inhibits the oxidation of As(III) by Fe(III) because of complexation reactions and competing reactions with free radicals. Consequently, fast abiotic As(III) oxidation reactions observed in the laboratory are not observed in natural water samples for one or more of the following reasons: (1) the As redox species have already stabilized, (2) most natural waters contain very low dissolved Fe(III) concentrations, (3) the As(III) oxidation caused by Fe(III) photoreduction is inhibited by Fe(II) or SO 4

  20. An ultrahigh vacuum, low-energy ion-assisted deposition system for III-V semiconductor film growth

    Science.gov (United States)

    Rohde, S.; Barnett, S. A.; Choi, C.-H.

    1989-06-01

    A novel ion-assisted deposition system is described in which the substrate and growing film can be bombarded with high current densities (greater than 1 mA/sq cm) of very low energy (10-200 eV) ions. The system design philosophy is similar to that used in III-V semiconductor molecular-beam epitaxy systems: the chamber is an all-metal ultrahigh vacuum system with liquid-nitrogen-cooled shrouds, Knudsen-cell evaporation sources, a sample insertion load-lock, and a 30-kV reflection high-energy electron diffraction system. III-V semiconductor film growth is achieved using evaporated group-V fluxes and group-III elemental fluxes sputtered from high-purity targets using ions extracted from a triode glow discharge. Using an In target and an As effusion cell, InAs deposition rates R of 2 microns/h have been obtained. Epitaxial growth of InAs was observed on both GaSb(100) and Si(100) substrates.

  1. Development of III-V p-MOSFETs with high-kappa gate stack for future CMOS applications

    Science.gov (United States)

    Nagaiah, Padmaja

    As the semiconductor industry approaches the limits of traditional silicon CMOS scaling, non-silicon materials and new device architectures are gradually being introduced to improve Si integrated circuit performance and continue transistor scaling. Recently, the replacement of SiO2 with a high-k material (HfO2) as gate dielectric has essentially removed one of the biggest advantages of Si as channel material. As a result, alternate high mobility materials are being considered to replace Si in the channel to achieve higher drive currents and switching speeds. III-V materials in particular have become of great interest as channel materials, owing to their superior electron transport properties. However, there are several critical challenges that need to be addressed before III-V based CMOS can replace Si CMOS technology. Some of these challenges include development of a high quality, thermally stable gate dielectric/III-V interface, and improvement in III-V p-channel hole mobility to complement the n-channel mobility, low source/drain resistance and integration onto Si substrate. In this thesis, we would be addressing the first two issues i.e. the development high performance III-V p-channels and obtaining high quality III-V/high-k interface. We start with using the device architecture of the already established InGaAs n-channels as a baseline to understand the effect of remote scattering from the high-k oxide and oxide/semiconductor interface on channel transport properties such as electron mobility and channel electron concentration. Temperature dependent Hall electron mobility measurements were performed to separate various scattering induced mobility limiting factors. Dependence of channel mobility on proximity of the channel to the oxide interface, oxide thickness, annealing conditions are discussed. The results from this work will be used in the design of the p-channel MOSFETs. Following this, InxGa1-xAs (x>0.53) is chosen as channel material for developing p

  2. Photon confinement in high-efficiency, thin-film III-V solar cells obtained by epitaxial lift-off

    International Nuclear Information System (INIS)

    Schermer, J.J.; Bauhuis, G.J.; Mulder, P.; Haverkamp, E.J.; Deelen, J. van; Niftrik, A.T.J. van; Larsen, P.K.

    2006-01-01

    Using the epitaxial lift-off (ELO) technique, a III-V device structure can be separated from its GaAs substrate by selective wet etching of a thin release layer. The thin-film structures obtained by the ELO process can be cemented or van der Waals bonded on arbitrary smooth surface carriers for further processing. It is shown that the ELO method, initially able to separate millimetre-sized GaAs layers with a lateral etch rate of about 1 mm/h, has been developed to a process capable to free the entire 2-in. epitaxial structures from their substrates with etch rates up to 30 mm/h. With these characteristics the method has a large potential for the production of high efficiency thin-film solar cells. By choosing the right deposition and ELO strategy, the thin-film III-V cells can be adequately processed on both sides allowing for an entire range of new cell structures. In the present work, the performance of semi-transparent bifacial solar cells, produced by the deposition of metal grid contacts on both sides, was evaluated. Reflection of light at the rear side of the bifacial GaAs solar cells was found to result in an enhanced collection probability of the photon-induced carriers compared to that of regular III-V cells on a GaAs substrate. To enhance this effect, thin-film GaAs cells with gold mirror back contacts were prepared. Even in their present premature stage of development, these single-junction thin-film cells reached a record efficiency of 24.5% which is already very close to the 24.9% efficiency that was obtained with a regular GaAs cell on a GaAs substrate. From this it could be concluded that, as a result of the photon confinement, ELO cells require a significantly thinner base layer than regular GaAs cells while at the same time they have the potential to reach a higher efficiency

  3. Substrate effects on the formation of flat Ag films on (110) surfaces of III-V compound semiconductors

    International Nuclear Information System (INIS)

    Chao, K.; Zhang, Z.; Ebert, P.; Shih, C.K.

    1999-01-01

    Ag films grown at 135 K on (110) surfaces of III-V compound semiconductors and annealed at room temperature are investigated by scanning tunneling microscopy and low-energy electron diffraction. Ag films on Ga-V semiconductors are well ordered, atomically flat, and exhibit a specific critical thickness, which is a function of the substrate material. Films grown on In-V semiconductors are still rather flat, but significantly more disordered. The (111) oriented Ag films on III-arsenides and III-phosphides exhibit a clear twofold superstructure. Films on III-antimonides exhibit threefold low-energy electron diffraction images. The morphology of the Ag films can be explained on the basis of the electronic growth mechanism. copyright 1999 The American Physical Society

  4. The Role of III-V Substrate Roughness and Deoxidation Induced by Digital Etch in Achieving Low Resistance Metal Contacts

    Directory of Open Access Journals (Sweden)

    Florent Ravaux

    2017-06-01

    Full Text Available To achieve low contact resistance between metal and III-V material, transmission-line-model (TLM structures of molybdenum (Mo were fabricated on indium phosphide (InP substrate on the top of an indium gallium arsenide (InGaAs layer grown by molecular beam epitaxy. The contact layer was prepared using a digital etch procedure before metal deposition. The contact resistivity was found to decrease significantly with the cleaning process. High Resolution Transmission & Scanning Electron Microscopy (HRTEM & HRSTEM investigations revealed that the surface roughness of treated samples was increased. Further analysis of the metal-semiconductor interface using Energy Electron Loss Spectroscopy (EELS showed that the amount of oxides (InxOy, GaxOy or AsxOy was significantly decreased for the etched samples. These results suggest that the low contact resistance obtained after digital etching is attributed to the combined effects of the induced surface roughness and oxides removal during the digital etch process.

  5. Broadband microwave photonic fully tunable filter using a single heterogeneously integrated III-V/SOI-microdisk-based phase shifter.

    Science.gov (United States)

    Lloret, Juan; Morthier, Geert; Ramos, Francisco; Sales, Salvador; Van Thourhout, Dries; Spuesens, Thijs; Olivier, Nicolas; Fédéli, Jean-Marc; Capmany, José

    2012-05-07

    A broadband microwave photonic phase shifter based on a single III-V microdisk resonator heterogeneously integrated on and coupled to a nanophotonic silicon-on-insulator waveguide is reported. The phase shift tunability is accomplished by modifying the effective index through carrier injection. A comprehensive semi-analytical model aiming at predicting its behavior is formulated and confirmed by measurements. Quasi-linear and continuously tunable 2π phase shifts at radiofrequencies greater than 18 GHz are experimentally demonstrated. The phase shifter performance is also evaluated when used as a key element in tunable filtering schemes. Distortion-free and wideband filtering responses with a tuning range of ~100% over the free spectral range are obtained.

  6. Pesan Sosial dalam Foto Jurnalistik (Analisis Semiotika dalam Buku ‘Jakarta Estetika Banal’, Bab I, III, V, dan VII

    Directory of Open Access Journals (Sweden)

    Jaka Priyo Nuswantara

    2014-01-01

    Full Text Available This study aims to determine the meaning of denotation and connotation, and social message in the book 'Aesthetics Jakarta Banal', Chapter I, III, V, and VII. The author uses the theory Semiotics of Roland Barthes. Where Semiotics of Roland Barthes uses two stages of analysis denotation and connotation. The research method used is a Roland Barthes semiotic analysis method on the basis that this study analyzes the messages conveyed in the book 'Aesthetics Jakarta Banal', which gives an explanation and overview of issues related to the formulation. Inferred outline text analysis results indicate that the social life of silence in the city with the concept of light to be seen. Of all the images examined, the object edges and political society into something dominant to be something that should be understood by the reader.

  7. Analysis of the Si(111) surface prepared in chemical vapor ambient for subsequent III-V heteroepitaxy

    International Nuclear Information System (INIS)

    Zhao, W.; Steidl, M.; Paszuk, A.; Brückner, S.; Dobrich, A.; Supplie, O.; Kleinschmidt, P.; Hannappel, T.

    2017-01-01

    Highlights: • We investigate the Si(111) surface prepared in CVD ambient at 1000 °C in 950 mbar H_2. • UHV-based XPS, LEED, STM and FTIR as well as ambient AFM are applied. • After processing the Si(111) surface is free of contamination and atomically flat. • The surface exhibits a (1 × 1) reconstruction and monohydride termination. • Wet-chemical pretreatment and homoepitaxy are required for a regular step structure. - Abstract: For well-defined heteroepitaxial growth of III-V epilayers on Si(111) substrates the atomic structure of the silicon surface is an essential element. Here, we study the preparation of the Si(111) surface in H_2-based chemical vapor ambient as well as its atomic structure after contamination-free transfer to ultrahigh vacuum (UHV). Applying complementary UHV-based techniques, we derive a complete picture of the atomic surface structure and its chemical composition. X-ray photoelectron spectroscopy measurements after high-temperature annealing confirm a Si surface free of any traces of oxygen or other impurities. The annealing in H_2 ambient leads to a monohydride surface termination, as verified by Fourier-transform infrared spectroscopy. Scanning tunneling microscopy confirms a well ordered, atomically smooth surface, which is (1 × 1) reconstructed, in agreement with low energy electron diffraction patterns. Atomic force microscopy reveals a significant influence of homoepitaxy and wet-chemical pretreatment on the surface morphology. Our findings show that wet-chemical pretreatment followed by high-temperature annealing leads to contamination-free, atomically flat Si(111) surfaces, which are ideally suited for subsequent III-V heteroepitaxy.

  8. Analysis of the Si(111) surface prepared in chemical vapor ambient for subsequent III-V heteroepitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, W.; Steidl, M.; Paszuk, A. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Brückner, S. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Helmholtz-Zentrum Berlin, Institut für Solare Brennstoffe, 14109 Berlin (Germany); Dobrich, A. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Supplie, O. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Helmholtz-Zentrum Berlin, Institut für Solare Brennstoffe, 14109 Berlin (Germany); Kleinschmidt, P. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Hannappel, T., E-mail: thomas.hannappel@tu-ilmenau.de [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Helmholtz-Zentrum Berlin, Institut für Solare Brennstoffe, 14109 Berlin (Germany)

    2017-01-15

    Highlights: • We investigate the Si(111) surface prepared in CVD ambient at 1000 °C in 950 mbar H{sub 2}. • UHV-based XPS, LEED, STM and FTIR as well as ambient AFM are applied. • After processing the Si(111) surface is free of contamination and atomically flat. • The surface exhibits a (1 × 1) reconstruction and monohydride termination. • Wet-chemical pretreatment and homoepitaxy are required for a regular step structure. - Abstract: For well-defined heteroepitaxial growth of III-V epilayers on Si(111) substrates the atomic structure of the silicon surface is an essential element. Here, we study the preparation of the Si(111) surface in H{sub 2}-based chemical vapor ambient as well as its atomic structure after contamination-free transfer to ultrahigh vacuum (UHV). Applying complementary UHV-based techniques, we derive a complete picture of the atomic surface structure and its chemical composition. X-ray photoelectron spectroscopy measurements after high-temperature annealing confirm a Si surface free of any traces of oxygen or other impurities. The annealing in H{sub 2} ambient leads to a monohydride surface termination, as verified by Fourier-transform infrared spectroscopy. Scanning tunneling microscopy confirms a well ordered, atomically smooth surface, which is (1 × 1) reconstructed, in agreement with low energy electron diffraction patterns. Atomic force microscopy reveals a significant influence of homoepitaxy and wet-chemical pretreatment on the surface morphology. Our findings show that wet-chemical pretreatment followed by high-temperature annealing leads to contamination-free, atomically flat Si(111) surfaces, which are ideally suited for subsequent III-V heteroepitaxy.

  9. III-V/Si Tandem Cells Utilizing Interdigitated Back Contact Si Cells and Varying Terminal Configurations: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Schnabel, Manuel; Klein, Talysa R.; Jain, Nikhil; Essig, Stephanie; Schulte-Huxel, Henning; Warren, Emily; van Hest, Maikel F. A. M.; Geisz, John; Stradins, Paul; Tamboli, Adele; Rienacker, Michael; Merkle, Agnes; Schmidt, Jan; Brendel, Rolf; Peibst, Robby

    2017-07-11

    Solar cells made from bulk crystalline silicon (c-Si) dominate the market, but laboratory efficiencies have stagnated because the current record efficiency of 26.3% is already very close to the theoretical limit of 29.4% for a single-junction c-Si cell. In order to substantially boost the efficiency of Si solar cells we have been developing stacked III-V/Si tandem cells, recently attaining efficiencies above 32% in four-terminal configuration. In this contribution, we use state-of-the-art III-V cells coupled with equivalent circuit simulations to compare four-terminal (4T) to three- and two-terminal (3T, 2T) operation. Equivalent circuit simulations are used to show that tandem cells can be operated just as efficiently using three terminals as with four terminals. However, care must be taken not to overestimate 3T efficiency, as the two circuits used to extract current interact, and a method is described to accurately determine this efficiency. Experimentally, a 4T GaInP/Si tandem cell utilizing an interdigitated back contact cell is shown, exhibiting a 4T efficiency of 31.5% and a 2T efficiency of 28.1%. In 3T configuration, it is used to verify the finding from simulation that 3T efficiency is overestimated when interactions between the two circuits are neglected. Considering these, a 3T efficiency approaching the 4T efficiency is found, showing that 3T operation is efficient, and an outlook on fully integrated high-efficiency 3T and 2T tandem cells is given.

  10. High-performance III-V MOSFET with nano-stacked high-k gate dielectric and 3D fin-shaped structure.

    Science.gov (United States)

    Chen, Szu-Hung; Liao, Wen-Shiang; Yang, Hsin-Chia; Wang, Shea-Jue; Liaw, Yue-Gie; Wang, Hao; Gu, Haoshuang; Wang, Mu-Chun

    2012-08-01

    A three-dimensional (3D) fin-shaped field-effect transistor structure based on III-V metal-oxide-semiconductor field-effect transistor (MOSFET) fabrication has been demonstrated using a submicron GaAs fin as the high-mobility channel. The fin-shaped channel has a thickness-to-width ratio (TFin/WFin) equal to 1. The nano-stacked high-k Al2O3 dielectric was adopted as a gate insulator in forming a metal-oxide-semiconductor structure to suppress gate leakage. The 3D III-V MOSFET exhibits outstanding gate controllability and shows a high Ion/Ioff ratio > 105 and a low subthreshold swing of 80 mV/decade. Compared to a conventional Schottky gate metal-semiconductor field-effect transistor or planar III-V MOSFETs, the III-V MOSFET in this work exhibits a significant performance improvement and is promising for future development of high-performance n-channel devices based on III-V materials.

  11. High-Throughput Multiple Dies-to-Wafer Bonding Technology and III/V-on-Si Hybrid Lasers for Heterogeneous Integration of Optoelectronic Integrated Circuits

    Directory of Open Access Journals (Sweden)

    Xianshu eLuo

    2015-04-01

    Full Text Available Integrated optical light source on silicon is one of the key building blocks for optical interconnect technology. Great research efforts have been devoting worldwide to explore various approaches to integrate optical light source onto the silicon substrate. The achievements so far include the successful demonstration of III/V-on-Si hybrid lasers through III/V-gain material to silicon wafer bonding technology. However, for potential large-scale integration, leveraging on mature silicon complementary metal oxide semiconductor (CMOS fabrication technology and infrastructure, more effective bonding scheme with high bonding yield is in great demand considering manufacturing needs. In this paper, we propose and demonstrate a high-throughput multiple dies-to-wafer (D2W bonding technology which is then applied for the demonstration of hybrid silicon lasers. By temporarily bonding III/V dies to a handle silicon wafer for simultaneous batch processing, it is expected to bond unlimited III/V dies to silicon device wafer with high yield. As proof-of-concept, more than 100 III/V dies bonding to 200 mm silicon wafer is demonstrated. The high performance of the bonding interface is examined with various characterization techniques. Repeatable demonstrations of 16-III/V-die bonding to pre-patterned 200 mm silicon wafers have been performed for various hybrid silicon lasers, in which device library including Fabry-Perot (FP laser, lateral-coupled distributed feedback (LC-DFB laser with side wall grating, and mode-locked laser (MLL. From these results, the presented multiple D2W bonding technology can be a key enabler towards the large-scale heterogeneous integration of optoelectronic integrated circuits (H-OEIC.

  12. New insights into thorium and uranium oxo-arsenic (III/V) and oxo-phosphates (V) crystal chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Na

    2015-12-11

    The fundamental chemistry of actinides is of great interest owing to the diverse number of valence states and complex coordination chemistry of the actinides. The phases based on actinides and oxo-salt fragments have been under thorough investigation in the last decades. These compounds can be widely found in nature and they affect the migration process of actinides in nature. A better understanding of the fundamental coordination chemistry of actinide compounds with oxo-salts of group V elements is not only important for understanding the actinides behavior within the migration process but can also be used to understand actinide properties in phosphate ceramics. Concerning the radioactive issues, the less radioactive early actinides (i.e. U, Th) can be taken as modeling elements to study the crystal chemistry of the transuranic elements (Np, Pu) without the major handling problems. This can be done as Th(IV) has a very similar coordination chemistry with An(IV) and U(VI) can be chosen as a modeling element for transuranic elements in higher valence states. Therefore, a systematic research on the actinides (U, Th) bearing phases with tetrahedral oxo-anions such as phosphates and arsenates have been performed in this work. High temperature (HT) solid state reaction, High pressure high temperature (HP-HT) solid state reaction and the hydrothermal method were the methods of choice for synthesizing actinide bearing oxo-arsenic(III/V) and oxo- phosphorus(V) phases in the past three years. As a result, numerous novel compounds containing actinides were obtained. The structures of all compounds were determined using single crystal X-ray diffraction data. Raman spectroscopy, EDS, DSC and high temperature powder X-ray diffraction (HT-PXRD) measurements were implemented to characterize the chemical and physical properties of the obtained compounds. The core of this dissertation is a fundamental study of the crystal chemistry of actinides (Th, U) oxo-arsenic (III/V) and oxo

  13. New insights into thorium and uranium oxo-arsenic (III/V) and oxo-phosphates (V) crystal chemistry

    International Nuclear Information System (INIS)

    Yu, Na

    2015-01-01

    The fundamental chemistry of actinides is of great interest owing to the diverse number of valence states and complex coordination chemistry of the actinides. The phases based on actinides and oxo-salt fragments have been under thorough investigation in the last decades. These compounds can be widely found in nature and they affect the migration process of actinides in nature. A better understanding of the fundamental coordination chemistry of actinide compounds with oxo-salts of group V elements is not only important for understanding the actinides behavior within the migration process but can also be used to understand actinide properties in phosphate ceramics. Concerning the radioactive issues, the less radioactive early actinides (i.e. U, Th) can be taken as modeling elements to study the crystal chemistry of the transuranic elements (Np, Pu) without the major handling problems. This can be done as Th(IV) has a very similar coordination chemistry with An(IV) and U(VI) can be chosen as a modeling element for transuranic elements in higher valence states. Therefore, a systematic research on the actinides (U, Th) bearing phases with tetrahedral oxo-anions such as phosphates and arsenates have been performed in this work. High temperature (HT) solid state reaction, High pressure high temperature (HP-HT) solid state reaction and the hydrothermal method were the methods of choice for synthesizing actinide bearing oxo-arsenic(III/V) and oxo- phosphorus(V) phases in the past three years. As a result, numerous novel compounds containing actinides were obtained. The structures of all compounds were determined using single crystal X-ray diffraction data. Raman spectroscopy, EDS, DSC and high temperature powder X-ray diffraction (HT-PXRD) measurements were implemented to characterize the chemical and physical properties of the obtained compounds. The core of this dissertation is a fundamental study of the crystal chemistry of actinides (Th, U) oxo-arsenic (III/V) and oxo

  14. Pressure-induced structural change of liquid InAs and the systematics of liquid III-V compounds

    International Nuclear Information System (INIS)

    Hattori, T.; Tsuji, K.; Miyata, Y.; Sugahara, T.; Shimojo, F.

    2007-01-01

    To understand the pressure-induced structural changes of liquid III-V compounds systematically, the pressure dependence of l-InAs was investigated using the synchrotron x-ray diffraction and an ab initio molecular-dynamics simulation (AIMD). The x-ray diffraction experiments revealed that the liquid changes its compression behavior from a nearly uniform type to a nonuniform one around 9 GPa. Corresponding to this change, the coordination number (China), which is maintained up to 9 GPa, markedly increases from 6.0 to 7.5. The AIMD simulation revealed that this change is related to the change in the pressure dependence of all three pair correlations. In particular, a marked change is observed in the As-As correlation; in the low-pressure region, the position of the first peak in g AsAs (r), r AsAs , increases while maintaining the CN AsAs , but in the high-pressure region, the r AsAs stops increasing and the CN AsAs begins to increase. The AIMD simulation also revealed that each partial structure of l-InAs is similar to that for the pure-element liquid with the same valence electron number. Upon compression, each partial structure approaches the respective one for a heavier element in the same group. These findings suggest that the structures of liquid compounds are locally controlled by the number of the valence electrons in each ion pair and that the change in each partial structure obeys the empirical rule that the high-pressure state resembles the ambient state of a heavier element in the same group. Comparing the pressure-induced structural change of l-InAs to those of other liquid III-V compounds (GaSb and InSb) has revealed that, although the high-pressure behaviors of these three liquids are apparently different, their structural changes are systematically understood by a common structural sequence. This systematics originates from the same effect on each partial structure between increasing the atomic number and the pressurization

  15. Study of the transport phenomena in III-V materials by the Monte Carlo method: application to INAS

    International Nuclear Information System (INIS)

    Bouazza, B.; Amer, L.; Guen-Bouazza, A.; Sayeh, C.; Chabanne-Sari, N.E.; Gontrand, C.

    2004-01-01

    Full text.The microelectronic comprehension of the phenomena which describes the behavior of the carriers in semiconductor materials requires the knowledge of energy distribution function. This distribution function is obtained by the resolution of Boltzmann equation which is very hard to solve analytically. Other methods based on modeling are actually successfully used to solve this equation. This Monte Carlo method is among of the most methods used for studying electronics components operations. It consists to follow the evolution of electron packets in real space, where each electron subjected to the electric field present in material goes interact with the crystal lattice. It is therefore an iterative process made up from a whole coasting flights stopped by acoustics interactions, polar and non polar optics, piezoelectric, inter-valley, impurity, ionization and surface. By applying this method to the III-V material: InAs. We can describe the behavior of the carriers from dynamic and energetic point of view (variation speed according to the field). The simulation is applied, taking into account variation of the carriers according to time in the non stationary mode, and the effect of temperature, and measurements doping. Results obtained are shown to be comparable to those of the theory

  16. Proteomic and metabolomic biomarkers for III-V semiconductors: And prospects for application to nano-materials

    International Nuclear Information System (INIS)

    Fowler, Bruce A.; Conner, Elizabeth A.; Yamauchi, Hiroshi

    2008-01-01

    There has been an increased appreciation over the last 20 years that chemical agents at very low dose levels can produce biological responses in protein expression patterns (proteomic responses) or alterations in sensitive metabolic pathways (metabolomic responses). Marked improvements in analytical methodologies, such as 2-D gel electrophoresis, matrix-assisted laser desorption-time of flight (MALDI-TOF) and surface enhanced laser desorption-time of flight (SELDI-TOF) technologies are capable of identifying specific protein patterns related to exposure to chemicals either alone or as mixtures. The detection and interpretation of early cellular responses to chemical agents have also made great advances through correlative ultrastructural morphometric and biochemical studies. Similarly, advances in analytical technologies such as HPLC, proton NMR, MALDI-TOF, and SELDI-TOF have permitted early detection of changes in a number of essential metabolic pathways following chemical exposures by measurement of alterations in metabolic products from those pathways. Data from these approaches are increasingly regarded as potentially useful biomarkers of chemical exposure and early cellular responses. Validation and establishment of linkages to biological outcomes are needed in order for biomarkers of effect to be established. This short review will cover a number of the above techniques and report data from chemical exposures to two binary III-V semiconductor compounds to illustrate gender differences in proteomic responses. In addition, the use of these methodologies in relation to rapid safety evaluations of nanotechnology products will be discussed. (Supported in part by NIH R01-ES4879)

  17. Two Dimensional Effective Electron Mass at the Fermi Level in Quantum Wells of III-V, Ternary and Quaternary Semiconductors.

    Science.gov (United States)

    Chakrabarti, S; Chatterjee, B; Debbarma, S; Ghatak, K P

    2015-09-01

    In this paper we study the influence of strong electric field on the two dimensional (2D)effective electron mass (EEM) at the Fermi level in quantum wells of III-V, ternary and quaternary semiconductors within the framework of k x p formalism by formulating a new 2D electron energy spectrum. It appears taking quantum wells of InSb, InAs, Hg(1-x)Cd(x)Te and In(1-x)Ga(x)As(1-y)P(y) lattice matched to InP as examples that the EEM increases with decreasing film thickness, increasing electric field and increases with increasing surface electron concentration exhibiting spikey oscillations because of the crossing over of the Fermi level by the quantized level in quantum wells and the quantized oscillation occurs when the Fermi energy touches the sub-band energy. The electric field makes the mass quantum number dependent and the oscillatory mass introduces quantum number dependent mass anisotropy in addition to energy. The EEM increases with decreasing alloy composition where the variations are totally band structure dependent. Under certain limiting conditions all the results for all the cases get simplified into the well-known parabolic energy bands and thus confirming the compatibility test. The content of this paper finds three applications in the fields of nano-science and technology.

  18. Atomic scale images of acceptors in III-V semiconductors. Band bending, tunneling paths and wave functions

    Energy Technology Data Exchange (ETDEWEB)

    Loth, S.

    2007-10-26

    This thesis reports measurements of single dopant atoms in III-V semiconductors with low temperature Scanning Tunneling Microscopy (STM) and Scanning Tunneling Spectroscopy (STS). It investigates the anisotropic spatial distribution of acceptor induced tunneling processes at the {l_brace}110{r_brace} cleavage planes. Two different tunneling processes are identified: conventional imaging of the squared acceptor wave function and resonant tunneling at the charged acceptor. A thorough analysis of the tip induced space charge layers identifies characteristic bias windows for each tunnel process. The symmetry of the host crystal's band structure determines the spatial distribution of the tunneling paths for both processes. Symmetry reducing effects at the surface are responsible for a pronounced asymmetry of the acceptor contrasts along the principal [001] axis. Uniaxial strain fields due to surface relaxation and spin orbit interaction of the tip induced electric field are discussed on the basis of band structure calculations. High-resolution STS studies of acceptor atoms in an operating p-i-n diode confirm that an electric field indeed changes the acceptor contrasts. In conclusion, the anisotropic contrasts of acceptors are created by the host crystal's band structure and concomitant symmetry reduction effects at the surface. (orig.)

  19. Exploiting strain to enhance the Bi incorporation in GaAs-based III/V semiconductors using MOVPE

    Science.gov (United States)

    Nattermann, L.; Ludewig, P.; Sterzer, E.; Volz, K.

    2017-07-01

    Bi containing III/V semiconductors are frequently mentioned for their importance as part of the next generation of optoelectronic devices. Bi containing ternary and quaternary materials like Ga(AsBi), Ga(NAsBi) or Ga(PAsBi) are promising candidates to meet the requirements for new laser structures for telecommunications and solar cell applications. However, in previous studies it was determined that the incorporation of sufficient amounts of Bi still poses a challenge, especially when using MOVPE (metalorganic vapour phase epitaxy) as the growth technique. In order to figure out which mechanisms are responsible for the limitation of Bi incorporation, this work deals with the question of whether there is a relationship between strain, induced by the large Bi atoms, and the saturation level of Bi incorporation in Ga(AsBi). Ga(NAsBi) structures were grown by MOVPE at a low temperature, 400 °C, and compared to Ga(PAsBi) as well as Ga(AsBi) growth. By using the two group V atoms P and N, which have a smaller covalent radius than Bi, the effect of local strain compensation was investigated systematically. The comparison of Bi incorporation in the two quaternary materials systems proved the importance of local strain for the limitation of Bi incorporation, in addition to other effects, like Bi surface coverage and hydrocarbon groups at the growth surface. This, of course, also opens up ways to strain-state-engineer the Bi incorporation in semiconductor alloys.

  20. Controlling and modelling the wetting properties of III-V semiconductor surfaces using re-entrant nanostructures.

    Science.gov (United States)

    Ng, Wing H; Lu, Yao; Liu, Huiyun; Carmalt, Claire J; Parkin, Ivan P; Kenyon, Anthony J

    2018-02-23

    Inorganic semiconductors such as III-V materials are very important in our everyday life as they are used for manufacturing optoelectronic and microelectronic components with important applications span from energy harvesting to telecommunications. In some applications, these components are required to operate in harsh environments. In these cases, having waterproofing capability is essential. Here we demonstrate design and control of the wettability of indium phosphide based multilayer material (InP/InGaAs/InP) using re-entrant structures fabricated by a fast electron beam lithography technique. This patterning technique enabled us to fabricate highly uniform nanostructure arrays with at least one order of magnitude shorter patterning times compared to conventional electron beam lithography methods. We reduced the surface contact fraction significantly such that the water droplets may be completely removed from our nanostructured surface. We predicted the wettability of our patterned surface by modelling the adhesion energies between the water droplet and both the patterned surface and the dispensing needle. This is very useful for the development of coating-free waterproof optoelectronic and microelectronic components where the coating may hinder the performance of such devices and cause problems with semiconductor fabrication compatibility.

  1. Ion beam nanopatterning of III-V semiconductors: consistency of experimental and simulation trends within a chemistry-driven theory.

    Science.gov (United States)

    El-Atwani, O; Norris, S A; Ludwig, K; Gonderman, S; Allain, J P

    2015-12-16

    Several proposed mechanisms and theoretical models exist concerning nanostructure evolution on III-V semiconductors (particularly GaSb) via ion beam irradiation. However, making quantitative contact between experiment on the one hand and model-parameter dependent predictions from different theories on the other is usually difficult. In this study, we take a different approach and provide an experimental investigation with a range of targets (GaSb, GaAs, GaP) and ion species (Ne, Ar, Kr, Xe) to determine new parametric trends regarding nanostructure evolution. Concurrently, atomistic simulations using binary collision approximation over the same ion/target combinations were performed to determine parametric trends on several quantities related to existing model. A comparison of experimental and numerical trends reveals that the two are broadly consistent under the assumption that instabilities are driven by chemical instability based on phase separation. Furthermore, the atomistic simulations and a survey of material thermodynamic properties suggest that a plausible microscopic mechanism for this process is an ion-enhanced mobility associated with energy deposition by collision cascades.

  2. Nonradiative lifetime extraction using power-dependent relative photoluminescence of III-V semiconductor double-heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Walker, A. W., E-mail: alexandre.walker@ise.fraunhofer.de; Heckelmann, S.; Karcher, C.; Höhn, O.; Went, C.; Niemeyer, M.; Bett, A. W.; Lackner, D. [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, 79110 Freiburg (Germany)

    2016-04-21

    A power-dependent relative photoluminescence measurement method is developed for double-heterostructures composed of III-V semiconductors. Analyzing the data yields insight into the radiative efficiency of the absorbing layer as a function of laser intensity. Four GaAs samples of different thicknesses are characterized, and the measured data are corrected for dependencies of carrier concentration and photon recycling. This correction procedure is described and discussed in detail in order to determine the material's Shockley-Read-Hall lifetime as a function of excitation intensity. The procedure assumes 100% internal radiative efficiency under the highest injection conditions, and we show this leads to less than 0.5% uncertainty. The resulting GaAs material demonstrates a 5.7 ± 0.5 ns nonradiative lifetime across all samples of similar doping (2–3 × 10{sup 17 }cm{sup −3}) for an injected excess carrier concentration below 4 × 10{sup 12 }cm{sup −3}. This increases considerably up to longer than 1 μs under high injection levels due to a trap saturation effect. The method is also shown to give insight into bulk and interface recombination.

  3. Error-free Dispersion-uncompensated Transmission at 20 Gb/s over SSMF using a Hybrid III-V/SOI DML with MRR Filtering

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Kamchevska, Valerija; Ding, Yunhong

    2016-01-01

    Error-free 20-Gb/s directly-modulated transmission is achieved by enhancing the dispersion tolerance of a III-V/SOI DFB laser with a silicon micro-ring resonator. Low (∼0.4 dB) penalty compared to back-to-back without ring is demonstrated after 5-km SSMF....

  4. Silicon photonics fiber-to-the-home transceiver array based on transfer-printing-based integration of III-V photodetectors.

    Science.gov (United States)

    Zhang, Jing; De Groote, Andreas; Abbasi, Amin; Loi, Ruggero; O'Callaghan, James; Corbett, Brian; Trindade, António José; Bower, Christopher A; Roelkens, Gunther

    2017-06-26

    A 4-channel silicon photonics transceiver array for Point-to-Point (P2P) fiber-to-the-home (FTTH) optical networks at the central office (CO) side is demonstrated. A III-V O-band photodetector array was integrated onto the silicon photonic transmitter through transfer printing technology, showing a polarization-independent responsivity of 0.39 - 0.49 A/W in the O-band. The integrated PDs (30 × 40 μm 2 mesa) have a 3 dB bandwidth of 11.5 GHz at -3 V bias. Together with high-speed C-band silicon ring modulators whose bandwidth is up to 15 GHz, operation of the transceiver array at 10 Gbit/s is demonstrated. The use of transfer printing for the integration of the III-V photodetectors allows for an efficient use of III-V material and enables the scalable integration of III-V devices on silicon photonics wafers, thereby reducing their cost.

  5. Characteristics of an Electron Cyclotron Resonance Plasma Source for the Production of Active Nitrogen Species in III-V Nitride Epitaxy

    Science.gov (United States)

    Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

    1997-01-01

    A simple analysis is provided to determine the characteristics of an electron cyclotron resonance (ECR) plasma source for the generation of active nitrogen species in the molecular beam epitaxy of III-V nitrides. The effects of reactor geometry, pressure, power, and flow rate on the dissociation efficiency and ion flux are presented. Pulsing the input power is proposed to reduce the ion flux.

  6. Comprehension of Postmetallization Annealed MOCVD-TiO2 on (NH42S Treated III-V Semiconductors

    Directory of Open Access Journals (Sweden)

    Ming-Kwei Lee

    2012-01-01

    Full Text Available The electrical characteristics of TiO2 films grown on III-V semiconductors (e.g., p-type InP and GaAs by metal-organic chemical vapor deposition were studied. With (NH42S treatment, the electrical characteristics of MOS capacitors are improved due to the reduction of native oxides. The electrical characteristics can be further improved by the postmetallization annealing, which causes hydrogen atomic ion to passivate defects and the grain boundary of polycrystalline TiO2 films. For postmetallization annealed TiO2 on (NH42S treated InP MOS, the leakage current densities can reach 2.7 × 10−7 and 2.3 × 10−7 A/cm2 at ±1 MV/cm, respectively. The dielectric constant and effective oxide charges are 46 and 1.96 × 1012 C/cm2, respectively. The interface state density is 7.13×1011 cm−2 eV−1 at the energy of 0.67 eV from the edge of valence band. For postmetallization annealed TiO2 on (NH42S treated GaAs MOS, The leakage current densities can reach 9.7×10−8 and 1.4×10−7 at ±1 MV/cm, respectively. The dielectric constant and effective oxide charges are 66 and 1.86×1012 C/cm2, respectively. The interface state density is 5.96×1011 cm−2 eV−1 at the energy of 0.7 eV from the edge of valence band.

  7. Influence of light waves on the thermoelectric power under large magnetic field in III-V, ternary and quaternary materials

    Energy Technology Data Exchange (ETDEWEB)

    Ghatak, K.P. [Department of Electronic Science, The University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Bhattacharya, S. [Post Graduate Department of Computer Science, St. Xavier' s College, 30 Park Street, Kolkata 700 016 (India); Pahari, S. [Department of Administration, Jadavpur University, Kolkata 700 032 (India); De, D. [Department of Computer Science and Engineering, West Bengal University of Technology, B. F. 142, Sector I, Salt Lake, Kolkata 700 064 (India); Ghosh, S.; Mitra, M. [Department of Electronics and Telecommunication Engineering, Bengal Engineering and Science University, Howrah 711 103 (India)

    2008-04-15

    We study theoretically the influence of light waves on the thermoelectric power under large magnetic field (TPM) for III-V, ternary and quaternary materials, whose unperturbed energy-band structures, are defined by the three-band model of Kane. The solution of the Boltzmann transport equation on the basis of this newly formulated electron dispersion law will introduce new physical ideas and experimental findings in the presence of external photoexcitation. It has been found by taking n-InAs, n-InSb, n-Hg{sub 1-x}Cd{sub x}Te and n-In{sub 1-x}Ga{sub x}As{sub y}P{sub 1-y} lattice matched to InP as examples that the TPM decreases with increase in electron concentration, and increases with increase in intensity and wavelength, respectively in various manners. The strong dependence of the TPM on both light intensity and wavelength reflects the direct signature of light waves that is in direct contrast as compared with the corresponding bulk specimens of the said materials in the absence of external photoexcitation. The rate of change is totally band-structure dependent and is significantly influenced by the presence of the different energy-band constants. The well-known result for the TPM for nondegenerate wide-gap materials in the absence of light waves has been obtained as a special case of the present analysis under certain limiting conditions and this compatibility is the indirect test of our generalized formalism. Besides, we have also suggested the experimental methods of determining the Einstein relation for the diffusivity:mobility ratio, the Debye screening length and the electronic contribution to the elastic constants for materials having arbitrary dispersion laws. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  8. Conformal, planarizing and bridging AZ5214-E layers deposited by a 'draping' technique on non-planar III V substrates

    Science.gov (United States)

    Eliás, P.; Strichovanec, P.; Kostic, I.; Novák, J.

    2006-12-01

    A draping technique was tested for the deposition of positive-tone AZ5214-E photo-resist layers on non-planar (1 0 0)-oriented III-V substrates, which had a variety of three-dimensional (3D) topographies micromachined in them that consisted, e.g., of mesa ridges confined to side facets with variable tilt, inverted pyramidal holes and stubs confined to perpendicular side facets. All objects were sharp-edged. In each draping experiment, an AZ5214-E sheet was (1) formed floating on the water surface, (2) lowered onto a non-planar substrate and (3) draped over it during drying to form either self-sustained, or conformal, or planarizing layers over the non-planar substrates. The draping process is based on the depression of the glass transition temperature Tg of AZ5214-E material induced by penetrant water molecules that interact with AZ5214-E. During the process, the molecules are initially trapped under an AZ5214-E sheet and then transported out through the sheet via permeation. The water-AZ5214-E interaction modifies the stiffness κ of the sheet. The magnitude of the effect depends on temperature T and on partial water vapour pressure difference p(T, P, κ): the net effect is that Tg = f(C(T, P), p(T, P, κ)) is lowered as the concentration C of water increases with T and p, where P is the permeability of the sheet. The interaction depressed the Tg of the sheets as low as or lower than 53 °C for 6 µm thick sheets. At room temperature T Tg, the sheet becomes rubbery and mouldable by adhesion and capillary forces. As a result, it can either contour or planarize the topography depending on its geometry and thickness of the sheet.

  9. High-grade renal injuries are often isolated in sports-related trauma

    OpenAIRE

    Patel, Darshan P.; Redshaw, Jeffrey D.; Breyer, Benjamin N.; Smith, Thomas G.; Erickson, Bradley A.; Majercik, Sarah D.; Gaither, Thomas W.; Craig, James R.; Gardner, Scott; Presson, Angela P.; Zhang, Chong; Hotaling, James M.; Brant, William O.; Myers, Jeremy B.

    2015-01-01

    © 2015 Elsevier Ltd. All rights reserved. Introduction: Most high-grade renal injuries (American Association for Surgery of Trauma (AAST) grades III-V) result from motor vehicle collisions associated with numerous concomitant injuries. Sports-related blunt renal injury tends to have a different mechanism, a solitary blow to the flank. We hypothesized that high-grade renal injury is often isolated in sports-related renal trauma. Material and methods: We identified patients with AAST grades III...

  10. III-V-on-Silicon Photonic Integrated Circuits for Spectroscopic Sensing in the 2-4 μm Wavelength Range.

    Science.gov (United States)

    Wang, Ruijun; Vasiliev, Anton; Muneeb, Muhammad; Malik, Aditya; Sprengel, Stephan; Boehm, Gerhard; Amann, Markus-Christian; Šimonytė, Ieva; Vizbaras, Augustinas; Vizbaras, Kristijonas; Baets, Roel; Roelkens, Gunther

    2017-08-04

    The availability of silicon photonic integrated circuits (ICs) in the 2-4 μm wavelength range enables miniature optical sensors for trace gas and bio-molecule detection. In this paper, we review our recent work on III-V-on-silicon waveguide circuits for spectroscopic sensing in this wavelength range. We first present results on the heterogeneous integration of 2.3 μm wavelength III-V laser sources and photodetectors on silicon photonic ICs for fully integrated optical sensors. Then a compact 2 μm wavelength widely tunable external cavity laser using a silicon photonic IC for the wavelength selective feedback is shown. High-performance silicon arrayed waveguide grating spectrometers are also presented. Further we show an on-chip photothermal transducer using a suspended silicon-on-insulator microring resonator used for mid-infrared photothermal spectroscopy.

  11. Multicolor (UV-IR) Photodetectors Based on Lattice-Matched 6.1 A II/VI and III/V Semiconductors

    Science.gov (United States)

    2015-08-27

    copyright information. 13. SUPPLEMENTARY NOTES. Enter information not included elsewhere such as: prepared in cooperation with; translation of; report...II-VI heterojunctions such as multi-color photodetectors and solar cells [2]. Mixing lattice-matched II-VI and III-V semiconductors could be an...at 77 K, further silicon oxide surface passivation can be done to suppress the surface leakage [10] in the future work. Figure 10 The dark I-V

  12. A comprehensive study of g-factors, elastic, structural and electronic properties of III-V semiconductors using hybrid-density functional theory

    Science.gov (United States)

    Bastos, Carlos M. O.; Sabino, Fernando P.; Sipahi, Guilherme M.; Da Silva, Juarez L. F.

    2018-02-01

    Despite the large number of theoretical III-V semiconductor studies reported every year, our atomistic understanding is still limited. The limitations of the theoretical approaches to yield accurate structural and electronic properties on an equal footing, is due to the unphysical self-interaction problem that mainly affects the band gap and spin-orbit splitting (SOC) in semiconductors and, in particular, III-V systems with similar magnitude of the band gap and SOC. In this work, we report a consistent study of the structural and electronic properties of the III-V semiconductors by using the screening hybrid-density functional theory framework, by fitting the α parameters for 12 different III-V compounds, namely, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb, to minimize the deviation between the theoretical and experimental values of the band gap and SOC. Structural relaxation effects were also included. Except for AlP, whose α = 0.127, we obtained α values that ranged from 0.209 to 0.343, which deviate by less than 0.1 from the universal value of 0.25. Our results for the lattice parameter and elastic constants indicate that the fitting of α does not affect those structural parameters when compared with the HSE06 functional, where α = 0.25. Our analysis of the band structure based on the k ṡ p method shows that the effective masses are in agreement with the experimental values, which can be attributed to the simultaneous fitting of the band gap and SOC. Also, we estimate the values of g-factors, extracted directly from the band structure, which are close to experimental results, which indicate that the obtained band structure produced a realistic set of k ṡ p parameters.

  13. InGaAsP Mach-Zehnder interferometer optical modulator monolithically integrated with InGaAs driver MOSFET on a III-V CMOS photonics platform.

    Science.gov (United States)

    Park, Jin-Kown; Takagi, Shinichi; Takenaka, Mitsuru

    2018-02-19

    We demonstrated the monolithic integration of a carrier-injection InGaAsP Mach-Zehnder interferometer (MZI) optical modulator and InGaAs metal-oxide-semiconductor field-effect transistor (MOSFET) on a III-V-on-insulator (III-V-OI) wafer. A low-resistivity lateral PIN junction was formed along an InGaAsP rib waveguide by Zn diffusion and Ni-InGaAsP alloy, enabling direct driving of the InGaAsP optical modulator by the InGaAs MOSFET. A π phase shift of the InGaAsP optical modulator was obtained through the injection of a drain current from the InGaAs MOSFET with a gate voltage of approximately 1 V. This proof-of-concept demonstration of the monolithic integration of the InGaAsP optical modulator and InGaAs driver MOSFET will enable us to develop high-performance and low-power electronic-photonic integrated circuits on a III-V CMOS photonics platform.

  14. Oxide-Free Bonding of III-V-Based Material on Silicon and Nano-Structuration of the Hybrid Waveguide for Advanced Optical Functions

    Directory of Open Access Journals (Sweden)

    Konstantinos Pantzas

    2015-10-01

    Full Text Available Oxide-free bonding of III-V-based materials for integrated optics is demonstrated on both planar Silicon (Si surfaces and nanostructured ones, using Silicon on Isolator (SOI or Si substrates. The hybrid interface is characterized electrically and mechanically. A hybrid InP-on-SOI waveguide, including a bi-periodic nano structuration of the silicon guiding layer is demonstrated to provide wavelength selective transmission. Such an oxide-free interface associated with the nanostructured design of the guiding geometry has great potential for both electrical and optical operation of improved hybrid devices.

  15. Diagnostic accuracy of circulating thyrotropin receptor messenger RNA combined with neck ultrasonography in patients with Bethesda III-V thyroid cytology.

    Science.gov (United States)

    Aliyev, Altay; Patel, Jinesh; Brainard, Jennifer; Gupta, Manjula; Nasr, Christian; Hatipoglu, Betul; Siperstein, Allan; Berber, Eren

    2016-01-01

    The aim of this study was to analyze the usefulness of thyrotropin receptor messenger RNA (TSHR-mRNA) combined with neck ultrasonography (US) in the management of thyroid nodules with Bethesda III-V cytology. Cytology slides of patients with a preoperative fine needle aspiration (FNA) and TSHR-mRNA who underwent thyroidectomy between 2002 and 2011 were recategorized based on the Bethesda classification. Results of thyroid FNA, TSHR-mRNA, and US were compared with the final pathology. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. There were 12 patients with Bethesda III, 112 with Bethesda IV, and 58 with Bethesda V cytology. The sensitivity of TSHR-mRNA in predicting cancer was 33%, 65%, and 79 %, and specificity was 67%, 66%, and 71%, for Bethesda III, IV, and V categories, respectively. For the same categories, the PPV of TSHR-mRNA was 25%, 33%, and 79%, respectively; whereas the NPV was 75%, 88%, and 71%, respectively. The addition of neck US to TSHR-mRNA increased the NPV to 100% for Bethesda III, and 86%, for Bethesda IV, and 82% for Bethesda V disease. This study documents the potential usefulness of TSHR-mRNA for thyroid nodules with Bethesda III-V FNA categories. TSHR-mRNA may be used to exclude Bethesda IV disease. A large sample analysis is needed to determine its accuracy for Bethesda category III nodules. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. A Review of Ultrahigh Efficiency III-V Semiconductor Compound Solar Cells: Multijunction Tandem, Lower Dimensional, Photonic Up/Down Conversion and Plasmonic Nanometallic Structures

    Directory of Open Access Journals (Sweden)

    Katsuaki Tanabe

    2009-07-01

    Full Text Available Solar cells are a promising renewable, carbon-free electric energy resource to address the fossil fuel shortage and global warming. Energy conversion efficiencies around 40% have been recently achieved in laboratories using III-V semiconductor compounds as photovoltaic materials. This article reviews the efforts and accomplishments made for higher efficiency III-V semiconductor compound solar cells, specifically with multijunction tandem, lower-dimensional, photonic up/down conversion, and plasmonic metallic structures. Technological strategies for further performance improvement from the most efficient (AlInGaP/(InGaAs/Ge triple-junction cells including the search for 1.0 eV bandgap semiconductors are discussed. Lower-dimensional systems such as quantum well and dot structures are being intensively studied to realize multiple exciton generation and multiple photon absorption to break the conventional efficiency limit. Implementation of plasmonic metallic nanostructures manipulating photonic energy flow directions to enhance sunlight absorption in thin photovoltaic semiconductor materials is also emerging.

  17. Graded core/shell semiconductor nanorods and nanorod barcodes

    Science.gov (United States)

    Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

    2010-12-14

    Graded core/shell semiconductor nanorods and shaped nanorods are disclosed comprising Group II-VI, Group III-V and Group IV semiconductors and methods of making the same. Also disclosed are nanorod barcodes using core/shell nanorods where the core is a semiconductor or metal material, and with or without a shell. Methods of labeling analytes using the nanorod barcodes are also disclosed.

  18. New III-V cell design approaches for very high efficiency. Annual subcontract report, 1 August 1990--31 July 1991

    Energy Technology Data Exchange (ETDEWEB)

    Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; O`Bradovich, G.J.; Young, M.P. [Purdue Univ., Lafayette, IN (United States)

    1993-01-01

    This report describes progress during the first year of a three-year project. The objective of the research is to examine new design approaches for achieving very high conversion efficiencies. The program is divided into two areas. The first centers on exploring new thin-film approaches specifically designed for III-V semiconductors. The second area centers on exploring design approaches for achieving high conversion efficiencies without requiring extremely high quality material. Research activities consisted of an experimental study of minority carrier recombination in n-type, metal-organic chemical vapor deposition (MOCVD)-deposited GaAs, an assessment of the minority carrier lifetimes in n-GaAs grown by molecular beam epitaxy, and developing a high-efficiency cell fabrication process.

  19. Vortex Laser based on III-V semiconductor metasurface: direct generation of coherent Laguerre-Gauss modes carrying controlled orbital angular momentum.

    Science.gov (United States)

    Seghilani, Mohamed S; Myara, Mikhael; Sellahi, Mohamed; Legratiet, Luc; Sagnes, Isabelle; Beaudoin, Grégoire; Lalanne, Philippe; Garnache, Arnaud

    2016-12-05

    The generation of a coherent state, supporting a large photon number, with controlled orbital-angular-momentum L = ħl (of charge l per photon) presents both fundamental and technological challenges: we demonstrate a surface-emitting laser, based on III-V semiconductor technology with an integrated metasurface, generating vortex-like coherent state in the Laguerre-Gauss basis. We use a first order phase perturbation to lift orbital degeneracy of wavefunctions, by introducing a weak anisotropy called here "orbital birefringence", based on a dielectric metasurface. The azimuthal symmetry breakdown and non-linear laser dynamics create "orbital gain dichroism" allowing selecting vortex handedness. This coherent photonic device was characterized and studied, experimentally and theoretically. It exhibits a low divergence (50 dB vortex purity), and single frequency operation in a stable low noise regime (0.1% rms). Such high performance laser opens the path to widespread new photonic applications.

  20. Ka-band to L-band frequency down-conversion based on III-V-on-silicon photonic integrated circuits

    Science.gov (United States)

    Van Gasse, K.; Wang, Z.; Uvin, S.; De Deckere, B.; Mariën, J.; Thomassen, L.; Roelkens, G.

    2017-12-01

    In this work, we present the design, simulation and characterization of a frequency down-converter based on III-V-on-silicon photonic integrated circuit technology. We first demonstrate the concept using commercial discrete components, after which we demonstrate frequency conversion using an integrated mode-locked laser and integrated modulator. In our experiments, five channels in the Ka-band (27.5-30 GHz) with 500 MHz bandwidth are down-converted to the L-band (1.5 GHz). The breadboard demonstration shows a conversion efficiency of - 20 dB and a flat response over the 500 MHz bandwidth. The simulation of a fully integrated circuit indicates that a positive conversion gain can be obtained on a millimeter-sized photonic integrated circuit.

  1. Reduction of bonding resistance of two-terminal III-V/Si tandem solar cells fabricated using smart-stack technology

    Science.gov (United States)

    Baba, Masaaki; Makita, Kikuo; Mizuno, Hidenori; Takato, Hidetaka; Sugaya, Takeyoshi; Yamada, Noboru

    2017-12-01

    This paper describes a method that remarkably reduces the bonding resistance of mechanically stacked two-terminal GaAs/Si and InGaP/Si tandem solar cells, where the top and bottom cells are bonded using a Pd nanoparticle array. A transparent conductive oxide (TCO) layer, which partially covers the surface of the Si bottom cell below the electrodes of the III-V top cell, significantly enhances the fill factor (FF) and cell conversion efficiency. The partial TCO layer reduces the bonding resistance and thus, increases the FF and efficiency of InGaP/Si by factors of 1.20 and 1.11, respectively. Eventually, the efficiency exceeds 15%. Minimizing the optical losses at the bonding interfaces of the TCO layer is important in the fabrication of high-efficiency solar cells. To help facilitate this, the optical losses in the tandem solar cells are thoroughly characterized through optical simulations and experimental verifications.

  2. Design and Analysis of CMOS-Compatible III-V Compound Electron-Hole Bilayer Tunneling Field-Effect Transistor for Ultra-Low-Power Applications.

    Science.gov (United States)

    Kim, Sung Yoon; Seo, Jae Hwa; Yoon, Young Jun; Lee, Ho-Young; Lee, Seong Min; Cho, Seongjae; Kang, In Man

    2015-10-01

    In this work, we design and analyze complementary metal-oxide-semiconductor (CMOS)-compatible III-V compound electron-hole bilayer (EHB) tunneling field-effect transistors (TFETs) by using two-dimensional (2D) technology computer-aided design (TCAD) simulations. A recently proposed EHB TFET exploits a bias-induced band-to-band tunneling (BTBT) across the electron-hole bilayer by an electric field from the top and bottom gates. This is in contrast to conventional planar p(+)-p(-)-n TFETs, which utilize BTBT across the source-to-channel junction. We applied III-V compound semiconductor materials to the EHB TFETs in order to enhance the current drivability and switching performance. Devices based on various compound semiconductor materials have been designed and analyzed in terms of their primary DC characteristics. In addition, the operational principles were validated by close examination of the electron concentrations and energy-band diagrams under various operation conditions. The simulation results of the optimally designed In0.533Ga0.47As EHB TFET show outstanding performance, with an on-state current (Ion) of 249.5 μA/μm, subthreshold swing (S) of 11.4 mV/dec, and threshold voltage (Vth) of 50 mV at VDS = 0.5 V. Based on the DC-optimized InGaAs EHB TFET, the CMOS inverter circuit was simulated in views of static and dynamic behaviors of the p-channel device with exchanges between top and bottom gates or between source and drain electrodes maintaining the device structure.

  3. Theoretical modeling and optimization of III-V GaInP/GaAs/Ge monolithic triple-junction solar cells

    International Nuclear Information System (INIS)

    Leem, Jung Woo; Yu, Jae Su; Kim, Jong Nam; Noh, Sam Kyu

    2014-01-01

    We design and optimize monolithic III-V GaInP/GaAs/Ge triple-junction (TJ) solar cells by using a commercial software Silvaco ATLAS simulator to obtain the maximum short-circuit current density J sc . The maximum J sc , which is a current matching value between the GaInP top and GaAs middle subcells, can be determined by varying the base thicknesses of the GaInP top and GaAs middle subcells. From the numerical simulation results, a matched maximum J sc value of 13.92 mA/cm 2 is obtained at base thicknesses of 0.57 μm and 3 μm for the GaInP top and GaAs middle subcells, respectively, under 1-sun air mass 1.5 global spectrum illumination, leading to a high power conversion efficiency of 30.72%. The open-circuit voltage and the fill factor are 2.55 V and 86.55%, respectively. For the optimized cell structure, the external quantum efficiency and the photogeneration rate distributions are also investigated. To obtain efficient antireflection coatings (ARCs), we perform optical reflectance calculations by using a rigorous coupled-wave analysis method. For this, a silicon oxide/titanium oxide double-layer is used as an ARC on the TJ solar cell.

  4. Theoretical modeling and optimization of III-V GaInP/GaAs/Ge monolithic triple-junction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Leem, Jung Woo; Yu, Jae Su [Kyung Hee University, Yongin (Korea, Republic of); Kim, Jong Nam [Pukyung National University, Pusan (Korea, Republic of); Noh, Sam Kyu [Korea Research Institute of Standards and Science, Daejon (Korea, Republic of)

    2014-05-15

    We design and optimize monolithic III-V GaInP/GaAs/Ge triple-junction (TJ) solar cells by using a commercial software Silvaco ATLAS simulator to obtain the maximum short-circuit current density J{sub sc}. The maximum J{sub sc}, which is a current matching value between the GaInP top and GaAs middle subcells, can be determined by varying the base thicknesses of the GaInP top and GaAs middle subcells. From the numerical simulation results, a matched maximum J{sub sc} value of 13.92 mA/cm{sup 2} is obtained at base thicknesses of 0.57 μm and 3 μm for the GaInP top and GaAs middle subcells, respectively, under 1-sun air mass 1.5 global spectrum illumination, leading to a high power conversion efficiency of 30.72%. The open-circuit voltage and the fill factor are 2.55 V and 86.55%, respectively. For the optimized cell structure, the external quantum efficiency and the photogeneration rate distributions are also investigated. To obtain efficient antireflection coatings (ARCs), we perform optical reflectance calculations by using a rigorous coupled-wave analysis method. For this, a silicon oxide/titanium oxide double-layer is used as an ARC on the TJ solar cell.

  5. Scattering amplitudes and static atomic correction factors for the composition-sensitive 002 reflection in sphalerite ternary III-V and II-VI semiconductors.

    Science.gov (United States)

    Schowalter, M; Müller, K; Rosenauer, A

    2012-01-01

    Modified atomic scattering amplitudes (MASAs), taking into account the redistribution of charge due to bonds, and the respective correction factors considering the effect of static atomic displacements were computed for the chemically sensitive 002 reflection for ternary III-V and II-VI semiconductors. MASAs were derived from computations within the density functional theory formalism. Binary eight-atom unit cells were strained according to each strain state s (thin, intermediate, thick and fully relaxed electron microscopic specimen) and each concentration (x = 0, …, 1 in 0.01 steps), where the lattice parameters for composition x in strain state s were calculated using continuum elasticity theory. The concentration dependence was derived by computing MASAs for each of these binary cells. Correction factors for static atomic displacements were computed from relaxed atom positions by generating 50 × 50 × 50 supercells using the lattice parameter of the eight-atom unit cells. Atoms were randomly distributed according to the required composition. Polynomials were fitted to the composition dependence of the MASAs and the correction factors for the different strain states. Fit parameters are given in the paper.

  6. “Direct modulation of a hybrid III-V/Si DFB laser with MRR filtering for 22.5-Gb/s error-free dispersion-uncompensated transmission over 2.5-km SSMF

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Da Ros, Francesco; Ding, Yunhong

    2016-01-01

    Error-free and penalty-free transmission over 2.5 km SSMF of a 22.5 Gb/s data signal from a directly modulated hybrid III-V/Si DFB laser is achieved by enhancing the dispersion tolerance using a silicon micro-ring resonator....

  7. Electron-beam-induced reactivation of Si dopants in hydrogenated two-dimensional AlGaAs heterostructures: a possible new route for III-V nanostructure fabrication

    International Nuclear Information System (INIS)

    Kurowski, Ludovic; Bernard, Dorothee; Constant, Eugene; Decoster, Didier

    2004-01-01

    Hydrogen incorporation in n-type Si-doped GaAs epilayers is a well-known process which leads to the neutralization of the active Si impurities with the formation of SiH complexes. Recently, we have shown that SiH complex dissociation and, consequently, Si-dopant reactivation could occur when the epilayers are exposed to an electron beam. Two epilayers have been studied: the first is a 0.35 μm thick hydrogenated Si-doped GaAs epilayer and the second is Si planar-doped AlGaAs/GaAs/InGaAs heterostructures. Firstly, Hall effect measurements have been carried out on the epilayers exposed, after RF hydrogen plasma exposition, to increasing electron doses with different injection energies. For the 2D heterostructures, we have observed that the free carrier density N s does not vary significantly for weak electron densities. This reactivation presents a threshold value, contrary to the 0.35 μm epilayer in which N s varies quite linearly. It will be shown that such phenomena might be attributed to the filling of surface states as the dopants are progressively reactivated. Then, using a high spatial resolution electron beam lithography system, nanometric conductive patterns have been fabricated starting from hydrogenated epilayers. Electric measurements have been performed and the results obtained show that about 15 nm spatial resolution could be expected. In conclusion, taking into account this spatial resolution, the high spatial contrast of conductivity which could be expected due to the existence of an electron dose threshold, and the high mobility of the AlGaAs/GaAs/InGaAs heterostructure, the effects described in this paper could open a new way for the fabrication of III-V 1D or 2D mesoscopic structures for electronic or optoelectronic applications

  8. Clinical factors that affect perceived quality of life in arthroscopic reconstruction for acromioclavicular joint dislocation.

    Science.gov (United States)

    Abat, F; Gich, I; Natera, L; Besalduch, M; Sarasquete, J

    To analyse the results of arthroscopic repair of acromioclavicular dislocation in terms of health-related quality of life. Prospective study of patients with acromioclavicular dislocation Rockwood grade iii-v, treated arthroscopically with a mean follow up of 25.4 months. The demographics of the series were recorded and evaluations were performed preoperatively, at 3 months and 2 years with validated questionnaires as Short Form-36 Health Survey (SF-36), visual analogue scale (VAS), The Disabilities of the Arm, Shoulder and Hand (DASH), Constant-Murley Shoulder Outcome Score (Constant) and Walch-Duplay Score (WD). Twenty patients, 17 men and 3 women with a mean age of 36.1 years, were analysed. According to the classification of Rockwood, 3 patients were grade iii, 3 grade iv and 14 grade v. Functional and clinical improvement was detected in all clinical tests (SF-36, VAS and DASH) at 3 months and 2 years follow up (Pacromioclavicular joint dislocation grades iii-v was not influenced by gender, age, grade, displacement, handedness, evolution of the VAS, scoring of the Constant or by the WD. However, it is correlated with the evolution in the DASH score. Copyright © 2017 SECOT. Publicado por Elsevier España, S.L.U. All rights reserved.

  9. Technological development for super-high efficiency solar cells. Technological development for crystalline compound solar cells (high-efficiency III-V tandem solar cells); Chokokoritsu taiyo denchi no gijutsu kaihatsu. Kessho kagobutsu taiyo denchi no gijutsu kaihatsu (III-V zoku kagobutsu handotai taiyo denchi no gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    Tatsuta, M [New Energy and Industrial Technology Development Organization, Tokyo (Japan)

    1994-12-01

    This paper reports the study results on technological development of III-V compound semiconductor solar cells in fiscal 1994. (1) On development of epitaxial growth technology of lattice mismatching systems, the optimum structure of InGaAs strain intermediate layers was studied for reducing a dislocation density by lattice mismatching of GaAs layer grown on Si substrate and difference in thermal expansion coefficient. The effect of strain layer on dislocation reduction was found only at 250dyne/cm in strain energy. Growth of GaAs layers on the Si substrate treated by hydrofluoric acid at low temperature was attempted by MBE method. As a dislocation distribution was controlled by laying different atoms at hetero-interface, the dislocation density of growing layer surfaces decreased by concentration of dislocation at hetero-interface. (2) On development of high-efficiency tandem cell structure, tunnel junction characteristics, cell formation process and optimum design method of lattice matching tandem cells were studied, while thin film cell formation was basically studied for lattice mismatching tandem cells. 45 figs., 8 tabs.

  10. Return-to-activity after anatomical reconstruction of acute high-grade acromioclavicular separation.

    Science.gov (United States)

    Saier, T; Plath, J E; Beitzel, K; Minzlaff, P; Feucht, J M; Reuter, S; Martetschläger, F; Imhoff, Andreas B; Aboalata, M; Braun, S

    2016-04-02

    To evaluate return-to-activity (RtA) after anatomical reconstruction of acute high-grade acromioclavicular joint (ACJ) separation. A total of 42 patients with anatomical reconstruction of acute high-grade ACJ-separation (Rockwood Type V) were surveyed to determine RtA at a mean 31 months follow-up (f-u). Sports disciplines, intensity, level of competition, participation in overhead and/or contact sports, as well as activity scales (DASH-Sport-Module, Tegner Activity Scale) were evaluated. Functional outcome evaluation included Constant score and QuickDASH. All patients (42/42) participated in sporting activities at f-u. Neither participation in overhead/contact sports, nor level of activity declined significantly (n.s.). 62 % (n = 26) of patients reported subjective sports specific ACJ integrity to be at least the same as prior to the trauma. Sporting intensity (hours/week: 7.3 h to 5.4 h, p = .004) and level of competition (p = .02) were reduced. If activity changed, in 50 % other reasons but clinical symptoms/impairment were named for modified behavior. QuickDASH (mean 6, range 0-54, SD 11) and DASH-Sport-Module (mean 6, range 0-56, SD 13) revealed only minor disabilities at f-u. Over time Constant score improved significant to an excellent score (mean 94, range 86-100, SD 4; p < .001). Functional outcome was not correlated with RtA (n.s.). All patients participated in sporting activities after anatomical reconstruction of high-grade (Rockwood Type V) ACJ-separation. With a high functional outcome there was no significant change in activity level (Tegner) and participation in overhead and/or contact sports observed. There was no correlation between functional outcome and RtA. Limiting, there were alterations in time spent for sporting activities and level of competition observed. But in 50 % those were not related to ACJ symptoms/impairment. Unrelated to successful re-established integrity and function of the ACJ it should be considered that

  11. Desarrollo de la tecnología de MOVPE para el crecimiento de semiconductores III-V : fabricación de células solares para concentraciones luminosas elevadas

    OpenAIRE

    Galiana Blanco, Beatriz

    2011-01-01

    El trabajo de estas tesis trata sobre el desarrollo en el IES-UPM de la tecnología de crecimiento epitaxial de fase vapor mediante precursores metalorgánicos (MOVPE) para el crecimiento de células solares de semiconductores III-V para concentraciones luminosas elevadas. En la primera parte de la memoria se presentan los principios de la MOVPE y el estudio de los materiales semiconductores utilizados a lo largo de la tesis: GaAs, AlGaAs, GaInP y AlInP. Para ello, se ha analizado cómo influ...

  12. Caractérisations de matériaux et tests de composants des cellules solaires à base des nitrures des éléments III-V

    OpenAIRE

    Gorge , Vanessa

    2012-01-01

    Among III-V nitrides, the InGaN material has intensively been studied since the year 2000 for photovoltaic applications, in particular for multi-junction solar cells, thanks to its large tunable band gap covering almost the entire solar spectrum. Then, it will be possible to reach high efficiency and low cost. However, one of the problems of InGaN material is the absence of lattice-matched substrate leading to high defect density which limits device performances. We have thus studied the feas...

  13. Physics and performances of III-V nanowire broken-gap heterojunction TFETs using an efficient tight-binding mode-space NEGF model enabling million-atom nanowire simulations.

    Science.gov (United States)

    Afzalian, A; Vasen, T; Ramvall, P; Shen, T-M; Wu, J; Passlack, M

    2018-06-27

    We report the capability to simulate in a quantum-mechanical atomistic fashion record-large nanowire devices, featuring several hundred to millions of atoms and a diameter up to 18.2 nm. We have employed a tight-binding mode-space NEGF technique demonstrating by far the fastest (up to 10 000  ×  faster) but accurate (error  <  1%) atomistic simulations to date. Such technique and capability opens new avenues to explore and understand the physics of nanoscale and mesoscopic devices dominated by quantum effects. In particular, our method addresses in an unprecedented way the technologically-relevant case of band-to-band tunneling (BTBT) in III-V nanowire broken-gap heterojunction tunnel-FETs (HTFETs). We demonstrate an accurate match of simulated BTBT currents to experimental measurements in a 12 nm diameter InAs NW and in an InAs/GaSb Esaki tunneling diode. We apply our TB MS simulations and report the first in-depth atomistic study of the scaling potential of III-V GAA nanowire HTFETs including the effect of electron-phonon scattering and discrete dopant impurity band tails, quantifying the benefits of this technology for low-power low-voltage CMOS applications.

  14. Studies on II-VI and III-V semiconductor nanostructures. Introduction of the core/shell/shell structure and development of CdSe nanocrystals in an automatized procedure; Untersuchungen an II-VI und III-V Halbleiternanostrukturen. Einfuehrung der Core/shell/shell-Struktur und Darstellung von CdSe-Nanokristallen in einem automatisierten Verfahren

    Energy Technology Data Exchange (ETDEWEB)

    Mekis, I.

    2005-11-15

    The work in this dissertation is focused on the development and characterization of fluorescent II-VI and III-V-Nanomaterials. Highly luminescent and photostable Nanocrystals with narrow size distributions were prepared. It was shown that nearly monodisperse CdSe-Nanocrystals could be prepared from Cd(Ac){sub 2} and TOPSe in a mixture of TOPO/TOP/HDA/TDPA. Nearly monodisperse CdSe/CdS-Core/shell-Nanocrystals have been prepared in a one-pot-synthesis by injection of H{sub 2}S-Gas into a freshly prepared crude solution of CdSe. The passivation of the CdSe-core with an inorganic shell of CdS resulted in the drastic improvement of the photoluminescence-efficiency of the colloidal solution. Reproducible room-temperature quantum yields reached up to a value of 85%. Photostability investigations have proved the enhanced stability of CdSe/CdS-Nanocrystals compared to CdSe-Nanocrystals under illumination with UV-Light. A novel type of luminescent semiconductor nanocrystal structure has been developed, consisting of a CdSe core and two anorganic shells. Highly fluorescent and nearly monodisperse CdSe/CdS/ZnS- and CdSe/ZnSe/ZnS-Core/shell/shell-nanocrystals have been prepared via organometallic- and acetate-precursors. The Core/she ll/shell particles reached reproducible room-temperature quantum yields up to 85%. Photostability investigations among CdSe-core, CdSe/CdS-Core/shell- and CdSe/CdS/ZnS- Core/shell/-shell-nanocrystals under illumination with UV-light have proved the highest photostability of the Core/shell/shell-particles. The photostabilities of CdSe/ZnSe/ZnS-and CdSe/ZnS-nanocrystals were compared under illumination with intense laser-beam in air. Another part of this work focused on the development of an automated synthesis procedure of CdSe-nanocrystals by constructing and implementing a flow-reactor system. The size and structure of prepared nanocrystals depended considerably on the Cd:Se-precursorratio and the flow-rate. The preparation of CdSe using Cd(Ac)2

  15. Hybrid III-V Silicon Lasers

    Science.gov (United States)

    Bowers, John

    2014-03-01

    Abstract: A number of important breakthroughs in the past decade have focused attention on Si as a photonic platform. We review here recent progress in this field, focusing on efforts to make lasers, amplifiers, modulators and photodetectors on or in silicon. We also describe optimum quantum well design and distributed feedback cavity design to reduce the threshold and increase the efficiency and power output. The impact active silicon photonic integrated circuits could have on interconnects, telecommunications and on silicon electronics is reviewed. Biography: John Bowers holds the Fred Kavli Chair in Nanotechnology, and is the Director of the Institute for Energy Efficiency and a Professor in the Departments of Electrical and Computer Engineering and Materials at UCSB. He is a cofounder of Aurrion, Aerius Photonics and Calient Networks. Dr. Bowers received his M.S. and Ph.D. degrees from Stanford University and worked for AT&T Bell Laboratories and Honeywell before joining UC Santa Barbara. Dr. Bowers is a member of the National Academy of Engineering and a fellow of the IEEE, OSA and the American Physical Society. He is a recipient of the OSA/IEEE Tyndall Award, the OSA Holonyak Prize, the IEEE LEOS William Streifer Award and the South Coast Business and Technology Entrepreneur of the Year Award. He and coworkers received the EE Times Annual Creativity in Electronics (ACE) Award for Most Promising Technology for the hybrid silicon laser in 2007. Bowers' research is primarily in optoelectronics and photonic integrated circuits. He has published ten book chapters, 600 journal papers, 900 conference papers and has received 54 patents. He has published 180 invited papers and conference papers, and given 16 plenary talks at conferences. As well as Chong Zhang.

  16. II-VI/III-V Heterojunction Lasers

    National Research Council Canada - National Science Library

    Gunshor, Robert

    1999-01-01

    ... in both. In the second part of the program we studied the growth and the optical evaluation of wide bandgap nitride heterostructures, an effort which included the first reporting of a GaN-based laser to be fabricated...

  17. Teachers' Grading Decision Making

    Science.gov (United States)

    Isnawati, Ida; Saukah, Ali

    2017-01-01

    This study investigated teachers' grading decision making, focusing on their beliefs underlying their grading decision making, their grading practices and assessment types, and factors they considered in grading decision making. Two teachers from two junior high schools applying different curriculum policies in grade reporting in Indonesian…

  18. Student Attitudes Toward Grades and Grading Practices.

    Science.gov (United States)

    Stallings, William M.; Leslie, Elwood K.

    The result of a study designed to assess student attitudes toward grading practices are discussed. Questionnaire responses of 3439 students in three institutions were tabulated. Responses were generally negative toward conventional grading systems. (MS)

  19. Synthesis, characterization, spectroscopic and catalytic oxidation studies of Fe(III), Ni(II), Co(III), V(IV) and U(VI) Schiff base complexes with N, O donor ligands derived from 2,3-diaminopyridine

    Energy Technology Data Exchange (ETDEWEB)

    Zabardasti, Abedien; Shangaie, Sayed Asad [Lorestan Univ., Khorramabad (Iran, Islamic Republic of). Dept. of Chemistry

    2016-10-15

    Fifteen new complexes of transition metals were designed using three Schiff base ligands and aldol condensation of 2,3-diaminopyridine with 5-R-2-hydroxybenzaldehyde (R = F, Cl, Br) in the 1:2 molar ratio. The tetradentate ligands N,N{sup '}-bis(5-R-2-hydroxybenzaldehyde) pyridine were acquired with the common formula H{sub 2}[(5-R-sal){sub 2}py] and characterized by IR, UV-Vis spectra, {sup 1}H-NMR and elemental analysis. These ligands produce 1:1 complexes M[(5-R-sal){sub 2}py] with Fe(III), Ni(II), Co(III), V(IV) and U(VI) metal ions. The electronic property and nature of complexes were identified by IR, UV-Vis spectra, elemental analysis, X-ray crystallography and cyclic voltammetric methods. The catalytic activity of complexes for epoxidation of styrene with UHP as primary oxidant at minimal temperature (10 C) has been planned. The spectral data of the ligands and their complexes are deliberate in connection with the structural changes which happen due to complex preparation. The electrochemical outcome has good conformability with what suggested for electronic interaction among metal center and ligand by the UV-Vis and IR measurements.

  20. Non-operative management versus operative management in high-grade blunt hepatic injury.

    Science.gov (United States)

    Cirocchi, Roberto; Trastulli, Stefano; Pressi, Eleonora; Farinella, Eriberto; Avenia, Stefano; Morales Uribe, Carlos Hernando; Botero, Ana Maria; Barrera, Luis M

    2015-08-24

    Surgery used to be the treatment of choice in cases of blunt hepatic injury, but this approach gradually changed over the last two decades as increasing non-operative management (NOM) of splenic injury led to its use for hepatic injury. The improvement in critical care monitoring and computed tomographic scanning, as well as the more frequent use of interventional radiology techniques, has helped to bring about this change to non-operative management. Liver trauma ranges from a small capsular tear, without parenchymal laceration, to massive parenchymal injury with major hepatic vein/retrohepatic vena cava lesions. In 1994, the Organ Injury Scaling Committee of the American Association for the Surgery of Trauma (AAST) revised the Hepatic Injury Scale to have a range from grade I to VI. Minor injuries (grade I or II) are the most frequent liver injuries (80% to 90% of all cases); severe injuries are grade III-V lesions; grade VI lesions are frequently incompatible with survival. In the medical literature, the majority of patients who have undergone NOM have low-grade liver injuries. The safety of NOM in high-grade liver lesions, AAST grade IV and V, remains a subject of debate as a high incidence of liver and collateral extra-abdominal complications are still described. To assess the effects of non-operative management compared to operative management in high-grade (grade III-V) blunt hepatic injury. The search for studies was run on 14 April 2014. We searched the Cochrane Injuries Group's Specialised Register, The Cochrane Library, Ovid MEDLINE(R), Ovid MEDLINE(R) In-Process & Other Non-Indexed Citations, Ovid MEDLINE(R) Daily and Ovid OLDMEDLINE(R), Embase Classic+Embase (Ovid), PubMed, ISI WOS (SCI-EXPANDED, SSCI, CPCI-S & CPSI-SSH), clinical trials registries, conference proceedings, and we screened reference lists. All randomised trials that compare non-operative management versus operative management in high-grade blunt hepatic injury. Two authors independently

  1. Analysis and evaluation for practical application of photovoltaic power generation system. Analysis and evaluation for development of extra-high efficiency solar cells (fundamental research on extra-high efficiency III-V compound semiconductor tandem solar cells); Taiyoko hatsuden system jitsuyoka no tame no kaiseki hyoka. Chokokoritsu taiyo denchi no gijutsu kaihatsu no tame no kaiseki hyoka (chokokoritsu III-V zoku kagobutsu taiyo denchi gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    Sekikawa, T; Kawanami, H; Sakata, I; Nagai, K; Matsumoto, K; Miki, K [Electrotechnical Laboratory, Tsukuba (Japan)

    1994-12-01

    Described herein are the results of the FY1994 research program for development of extra-high efficiency III-V compound semiconductor tandem solar cells. Heteroepitaxial structures of compound semiconductors, such as GaAs, on silicon substrates are analyzed and evaluated by EXAFS, Raman and RHEED for the initial stage of the film growth and heterointerfaces. The device capable of in-situ observation of the growing surface structures during the period of heteroepitaxial film growth is introduced, to investigate the effects of rise-up and initial growth conditions on defects. The effects of atomic hydrogen on growth of a GaAs film on a silicon substrate are investigated from photoluminescence and solar cell characteristics, to confirm the effects of reducing defects. Heteroepitaxial growth of InGaP, which has the optimum band width for forming multi-junction silicon solar cells, on a silicon substrate is investigated, to find that an interfacial buffer layer is necessary to form a good film. 2 figs.

  2. High-grade renal injuries are often isolated in sports-related trauma.

    Science.gov (United States)

    Patel, Darshan P; Redshaw, Jeffrey D; Breyer, Benjamin N; Smith, Thomas G; Erickson, Bradley A; Majercik, Sarah D; Gaither, Thomas W; Craig, James R; Gardner, Scott; Presson, Angela P; Zhang, Chong; Hotaling, James M; Brant, William O; Myers, Jeremy B

    2015-07-01

    Most high-grade renal injuries (American Association for Surgery of Trauma (AAST) grades III-V) result from motor vehicle collisions associated with numerous concomitant injuries. Sports-related blunt renal injury tends to have a different mechanism, a solitary blow to the flank. We hypothesized that high-grade renal injury is often isolated in sports-related renal trauma. We identified patients with AAST grades III-V blunt renal injuries from four level 1 trauma centres across the United States between 1/2005 and 1/2014. Patients were divided into "Sport" or "Non-sport" related groups. Outcomes included rates of hypotension (systolic blood pressure 110bpm), concomitant abdominal injury, and procedural/surgical intervention between sports and non-sports related injury. 320 patients met study criteria. 18% (59) were sports-related injuries with the most common mechanisms being skiing, snowboarding and contact sports (25%, 25%, and 24%, respectively). Median age was 24 years for sports and 30 years for non-sports related renal injuries (p=0.049). Males were more commonly involved in sports related injuries (85% vs. 72%, p=0.011). Median injury severity score was lower for sports related injuries (10 vs. 27, pinjury scale scores. Sports related trauma was more likely to be isolated without other significant injury (69% vs. 39% (psports and non-sports renal injuries (p=0.30). Sports injuries had lower transfusion (7% vs. 47%, psports vs. 18% non-sports, p=0.95). High-grade sports-related blunt renal trauma is more likely to occur in isolation without other abdominal or thoracic injuries and clinicians must have a high suspicion of renal injury with significant blows to the flank during sports activities. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. The C-terminal N-glycosylation sites of the human alpha1,3/4-fucosyltransferase III, -V, and -VI (hFucTIII, -V, adn -VI) are necessary for the expression of full enzyme activity.

    Science.gov (United States)

    Christensen, L L; Jensen, U B; Bross, P; Orntoft, T F

    2000-09-01

    The alpha1,3/4-fucosyltransferases are involved in the synthesis of fucosylated cell surface glycoconjugates. Human alpha1,3/4-fucosyltransferase III, -V, and -VI (hFucTIII, -V, and -VI) contain two conserved C-terminal N-glycosylation sites (hFucTIII: Asn154 and Asn185; hFucTV: Asn167 and Asn198; and hFucTVI: Asn153 and Asn184). In the present study, we have analyzed the functional role of these potential N-glycosylation sites, laying the main emphasis on the sites in hFucTIII. Tunicamycin treatment completely abolished hFucTIII enzyme activity while castanospermine treatment diminished hFucTIII enzyme activity to approximately 40% of the activity of the native enzyme. To further analyze the role of the conserved N-glycosylation sites in hFucTIII, -V, and -VI, we made a series of mutant genomic DNAs in which the asparagine residues in the potential C-terminal N-glycosylation sites were replaced by glutamine. Subsequently, the hFucTIII, -V, and -VI wild type and the mutants were expressed in COS-7 cells. All the mutants exhibited lower enzyme activity than the wild type and elimination of individual sites had different effects on the activity. The mutations did not affect the protein level of the mutants in the cells, but reduced the molecular mass as predicted. Kinetic analysis of hFucTIII revealed that lack of glycosylation at Asn185 did not change the Km values for the oligosaccharide acceptor and the nucleotide sugar donor. The present study demonstrates that hFucTIII, -V, and -VI require N-glycosylation at the two conserved C-terminal N-glycosylation sites for expression of full enzyme activity.

  4. Electric dipole (hyper)polarizabilities of selected X2Y2 and X3Y3 (X = Al, Ga, In and Y = P, As): III-V semiconductor clusters. An ab initio comparative study.

    Science.gov (United States)

    Karamanis, Panaghiotis; Pouchan, Claude; Leszczynski, Jerzy

    2008-12-25

    A systematic ab initio comparative study of the (hyper)polarizabilities of selected III-V stoichiometric semiconductor clusters has been carried out. Our investigation focuses on the ground state structures of the dimers and on two dissimilar trimer configurations of aluminum, gallium, indium phosphide and arsenide. The basis set effect on both the polarizabilities and hyperpolarizabilities of the studied systems has been explicitly taken into account relying on the augmented correlation consistent aug-cc-pVnZ (n = D, T, Q, and 5) basis sets series. In addition, a rough estimation of the effects of the relativistic effects on the investigated properties is provided by extension of the study to include calculations performed with relativistic electron core potentials (or pseudopotentials). Electron correlation effects have been estimated utilizing methods of increasing predictive reliability, e.g., the Møller-Plesset many body perturbation theory and the couple cluster approach. Our results reveal that in the considered semiconductor species the Group III elements (Al, Ga, In) play a vital role on the values of their relative (hyper)polarizability. At all levels of theory employed the most hyperpolarizable clusters are the indium derivatives while the aluminum arsenide clusters also exhibit high, comparable hyperpolarizabilities. The less hyperpolarizable species are those composed of gallium and this is associated with the strong influence of the nuclear charge on the valence electrons of Ga due to the poor shielding that is provided by the semicore d electrons. In addition, the analysis of the electronic structure and the hyperpolarizability magnitudes reveals that clusters, in which their bonding is characterized by strong electron transfer from the electropositive to the electronegative atoms, are less hyperpolarizable than species in which the corresponding electron transfer is weaker. Lastly, from the methodological point of view our results point out that

  5. Towards III-V solar cells on Si: Improvement in the crystalline quality of Ge-on-Si virtual substrates through low porosity porous silicon buffer layer and annealing

    International Nuclear Information System (INIS)

    Calabrese, Gabriele; Baricordi, Stefano; Bernardoni, Paolo; Fin, Samuele; Guidi, Vincenzo; Vincenzi, Donato

    2014-01-01

    A comparison between the crystalline quality of Ge grown on bulk Si and on a low porosity porous Si (pSi) buffer layer using low energy plasma enhanced chemical vapor deposition is reported. Omega/2Theta coupled scans around the Ge and Si (004) diffraction peaks show a reduction of the Ge full-width at half maximum (FWHM) of 22.4% in presence of the pSi buffer layer, indicating it is effective in improving the epilayer crystalline quality. At the same time atomic force microscopy analysis shows an increase in root means square roughness for Ge grown on pSi from 38.5 nm to 48.0 nm, as a consequence of the larger surface roughness of pSi compared to bulk Si. The effect of 20 minutes vacuum annealing at 580°C is also investigated. The annealing leads to a FWHM reduction of 23% for Ge grown on Si and of 36.5% for Ge on pSi, resulting in a FWHM of 101 arcsec in the latter case. At the same time, the RMS roughness is reduced of 8.8% and of 46.5% for Ge grown on bulk Si and on pSi, respectively. The biggest improvement in the crystalline quality of Ge grown on pSi with respect to Ge grown on bulk Si observed after annealing is a consequence of the simultaneous reorganization of the Ge epilayer and the buffer layer driven by energy minimization. A low porosity buffer layer can thus be used for the growth of low defect density Ge on Si virtual substrates for the successive integration of III-V multijunction solar cells on Si. The suggested approach is simple and fast –thus allowing for high throughput-, moreover is cost effective and fully compatible with subsequent wafer processing. Finally it does not introduce new chemicals in the solar cell fabrication process and can be scaled to large area silicon wafers

  6. On arbitrarily graded rings

    Indian Academy of Sciences (India)

    58

    paper is devoted to the study of arbitrary rings graded through arbitrary sets. .... which recover certain multiplicative relations among the homogeneous components ... instance the case in which the grading set A is an Abelian group, where the ...

  7. Graded manifolds and supermanifolds

    International Nuclear Information System (INIS)

    Batchelor, M.

    1984-01-01

    In this paper, a review is presented on graded manifolds and supermanifolds. Many theorems, propositions, corrollaries, etc. are given with proofs or sketch proofs. Graded manifolds, supereuclidian space, Lie supergroups, etc. are dealt with

  8. GRADE Equity Guidelines 3

    DEFF Research Database (Denmark)

    Welch, Vivian A; Akl, Elie A; Pottie, Kevin

    2017-01-01

    OBJECTIVE: The aim of this paper is to describe a conceptual framework for how to consider health equity in the GRADE (Grading Recommendations Assessment and Development Evidence) guideline development process. STUDY DESIGN AND SETTING: Consensus-based guidance developed by the GRADE working grou...

  9. Quantum transport in III-V-semiconductor nanocolumns; Quantentransport in III-V-Halbleiternanosaeulen

    Energy Technology Data Exchange (ETDEWEB)

    Wensorra, Jakob

    2009-03-20

    The goal of this work has been to investigate und understand the electronic transport properties of vertical GaAs/AlAs nanocolumn resonant tunneling diodes (RTDs) and field effect transistors (RTTs) as well as of vertical InAs nanocolumn phase interference diodes. Besides the fabrication and electrical characterization of the devices, numerical calculations, simulations and quantum transport models represent the second important part of the work. GaAs/AlAs and InAs nanocolumns with lateral dimensions down to 30 nm have been processed by top-down approach. Room temperature DC electrical measurements on the nano-RTDs show a distinct negative differential resistance in the I-V characteristics for devices down to 30 nm lateral dimension. The miniaturization of the RTDs leads to the degradation of the transport properties, especially of the peak to valley current ratio (PVR), due to the increased surface scattering. Apart from the main current peak, new substructures can be observed in the I-V characteristics. These are shoulder like features for columns with diameters between 80 nm and 100 nm but become clear peaks when the column diameters are in the 55-75 nm range. For sub-65 nm column lateral dimensions, a strong increase of the PVR and a sharp single peak is observed. A local maximum of the PVR of 3 is reached for columns with 50 nm diameter. The sub-40 nm devices show only space charge limited currents in the I-V characteristics. This behavior can be shifted to smaller or larger diameters by increasing or reduction of the channel doping. For the smallest nanocolumns the lateral quantum confinement, caused by the low dimensionality of the system, leads to the formation of a 3D quantum-point-contact (QPC) in front of the DBQW structure. The quantization in this QPC depends on the column diameter and for a 50 nm column it exceeds the room temperature thermal broadening of the Fermi distribution function of about 25 meV. The measurements of the nano-RTTs indicate a good control of the device current by the gate voltage, without gate leakage. The peak current swing factor (the ratio between peak currents corresponding to the limits of a certain interval of the gate voltage) is about 3 for 150 nm diameter nano-RTTs but reach 6 for 60 nm diameter nano-RTTs (functionality based on the quantum collimation effect). Apart from GaAs/AlAs nanocolumns, InAs nanocolumns have been investigated as well. Nano-diodes were characterized by DC room temperature measurements and low temperature magneto-transport measurements. At room temperature, a linear behavior is observed in the I-V characteristics. Periodic oscillations of the resistance were measured by varying magnetic field at low temperatures. (orig.)

  10. Graded gauge theory

    International Nuclear Information System (INIS)

    Kerner, R.

    1983-01-01

    The mathematical background for a graded extension of gauge theories is investigated. After discussing the general properties of graded Lie algebras and what may serve as a model for a graded Lie group, the graded fiber bundle is constructed. Its basis manifold is supposed to be the so-called superspace, i.e. the product of the Minkowskian space-time with the Grassmann algebra spanned by the anticommuting Lorentz spinors; the vertical subspaces tangent to the fibers are isomorphic with the graded extension of the SU(N) Lie algebra. The connection and curvature are defined then on this bundle; the two different gradings are either independent of each other, or may be unified in one common grading, which is equivalent to the choice of the spin-statistics dependence. The Yang-Mills lagrangian is investigated in the simplified case. The conformal symmetry breaking is discussed, as well as some other physical consequences of the model. (orig.)

  11. Graded tensor calculus

    International Nuclear Information System (INIS)

    Scheunert, M.

    1982-10-01

    We develop a graded tensor calculus corresponding to arbitrary Abelian groups of degrees and arbitrary commutation factors. The standard basic constructions and definitions like tensor products, spaces of multilinear mappings, contractions, symmetrization, symmetric algebra, as well as the transpose, adjoint, and trace of a linear mapping, are generalized to the graded case and a multitude of canonical isomorphisms is presented. Moreover, the graded versions of the classical Lie algebras are introduced and some of their basic properties are described. (orig.)

  12. Classroom: Efficient Grading

    Science.gov (United States)

    Shaw, David D.; Pease, Leonard F., III.

    2014-01-01

    Grading can be accelerated to make time for more effective instruction. This article presents specific time management strategies selected to decrease administrative time required of faculty and teaching assistants, including a multiple answer multiple choice interface for exams, a three-tier grading system for open ended problem solving, and a…

  13. Grain Grading and Handling.

    Science.gov (United States)

    Rendleman, Matt; Legacy, James

    This publication provides an introduction to grain grading and handling for adult students in vocational and technical education programs. Organized in five chapters, the booklet provides a brief overview of the jobs performed at a grain elevator and of the techniques used to grade grain. The first chapter introduces the grain industry and…

  14. Vascular grading of angiogenesis

    DEFF Research Database (Denmark)

    Hansen, S; Grabau, D A; Sørensen, Flemming Brandt

    2000-01-01

    The study aimed to evaluate the prognostic value of angiogenesis by vascular grading of primary breast tumours, and to evaluate the prognostic impact of adding the vascular grade to the Nottingham Prognostic Index (NPI). The investigation included 836 patients. The median follow-up time was 11...... years and 4 months. The microvessels were immunohistochemically stained by antibodies against CD34. Angiogenesis was graded semiquantitatively by subjective scoring into three groups according to the expected number of microvessels in the most vascular tumour area. The vascular grading between observers...... for 24% of the patients, who had a shift in prognostic group, as compared to NPI, and implied a better prognostic dissemination. We concluded that the angiogenesis determined by vascular grading has independent prognostic value of clinical relevance for patients with breast cancer....

  15. Vascular grading of angiogenesis

    DEFF Research Database (Denmark)

    Hansen, S; Grabau, D A; Sørensen, Flemming Brandt

    2000-01-01

    The study aimed to evaluate the prognostic value of angiogenesis by vascular grading of primary breast tumours, and to evaluate the prognostic impact of adding the vascular grade to the Nottingham Prognostic Index (NPI). The investigation included 836 patients. The median follow-up time was 11...... years and 4 months. The microvessels were immunohistochemically stained by antibodies against CD34. Angiogenesis was graded semiquantitatively by subjective scoring into three groups according to the expected number of microvessels in the most vascular tumour area. The vascular grading between observers...... impact for 24% of the patients, who had a shift in prognostic group, as compared to NPI, and implied a better prognostic dissemination. We concluded that the angiogenesis determined by vascular grading has independent prognostic value of clinical relevance for patients with breast cancer....

  16. Combined arthroscopically assisted coraco- and acromioclavicular stabilization of acute high-grade acromioclavicular joint separations.

    Science.gov (United States)

    Hann, Carmen; Kraus, Natascha; Minkus, Marvin; Maziak, Nina; Scheibel, Markus

    2018-01-01

    Due to high rate of persisting dynamic posterior translation (DPT) following isolated coracoclavicular double-button technique for reconstruction of the acromioclavicular (AC) joint reported in the literature, an additional acromioclavicular cerclage was added to the procedure. The aim of this study was to evaluate the clinical and radiological results of patients with high-grade AC-joint instability treated with a double TightRope technique with an additional percutaneous acromioclavicular cerclage. Fifty-nine patients (6 f/53 m; median age 38.3 (range 21.5-63.4 years) who sustained an acute high-grade AC-joint dislocation (Rockwood type V) were treated using the above-mentioned technique. At the final follow-up, the constant score (CS), the subjective shoulder value (SSV), the Taft score (TF) and the acromioclavicular joint instability score (ACJI) as well as bilateral anteroposterior stress views with 10 kg of axial load and bilateral modified Alexander views were obtained. At a median follow-up of 26.4 (range 20.3-61.0) months, 34 patients scored a median of 90 (33-100) points in the CS, 90 (25-100) % in the SSV, 11 (4-12) points in the TF and 87 (43-100) points in the ACJI. The coracoclavicular (CC) distance was 12.1 (6.5-19.8) mm and the CC difference 2.0 (0.0-11.0) mm. Two patients (5.8%) showed a complete DPT of the AC joint, and fourteen patients (41.1%) displayed a partial DPT. The overall revision rate was 11.7%. Two patients presented implant irritation, one patient a recurrent instability, and one patient suffered from a local infection. The arthroscopically assisted and image-intensifier-controlled double TightRope technique with an additional percutaneous acromioclavicular cerclage leads to good and excellent clinical results after a follow-up of 2 years. The incidence of persisting dynamic horizontal translation is lower compared to isolated coracoclavicular stabilization. Thus, we recommend using the double TightRope implant with an additional

  17. CRA Grade Inflation

    OpenAIRE

    Kenneth H. Thomas

    2000-01-01

    Community Reinvestment Act of 1977 (CRA) ratings and performance evaluations are the only bank and thrift exam findings disclosed by financial institution regulators. Inflation of CRA ratings has been alleged by community activists for two decades, but there has been no quantification or empirical investigation of grade inflation. Using a unique grade inflation methodology on actual ratings and evaluation data for 1,407 small banks and thrifts under the revised CRA regulations, this paper con...

  18. Functionally graded materials

    CERN Document Server

    Mahamood, Rasheedat Modupe

    2017-01-01

    This book presents the concept of functionally graded materials as well as their use and different fabrication processes. The authors describe the use of additive manufacturing technology for the production of very complex parts directly from the three dimension computer aided design of the part by adding material layer after layer. A case study is also presented in the book on the experimental analysis of functionally graded material using laser metal deposition process.

  19. Contractions from grading

    Science.gov (United States)

    Krishnan, Chethan; Raju, Avinash

    2018-04-01

    We note that large classes of contractions of algebras that arise in physics can be understood purely algebraically via identifying appropriate Zm-gradings (and their generalizations) on the parent algebra. This includes various types of flat space/Carroll limits of finite and infinite dimensional (A)dS algebras, as well as Galilean and Galilean conformal algebras. Our observations can be regarded as providing a natural context for the Grassmann approach of Krishnan et al. [J. High Energy Phys. 2014(3), 36]. We also introduce a related notion, which we call partial grading, that arises naturally in this context.

  20. Endangered Animals. Second Grade.

    Science.gov (United States)

    Popp, Marcia

    This second grade teaching unit centers on endangered animal species around the world. Questions addressed are: What is an endangered species? Why do animals become extinct? How do I feel about the problem? and What can I do? Students study the definition of endangered species and investigate whether it is a natural process. They explore topics…

  1. Calculating Student Grades.

    Science.gov (United States)

    Allswang, John M.

    1986-01-01

    This article provides two short microcomputer gradebook programs. The programs, written in BASIC for the IBM-PC and Apple II, provide statistical information about class performance and calculate grades either on a normal distribution or based on teacher-defined break points. (JDH)

  2. Grades as Information

    Science.gov (United States)

    Grant, Darren

    2007-01-01

    We determine how much observed student performance in microeconomics principles can be attributed, inferentially, to three kinds of student academic "productivity," the instructor, demographics, and unmeasurables. The empirical approach utilizes an ordered probit model that relates student performance in micro to grades in prior…

  3. First Grade Baseline Evaluation

    Science.gov (United States)

    Center for Innovation in Assessment (NJ1), 2013

    2013-01-01

    The First Grade Baseline Evaluation is an optional tool that can be used at the beginning of the school year to help teachers get to know the reading and language skills of each student. The evaluation is composed of seven screenings. Teachers may use the entire evaluation or choose to use those individual screenings that they find most beneficial…

  4. The Fifth Grade Classroom.

    Science.gov (United States)

    Hartman, Michael; And Others

    An interdisciplinary design project report investigates the relationship of the fifth grade educational facility to the student and teacher needs in light of human and environmental factors. The classroom, activity and teaching spaces are analyzed with regard to the educational curriculum. Specifications and design criteria concerning equipment…

  5. Cutting Class Harms Grades

    Science.gov (United States)

    Taylor, Lewis A., III

    2012-01-01

    An accessible business school population of undergraduate students was investigated in three independent, but related studies to determine effects on grades due to cutting class and failing to take advantage of optional reviews and study quizzes. It was hypothesized that cutting classes harms exam scores, attending preexam reviews helps exam…

  6. Acute high-grade acromioclavicular dislocations treated with triple button device (MINAR): Preliminary results.

    Science.gov (United States)

    Cano-Martínez, José Antonio; Nicolás-Serrano, Gregorio; Bento-Gerard, Julio; Picazo-Marín, Francisco; Andrés-Grau, Josefina

    2016-11-01

    Describe the clinical and radiological results of triple button device in the treatment of high-grade AC dislocations (Rockwood, type V) and assess whether improves vertical and horizontal stability compared to the techniques previously described. This retrospective study included 39 patients with type V acromioclavicular dislocations treated with Twin Tail TightRope™ system (triple button device). Of the 39 patients, 33 (26 men and 7 women) were able to participate in clinical and radiographic follow up. At the time of surgery, the mean age was 25years±7(range, 17-49). All patients underwent bilateral-weighted Zanca (CC distance) and Alexander view (AC distance) as well as the Constant Score (CS) and Acromioclavicular Joint Instability Scoring System (ACJI). Radiological and clinical outcome was assessed during routine follow-up examinations preoperatively, postoperatively, 1, 3, 6 months and every year after the surgery. The presence of calcification, degenerative changes, mobilization of implants and bone resorption were also assessed. After a mean follow up of 25±4months (range 14-38), the results of the Constant (CS) were 94.1±5,5 (range 76-100) and test ACJI 87.3±9,8 (range 65-100), showing no significant differences with the uninjured shoulder (CS 95.8±2.5, range 83-100; ACJI 94.1±3.7, range 80-100). At final review, we observed that preoperative coracoclavicular distance (Zanca View) improved from 21,75±1.97mm to 8,73mm±0.75 and the acromioclavicular distance (Alexander View) from 12,65mm±1.99 to 0,35±0.3mm. Compared with healthy shoulder, these differences were not significant. There was no loss of reduction with this system in the vertical plane. 4 patients (12.12%) revealed signs of posterior instability with worse clinical test results. The presence of degenerative joint changes (6,06%), calcifications (27,2%) or mobilization of the implant (18,18%) was not associated with worse clinical outcomes. Twin Tail device using minimally invasive

  7. Inflated Grades, Enrollments & Budgets

    Directory of Open Access Journals (Sweden)

    J. E. Stone

    1995-06-01

    Full Text Available Reports of the past 13 years that call attention to deficient academic standards in American higher education are enumerated. Particular attention is given the Wingspread Group's recent An American Imperative: Higher Expectations for Higher Education. Low academic standards, grade inflation, and budgetary incentives for increased enrollment are analyzed and a call is made for research at the state level. Reported trends in achievement and GPAs are extrapolated to Tennessee and combined with local data to support the inference that 15% of the state's present day college graduates would not have earned a diploma by mid 1960s standards. A conspicuous lack of interest by public oversight bodies is noted despite a growing public awareness of low academic expectations and lenient grading and an implicit budgetary impact of over $100 million. Various academic policies and the dynamics of bureaucratic control are discussed in relationship to the maintenance of academic standards. The disincentives for challenging course requirements and responsible grading are examined, and the growing movement to address academic quality issues through better training and supervision of faculty are critiqued. Recommendations that would encourage renewed academic integrity and make learning outcomes visible to students, parents, employers, and the taxpaying public are offered and briefly discussed.

  8. TCGA_LowerGradeGliomas

    Science.gov (United States)

    TCGA researchers analyzed nearly 300 cases of diffuse low- and intermediate-grade gliomas, which together comprise lower-grade gliomas. LGGs occur mainly in adults and include astrocytomas, oligodendrogliomas and oligoastrocytomas.

  9. Let's End the Grading Game.

    Science.gov (United States)

    Edwards, Clifford H.; Edwards, Laurie

    1999-01-01

    Argues that grades have negative effects on learning and self-concept. States that while grading has a long tradition of sorting children for college entrance, there is limited evidence that grades serve a valid purpose. Argues that this practice should be abolished and an evaluation system established that provides a more valid estimate of…

  10. Four Steps in Grading Reform

    Science.gov (United States)

    Guskey, Thomas R.; Jung, Lee Ann

    2012-01-01

    The field of education is moving rapidly toward a standards-based approach to grading. School leaders have become increasingly aware of the tremendous variation that exists in grading practices, even among teachers of the same courses in the same department in the same school. Consequently, students' grades often have little relation to their…

  11. nBn Infrared Detector Containing Graded Absorption Layer

    Science.gov (United States)

    Gunapala, Sarath D.; Ting, David Z.; Hill, Cory J.; Bandara, Sumith V.

    2009-01-01

    It has been proposed to modify the basic structure of an nBn infrared photodetector so that a plain electron-donor- type (n-type) semiconductor contact layer would be replaced by a graded n-type III V alloy semiconductor layer (i.e., ternary or quarternary) with appropriate doping gradient. The abbreviation nBn refers to one aspect of the unmodified basic device structure: There is an electron-barrier ("B" ) layer between two n-type ("n" ) layers, as shown in the upper part of the figure. One of the n-type layers is the aforementioned photon-absorption layer; the other n-type layer, denoted the contact layer, collects the photocurrent. The basic unmodified device structure utilizes minority-charge-carrier conduction, such that, for reasons too complex to explain within the space available for this article, the dark current at a given temperature can be orders of magnitude lower (and, consequently, signal-to-noise ratios can be greater) than in infrared detectors of other types. Thus, to obtain a given level of performance, less cooling (and, consequently, less cooling equipment and less cooling power) is needed. [In principle, one could obtain the same advantages by means of a structure that would be called pBp because it would include a barrier layer between two electron-acceptor- type (p-type) layers.] The proposed modifications could make it practical to utilize nBn photodetectors in conjunction with readily available, compact thermoelectric coolers in diverse infrared- imaging applications that could include planetary exploration, industrial quality control, monitoring pollution, firefighting, law enforcement, and medical diagnosis.

  12. Elastic constants of nanoporous III-V semiconductors

    Czech Academy of Sciences Publication Activity Database

    Janovská, Michaela; Sedlák, Petr; Kruisová, Alena; Seiner, Hanuš; Landa, Michal; Grym, Jan

    2015-01-01

    Roč. 48, č. 24 (2015) ISSN 0022-3727 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61388998 ; RVO:67985882 Keywords : nanoporous semiconductors * resonant ultrasound spectroscopy * finite elements modelling Subject RIV: BM - Solid Matter Physics ; Magnetism; BM - Solid Matter Physics ; Magnetism (URE-Y) Impact factor: 2.772, year: 2015 http://iopscience.iop.org/0022-3727/48/24/245102/article

  13. [Update of breast cancer in Primary Care (III/V)].

    Science.gov (United States)

    Álvarez Hernández, C; Vich Pérez, P; Brusint, B; Cuadrado Rouco, C; Díaz García, N; Robles Díaz, L

    2014-01-01

    Breast cancer is a prevalent disease with implications in all aspects of patientś life, therefore, family doctors must know this pathology in depth, in order to optimize the health care provided to these patients with the best available resources. This series of five articles on breast cancer is based on a review of the scientific literature of the last ten years. This third article will review the clinical context and the staging and prognostic factors of the disease. This summary report aims to provide a global, current and practical review about this problem, providing answers to family doctors and helping them to be by the patients for their benefit throughout their illness. Copyright © 2014 Sociedad Española de Médicos de Atención Primaria (SEMERGEN). Publicado por Elsevier España. All rights reserved.

  14. Characterization of Hydrogen Complex Formation in III-V Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Michael D

    2006-09-28

    Atomic hydrogen has been found to react with some impurity species in semiconductors. Hydrogenation is a methodology for the introduction of atomic hydrogen into the semiconductor for the express purpose of forming complexes within the material. Efforts to develop hydrogenation as an isolation technique for AlGaAs and Si based devices failed to demonstrate its commercial viability. This was due in large measure to the low activation energies of the formed complexes. Recent studies of dopant passivation in long wavelength (0.98 - 1.55m) materials suggested that for the appropriate choice of dopants much higher activation energies can be obtained. This effort studied the formation of these complexes in InP, This material is extensively used in optoelectronics, i.e., lasers, modulators and detectors. The experimental techniques were general to the extent that the results can be applied to other areas such as sensor technology, photovoltaics and to other material systems. The activation energies for the complexes have been determined and are reported in the scientific literature. The hydrogenation process has been shown by us to have a profound effect on the electronic structure of the materials and was thoroughly investigated. The information obtained will be useful in assessing the long term reliability of device structures fabricated using this phenomenon and in determining new device functionalities.

  15. Hybrid III-V/SOI resonant cavity enhanced photodetector

    DEFF Research Database (Denmark)

    Learkthanakhachon, Supannee; Taghizadeh, Alireza; Park, Gyeong Cheol

    2016-01-01

    A hybrid III–V/SOI resonant-cavity-enhanced photodetector (RCE-PD) structure comprising a high-contrast grating (HCG) reflector, a hybrid grating (HG) reflector, and an air cavity between them, has been proposed and investigated. In the proposed structure, a light absorbing material is integrated...... as part of the HG reflector, enabling a very compact vertical cavity. Numerical investigations show that a quantum efficiency close to 100 % and a detection linewidth of about 1 nm can be achieved, which are desirable for wavelength division multiplexing applications. Based on these results, a hybrid RCE...

  16. Free Surface Properties of III-V Compound Semiconductor Surfaces.

    Science.gov (United States)

    1980-06-01

    selvage. Most important is the fact that atomic displacements also occur up to two layers into the substrate in the IaSb (ll0) selvage, presumably because of...result is that the interaction is of a disordering nature. 1 2,1 3 We took LEED measurements for a very large range of exposure to molecular oxygen (103...which the Al replaces the Ga. Arguments in favor of this reaction are given by measured photoemission peak shifts: 1 8󈧗 the Ga 3-d core level shifts

  17. Theory of Doping and Defects in III-V Nitrides

    OpenAIRE

    van de Walle, Chris G.; Stampfl, Catherine; Neugebauer, Joerg

    1998-01-01

    Doping problems in GaN and in AlGaN alloys are addressed on the basis of state-of-the-art first-principles calculations. For n-type doping we find that nitrogen vacancies are too high in energy to be incorporated during growth, but silicon and oxygen readily form donors. The properties of oxygen, including DX-center formation, support it as the main cause of unintentional n-type conductivity. For p-type doping we find that the solubility of Mg is the main factor limiting the hole concentratio...

  18. Ion implantation and annealing studies in III-V nitrides

    International Nuclear Information System (INIS)

    Zolper, J.C.; Pearton, S.J.

    1996-01-01

    Ion implantation doping and isolation is expected to play an enabling role for the realization of advanced III-Nitride based devices. In fact, implantation has already been used to demonstrate n- and p-type doping of GaN with Si and Mg or Ca, respectively, as well as to fabricate the first GaN junction field effect transistor. Although these initial implantation studies demonstrated the feasibility of this technique for the III-Nitride materials, further work is needed to realize its full potential. After reviewing some of the initial studies in this field, the authors present new results for improved annealing sequences and defect studies in GaN. First, sputtered AlN is shown by electrical characterization of Schottky and Ohmic contacts to be an effect encapsulant of GaN during the 1,100 C implant activation anneal. The AlN suppresses N-loss from the GaN surface and the formation of a degenerate n + -surface region that would prohibit Schottky barrier formation after the implant activation anneal. Second, they examine the nature of the defect generation and annealing sequence following implantation using both Rutherford Backscattering (RBS) and Hall characterization. They show that for a Si-dose of 1 x 10 16 cm -2 50% electrical donor activation is achieved despite a significant amount of residual implantation-induced damage in the material

  19. Likviditní riziko podle Basel III v EU

    OpenAIRE

    Mošnová, Alžběta

    2014-01-01

    In order to address the deficiencies in the banking regulation revealed by the recent financial crisis the Basel III introduces two minimum standards for funding liquidity, Liquidity Coverage Ratio (LCR) and Net Stable Funding Ratio (NSFR). The goal of this thesis is to analyze whether the NSFR is defined optimally or whether the Basel Committee on Banking Supervision (BCBS) will be forced to relax NSFR conditions similarly as happened by the LCR. Based on the approximation of the NSFR betwee...

  20. Nonlinear Frequency Conversion in III-V Semiconductor Photonic Crystals

    Science.gov (United States)

    2012-03-01

    benefited early in my PhD from the assistance of Dirk Englund and Vanessa Sih. Subsequently, I was fortunate to collab- orate with newer members of the...to defense practice talks. I would also like to acknowledge Seth Lloyd, Vicky Wen, Jason Pelc, Qiang Zhang, Peter McMahon, Liz Edwards , Stephanie...2006. [67] Z. Yang, P. Chak, A. D. Bristow, H. M. van Driel, R. Iyer, J. S. Aitchison, A. L. Smirl, and J. E. Sipe, “Enhanced second-harmonic

  1. Growth far from equilibrium: Examples from III-V semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kuech, Thomas F. [Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Babcock, Susan E. [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Mawst, Luke [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2016-12-15

    The development of new applications has driven the field of materials design and synthesis to investigate materials that are not thermodynamically stable phases. Materials which are not thermodynamically stable can be synthesized and used in many applications. These materials are kinetically stabilized during use. The formation of such metastable materials requires both an understanding of the associated thermochemistry and the key surface transport processes present during growth. Phase separation is most easily accomplished at the growth surface during synthesis where mass transport is most rapid. These surface transport processes are sensitive to the surface stoichiometry, reconstruction, and chemistry as well as the growth temperature. The formation of new metastable semiconducting alloys with compositions deep within a compositional miscibility gap serves as model systems for the understanding of the surface chemical and physical processes controlling their formation. The GaAs{sub 1−y}Bi{sub y} system is used here to elucidate the role of surface chemistry in the formation of a homogeneous metastable composition during the chemical vapor deposition of the alloy system.

  2. Enhancing Hole Mobility in III-V Semiconductors

    Science.gov (United States)

    2012-05-21

    offset, and the identification of the dominant scattering mechanism. Section V reports on gated Hall bar measure- ments and mobility results. Finally, the...achieved using the AlAsxSb1x barrier (approach B) as compared to AlyGa1ySb barrier (approach A), which was also expected from the bulk band lineup in

  3. Theoretical models of ferromagnetic III-V semiconductors

    Czech Academy of Sciences Publication Activity Database

    Jungwirth, Tomáš; Sinova, J.; Kučera, Jan; MacDonald, A. H.

    2003-01-01

    Roč. 3, - (2003), s. 461-464 ISSN 1567-1739. [Mesoscopic Electronics COST Workshop. Catania, 16.10.2002-19.10.2002] Institutional research plan: CEZ:AV0Z1010914 Keywords : ferromagnetic semiconductors * diluted magnetic semiconductors * magneto-transport Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.117, year: 2002

  4. Critical thickness of atomically ordered III-V alloys

    Energy Technology Data Exchange (ETDEWEB)

    France, R. M.; McMahon, W. E.; Guthrey, H. L. [National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401 (United States)

    2015-10-12

    The critical thickness model is modified with a general boundary energy that describes the change in bulk energy as a dislocation regularly alters the atomic structure of an ordered material. The model is evaluated for dislocations gliding through CuPt-ordered GaInP and GaInAs, where the boundary energy is negative and the boundary is stable. With ordering present, the critical thickness is significantly lowered and remains finite as the mismatch strain approaches zero. The reduction in critical thickness is most significant when the order parameter is greatest and the amount of misfit energy is low. The modified model is experimentally validated for low-misfit GaInP epilayers with varying order parameters using in situ wafer curvature and ex situ cathodoluminescence. With strong ordering, relaxation begins at a lower thickness and occurs at a greater rate, which is consistent with a lower critical thickness and increased glide force. Thus, atomic ordering is an important consideration for the stability of lattice-mismatched devices.

  5. Ion Implantation in III-V Compound Semiconductors

    Science.gov (United States)

    1984-09-01

    340 keV H + -0 Ga P  O UES-723-292 !:• (H o>ray *P-K X - rayO Ga-K X -ray iii! RBS * ..I -iO.. 0 10I to1. 01 • .0 -. I0 1 LI =i, O I 0 01 0.J 10...Identity by blo ," pume) Ion Implantation, GaAs, Hall effect, electrical resistivity, Rutherford Backscattering (RBS), channeling, Proton induced x -ray...Mebility (jH) upon Aiinealing Temperature (TA) for 1 X 101 /cm• Dose Samples of GaAs:Mg with Three Different Capping Methods 33 p 14 Dependence of Surface

  6. Diffusion in Intrinsic and Highly Doped III-V Semiconductors

    CERN Multimedia

    Stolwijk, N

    2002-01-01

    %title\\\\ \\\\Diffusion plays a key role in the fabrication of semiconductor devices. The diffusion of atoms in crystals is mediated by intrinsic point defects. Investigations of the diffusion behaviour of self- and solute atoms on the Ga sublattice of gallium arsenide led to the conclusion that in intrinsic and n-type material charged Ga vacancies are involved in diffusion processes whereas in p-type material diffusion if governed by charged Ga self-interstitials. Concerning the As sublattice of gallium arsenide there is a severe lack of reliable diffusion data. The few available literature data on intrinsic GaAs are not mutually consistent. A systematic study of the doping dependence of diffusion is completely missing. The most basic diffusion process - self-diffusion of As and its temperature and doping dependence - is practically not known. For GaP a similar statement holds.\\\\ \\\\The aim of the present project is to perform a systematic diffusion study of As diffusion in intrinsic and doped GaAs and in GaP. P...

  7. Large, Tunable Magnetoresistance in Nonmagnetic III-V Nanowires.

    Science.gov (United States)

    Li, Sichao; Luo, Wei; Gu, Jiangjiang; Cheng, Xiang; Ye, Peide D; Wu, Yanqing

    2015-12-09

    Magnetoresistance, the modulation of resistance by magnetic fields, has been adopted and continues to evolve in many device applications including hard-disk, memory, and sensors. Magnetoresistance in nonmagnetic semiconductors has recently raised much attention and shows great potential due to its large magnitude that is comparable or even larger than magnetic materials. However, most of the previous work focus on two terminal devices with large dimensions, typically of micrometer scales, which severely limit their performance potential and more importantly, scalability in commercial applications. Here, we investigate magnetoresistance in the impact ionization region in InGaAs nanowires with 20 nm diameter and 40 nm gate length. The deeply scaled dimensions of these nanowires enable high sensibility with less power consumption. Moreover, in these three terminal devices, the magnitude of magnetoresistance can be tuned by the transverse electric field controlled by gate voltage. Large magnetoresistance between 100% at room temperature and 2000% at 4.3 K can be achieved at 2.5 T. These nanoscale devices with large magnetoresistance offer excellent opportunity for future high-density large-scale magneto-electric devices using top-down fabrication approaches, which are compatible with commercial silicon platform.

  8. Catalyst-free, III-V nanowire photovoltaics

    Science.gov (United States)

    Davies, D. G.; Lambert, N.; Fry, P. W.; Foster, A.; Krysa, A. B.; Wilson, L. R.

    2014-05-01

    We report on room temperature, photovoltaic operation of catalyst-free GaAs p-i-n junction nanowire arrays. Growth studies were first performed to determine the optimum conditions for controlling the vertical and lateral growth of the nanowires. Following this, devices consisting of axial p-i-n junctions were fabricated by planarising the nanowire arrays with a hard baked polymer. We discuss the photovoltaic properties of this proof-of-concept device, and significant improvements to be made during the growth.

  9. Functionally Graded Materials Database

    Science.gov (United States)

    Kisara, Katsuto; Konno, Tomomi; Niino, Masayuki

    2008-02-01

    Functionally Graded Materials Database (hereinafter referred to as FGMs Database) was open to the society via Internet in October 2002, and since then it has been managed by the Japan Aerospace Exploration Agency (JAXA). As of October 2006, the database includes 1,703 research information entries with 2,429 researchers data, 509 institution data and so on. Reading materials such as "Applicability of FGMs Technology to Space Plane" and "FGMs Application to Space Solar Power System (SSPS)" were prepared in FY 2004 and 2005, respectively. The English version of "FGMs Application to Space Solar Power System (SSPS)" is now under preparation. This present paper explains the FGMs Database, describing the research information data, the sitemap and how to use it. From the access analysis, user access results and users' interests are discussed.

  10. The Implications of Grade Inflation

    DEFF Research Database (Denmark)

    Smith, David E.; Fleisher, Steven

    2011-01-01

    The authors review current and past practices of the grade inflation controversy and present ways to return to each institution’s established grading guidelines. Students are graded based on knowledge gathered. Certain faculty members use thorough evaluative methods, such as written and oral pres...... have been profiled in the news. The model is provided to ensure that degree candidates are academic experts in their field, having earned the credential through rigorous study....

  11. Practicing Good Habits, Grade 4.

    Science.gov (United States)

    Van Cong Lau; And Others

    This illustrated textbook was designed for teaching civics and values to fourth grade students in Vietnam. It is divided into six chapters: (1) At School (recapitulation of the grade three program, friendship, respect for the teacher, team work, discipline, honor); (2) In the Street: Traffic Regulations; (3) At Home (the extended family spirit,…

  12. Graded geometry and Poisson reduction

    OpenAIRE

    Cattaneo, A S; Zambon, M

    2009-01-01

    The main result of [2] extends the Marsden-Ratiu reduction theorem [4] in Poisson geometry, and is proven by means of graded geometry. In this note we provide the background material about graded geometry necessary for the proof in [2]. Further, we provide an alternative algebraic proof for the main result. ©2009 American Institute of Physics

  13. Compositionally Graded Multilayer Ceramic Capacitors.

    Science.gov (United States)

    Song, Hyun-Cheol; Zhou, Jie E; Maurya, Deepam; Yan, Yongke; Wang, Yu U; Priya, Shashank

    2017-09-27

    Multilayer ceramic capacitors (MLCC) are widely used in consumer electronics. Here, we provide a transformative method for achieving high dielectric response and tunability over a wide temperature range through design of compositionally graded multilayer (CGML) architecture. Compositionally graded MLCCs were found to exhibit enhanced dielectric tunability (70%) along with small dielectric losses (filters and power converters.

  14. Long-term Outcomes With Planned Multistage Reduced Dose Repeat Stereotactic Radiosurgery for Treatment of Inoperable High-Grade Arteriovenous Malformations: An Observational Retrospective Cohort Study.

    Science.gov (United States)

    Marciscano, Ariel E; Huang, Judy; Tamargo, Rafael J; Hu, Chen; Khattab, Mohamed H; Aggarwal, Sameer; Lim, Michael; Redmond, Kristin J; Rigamonti, Daniele; Kleinberg, Lawrence R

    2017-07-01

    There is no consensus regarding the optimal management of inoperable high-grade arteriovenous malformations (AVMs). This long-term study of 42 patients with high-grade AVMs reports obliteration and adverse event (AE) rates using planned multistage repeat stereotactic radiosurgery (SRS). To evaluate the efficacy and safety of multistage SRS with treatment of the entire AVM nidus at each treatment session to achieve complete obliteration of high-grade AVMs. Patients with high-grade Spetzler-Martin (S-M) III-V AVMs treated with at least 2 multistage SRS treatments from 1989 to 2013. Clinical outcomes of obliteration rate, minor/major AEs, and treatment characteristics were collected. Forty-two patients met inclusion criteria (n = 26, S-M III; n = 13, S-M IV; n = 3, S-M V) with a median follow-up was 9.5 yr after first SRS. Median number of SRS treatment stages was 2, and median interval between stages was 3.5 yr. Twenty-two patients underwent pre-SRS embolization. Complete AVM obliteration rate was 38%, and the median time to obliteration was 9.7 yr. On multivariate analysis, higher S-M grade was significantly associated ( P = .04) failure to achieve obliteration. Twenty-seven post-SRS AEs were observed, and the post-SRS intracranial hemorrhage rate was 0.027 events per patient year. Treatment of high-grade AVMs with multistage SRS achieves AVM obliteration in a meaningful proportion of patients with acceptable AE rates. Lower obliteration rates were associated with higher S-M grade and pre-SRS embolization. This approach should be considered with caution, as partial obliteration does not protect from hemorrhage. Copyright © 2017 by the Congress of Neurological Surgeons

  15. Contemporary management of high-grade renal trauma: Results from the American Association for the Surgery of Trauma Genitourinary Trauma study.

    Science.gov (United States)

    Keihani, Sorena; Xu, Yizhe; Presson, Angela P; Hotaling, James M; Nirula, Raminder; Piotrowski, Joshua; Dodgion, Christopher M; Black, Cullen M; Mukherjee, Kaushik; Morris, Bradley J; Majercik, Sarah; Smith, Brian P; Schwartz, Ian; Elliott, Sean P; DeSoucy, Erik S; Zakaluzny, Scott; Thomsen, Peter B; Erickson, Bradley A; Baradaran, Nima; Breyer, Benjamin N; Miller, Brandi; Santucci, Richard A; Carrick, Matthew M; Hewitt, Timothy; Burks, Frank N; Kocik, Jurek F; Askari, Reza; Myers, Jeremy B

    2018-03-01

    The rarity of renal trauma limits its study and the strength of evidence-based guidelines. Although management of renal injuries has shifted toward a nonoperative approach, nephrectomy remains the most common intervention for high-grade renal trauma (HGRT). We aimed to describe the contemporary management of HGRT in the United States and also evaluate clinical factors associated with nephrectomy after HGRT. From 2014 to 2017, data on HGRT (American Association for the Surgery of Trauma grades III-V) were collected from 14 participating Level-1 trauma centers. Data were gathered on demographics, injury characteristics, management, and short-term outcomes. Management was classified into three groups-expectant, conservative/minimally invasive, and open operative. Descriptive statistics were used to report management of renal trauma. Univariate and multivariate logistic mixed effect models with clustering by facility were used to look at associations between proposed risk factors and nephrectomy. A total of 431 adult HGRT were recorded; 79% were male, and mechanism of injury was blunt in 71%. Injuries were graded as III, IV, and V in 236 (55%), 142 (33%), and 53 (12%), respectively. Laparotomy was performed in 169 (39%) patients. Overall, 300 (70%) patients were managed expectantly and 47 (11%) underwent conservative/minimally invasive management. Eighty-four (19%) underwent renal-related open operative management with 55 (67%) of them undergoing nephrectomy. Nephrectomy rates were 15% and 62% for grades IV and V, respectively. Penetrating injuries had significantly higher American Association for the Surgery of Trauma grades and higher rates of nephrectomy. In multivariable analysis, only renal injury grade and penetrating mechanism of injury were significantly associated with undergoing nephrectomy. Expectant and conservative management is currently utilized in 80% of HGRT; however, the rate of nephrectomy remains high. Clinical factors, such as surrogates of

  16. Effect of Grade Retention in First Grade on Psychosocial Outcomes

    OpenAIRE

    Wu, Wei; West, Stephen G.; Hughes, Jan N.

    2010-01-01

    In a 4-year longitudinal study, the authors investigated effects of retention in first grade on children’s externalizing and internalizing behaviors; social acceptance; and behavioral, cognitive, and affective engagement. From a large multiethnic sample (n = 784) of children below the median on literacy at school entrance, 124 retained children were matched with 251 promoted children on the basis of propensity scores (probability of being retained in first grade estimated from 72 baseline var...

  17. Gender discrimination in exam grading?

    DEFF Research Database (Denmark)

    Rangvid, Beatrice Schindler

    2018-01-01

    Girls, on average, obtain higher test scores in school than boys, and recent research suggests that part of this difference may be due to discrimination against boys in grading. This bias is consequential if admission to subsequent education programs is based on exam scores. This study assesses t...... tendencies are in accordance with statistical discrimination as a mechanism for grading bias in essay writing and with gender-stereotyped beliefs of math being a male domain....... are scored twice (blind and non-blind). Both strategies use difference-in-differences methods. Although imprecisely estimated, the point estimates indicate a blind grading advantage for boys in essay writing of approximately 5-8% SD, corresponding to 9-15% of the gender gap in essay exam grades. The effect...

  18. Progressive problems higher grade physics

    CERN Document Server

    Kennedy, William

    2001-01-01

    This book fully covers all three Units studied in Scotland's Higher Grade Physics course, providing a systematic array of problems (from the simplest to the most difficult) to lead variously abled pupils to examination success.

  19. Grade 6 Science Curriculum Specifications.

    Science.gov (United States)

    Alberta Dept. of Education, Edmonton. Curriculum Branch.

    This material describes curriculum specifications for grade 6 science in Alberta. Emphases recommended are: (1) process skills (50%); (2) psychomotor skills (10%); (3) attitudes (10%); and (4) subject matter (30%). Priorities within each category are identified. (YP)

  20. Improving GRADE evidence tables part 2

    DEFF Research Database (Denmark)

    Langendam, Miranda; Carrasco-Labra, Alonso; Santesso, Nancy

    2016-01-01

    OBJECTIVES: The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) working group has developed GRADE evidence profiles (EP) and summary of findings (SoF) tables to present evidence summaries in systematic reviews, clinical guidelines, and health technology assessments. Exp...

  1. Cracks in functionally graded materials

    International Nuclear Information System (INIS)

    Bahr, H.-A.; Balke, H.; Fett, T.; Hofinger, I.; Kirchhoff, G.; Munz, D.; Neubrand, A.; Semenov, A.S.; Weiss, H.-J.; Yang, Y.Y.

    2003-01-01

    The weight function method is described to analyze the crack growth behavior in functionally graded materials and in particular materials with a rising crack growth resistance curve. Further, failure of graded thermal barrier coatings (TBCs) under cyclic surface heating by laser irradiation is modeled on the basis of fracture mechanics. The damage of both graded and non-graded TBCs is found to develop in several distinct stages: vertical cracking→delamination→blistering→spalling. This sequence can be understood as an effect of progressive shrinkage due to sintering and high-temperature creep during thermal cycling, which increases the energy-release rate for vertical cracks which subsequently turn into delamination cracks. The results of finite element modeling, taking into account the TBC damage mechanisms, are compatible with experimental data. An increase of interface fracture toughness due to grading and a decrease due to ageing have been measured in a four-point bending test modified by a stiffening layer. Correlation with the damage observed in cyclic heating is discussed. It is explained in which way grading is able to reduce the damage

  2. Graded/Gradient Porous Biomaterials

    Directory of Open Access Journals (Sweden)

    Xigeng Miao

    2009-12-01

    Full Text Available Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. On the other hand, porous biomaterials exhibit the potential of bone ingrowth, which will depend on porous parameters such as pore size, pore interconnectivity, and porosity. Unfortunately, a highly porous biomaterial results in poor mechanical properties. To optimise the mechanical and the biological properties, porous biomaterials with graded/gradient porosity, pores size, and/or composition have been developed. Graded/gradient porous biomaterials have many advantages over graded/gradient dense biomaterials and uniform or homogenous porous biomaterials. The internal pore surfaces of graded/gradient porous biomaterials can be modified with organic, inorganic, or biological coatings and the internal pores themselves can also be filled with biocompatible and biodegradable materials or living cells. However, graded/gradient porous biomaterials are generally more difficult to fabricate than uniform or homogenous porous biomaterials. With the development of cost-effective processing techniques, graded/gradient porous biomaterials can find wide applications in bone defect filling, implant fixation, bone replacement, drug delivery, and tissue engineering.

  3. Hardwood log grades and lumber grade yields for factory lumber logs

    Science.gov (United States)

    Leland F. Hanks; Glenn L. Gammon; Robert L. Brisbin; Everette D. Rast

    1980-01-01

    The USDA Forest Service Standard Grades for Hardwood Factory Lumber Logs are described, and lumber grade yields for 16 species and 2 species groups are presented by log grade and log diameter. The grades enable foresters, log buyers, and log sellers to select and grade those log suitable for conversion into standard factory grade lumber. By using the apropriate lumber...

  4. 7 CFR 810.2204 - Grades and grade requirements for wheat.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Grades and grade requirements for wheat. 810.2204... OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Wheat Principles Governing the Application of Standards § 810.2204 Grades and grade requirements for wheat. (a) Grades and grade requirements...

  5. The accuracy of FAST in relation to grade of solid organ injuries: A retrospective analysis of 226 trauma patients with liver or splenic lesion

    Directory of Open Access Journals (Sweden)

    Candinas Daniel

    2009-03-01

    Full Text Available Abstract Background This study investigated the role of a negative FAST in the diagnostic and therapeutic algorithm of multiply injured patients with liver or splenic lesions. Methods A retrospective analysis of 226 multiply injured patients with liver or splenic lesions treated at Bern University Hospital, Switzerland. Results FAST failed to detect free fluid or organ lesions in 45 of 226 patients with spleen or liver injuries (sensitivity 80.1%. Overall specificity was 99.5%. The positive and negative predictive values were 99.4% and 83.3%. The overall likelihood ratios for a positive and negative FAST were 160.2 and 0.2. Grade III-V organ lesions were detected more frequently than grade I and II lesions. Without the additional diagnostic accuracy of a CT scan, the mean ISS of the FAST-false-negative patients would be significantly underestimated and 7 previously unsuspected intra-abdominal injuries would have been missed. Conclusion FAST is an expedient tool for the primary assessment of polytraumatized patients to rule out high grade intra-abdominal injuries. However, the low overall diagnostic sensitivity of FAST may lead to underestimated injury patterns and delayed complications may occur. Hence, in hemodynamically stable patients with abdominal trauma, an early CT scan should be considered and one must be aware of the potential shortcomings of a "negative FAST".

  6. Functionally Graded Mo sintered steels

    Directory of Open Access Journals (Sweden)

    Manuel Cisneros-Belmonte

    2016-12-01

    Full Text Available Functionally graded materials (FGM, the multi-materials, strive to satisfy the numerous requirements demanded of parts in a given combination of compositions and microstructures. The required material compatibility lead the manufacturing process and the achieving of an interface, not always diffuse. Powder metallurgy is one of the techniques used in manufacturing functionally graded materials, in particular the compaction matrix of the possible techniques for forming these materials. In this paper, a process of forming a functionally graded steel based on the use of a high molybdenum steel with cooper and other steel with copper, without molybdenum, is proposed with the aim of concentrating this element to the surface of the workpiece, increasing the mechanical strength. The study is completed with the evaluation of physical properties (density and porosity distribution, mechanical properties (hardness, tensile strength and elongation and microstructural analysis by optical and scanning electron microscopy.

  7. 7 CFR 51.304 - Combination grades.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE REGULATIONS AND STANDARDS UNDER THE AGRICULTURAL MARKETING ACT OF 1946... Standards for Grades of Apples Grades § 51.304 Combination grades. (a) Combinations of the above grades may...

  8. On-Demand Grades: The Effect of Online Grade Book Access on Student Mastery and Performance Goal Orientations, Grade Orientation, Academic Self Efficacy, and Grades

    Science.gov (United States)

    Seldow, Adam Lowell

    2010-01-01

    With the widespread growth of broadband Internet access, teachers, and in many cases, schools and school districts are transitioning from traditional paper-based grade books to student accessible online (Web-based) grade books. Online grade books offer students 24/7, on demand access to grades and various other student data, and have the potential…

  9. Functionally Graded Material: An overview

    CSIR Research Space (South Africa)

    Mahamood, RM

    2012-07-01

    Full Text Available -3146. [50] X. Jin, L. Wu, L. Guo, H. Yu, and Y. Sun, ?Experimental investigation of the mixed-mode crack propagation in ZrO2/NiCr functionally graded materials,? Engineering Fracture Mechanics, vol. 76(12), (2009), pp. 1800-1810. [51] Z. Cheng, D. Gao... by stable crack growth,? Engineering Fracture Mechanics, vol.72(15), (2005), pp. 2359-2372. [47] Z.-H. Jin, and R.H. Dodds Jr, ?Crack growth resistance behavior of a functionally graded material: computational studies,? Engineering Fracture Mechanics...

  10. On the union of graded prime ideals

    Directory of Open Access Journals (Sweden)

    Uregen Rabia Nagehan

    2016-01-01

    Full Text Available In this paper we investigate graded compactly packed rings, which is defined as; if any graded ideal I of R is contained in the union of a family of graded prime ideals of R, then I is actually contained in one of the graded prime ideals of the family. We give some characterizations of graded compactly packed rings. Further, we examine this property on h – Spec(R. We also define a generalization of graded compactly packed rings, the graded coprimely packed rings. We show that R is a graded compactly packed ring if and only if R is a graded coprimely packed ring whenever R be a graded integral domain and h – dim R = 1.

  11. 7 CFR 810.404 - Grades and grade requirements for corn.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Grades and grade requirements for corn. 810.404... OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Corn Principles Governing the Application of Standards § 810.404 Grades and grade requirements for corn. Grade Minimum test weight per...

  12. 7 CFR 810.1804 - Grades and grade requirements for sunflower seed.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Grades and grade requirements for sunflower seed. 810... AGRICULTURE OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Sunflower Seed Principles Governing the Application of Standards § 810.1804 Grades and grade requirements for sunflower seed. Grade...

  13. Attendance Policies and Student Grades

    Science.gov (United States)

    Risen, D. Michael

    2007-01-01

    The details described in this case study examine the issues related to attendance policies and how such policies might be legally used to affect student grades. Concepts discussed should cause graduate students in educational administration to reflect on the issues presented from various points of view when the students complete an analysis of the…

  14. Grading Rubrics: Hoopla or Help?

    Science.gov (United States)

    Howell, Rebecca J.

    2014-01-01

    The purpose of the study was to offer some quantitative, multivariate evidence concerning the impact of grading rubric use on academic outcome among American higher education students. Using a pre-post, quasi-experimental research design, cross-sectional data were derived from undergraduates enrolled in an elective during spring and fall 2009 at…

  15. Transportation: Grade 8. Cluster IV.

    Science.gov (United States)

    Calhoun, Olivia H.

    A curriculum guide for grade 8, the document is devoted to the occupational cluster "Transportation." It is divided into five units: surface transportation, interstate transportation, air transportation, water transportation, and subterranean transportation (the Metro). Each unit is introduced by a statement of the topic, the unit's…

  16. Smartphone-based grading of apple quality

    Science.gov (United States)

    Li, Xianglin; Li, Ting

    2018-02-01

    Apple quality grading is a critical issue in apple industry which is one economical pillar of many countries. Artificial grading is inefficient and of poor accuracy. Here we proposed to develop a portable, convenient, real-time, and low cost method aimed at grading apple. Color images of the apples were collected with a smartphone and the grade of sampled apple was assessed by a customized smartphone app, which offered the functions translating RGB color values of the apple to color grade and translating the edge of apple image to weight grade. The algorithms are based on modeling with a large number of apple image at different grades. The apple grade data evaluated by the smartphone are in accordance with the actual data. This study demonstrated the potential of smart phone in apple quality grading/online monitoring at gathering and transportation stage for apple industry.

  17. Anaplasia and grading in medulloblastomas.

    Science.gov (United States)

    Eberhart, Charles G; Burger, Peter C

    2003-07-01

    The variable clinical outcomes of medulloblastoma patients have prompted a search for markers with which to tailor therapies to individuals. In this review, we discuss clinical, histological and molecular features that can be used in such treatment customization, focusing on how histopathological grading can impact both patient care and research on the molecular basis of CNS embryonal tumors. Medulloblastomas span a histological spectrum ending in overtly malignant large cell/anaplastic lesions characterized by increased nuclear size, marked cytological anaplasia, and increased mitotic and apoptotic rates. These "high-grade" lesions make up approximately one quarter of medulloblastomas, and recur and metastasize more frequently than tumors lacking anaplasia. We believe anaplastic change represents a type of malignant progression common to many medulloblastoma subtypes and to other CNS embryonal lesions as well. Correlation of these histological changes with the accumulation of genetic events suggests a model for the histological and molecular progression of medulloblastoma.

  18. Gradings on simple Lie algebras

    CERN Document Server

    Elduque, Alberto

    2013-01-01

    Gradings are ubiquitous in the theory of Lie algebras, from the root space decomposition of a complex semisimple Lie algebra relative to a Cartan subalgebra to the beautiful Dempwolff decomposition of E_8 as a direct sum of thirty-one Cartan subalgebras. This monograph is a self-contained exposition of the classification of gradings by arbitrary groups on classical simple Lie algebras over algebraically closed fields of characteristic not equal to 2 as well as on some nonclassical simple Lie algebras in positive characteristic. Other important algebras also enter the stage: matrix algebras, the octonions, and the Albert algebra. Most of the presented results are recent and have not yet appeared in book form. This work can be used as a textbook for graduate students or as a reference for researchers in Lie theory and neighboring areas.

  19. Grading of quality assurance requirements

    International Nuclear Information System (INIS)

    1991-01-01

    The present Manual provides guidance and illustrative examples for applying a method by which graded quality assurance requirements may be determined and adapted to the items and services of a nuclear power plant in conformance with the requirements of the IAEA Nuclear Safety Standards (NUSS) Code and Safety Guides on quality assurance. The Manual replaces the previous publication IAEA-TECDOC-303 on the same subject. Various methods of grading quality assurance are available in a number of Member States. During the development of the present Manual it was not considered practical to attempt to resolve the differences between those methods and it was preferred to identify and benefit from the good practices available in all the methods. The method presented in this Manual deals with the aspects of management, documentation, control, verification and administration which affect quality. 1 fig., 4 tabs

  20. Grade Expectations: Rationality and Overconfidence

    Science.gov (United States)

    Magnus, Jan R.; Peresetsky, Anatoly A.

    2018-01-01

    Confidence and overconfidence are essential aspects of human nature, but measuring (over)confidence is not easy. Our approach is to consider students' forecasts of their exam grades. Part of a student's grade expectation is based on the student's previous academic achievements; what remains can be interpreted as (over)confidence. Our results are based on a sample of about 500 second-year undergraduate students enrolled in a statistics course in Moscow. The course contains three exams and each student produces a forecast for each of the three exams. Our models allow us to estimate overconfidence quantitatively. Using these models we find that students' expectations are not rational and that most students are overconfident, in agreement with the general literature. Less obvious is that overconfidence helps: given the same academic achievement students with larger confidence obtain higher exam grades. Female students are less overconfident than male students, their forecasts are more rational, and they are also faster learners in the sense that they adjust their expectations more rapidly. PMID:29375449

  1. Grade Expectations: Rationality and Overconfidence

    Directory of Open Access Journals (Sweden)

    Jan R. Magnus

    2018-01-01

    Full Text Available Confidence and overconfidence are essential aspects of human nature, but measuring (overconfidence is not easy. Our approach is to consider students' forecasts of their exam grades. Part of a student's grade expectation is based on the student's previous academic achievements; what remains can be interpreted as (overconfidence. Our results are based on a sample of about 500 second-year undergraduate students enrolled in a statistics course in Moscow. The course contains three exams and each student produces a forecast for each of the three exams. Our models allow us to estimate overconfidence quantitatively. Using these models we find that students' expectations are not rational and that most students are overconfident, in agreement with the general literature. Less obvious is that overconfidence helps: given the same academic achievement students with larger confidence obtain higher exam grades. Female students are less overconfident than male students, their forecasts are more rational, and they are also faster learners in the sense that they adjust their expectations more rapidly.

  2. Measure of uncertainty in regional grade variability

    NARCIS (Netherlands)

    Tutmez, B.; Kaymak, U.; Melin, P.; Castillo, O.; Gomez Ramirez, E.; Kacprzyk, J.; Pedrycz, W.

    2007-01-01

    Because the geological events are neither homogeneous nor isotropic, the geological investigations are characterized by particularly high uncertainties. This paper presents a hybrid methodology for measuring of uncertainty in regional grade variability. In order to evaluate the fuzziness in grade

  3. The grading management of the quality assurance

    International Nuclear Information System (INIS)

    Ma Xiaozheng; Han Shufang; Yu Bei; Tian Xuehang

    2009-01-01

    This paper introduces the quality assurance grading management of the items, services and technology process on nuclear power plants (nuclear island, conventional island, BOP), such as the requirements and aim in the related code, guide, technical document, the requirements for the related units, the grading principle and grading, the considering method for the differences of QA requirements of the each QA grand, as well as the status and propositions in the QA grading management in China. (authors)

  4. The pathologist's mean grade is constant and individualizes the prognostic value of bladder cancer grading.

    Science.gov (United States)

    van Rhijn, Bas W G; van Leenders, Geert J L H; Ooms, Bert C M; Kirkels, Wim J; Zlotta, Alexandre R; Boevé, Egbert R; Jöbsis, Adriaan C; van der Kwast, Theo H

    2010-06-01

    A new grading system for bladder cancer (BCa) was adopted in 2004 to reduce observer variability and provide better prognostic information. We compared the World Health Organization (WHO) 1973 and 2004 systems for observer variability and prognosis. Slides of 173 primary non-muscle-invasive BCa were reviewed two times by four pathologists. Intra- and interobserver variability were assessed using κ statistics. We determined the mean grade (eg, G1/low malignant potential is 1 grade point, G2/low grade is 2 grade points) of the pathologists per grading cycle. Kaplan-Meier analyses were applied for prediction of recurrence and progression. For WHO 2004 and 1973 grading, the agreement between the pathologists was 39-74% (κ: 0.14-0.58) and 39-64% (κ: 0.15-0.41), respectively. The intraobserver agreement varied from 71% to 88% (κ: 0.55-0.81). The mean grade of a pathologist was constant (difference below 0.1 grade point) irrespective of the grading system. Conversely, mean-grade differences among the pathologists were high, up to 0.7 grade point. The mean grades for the WHO 2004 system were 0.3-0.5 grade point higher than those of WHO 1973. Mean grade distinguished low and high graders among the pathologists and was strongly linked with risk of progression in each grade category. The variation in mean grade among individual pathologists exceeded the grade shift caused by WHO 2004 grading. Knowledge of the pathologist's mean grade allows a better assessment of the prognostic value of grading. Mean grade has the potential to become a tool for quality assurance in pathology. Copyright © 2009 European Association of Urology. Published by Elsevier B.V. All rights reserved.

  5. Examining Text Complexity in the Early Grades

    Science.gov (United States)

    Fitzgerald, Jill; Elmore, Jeff; Hiebert, Elfrieda H.; Koons, Heather H.; Bowen, Kimberly; Sanford-Moore, Eleanor E.; Stenner, A. Jackson

    2016-01-01

    The Common Core raises the stature of texts to new heights, creating a hubbub. The fuss is especially messy at the early grades, where children are expected to read more complex texts than in the past. But early-grades teachers have been given little actionable guidance about text complexity. The authors recently examined early-grades texts to…

  6. Registration Patterns Under Two Different Grading Systems.

    Science.gov (United States)

    Remley, Audrey W.

    In the early 1960's, Westminster College adopted a new grading system, with the traditional grade levels of A, B, C, D, and F converted to DN (Distinction), HP (High Pass), P (Pass), and NC (No Credit). NC replaced both D and F of the old system, and grade point averages were abolished, in an effort to encourage students to register in more…

  7. Forecasting and recruitment in graded manpower systems

    NARCIS (Netherlands)

    van Nunen, J.A.E.E.; Wessels, J.

    1977-01-01

    In this paper a generalized Markov model is introduced to describe the dynamic behaviour of an individual employee in a graded Manpower system. Characteristics like the employee's grade, his educational level, his age and the time spent in his actual grade, can be incorporated in the Markov model.

  8. Demystify Learning Expectations to Address Grade Inflation

    Science.gov (United States)

    Hodges, Linda C.

    2014-01-01

    This article describes the subject of "grade inflation," a reference to educators giving higher grades to student work than their expectations for student achievement warrant. Of the many reasons why this practice happens, Hodges specifically discusses inflating grades as "a natural consequence" when the faculty really…

  9. Grade Inflation: An Issue for Higher Education?

    Science.gov (United States)

    Caruth, Donald L.; Caruth, Gail D.

    2013-01-01

    Grade inflation impacts university credibility, student courses of study, choices of institution, and other areas. There has been an upward shift in grades without a corresponding upward shift in knowledge gained. Some of the most frequently mentioned causes of grade inflation are: (1) student evaluations of professors; (2) student teacher…

  10. Does Education Corrupt? Theories of Grade Inflation

    Science.gov (United States)

    Oleinik, Anton

    2009-01-01

    Several theories of grade inflation are discussed in this review article. It is argued that grade inflation results from the substitution of criteria specific to the search for truth by criteria of quality control generated outside of academia. Particular mechanisms of the grade inflation that occurs when a university is transformed into a…

  11. The Relationship of Grade Span in 9th Grade to Math Achievement in High School

    Science.gov (United States)

    West, John; Miller, Mary Lou; Myers, Jim; Norton, Timothy

    2015-01-01

    Purpose, Scope, and Method of Study: The purpose of this study was to determine if a correlation exists between grade span for ninth grade and gains in math achievement test scores in 10th grade and 12th grade. A quantitative, longitudinal, correlational research design was employed to investigate the research questions. The population was high…

  12. High grade glioma: Imaging combined with pathological grade defines management and predicts prognosis

    International Nuclear Information System (INIS)

    Burnet, Neil G.; Lynch, Andrew G.; Jefferies, Sarah J.; Price, Stephen J.; Jones, Phil H.; Antoun, Nagui M.; Xuereb, John H.; Pohl, Ute

    2007-01-01

    Introduction: There is ambiguity in pathological grading of high grade gliomas within the WHO 2000 classification, especially those with predominant oligodendroglial differentiation. Patients and methods: All adult high grade gliomas treated radically, 1996-2005, were assessed. Cases in which pathology was grade III but radiology suggested glioblastoma (GBM) were classified as 'grade III/IV'; their pathology was reviewed. Results: Data from 245 patients (52 grade III, 18 grade III/IV, 175 GBM) were analysed using a Cox Proportional Hazards model. On pathology review, features suggestive of more aggressive behaviour were found in all 18 grade III/IV tumours. Oligodendroglial components with both necrosis and microvascular proliferation were present in 7. MIB-1 counts for the last 8 were all above 14%, mean 27%. Median survivals were: grade III 34 months, grade III/IV 10 months, GBM 11 months. Survival was not significantly different between grade III/IV and GBM. Patients with grade III/IV tumours had significantly worse outcome than grade III, with a hazard of death 3.7 times higher. Conclusions: The results highlight the current inconsistency in pathological grading of high grade tumours, especially those with oligodendroglial elements. Patients with histological grade III tumours but radiological appearances suggestive of GBM should be managed as glioblastoma

  13. Association of Grade Configuration with School Climate for 7th and 8th Grade Students

    Science.gov (United States)

    Malone, Marisa; Cornell, Dewey; Shukla, Kathan

    2017-01-01

    Educational authorities have questioned whether middle schools provide the best school climate for 7th and 8th grade students, and proposed that other grade configurations such as K-8th grade schools may provide a better learning environment. The purpose of this study was to compare 7th and 8th grade students' perceptions of 4 key features of…

  14. Comparing Dropout Predictors for Two State-Level Panels Using Grade 6 and Grade 8 Data

    Science.gov (United States)

    Franklin, Bobby J.; Trouard, Stephen B.

    2016-01-01

    The purpose of this study was to examine the effectiveness of dropout predictors across time. Two state-level high school graduation panels were selected to begin with the seventh and ninth grades but end at the same time. The first panel (seventh grade) contained 29,554 students and used sixth grade predictors. The second panel (ninth grade)…

  15. Grade Inflation Marches On: Grade Increases from the 1990s to 2000s

    Science.gov (United States)

    Kostal, Jack W.; Kuncel, Nathan R.; Sackett, Paul R.

    2016-01-01

    Grade inflation threatens the integrity of college grades as indicators of academic achievement. In this study, we contribute to the literature on grade inflation by providing the first estimate of the size of grade increases at the student level between the mid-1990s and mid-2000s. By controlling for student characteristics and course-taking…

  16. The effect of various grading scales on student grade point averages.

    Science.gov (United States)

    Barnes, Kelli D; Buring, Shauna M

    2012-04-10

    To investigate changes in and the impact of grading scales from 2005 to 2010 and explore pharmacy faculty and student perceptions of whole-letter and plus/minus grading scales on cumulative grade point averages (GPAs) in required courses. Grading scales used in 2010 at the University of Cincinnati College of Pharmacy were retrospectively identified and compared to those used in 2005. Mean GPA was calculated using a whole-letter grading scale and a plus/minus grading scale to determine the impact of scales on GPA. Faculty members and students were surveyed regarding their perceptions of plus/minus grading. Nine unique grading scales were used throughout the curriculum, including plus/minus (64%) and whole-letter (21%) grading scales. From 2005 to 2010 there was transition from use of predominantly whole-letter scales to plus/minus grading scales. The type of grading scale used did not affect the mean cumulative GPA. Students preferred use of a plus-only grading scale while faculty members preferred use of a plus/minus grading scale. The transition from whole-letter grading to plus/minus grading in courses from 2005 to 2010 reflects pharmacy faculty members' perception that plus/minus grading allows for better differentiation between students' performances.

  17. Is the Sky Falling? Grade Inflation and the Signaling Power of Grades.

    Science.gov (United States)

    Pattison, Evangeleen; Grodsky, Eric; Muller, Chandra

    2013-06-01

    Grades are the fundamental currency of our educational system; they signal academic achievement and non-cognitive skills to parents, employers, postsecondary gatekeepers, and students themselves. Grade inflation compromises the signaling value of grades, undermining their capacity to achieve the functions for which they are intended. We challenge the 'increases in grade point average' definition of grade inflation and argue that grade inflation must be understood in terms of the signaling power of grades. Analyzing data from four nationally representative samples, we find that in the decades following 1972: (a) grades have risen at high schools and dropped at four-year colleges, in general, and selective four-year institutions, in particular; and (b) the signaling power of grades has attenuated little, if at all.

  18. Production of Food Grade Yeasts

    Directory of Open Access Journals (Sweden)

    Argyro Bekatorou

    2006-01-01

    Full Text Available Yeasts have been known to humans for thousands of years as they have been used in traditional fermentation processes like wine, beer and bread making. Today, yeasts are also used as alternative sources of high nutritional value proteins, enzymes and vitamins, and have numerous applications in the health food industry as food additives, conditioners and flavouring agents, for the production of microbiology media and extracts, as well as livestock feeds. Modern scientific advances allow the isolation, construction and industrial production of new yeast strains to satisfy the specific demands of the food industry. Types of commercial food grade yeasts, industrial production processes and raw materials are highlighted. Aspects of yeast metabolism, with respect to carbohydrate utilization, nutritional aspects and recent research advances are also discussed.

  19. Processing of low-grade uranium ores

    International Nuclear Information System (INIS)

    Michel, P.

    1975-01-01

    Four types of low grade ores are studied. Low grade ores which must be extracted because they are enclosed in a normal grade deposit. Heap leaching is the processing method which is largely used. It allows to obtain solutions or preconcentrates which may be delivered at the nearest plant. Normal grade ores contained in a low amplitude deposit which can be processed using leaching as far as the operation does not need any large expensive equipment. Medium grade ores in medium amplitude deposits to which a simplified conventional process can be applied using fast heap leaching. Low grade ores in large deposits. The processing possibilities leading to use in place leaching are explained. The operating conditions of the method are studied (leaching agent, preparation of the ore deposit to obtain a good tightness with regard to the hydrological system and to have a good contact between ore and reagent) [fr

  20. Processing of low grade uranium ores

    International Nuclear Information System (INIS)

    Michel, P.

    1978-10-01

    Four types of low-grade ores are studied: (1) Low-grade ores that must be extracted because they are enclosed in a normal-grade deposit. Heap leaching is the processing method which is largely used. (2) Normal-grade ores contained in low-amplitude deposits. They can be processed using in-place leaching as far as the operation does not need any large and expensive equipment. (3) Medium-grade ores in medium-amplitude deposits. A simplified conventional process can be applied using fast heap leaching. (4) Low-grade ores in large deposits. The report explains processing possibilities leading in most cases to the use of in-place leaching. The operating conditions of this method are laid out, especially the selection of the leaching agents and the preparation of the ore deposit

  1. MRI differentiation of low-grade from high-grade appendicular chondrosarcoma

    International Nuclear Information System (INIS)

    Douis, Hassan; Singh, Leanne; Saifuddin, Asif

    2014-01-01

    To identify magnetic resonance imaging (MRI) features which differentiate low-grade chondral lesions (atypical cartilaginous tumours/grade 1 chondrosarcoma) from high-grade chondrosarcomas (grade 2, grade 3 and dedifferentiated chondrosarcoma) of the major long bones. We identified all patients treated for central atypical cartilaginous tumours and central chondrosarcoma of major long bones (humerus, femur, tibia) over a 13-year period. The MRI studies were assessed for the following features: bone marrow oedema, soft tissue oedema, bone expansion, cortical thickening, cortical destruction, active periostitis, soft tissue mass and tumour length. The MRI-features were compared with the histopathological tumour grading using univariate, multivariate logistic regression and receiver operating characteristic curve (ROC) analyses. One hundred and seventy-nine tumours were included in this retrospective study. There were 28 atypical cartilaginous tumours, 79 grade 1 chondrosarcomas, 36 grade 2 chondrosarcomas, 13 grade 3 chondrosarcomas and 23 dedifferentiated chondrosarcomas. Multivariate analysis demonstrated that bone expansion (P = 0.001), active periostitis (P = 0.001), soft tissue mass (P < 0.001) and tumour length (P < 0.001) were statistically significant differentiating factors between low-grade and high-grade chondral lesions with an area under the ROC curve of 0.956. On MRI, bone expansion, active periostitis, soft tissue mass and tumour length can reliably differentiate high-grade chondrosarcomas from low-grade chondral lesions of the major long bones. (orig.)

  2. MRI differentiation of low-grade from high-grade appendicular chondrosarcoma

    Energy Technology Data Exchange (ETDEWEB)

    Douis, Hassan; Singh, Leanne; Saifuddin, Asif [The Royal National Orthopaedic Hospital NHS Trust, Department of Radiology, Stanmore, Middlesex (United Kingdom)

    2014-01-15

    To identify magnetic resonance imaging (MRI) features which differentiate low-grade chondral lesions (atypical cartilaginous tumours/grade 1 chondrosarcoma) from high-grade chondrosarcomas (grade 2, grade 3 and dedifferentiated chondrosarcoma) of the major long bones. We identified all patients treated for central atypical cartilaginous tumours and central chondrosarcoma of major long bones (humerus, femur, tibia) over a 13-year period. The MRI studies were assessed for the following features: bone marrow oedema, soft tissue oedema, bone expansion, cortical thickening, cortical destruction, active periostitis, soft tissue mass and tumour length. The MRI-features were compared with the histopathological tumour grading using univariate, multivariate logistic regression and receiver operating characteristic curve (ROC) analyses. One hundred and seventy-nine tumours were included in this retrospective study. There were 28 atypical cartilaginous tumours, 79 grade 1 chondrosarcomas, 36 grade 2 chondrosarcomas, 13 grade 3 chondrosarcomas and 23 dedifferentiated chondrosarcomas. Multivariate analysis demonstrated that bone expansion (P = 0.001), active periostitis (P = 0.001), soft tissue mass (P < 0.001) and tumour length (P < 0.001) were statistically significant differentiating factors between low-grade and high-grade chondral lesions with an area under the ROC curve of 0.956. On MRI, bone expansion, active periostitis, soft tissue mass and tumour length can reliably differentiate high-grade chondrosarcomas from low-grade chondral lesions of the major long bones. (orig.)

  3. Peer Victimization in Fifth Grade and Health in Tenth Grade

    Science.gov (United States)

    Elliott, Marc N.; Klein, David J.; Tortolero, Susan R.; Mrug, Sylvie; Peskin, Melissa F.; Davies, Susan L.; Schink, Elizabeth T.; Schuster, Mark A.

    2014-01-01

    BACKGROUND AND OBJECTIVES: Children who experience bullying, a type of peer victimization, show worse mental and physical health cross-sectionally. Few studies have assessed these relationships longitudinally. We examined longitudinal associations of bullying with mental and physical health from elementary to high school, comparing effects of different bullying histories. METHODS: We analyzed data from 4297 children surveyed at 3 time points (fifth, seventh, and tenth grades) in 3 cities. We used multivariable regressions to test longitudinal associations of bullying with mental and physical health by comparing youth who experienced bullying in both the past and present, experienced bullying in the present only, experienced bullying in the past only, or did not experience bullying. RESULTS: Bullying was associated with worse mental and physical health, greater depression symptoms, and lower self-worth over time. Health was significantly worse for children with both past and present bullying experiences, followed by children with present-only experiences, children with past-only experiences, and children with no experiences. For example, 44.6% of children bullied in both the past and present were at the lowest decile of psychosocial health, compared with 30.7% of those bullied in the present only (P = .005), 12.1% of those bullied in the past only (P bullied (P bullying are associated with substantially worse health. Clinicians who recognize bullying when it first starts could intervene to reverse the downward health trajectory experienced by youth who are repeated targets. PMID:24534401

  4. How Does the Severity of Injury Vary between Motorcycle and Automobile Accident Victims Who Sustain High-Grade Blunt Hepatic and/or Splenic Injuries? Results of a Retrospective Analysis.

    Science.gov (United States)

    Hsieh, Ting-Min; Tsai, Tsung-Cheng; Liu, Yueh-Wei; Hsieh, Ching-Hua

    2016-07-21

    High-grade blunt hepatic and/or splenic injuries (BHSI) remain a great challenge for trauma surgeons. The main aim of this study was to investigate the characteristics, mortality rates, and outcomes of high-grade BHSI in motorcyclists and car occupants hospitalized for treatment of traumatic injuries in a Level I trauma center in southern Taiwan. High-grade BHSI are defined as grade III-VI blunt hepatic injuries and grade III-V blunt splenic injuries. This retrospective study reviewed the data of 101 motorcyclists and 32 car occupants who experienced a high-grade BHSI from 1 January 2011 to 31 December 2013. Two-sided Fisher's exact or Pearson's chi-square tests were used to compare categorical data, unpaired Student's t-test was used to analyze normally distributed continuous data, and Mann-Whitney's U test was used to compare non-normally distributed data. In this study, the majority (76%, 101/133) of high-grade BHSI were due to motorcycle crashes. Car occupants had a significantly higher injury severity score (ISS; 26.8 ± 10.9 vs. 20.7 ± 10.4, respectively, p = 0.005) and organ injured score (OIS; 3.8 ± 1.0 vs. 3.4 ± 0.6, respectively, p = 0.033), as well as a significantly longer hospital length of stay (LOS; 21.2 days vs. 14.6 days, respectively, p = 0.038) than did motorcyclists. Car occupants with high-grade BHSI also had worse clinical presentations than their motorcyclist counterparts, including a significantly higher incidence of hypotension, hyperpnea, tube thoracostomy, blood transfusion >4 units, LOS in intensive care unit >5 days, and complications. However, there were no differences in the percentage of angiography or laparotomy performed or mortality rate between these two groups of patients. This study demonstrated that car occupants with high-grade BHSI were injured more severely, had a higher incidence of worse clinical presentation, had a longer hospital LOS, and had a higher incidence of complications than motorcyclists. The results also

  5. How Does the Severity of Injury Vary between Motorcycle and Automobile Accident Victims Who Sustain High-Grade Blunt Hepatic and/or Splenic Injuries? Results of a Retrospective Analysis

    Directory of Open Access Journals (Sweden)

    Ting-Min Hsieh

    2016-07-01

    Full Text Available Background: High-grade blunt hepatic and/or splenic injuries (BHSI remain a great challenge for trauma surgeons. The main aim of this study was to investigate the characteristics, mortality rates, and outcomes of high-grade BHSI in motorcyclists and car occupants hospitalized for treatment of traumatic injuries in a Level I trauma center in southern Taiwan. Methods: High-grade BHSI are defined as grade III-VI blunt hepatic injuries and grade III-V blunt splenic injuries. This retrospective study reviewed the data of 101 motorcyclists and 32 car occupants who experienced a high-grade BHSI from 1 January 2011 to 31 December 2013. Two-sided Fisher’s exact or Pearson’s chi-square tests were used to compare categorical data, unpaired Student’s t-test was used to analyze normally distributed continuous data, and Mann–Whitney’s U test was used to compare non-normally distributed data. Results: In this study, the majority (76%, 101/133 of high-grade BHSI were due to motorcycle crashes. Car occupants had a significantly higher injury severity score (ISS; 26.8 ± 10.9 vs. 20.7 ± 10.4, respectively, p = 0.005 and organ injured score (OIS; 3.8 ± 1.0 vs. 3.4 ± 0.6, respectively, p = 0.033, as well as a significantly longer hospital length of stay (LOS; 21.2 days vs. 14.6 days, respectively, p = 0.038 than did motorcyclists. Car occupants with high-grade BHSI also had worse clinical presentations than their motorcyclist counterparts, including a significantly higher incidence of hypotension, hyperpnea, tube thoracostomy, blood transfusion >4 units, LOS in intensive care unit >5 days, and complications. However, there were no differences in the percentage of angiography or laparotomy performed or mortality rate between these two groups of patients. Conclusions: This study demonstrated that car occupants with high-grade BHSI were injured more severely, had a higher incidence of worse clinical presentation, had a longer hospital LOS, and had a

  6. What's in a Grade? Grading Policies and Practices in Principles of Economics

    Science.gov (United States)

    Walstad, William B.; Miller, Laurie A.

    2016-01-01

    Survey results from a national sample of economics instructors describe the grading policies and practices in principles of economics courses. The survey results provide insights about absolute and relative grading systems used by instructors, the course components and their weights that determine grades, and the type of assessment items used for…

  7. [Reproducibility of Fuhrman nuclear grade: advantages of a two-grade system].

    Science.gov (United States)

    Letourneux, Hervé; Lindner, Véronique; Lang, Hervé; Massfelder, Thierry; Meyer, Nicolas; Saussine, Christian; Jacqmin, Didier

    2006-06-01

    The Fuhrman nuclear grade is the reference histoprognostic grading system routinely used all over the world for renal cell carcinoma. Studies measuring the inter-observer and intra-observer concordance of Fuhrman grade show poor results in terms of reproducibility and repeatability. These variations are due to a certain degree of subjectivity of the pathologist in application of the definition of tumour grade, particularly nuclear grade. Elements able to account for this subjectivity in renal cell carcinoma are identified from a review of the literature. To improve the reliability of nuclear grade, the territory occupied by the highest grade must be specified and the grades should probably be combined. At the present time, regrouping of grade 1 and 2 tumours as low grade and grade 3 and 4 tumours as high grade would achieve better reproducibility, while preserving the prognostic: value for overall survival. The development of new treatment modalities and their use in adjuvant situations will imply the use of reliable histoprognostic factors to specify, indications.

  8. Teachers grading practices : an analysis of the reliability of teacher-assigned grade point average (GPA)

    NARCIS (Netherlands)

    van der Lans, R. M.; van de Grift, W. J. C. M.; van Veen, K.

    2015-01-01

    In previous research, teachers report that they use a hodgepodge of factors when grading students. This has led researchers to suspect that teacher-assigned grades are inflated by teacher-student interactions; the hodgepodge hypothesis. Teachers also are reported to differ in grading leniency; the

  9. The Impact of Early Exposure of Eighth Grade Math Standards on End of Grade Assessments

    Science.gov (United States)

    Robertson, Tonjai E.

    2016-01-01

    The purpose of this study was to examine the Cumberland County Schools district-wide issue surrounding the disproportional performance of eighth grade Math I students' proficiency scores on standardized end-of-grade and end-of-course assessments. The study focused on the impact of the school district incorporating eighth grade math standards in…

  10. Are Flunkers Social Outcasts? A Multilevel Study of Grade Retention Effects on Same-Grade Friendships

    Science.gov (United States)

    Demanet, Jannick; Van Houtte, Mieke

    2016-01-01

    We examine the association between grade retention and the number of same-grade friendships. Moreover, we investigate the effect of a school's proportion of retained students on these friendships and the moderating effect of this school characteristic on the relationship between retention and the number of same-grade friendships. Multilevel…

  11. Fifth Grade Elementary Students' Conceptions of Earthquakes

    Science.gov (United States)

    Savasci, Funda; Uluduz, Hatice

    2013-01-01

    This study intends to investigate the fifth grade students' conceptions of earthquakes. Twenty two grade 5 students (11-12 years old) from five different elementary schools in Istanbul voluntarily participated in the study. Data were collected from semi-structured interviews with each participant. Six interview questions were designed by…

  12. Matriculation Research Report: Incomplete Grades; Data & Analysis.

    Science.gov (United States)

    Gerda, Joe

    The policy on incomplete grades at California's College of the Canyons states that incompletes may only be given under circumstances beyond students' control and that students must make arrangements with faculty prior to the end of the semester to clear the incomplete. Failure to complete an incomplete may result in an "F" grade. While…

  13. The Leap into 4th Grade

    Science.gov (United States)

    Anderson, Mike

    2011-01-01

    Fourth grade is a pivotal year, in which students commonly face increased academic demands. According to Anderson, teachers can help students make a smooth transition to 4th grade by introducing these new challenges in ways that are in line with 4th graders' common developmental characteristics: incredible energy and emotion, industriousness and…

  14. Bruxism defined and graded: an international consensus

    NARCIS (Netherlands)

    Lobbezoo, F.; Ahlberg, J.; Glaros, A.G.; Kato, T.; Koyano, K.; Lavigne, G.J.; de Leeuw, R.; Manfredini, D.; Svensson, P.; Winocur, E.

    2013-01-01

    To date, there is no consensus about the definition and diagnostic grading of bruxism. A written consensus discussion was held among an international group of bruxism experts as to formulate a definition of bruxism and to suggest a grading system for its operationalisation. The expert group defined

  15. Perceptions of restaurateurs on quality grading

    Directory of Open Access Journals (Sweden)

    Joseph Roberson

    2014-01-01

    Full Text Available A restaurateur's strategic focus is to maximise wealth for the owner(s. To achieve wealth maximisation, a restaurateur could implement one or more of the following strategies: focus strategy, cost-leadership strategy and/or differentiation strategy. A management intervention a restaurateur could implement to achieve this is quality differentiation. Grading of an establishment will assist a restaurateur in becoming a market leader. Currently there no national restaurant grading system exists in South Africa. As support and participation of restaurateurs in any future quality grading system are essential, it is imperative to test their perceptions of the implementation of a quality grading scale. The aim of this paper is to gather the perceptions of restaurateurs of an envisaged scale that could be used to grade independent full-service restaurants. In this study the researcher tested the perceptions of restaurateurs using nine possible outcomes of implementing quality grading in the independent fullservice restaurant segment. The outcomes to be tested were presented to restaurateurs in a questionnaire uploaded on "survey monkey". This was emailed to 3 286 restaurateurs and 265 responses were received. Respondents who were positive regarding grading indicated that they were enthusiastic about the impact grading would have on international tourism, as well as the fact that it could contribute to an increase in the value of their establishments.

  16. 7 CFR 51.2556 - Grades.

    Science.gov (United States)

    2010-01-01

    ... Standards for Grades of Shelled Pistachio Nuts § 51.2556 Grades. (a) “U.S. Fancy,” “U.S. Extra No. 1,” and “U.S. No. 1” consist of pistachio kernels which meet the following requirements: (1) Well dried, or...

  17. Contraction of graded su(2) algebra

    International Nuclear Information System (INIS)

    Patra, M.K.; Tripathy, K.C.

    1989-01-01

    The Inoenu-Wigner contraction scheme is extended to Lie superalgebras. The structure and representations of extended BRS algebra are obtained from contraction of the graded su(2) algebra. From cohomological consideration, we demonstrate that the graded su(2) algebra is the only superalgebra which, on contraction, yields the full BRS algebra. (orig.)

  18. What's ahead in automated lumber grading

    Science.gov (United States)

    D. Earl Kline; Richard Conners; Philip A. Araman

    1998-01-01

    This paper discusses how present scanning technologies are being applied to automatic lumber grading. The presentation focuses on 1) what sensing and scanning devices are needed to measure information for accurate grading feature detection, 2) the hardware and software needed to efficiently process this information, and 3) specific issues related to softwood lumber...

  19. Liberal Grading Improves Evaluations But Not Performance.

    Science.gov (United States)

    Vasta, Ross; Sarmiento, Robert F.

    Two grading distributions--a liberal and a more stringent curve--were compared between two sections of an undergraduate psychology course. The two classes were team taught and treated as similarly as possible. Four unit exams and an optional final were administered, with one section consistently receiving a more lenient grade distribution. No…

  20. Examining First Grade Teachers' Handwriting Instruction

    Science.gov (United States)

    Arslan, Derya

    2012-01-01

    The purpose of this study is to examine the first grade teachers' practices of handwriting instructions in terms of teaching, evaluation and handwriting difficulties. From qualitative research patterns, phenomenology was used. The study was applied to the 54 First grade teachers who work at central Burdur and Burdur county centre primary education…

  1. Extrauterine Low-Grade Endometrial Stromal Sarcoma

    Directory of Open Access Journals (Sweden)

    Yu-Ju Chen

    2005-12-01

    Conclusions: Low-grade endometrial stromal sarcoma typically has an indolent clinical course and favorable prognosis. Surgical resection is the primary therapeutic approach, and adjuvant therapy with radiotherapy, chemotherapy, or progesterone therapy should be considered for the management of residual or recurrent low-grade endometrial stromal sarcomas.

  2. Grade Repetition in Queensland State Prep Classes

    Science.gov (United States)

    Anderson, Robyn

    2012-01-01

    The current study considers grade repetition rates in the early years of schooling in Queensland state schools with specific focus on the pre-schooling year, Prep. In particular, it provides empirical evidence of grade repetition in Queensland state schools along with groups of students who are more often repeated. At the same time, much of the…

  3. Consumer Preference for Graded Maple Syrup

    Science.gov (United States)

    Paul E. Sendak

    1978-01-01

    The three grades of maple syrup and a commercial table syrup containing artificial flavor and 3 percent pure maple syrup were evaluated by 1,018 women in four cities. The results indicate that differences in preference for flavor are related to how close the respondents are to a maple syrup-production region. Differences in preference among grades of pure maple syrup...

  4. Determinants of College Grade Point Averages

    Science.gov (United States)

    Bailey, Paul Dean

    2012-01-01

    Chapter 2: The Role of Class Difficulty in College Grade Point Averages. Grade Point Averages (GPAs) are widely used as a measure of college students' ability. Low GPAs can remove a students from eligibility for scholarships, and even continued enrollment at a university. However, GPAs are determined not only by student ability but also by the…

  5. Grading sugar pine saw logs in trees.

    Science.gov (United States)

    John W. Henley

    1972-01-01

    Small limbs and small overgrown limbs cause problems when grading saw logs in sugar pine trees. Surface characteristics and lumber recovery information for 426 logs from 64 sugar pine trees were examined. Resulting modifications in the grading specification that allow a grader to ignore small limbs and small limb indicators do not appear to decrease the performance of...

  6. Graded activity: legacy of the sanatorium.

    Science.gov (United States)

    Creighton, C

    1993-08-01

    Occupational therapists in all areas of practice grade therapeutic activities to help patients progress toward their goals. It is proposed in this paper that the concept of graded activity originated in German tuberculosis sanatoria in the late 1800s, when patients were required to walk on graded (sloped) land for exercise. British physician Marcus Paterson included work, as well as walking, in his graduated exercise program for tuberculosis patients and was honored for this innovation at the founding meeting of the National Society for the Promotion of Occupational Therapy (NSPOT). George Barton, Susan Tracy, and Herbert Hall were among the NSPOT members who contributed to the development of graded activity as a principle in occupational therapy intervention. The military rehabilitation programs established during World War I provided additional impetus, and by the mid-1920s, graded activity was recognized as central to the profession.

  7. Functionally Graded Adhesives for Composite Joints

    Science.gov (United States)

    Stapleton, Scott E.; Waas, Anthony M.; Arnold, Steven M.

    2012-01-01

    Adhesives with functionally graded material properties are being considered for use in adhesively bonded joints to reduce the peel stress concentrations located near adherend discontinuities. Several practical concerns impede the actual use of such adhesives. These include increased manufacturing complications, alterations to the grading due to adhesive flow during manufacturing, and whether changing the loading conditions significantly impact the effectiveness of the grading. An analytical study is conducted to address these three concerns. An enhanced joint finite element, which uses an analytical formulation to obtain exact shape functions, is used to model the joint. Furthermore, proof of concept testing is conducted to show the potential advantages of functionally graded adhesives. In this study, grading is achieved by strategically placing glass beads within the adhesive layer at different densities along the joint.

  8. Foraminal syringomyelia: suggestion for a grading system.

    Science.gov (United States)

    Versari, P P; D'Aliberti, G; Talamonti, G; Collice, M

    1993-01-01

    The standard treatment of foraminal syringomyelia includes foramen magnum decompression and duraplasty. Improvement or stabilization of the disease are achieved in most of cases. However, at least one third of patients are reported to receive little or no benefit. In this paper we retrospectively reviewed a series of 40 consecutive foramen magnum decompressions in order to identify the possible pre-operative outcome predictors. Based on clinical evolution, neurological impairment and radiological features, a scale of severity was fixed and retrospectively tested. A pre-operative score was obtained for each patient and was correlated with the surgical results. Then a four level grading system was derived. All grade I and grade II patients achieved good results (improvement or stabilization), whereas grade III patients showed intermediate behaviour and grade IV invariably worsened. On this basis, surgical results of foramen magnum decompression might be further improved provided that a careful pre-operative selection is made.

  9. Arthroscopically assisted stabilization of acute high-grade acromioclavicular joint separations in a coracoclavicular Double-TightRope technique: V-shaped versus parallel drill hole orientation.

    Science.gov (United States)

    Kraus, Natascha; Haas, Norbert P; Scheibel, Markus; Gerhardt, Christian

    2013-10-01

    The arthroscopically assisted Double-TightRope technique has recently been reported to yield good to excellent clinical results in the treatment of acute, high-grade acromioclavicular dislocation. However, the orientation of the transclavicular-transcoracoidal drill holes remains a matter of debate. A V-shaped drill hole orientation leads to better clinical and radiologic results and provides a higher vertical and horizontal stability compared to parallel drill hole placement. This was a cohort study; level of evidence, 2b. Two groups of patients with acute high-grade acromioclavicular joint instability (Rockwood type V) were included in this prospective, non-randomized cohort study. 15 patients (1 female/14 male) with a mean age of 37.7 (18-66) years were treated with a Double-TightRope technique using a V-shaped orientation of the drill holes (group 1). 13 patients (1 female/12 male) with a mean age of 40.9 (21-59) years were treated with a Double-TightRope technique with a parallel drill hole placement (group 2). After 2 years, the final evaluation consisted of a complete physical examination of both shoulders, evaluation of the Subjective Shoulder Value (SSV), Constant Score (CS), Taft Score (TF) and Acromioclavicular Joint Instability Score (ACJI) as well as a radiologic examination including bilateral anteroposterior stress views and bilateral Alexander views. After a mean follow-up of 2 years, all patients were free of shoulder pain at rest and during daily activities. Range of motion did not differ significantly between both groups (p > 0.05). Patients in group 1 reached on average 92.4 points in the CS, 96.2 % in the SSV, 10.5 points in the TF and 75.9 points in the ACJI. Patients in group 2 scored 90.5 points in the CS, 93.9 % in the SSV, 10.5 points in the TF and 84.5 points in the ACJI (p > 0.05). Radiographically, the coracoclavicular distance was found to be 13.9 mm (group 1) and 13.4 mm (group 2) on the affected side and 9.3 mm (group 1

  10. Automated tone grading of granite

    International Nuclear Information System (INIS)

    Catalina Hernández, J.C.; Fernández Ramón, G.

    2017-01-01

    The production of a natural stone processing plant is subject to the intrinsic variability of the stone blocks that constitute its raw material, which may cause problems of lack of uniformity in the visual appearance of the produced material that often triggers complaints from customers. The best way to tackle this problem is to classify the product according to its visual features, which is traditionally done by hand: an operator observes each and every piece that comes out of the production line and assigns it to the closest match among a number of predefined classes, taking into account visual features of the material such as colour, texture, grain, veins, etc. However, this manual procedure presents significant consistency problems, due to the inherent subjectivity of the classification performed by each operator, and the errors caused by their progressive fatigue. Attempts to employ automated sorting systems like the ones used in the ceramic tile industry have not been successful, as natural stone presents much higher variability than ceramic tiles. Therefore, it has been necessary to develop classification systems specifically designed for the treatment of the visual parameters that distinguish the different types of natural stone. This paper describes the details of a computer vision system developed by AITEMIN for the automatic classification of granite pieces according to their tone, which provides an integral solution to tone grading problems in the granite processing and marketing industry. The system has been designed to be easily trained by the end user, through the learning of the samples established as tone patterns by the user. [es

  11. GRADE INFLATION: An Issue for Higher Education?

    Directory of Open Access Journals (Sweden)

    Donald L. CARUTH,

    2013-01-01

    Full Text Available Grade inflation impacts university credibility, student courses of study, choices of institution, and other areas. There has been an upward shift in grades without a corresponding upward shift in knowledge gained. Some of the most frequently mentioned causes of grade inflation are: Ø student evaluations of professors, Ø student teacher dynamics, Ø merit-based financial aid, and Ø student expectations. Ø Among the reasons for higher student grades on the part of professors are: Ø fear of student evaluations, Ø avoidance of bad relations with students, Ø below average teaching skills,Ø lack of experience, Ø a lack of clearly stated objectives, and Ø job security. While grades are not a perfect answer to assessing student performance in a course they are still the best answer we have for evaluating students. In order to evaluate students more accurately, universities must identify the problems in grading and grading practices. Once this is accomplished new practices can be designed and policies implemented.

  12. Power calculation of grading device in desintegrator

    Science.gov (United States)

    Bogdanov, V. S.; Semikopenko, I. A.; Vavilov, D. V.

    2018-03-01

    This article describes the analytical method of measuring the secondary power consumption, necessitated by the installation of a grading device in the peripheral part of the grinding chamber in the desintegrator. There is a calculation model for defining the power input of the disintegrator increased by the extra power demand, required to rotate the grading device and to grind the material in the area between the external row of hammers and the grading device. The work has determined the inertia moments of a cylindrical section of the grading device with armour plates. The processing capacity of the grading device is adjusted to the conveying capacity of the auger feeder. The grading device enables one to increase the concentration of particles in the peripheral part of the grinding chamber and the amount of interaction between particles and armour plates as well as the number of colliding particles. The perforated sections provide the output of the ground material with the proper size granules, which together with the effects of armour plates, improves the efficiency of grinding. The power demand to rotate the grading device does not exceed the admissible value.

  13. Alternative Grading Systems. The Practitioner, Vol. III, No. 3.

    Science.gov (United States)

    De Leonibus, Nancy; Thomson, Scott

    After examining some of the pros and cons of traditional grading, the demands colleges make on grading practices, and the responses of people interested in grading, a number of examples of operating alternative systems are given. The alternatives include a dual (pass/withdraw grading in some courses, traditional grading in others) system, a…

  14. 7 CFR 51.1578 - Off-Grade potatoes.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Off-Grade potatoes. 51.1578 Section 51.1578... STANDARDS) United States Consumer Standards for Potatoes Off-Grade § 51.1578 Off-Grade potatoes. Potatoes which fail to meet the requirements of any of the foregoing grades shall be Off-Grade potatoes...

  15. Asymmetric acoustic transmission in graded beam

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Li, E-mail: lj94172350@hotmail.com [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Wu, Jiu Hui, E-mail: ejhwu@mail.xjtu.edu.cn [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Guan, Dong; Lu, Kuan [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Gao, Nansha [School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China); Songhua, Cao [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China)

    2016-12-01

    We demonstrate the dynamic effective material parameters and vibration performance of a graded beam. The structure of the beam was composed of several unit cells with different fill factors. The dispersion relations and energy band structures of each unit cell were calculated using the finite element method (FEM). The dynamic effective material parameters in each unit cell of the graded beam were determined by the dispersion relations and energy band structures. Longitudinal wave propagation was investigated using a numerical method and FEM. The results show that the graded beam allows asymmetric acoustic transmission over a wide range of frequencies.

  16. Graded Alternating-Time Temporal Logic

    Science.gov (United States)

    Faella, Marco; Napoli, Margherita; Parente, Mimmo

    Graded modalities enrich the universal and existential quantifiers with the capability to express the concept of at least k or all but k, for a non-negative integer k. Recently, temporal logics such as μ-calculus and Computational Tree Logic, Ctl, augmented with graded modalities have received attention from the scientific community, both from a theoretical side and from an applicative perspective. Both μ-calculus and Ctl naturally apply as specification languages for closed systems: in this paper, we add graded modalities to the Alternating-time Temporal Logic (Atl) introduced by Alur et al., to study how these modalities may affect specification languages for open systems.

  17. Phase-coherent transport and spin-orbit-coupling in III/V-semiconductor nanowires; Phasenkohaerenter Transport und Spin-Bahn-Wechselwirkung in III/V-Halbleiternanodraehten

    Energy Technology Data Exchange (ETDEWEB)

    Estevez Hernandez, Sergio

    2009-10-16

    Semiconductor nanowires fabricated by a bottom-up approach are not only interesting for the realization of future nanoscaled devices but also appear to be very attractive model systems to tackle fundamental questions concerning the transport in strongly confined systems. In order to avoid the problem connected with carrier depletion, narrowband gap semiconductors, i.e., InAs or InN, or core-shell Nanowires, i.e., GaAs/AlGaAs, are preferred. The underlying reason is that in InAs or InN the Fermi-level pinning in the conduction band results in a carrier accumulation at the surface. In fact, the tubular topology of the surface electron gas opens up the possibility to observe unconventional quantum transport phenomena. When the phase-coherence length in the nanowire is comparable to its dimensions the conductance fluctuates if a magnetic field is applied or if the electron concentration is changed by means of a gate electrode. These so-called universal conductance fluctuations being in the order of e{sup 2}/h originate from the fact that in small disordered samples, electron interference effects are not averaged out. In this work are analyzed universal conductance fluctuations to study the quantum transport properties in InN, InAs and GaAs/AlGaAs nanowires. With the use of a magnetic field and a back-gate electrode the universal conductance fluctuations and localizations effects were analyzed. Since InN and InAs are narrow band gap semiconductors, one naturally expects spin-orbit coupling effects. Because this phenomena is of importance for spin electronic applications. However, owing to the cylindrical symmetry of the InN and InAs nanowires, the latter effect was observable and actually be used to determine the strength of spin-orbit coupling. In order to clearly separate the weak antilocalization effect from the conductance fluctuations, the averaging of the magnetoconductance at different gate voltages was essential. The low-temperature quantum transport properties of gated InN, InAs and GaAs/AlGaAs nanowires were investigated. Magnetic field-dependent as well as gate-dependent measurements of universal conductance fluctuations were performed to gain information on the phase coherence in the electron transport. In this work was found a pronounced decrease in the variance of the conductance by about a factor of 2 in gate-dependent fluctuation measurements if a magnetic field is applied. This effect is explained by the suppression of the Cooperon channel of the electron correlation contributing to the conductance fluctuations. Despite the fact that the diameter of the nanowire is less than 100 nm a clear weak antilocalization effect is found in the averaged magnetoconductance being in strong contrast to the suppression of weak antilocalization for narrow quantum wires based on planar two-dimensional electron gases. The unexpected robustness of the weak antilocalization effect observed here is attributed to the tubular topology of the surface electron gas in InN and InAs nanowires. (orig.)

  18. Surface characterization of III-V MOCVD films from heterocyclic single-source precursors; Oberflaechencharakterisierung von III-V MOCVD-Filmen aus heterozyklischen Single Source Precursoren

    Energy Technology Data Exchange (ETDEWEB)

    Seemayer, Andreas

    2009-07-13

    In the present thesis the sublimation and evaporation properties of heterocyclic gallium and antimony containing single-source precursors as well as the chemical composition and morphology of the films fabricated from this were studied. The single-source precursors available by a new synthesis route were characterized concerning their evaporation properties and the obtained films studied surface-physically. By this way the process parameters were optimized and the applicability of the single-source precursors in HV-MOCVD processes studied. By evaporation experiments in the UHV it could be shown that thereby lighter ligands like ethyl- and methyl-groups lead to a lower contamination of the reaction space with carbon containing molecules. Furthermore it was expected that the 6-rings synthetized with short ligands exhibit a high stability. This however could not be confirmed. By unwanted parasitary reactions in the gaseous phase respectively dissociative sublimation in the gaseous phase a deposition of GaSb with these precursors was not possible. The 4-ring stabilized with tertiary-butyl and ethyl-groups caused in the evaporation the largest contamination of the gaseous phase, becauselonger-chain hydrocarbons exhibil only a bad pump cross section. By parasitary reactions originating elementary antimony is detectable in the gaseous phase. The films were studied concerning their chemical composition and their transport- respectively storage-conditioned surface contamination. Furthermore it has become clear that not only a purely synthetized precursor substance but also the reactor design is deciding for a successful deposition and a high film quality. First by successive optimization of the evaporation geometry it was possible to reduce the roughness of the produced GaSb films down to about 10 nm-30 nm.

  19. The influence of nitrogen on the photoluminescence of metastable III-V nitrides; Einflussvon Stickstoff auf die Photolumineszenz von metastabilen III-V-Nitriden

    Energy Technology Data Exchange (ETDEWEB)

    Hantke, K.

    2005-12-20

    The work presented here mainly summarizes experimental and theoretical results enlightening the material-specific, optical properties of (GaIn)(NAs). The primarily used experiment is the time-resolved photoluminescence spectroscopy. The comparison of experiment and theory yields a simple exponential form for the density of localized states. Furthermore it can be confirmed that the typical energy scale of the localization is diminished by the annealing step as well as by the hydrogenation process. In a next step, the investigation of (GaIn)(NAs) epitactical layers, that were optimized for solar cell application, reveals astonishing features: The minority-carrier diffusion-length of the p-doped layers is found to be slightly higher than for the n-doped material implying that (GaIn)(NAs) solar cells with a p-on-n structure should be preferred in terms of higher quantum efficiency. A new effect found during the investigations is the optimization of the internal quantum efficiency of the (GaIn)(NAs) structures after irradiation with intensive laser light attributed to the laser-induced annealing of defects. The final paragraph concentrates on the successful comparison of time-resolved photoluminescence, photo-modulated reflection measurements and a microscopic many-body theory. A profound understanding of the type-I type-II transition in (GaIn)As/Ga(NAs) heterostructures is achieved resulting in material-specific information as e.g. the temperature-dependent bandgap energies, the band offsets in Ga(NAs)/GaAs and (GaIn)As/Ga(NAs) respectively, as well as the interaction potential VN dependent on the nitrogen content. Finally, the fundamental dependence on excitation density investigated in the experiment is theoretically quantified not only for the photoluminescence intensity and but for the lifetimes, too. (orig.)

  20. ENERGY STAR Laboratory Grade Refrigerators and Freezers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 1.0 ENERGY STAR Program Requirements for Laboratory Grade Refrigerators and Freezers that...

  1. High Performance Graded Index Polymer Optical Fibers

    National Research Council Canada - National Science Library

    Garito, Anthony

    1998-01-01

    ...) plastic optical fibers (POF) and graded index (GI) POFs are reported. A set of criteria and analyses of physical parameters are developed in context to the major issues of POF applications in short-distance communication systems...

  2. Bruxism defined and graded: an international consensus.

    Science.gov (United States)

    Lobbezoo, F; Ahlberg, J; Glaros, A G; Kato, T; Koyano, K; Lavigne, G J; de Leeuw, R; Manfredini, D; Svensson, P; Winocur, E

    2013-01-01

    To date, there is no consensus about the definition and diagnostic grading of bruxism. A written consensus discussion was held among an international group of bruxism experts as to formulate a definition of bruxism and to suggest a grading system for its operationalisation. The expert group defined bruxism as a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. Bruxism has two distinct circadian manifestations: it can occur during sleep (indicated as sleep bruxism) or during wakefulness (indicated as awake bruxism). For the operationalisation of this definition, the expert group proposes a diagnostic grading system of 'possible', 'probable' and 'definite' sleep or awake bruxism. The proposed definition and grading system are suggested for clinical and research purposes in all relevant dental and medical domains. © 2012 Blackwell Publishing Ltd.

  3. Kindergarten Predictors of Third Grade Writing

    Science.gov (United States)

    Kim, Young-Suk; Al Otaiba, Stephanie; Wanzek, Jeanne

    2015-01-01

    The primary goal of the present study was to examine the relations of kindergarten transcription, oral language, word reading, and attention skills to writing skills in third grade. Children (N = 157) were assessed on their letter writing automaticity, spelling, oral language, word reading, and attention in kindergarten. Then, they were assessed on writing in third grade using three writing tasks – one narrative and two expository prompts. Children’s written compositions were evaluated in terms of writing quality (the extent to which ideas were developed and presented in an organized manner). Structural equation modeling showed that kindergarten oral language and lexical literacy skills (i.e., word reading and spelling) were independently predicted third grade narrative writing quality, and kindergarten literacy skill uniquely predicted third grade expository writing quality. In contrast, attention and letter writing automaticity were not directly related to writing quality in either narrative or expository genre. These results are discussed in light of theoretical and practical implications. PMID:25642118

  4. Statistical Content in Middle Grades Mathematics Textbooks

    Science.gov (United States)

    Pickle, Maria Consuelo Capiral

    2012-01-01

    This study analyzed the treatment and scope of statistical concepts in four, widely-used, contemporary, middle grades mathematics textbook series: "Glencoe Math Connects," "Prentice Hall Mathematics," "Connected Mathematics Project," and "University of Chicago School Mathematics Project." There were three…

  5. Doubly graded sigma model with torsion

    International Nuclear Information System (INIS)

    Kowalski-Glikman, J.

    1986-08-01

    Using the Hull-Witten construction we show how to introduce torsion to the doubly graded sigma model. This construction enables us to find a link between this model and the ten-dimensional supergravity theory in superspace. (Auth.)

  6. Graded contractions of Jordan algebras and of their representations

    International Nuclear Information System (INIS)

    Kashuba, Iryna; Patera, JirI

    2003-01-01

    Contractions of Jordan algebras and Jordan superalgebras which preserve a chosen grading are defined and studied. Simultaneous grading of Jordan algebras and their representation spaces is used to develop a theory of grading, preserving contractions of representations of Jordan algebras

  7. Pollination biology of basal angiosperms (ANITA Grade)

    Science.gov (United States)

    Leonard B. Thien; Peter Bernhardt; Margaret S. Devall; Zhi-Duan Chen; Yi-bo Luo; Jian-Hua Fan; Liang-Chen Yuan; Joseph H. Williams

    2009-01-01

    The fi rst three branches of the angiosperm phylogenetic tree consist of eight families with ~201 species of plants (the ANITA grade). The oldest fl ower fossil for the group is dated to the Early Cretaceous (115 – 125 Mya) and identifi ed to the Nymphaeales. The fl owers of extant plants in the ANITA grade are small, and pollen is the edible reward (rarely nectar or...

  8. Meat standards and grading: a world view.

    Science.gov (United States)

    Polkinghorne, R J; Thompson, J M

    2010-09-01

    This paper addresses the principles relating to meat standards and grading of beef and advances the concept that potential exists to achieve significant desirable change from adopting more consumer focused systems within accurate value-based payment frameworks. The paper uses the definitions that classification is a set of descriptive terms describing features of the carcass that are useful to those involved in the trading of carcasses, whereas grading is the placing of different values on carcasses for pricing purposes, depending on the market and requirements of traders. A third definition is consumer grading, which refers to grading systems that seek to define or predict consumer satisfaction with a cooked meal. The development of carcass classification and grading schemes evolved from a necessity to describe the carcass using standard terms to facilitate trading. The growth in world trade of meat and meat products and the transition from trading carcasses to marketing individual meal portions raises the need for an international language that can service contemporary needs. This has in part been addressed by the United Nations promoting standard languages on carcasses, cuts, trim levels and cutting lines. Currently no standards exist for describing consumer satisfaction. Recent Meat Standards Australia (MSA) research in Australia, Korea, Ireland, USA, Japan and South Africa showed that consumers across diverse cultures and nationalities have a remarkably similar view of beef eating quality, which could be used to underpin an international language on palatability. Consumer research on the willingness to pay for eating quality shows that consumers will pay higher prices for better eating quality grades and generally this was not affected by demographic or meat preference traits of the consumer. In Australia the MSA eating quality grading system has generated substantial premiums to retailers, wholesalers and to the producer. Future grading schemes which measure

  9. Fatigue Characterization of Functionally Graded Metallic Alloys

    International Nuclear Information System (INIS)

    Silva, F. S.

    2008-01-01

    Functionally graded components exhibit spatial variations of mechanical properties in contrast with, and as an alternative to, purely homogeneous components. A large class of graded materials, however, are in fact mostly homogeneous materials with property variations (chemical or mechanical) restricted to a specific area or layer produced by applying for example a coating or by introducing sub-surface residual stresses. However, it is also possible to obtain graded materials with a smooth transition of mechanical properties along the entire component, for example in a 40 mm component. This is possible, for example, by using centrifugal casting technique or incremental melting and solidification technique. In this paper we will study fully metallic functionally graded components with a smooth gradient, focusing on fatigue crack propagation. Fatigue propagation will be assessed in the direction parallel to the gradation (in different homogeneous layers of the functionally graded component) to assess what would be fatigue crack propagation on the direction perpendicular to the gradation. Fatigue crack growth rate (standard mode I fatigue crack growth) will be correlated to the mode I stress intensity factor range. Other mechanical properties of different layers of the component (Young's modulus) will also be considered in this analysis. The effect of residual stresses along the component gradation on crack propagation will also be taken into account. A qualitative analysis of the effects of some important features, present in functionally graded materials, will be made based on the obtained results

  10. Age-Related Grade Inflation Expectancies in a University Environment

    Directory of Open Access Journals (Sweden)

    Donald A. Loffredo

    2012-01-01

    Full Text Available Grade inflation is a recognized problem in higher education in the United States. Age, gender, and ethnic differences in discrepancies between student reports of their expected grade in each course and their expectations for general university grading practices were explored in a survey of 166 (mostly female participants at a small upper-division university. Results revealed that while a small minority of students agreed that grading systems in college should only include A or B grades, a large majority of students expected A or B grades. Thus, student discrepancies between their expectations for grading systems and their expected class grades were in line with expectations that they should receive inflated grades. Results also revealed statistically significant age differences in grade expectation with students older than the age of 55 expecting lower grades relative to their younger counterparts.

  11. Burning weapons-grade plutonium in reactors

    International Nuclear Information System (INIS)

    Newman, D.F.

    1993-06-01

    As a result of massive reductions in deployed nuclear warheads, and their subsequent dismantlement, large quantities of surplus weapons- grade plutonium will be stored until its ultimate disposition is achieved in both the US and Russia. Ultimate disposition has the following minimum requirements: (1) preclude return of plutonium to the US and Russian stockpiles, (2) prevent environmental damage by precluding release of plutonium contamination, and (3) prevent proliferation by precluding plutonium diversion to sub-national groups or nonweapons states. The most efficient and effective way to dispose of surplus weapons-grade plutonium is to fabricate it into fuel and use it for generation of electrical energy in commercial nuclear power plants. Weapons-grade plutonium can be used as fuel in existing commercial nuclear power plants, such as those in the US and Russia. This recovers energy and economic value from weapons-grade plutonium, which otherwise represents a large cost liability to maintain in safeguarded and secure storage. The plutonium remaining in spent MOX fuel is reactor-grade, essentially the same as that being discharged in spent UO 2 fuels. MOX fuels are well developed and are currently used in a number of LWRs in Europe. Plutonium-bearing fuels without uranium (non-fertile fuels) would require some development. However, such non-fertile fuels are attractive from a nonproliferation perspective because they avoid the insitu production of additional plutonium and enhance the annihilation of the plutonium inventory on a once-through fuel cycle

  12. Multiparametric Magnetic Resonance Imaging for Discriminating Low-Grade From High-Grade Prostate Cancer

    NARCIS (Netherlands)

    Vos, E.K.; Kobus, T.; Litjens, G.J.S.; Hambrock, T.; Hulsbergen-van de Kaa, C.A.; Barentsz, J.O.; Maas, M.C.; Scheenen, T.W.J.

    2015-01-01

    The aim of this study was to determine and validate the optimal combination of parameters derived from 3-T diffusion-weighted imaging, dynamic contrast-enhanced imaging, and magnetic resonance (MR) spectroscopic imaging for discriminating low-grade from high-grade prostate cancer (PCa).The study was

  13. 7 CFR 810.804 - Grades and grade requirements for mixed grain.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Grades and grade requirements for mixed grain. 810.804 Section 810.804 Agriculture Regulations of the Department of Agriculture (Continued) GRAIN INSPECTION, PACKERS AND STOCKYARD ADMINISTRATION (FEDERAL GRAIN INSPECTION SERVICE), DEPARTMENT OF AGRICULTURE...

  14. Does Grade Inflation Affect the Credibility of Grades? Evidence from US Law School Admissions

    Science.gov (United States)

    Wongsurawat, Winai

    2009-01-01

    While the nature and causes of university grade inflation have been extensively studied, little empirical research on the consequence of this phenomenon is currently available. The present study uses data for 48 US law schools to analyze admission decisions in 1995, 2000, and 2007, a period during which university grade inflation appears to have…

  15. Colorado Student Assessment Program: 2001 Released Passages, Items, and Prompts. Grade 4 Reading and Writing, Grade 4 Lectura y Escritura, Grade 5 Mathematics and Reading, Grade 6 Reading, Grade 7 Reading and Writing, Grade 8 Mathematics, Reading and Science, Grade 9 Reading, and Grade 10 Mathematics and Reading and Writing.

    Science.gov (United States)

    Colorado State Dept. of Education, Denver.

    This document contains released reading comprehension passages, test items, and writing prompts from the Colorado Student Assessment Program for 2001. The sample questions and prompts are included without answers or examples of student responses. Test materials are included for: (1) Grade 4 Reading and Writing; (2) Grade 4 Lectura y Escritura…

  16. Grades and Incentives: Assessing Competing Grade Point Average Measures and Postgraduate Outcomes

    Science.gov (United States)

    Bailey, Michael A.; Rosenthal, Jeffrey S.; Yoon, Albert H.

    2016-01-01

    In many educational settings, students may have an incentive to take courses where high grades are easier to achieve, potentially corroding student learning, evaluation of student achievement, and the fairness and efficiency of post-graduation labor outcomes. A grading system that takes into account heterogeneity of teacher standards and student…

  17. Comparing 2 Whiplash Grading Systems to Predict Clinical Outcomes.

    Science.gov (United States)

    Croft, Arthur C; Bagherian, Alireza; Mickelsen, Patrick K; Wagner, Stephen

    2016-06-01

    Two whiplash severity grading systems have been developed: Quebec Task Force on Whiplash-Associated Disorders (QTF-WAD) and the Croft grading system. The majority of clinical studies to date have used the modified grading system published by the QTF-WAD in 1995 and have demonstrated some ability to predict outcome. But most studies include only injuries of lower severity (grades 1 and 2), preventing a broader interpretation. The purpose of this study was assess the ability of these grading systems to predict clinical outcome within the context of a broader injury spectrum. This study evaluated both grading systems for their ability to predict the bivalent outcome, recovery, within a sample of 118 whiplash patients who were part of a previous case-control designed study. Of these, 36% (controls) had recovered, and 64% (cases) had not recovered. The discrete bivariate distribution between recovery status and whiplash grade was analyzed using the 2-tailed cross-tabulation statistics. Applying the criteria of the original 1993 Croft grading system, the subset comprised 1 grade 1 injury, 32 grade 2 injuries, 53 grade 3 injuries, and 32 grade 4 injuries. Applying the criteria of the modified (QTF-WAD) grading system, there were 1 grade 1 injury, 89 grade 2 injuries, and 28 grade 3 injuries. Both whiplash grading systems correlated negatively with recovery; that is, higher severity grades predicted a lower probability of recovery, and statistically significant correlations were observed in both, but the Croft grading system substantially outperformed the QTF-WAD system on this measure. The Croft grading system for whiplash injury severity showed a better predictive measure for recovery status from whiplash injuries as compared with the QTF-WAD grading system.

  18. Grading as a Sadomasochistic Activity or an Erotic Benevolent Activity?

    Science.gov (United States)

    Tjarks, Larry D.

    Numerous research studies have been conducted concerning the negative aspects of grading: the low correlations between academic success (high grades) and later vocational or professional success, possible sadomasochistic motives of teachers in awarding grades, and grade assignment resulting from the teacher's sense of duty or responsibility to…

  19. A Machine Vision System for Automatically Grading Hardwood Lumber - (Proceedings)

    Science.gov (United States)

    Richard W. Conners; Tai-Hoon Cho; Chong T. Ng; Thomas H. Drayer; Joe G. Tront; Philip A. Araman; Robert L. Brisbon

    1990-01-01

    Any automatic system for grading hardwood lumber can conceptually be divided into two components. One of these is a machine vision system for locating and identifying grading defects. The other is an automatic grading program that accepts as input the output of the machine vision system and, based on these data, determines the grade of a board. The progress that has...

  20. Effects of Instructions on Theme Grading: Grammatical vs. Holistic

    Science.gov (United States)

    Follman, John; And Others

    1971-01-01

    Twelve college seniors in an English methods course were assigned to three treatment groups, Grammatical, Holistic, and Both. Each group received different instructions but graded the same 10 themes. Themes graded for grammatical errors received lower grades than the same themes graded holistically. (NH)

  1. What Is Wrong with Grade Inflation (If Anything)?

    Science.gov (United States)

    Finefter-Rosenbluh, Ilana; Levinson, Meira

    2015-01-01

    Grade inflation is a global phenomenon that has garnered widespread condemnation among educators, researchers, and the public. Yet, few have deliberated over the ethics of grading, let alone the ethics of grade inflation. The purpose of this paper is to map out and examine the ethics of grade inflation. By way of beginning, we clarify why grade…

  2. 7 CFR 70.105 - Procedures for appeal gradings.

    Science.gov (United States)

    2010-01-01

    ... conducting the appeal grading. Whether defrosting poultry or rabbit carcasses for other types of appeals will... 7 Agriculture 3 2010-01-01 2010-01-01 false Procedures for appeal gradings. 70.105 Section 70.105... PRODUCTS AND RABBIT PRODUCTS Grading of Poultry Products and Rabbit Products Appeal of A Grading Or...

  3. Advantages and Disadvantages of Weighted Grading. Research Brief

    Science.gov (United States)

    Walker, Karen

    2004-01-01

    What are the advantages and disadvantages of weighted grading? The primary purpose of weighted grading has been to encourage high school students to take more rigorous courses. This effort is then acknowledged by more weight being given to the grade for a specified class. There are numerous systems of weighted grading cited in the literature from…

  4. 77 FR 6772 - United States Standards for Grades of Cauliflower

    Science.gov (United States)

    2012-02-09

    ... Service [Doc. AMS-FV-10-0047] United States Standards for Grades of Cauliflower AGENCY: Agricultural... Standards for Grades of Cauliflower. AMS is reviewing all fresh fruit and vegetable grade standards for... provisions for grading purple, orange or green cauliflower. The proposed revision will amend the color...

  5. Properties of textile grade ceramic fibers

    International Nuclear Information System (INIS)

    Pudnos, E.

    1992-01-01

    The availability of textile grade ceramic fibers has sparked great interest for applications in composite reinforcement and high temperature insulation. This paper summarizes the properties of various small diameter textile grade ceramic fibers currently available. Room temperature mechanical and electrical properties of the fibers are discussed for three cases: ambient conditions, after heat aging in argon, and after heat aging in wet air. Dow Corning (R) HPZ Ceramic Fiber, a silicon nitride type fiber, is shown to have improved retention of mechanical and electrical properties above 1200 C

  6. Graded thermal insulation layer systems; Gradierte Waermedaemmschichtsysteme

    Energy Technology Data Exchange (ETDEWEB)

    Leushake, U.; Krell, T. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Koeln (Germany). Inst. fuer Werkstoff-Forschung

    1996-12-31

    Graded thermal insulation systems reduce local stresses between two layers. Grading usually involves a concentration variation in a second phase but may also involve variations of the microstructure or chemical composition. The contribution discusses the application of this technique for thermal protection of turbine blades in aircraft propulsion systems. [Deutsch] Mit Hilfe gradierter Waermeschichtsysteme ist es moeglich die lokalen Spannungen zwischen zwei Schichten zu verringern. Die Gradierung umfasst meistens eine Variation des Gehaltes einer zweiten Phase, kann aber auch die Variation der Mikrostruktur oder der chemischen Zusammensetzung beinhalten. In diesem Beitrag wird auf die Anwendung als thermischer Schutz von Turbinenschaufeln fuer Flugtriebwerke eingegangen.

  7. Studies on high grade cerebral gliomas

    International Nuclear Information System (INIS)

    Bleehen, N.M.

    1990-01-01

    A brief review of attempts in the United Kingdom to improve the results of treatment of high grade (grade 3, 4) supra-tentorial astrocytomas is presented. The radiosensitizer misonidazole failed to improve the results of post-surgical radiotherapy, however, multivariate analysis of data from these patients has provided a prognostic index of use in defining good and poor prognosis patients. An overview study of adjuvant nitrosourea therapy trials has shown a small significant advantage for the chemotherapy. A study of chemosensitization by benznidazole of CCNU treatment of patients in relapse failed to demonstrate any effect. 13 references

  8. Graded photonic crystals by optical interference holography

    International Nuclear Information System (INIS)

    Han, Chunrui; Tam, Wing Yim

    2012-01-01

    We report on the fabrication of graded photonic crystals in dye doped dichromate gelatin emulsions using an optical interference holographic technique. The gradedness is achieved by imposing a gradient form factor in the interference intensity resulting from the absorption of the dye in the dichromate gelatin. Wider and deeper photonic bandgaps are observed for the dyed samples as compared to the un-dyed samples. Our method could open up a new direction in fabricating graded photonic crystals which cannot be achieved easily using other techniques. (paper)

  9. Graded associative conformal algebras of finite type

    OpenAIRE

    Kolesnikov, Pavel

    2011-01-01

    In this paper, we consider graded associative conformal algebras. The class of these objects includes pseudo-algebras over non-cocommutative Hopf algebras of regular functions on some linear algebraic groups. In particular, an associative conformal algebra which is graded by a finite group $\\Gamma $ is a pseudo-algebra over the coordinate Hopf algebra of a linear algebraic group $G$ such that the identity component $G^0$ is the affine line and $G/G^0\\simeq \\Gamma $. A classification of simple...

  10. Kinetics and Mechanism of the Iron(II-Iron(III) Electron-Exchange Reaction in Mixed Solvent Media; Cinetique et Mecanisme de l'Echange d'Electrons entre Fer (II) et Fer (III), dans des Melanges de Solvants; Ikinetika i mekhanizm reaktsii ehlektronnogo obmena zheleza (I) - zheleza (III) v smeshannoj rastvoryayushchej srede; Cinetica y Mecanismo del Intercambio de Electrones Entre Fe{sup II} Y Fe{sup lII} en Mezclas de Disolventes

    Energy Technology Data Exchange (ETDEWEB)

    Horne, R. A. [Arthur D. Little, Inc. Cambridge, MA (United States)

    1965-10-15

    de intercambio electronico entre Fe{sup II} y Fe{sup III} a diversas temperaturas, grados de acidez y fuerzas ionicas, en soluciones de aguaacetona, agua-metanol y agua-etanol. La velocidad de reaccion disminuye apreciablemente al aumentar la concentracion de agua en el ultimo de estos sistemas, tendiendo a cero con la concentracion. La energfa de activacion del intercambio es la misma en mezclas de disolventes que en solucion acuosa. La constante dielectrica efectiva que interviene entre los reactivos sigue siendo la misma que en agua pura, incluso par a soluciones en agua-etanol bastante pobres en agua. Las mediciones espectroscopicas y del intercambio electronico reflejan las alteraciones de la composicion de la vaina de solvatacion del Fe{sup III} en disolventes mixtos. Estos resultados corroboran la teoria de que el intercambio electronico se efectua por intermedio de puentes agua. (author) [Russian] Byli izmereny udel'nye kon stanty skorosti reakcii jelektronnogo obmena Fe{sup II} - Fe{sup III} n pri razlichnyh temperaturah kislotnostjah i ionnyh silah v sredah: voda - aceton, voda - metanal i voda - jetanol. Sko rost' reakcii zametno snizhaetsja s umen'sheniem koncentracii vody v poslednej sistem i priblizhaetsja k nulju, kogda koncentracija vody priblizhaetsja k nulju. Jenergija aktivaci obmena javljaetsja toj zhe samoj v.smeshannom rastvore, kak i v vodnom rastvore. Jeffektiv naja dijelektricheskaja konstanta, kotoruju 'vidjat' reagirujushhie veshhestva, prodolzhaet byt konstantoj chistoj vody dazhe v rastvorah - jetanol, vpolne rastvorimyh v vode. Iz menenija v sostave obolochki sol'vatacii Fe{sup III} v smeshannoj srede otrazhajutsja kak v jelek tronnom obmene, tak i v spektroskopicheskih izmerenijah. Jeti vyvody, poluchennye na osnov rezul'tatov v smeshannoj rastvorjajushhej srede, podtverzhdajut teoriju vodjanogo mostika pr jelektronnom obmene. (author)

  11. Fibrocartilaginous mesenchymoma with low-grade malignancy

    International Nuclear Information System (INIS)

    Dahlin, D.C.; Bertoni, F.; Beabout, J.W.; Campanacci, M.

    1984-01-01

    In a review of cases of fibrous cartilaginous dysplasia of bone, five of fibrocartilaginous lesions were found to be different in clinical behavior and radiographic and morphologic features from the others. We have named these previously undescribed tumors ''fibrocartilaginous mesenchymomas with low-grade malignancy in the fibrous elements.'' (orig.)

  12. Do Class Size Effects Differ across Grades?

    Science.gov (United States)

    Nandrup, Anne Brink

    2016-01-01

    This paper contributes to the class size literature by analysing whether short-run class size effects are constant across grade levels in compulsory school. Results are based on administrative data on all pupils enrolled in Danish public schools. Identification is based on a government-imposed class size cap that creates exogenous variation in…

  13. Compressive properties of sandwiches with functionally graded

    Indian Academy of Sciences (India)

    The compressive behaviour of a new class of sandwich composite made up of jute fiber reinforced epoxy skins and piece-wise linear fly ash reinforced functionally graded (FG) rubber core is investigated in flat-wise mode. FG samples are prepared using conventional casting technique. Presence of gradation is quantified ...

  14. Does Social Background Influence Political Science Grades?

    Science.gov (United States)

    Tiruneh, Gizachew

    2013-01-01

    This paper tests a hypothesized linear relationship between social background and final grades in several political science courses that I taught at the University of Central Arkansas. I employ a cross-sectional research design and ordinary least square (OLS) estimators to test the foregoing hypothesis. Relying on a sample of up to 204…

  15. Teacher Grading Decisions: Influences, Rationale, and Practices

    Science.gov (United States)

    Kunnath, Joshua P.

    2017-01-01

    This mixed-methods study applied a decision-making theoretical framework to an investigation of teacher grading in a large urban school district in California. A sample of 251 high school teachers of core subjects were surveyed, and 15 teachers participated in four focus group interviews in order provide data on the influences, rationale, and…

  16. Mechanical Drawing: Grades 7-12.

    Science.gov (United States)

    Instructional Objectives Exchange, Los Angeles, CA.

    Eighty-five behavioral objectives and related evaluation items for mechanical drawing in grades 7 through 12 are presented. Each sample contains the objective, test items, and means for judging the adequacy of the response. The following categories are included: (1) basic drafting skills; (2) beginning lettering; (3) drawing; (4) orthographic…

  17. High grade magnesium from waste bittern

    International Nuclear Information System (INIS)

    El-Yamani, I.S.; Farah, M.Y.; Isaac, S.L.

    1979-01-01

    The production of high grade magnesia for nuclear purposes from sea water by use of both aqueous and gaseous ammonia has been described. The effect of precipitating conditions on the settling rate and magnesium recovery, was thoroughly examined. Ammonia gas approach was recommended and justified

  18. Lumber stress grades and design properties

    Science.gov (United States)

    David E. Kretschmann; David W. Green

    1999-01-01

    Lumber sawn from a log, regardless of species and size, is quite variable in mechanical properties. Pieces may differ in strength by several hundred percent. For simplicity and economy in use, pieces of lumber of similar mechanical properties are placed in categories called stress grades, which are characterized by (a) one or more sorting criteria, (b) a set of...

  19. Better utilization of low-grade woods

    Science.gov (United States)

    Peter Koch

    1957-01-01

    The objective of this paper is threefold: to outline briefly some of the avenues of approach so far employed in utilizing low-grade wood, to comment on the economic aspects of the problem, and finally, to speculate about what developments the future might bring to the field of utilization.

  20. Does Relative Grading help Male Students?

    DEFF Research Database (Denmark)

    Czibor, Eszter; Onderstal, Sander; Sloof, Randolph

    The provision of non-pecuniary incentives in education is a topic that has received much scholarly attention lately. Our paper contributes to this discussion by investigating the effectiveness of grade incentives in increasing student performance. We perform a direct comparison of the two most co...

  1. Ia diastolic dysfunction: an echocardiographic grade.

    Science.gov (United States)

    Pandit, Anil; Mookadam, Farouk; Hakim, Fayaz A; Mulroy, Eoin; Saadiq, Rayya; Doherty, Mairead; Cha, Stephen; Seward, James; Wilansky, Susan

    2015-01-01

    To demonstrate that a distinct group of patients with Grade Ia diastolic dysfunction who do not conform to present ASE/ESE diastolic grading exists. Echocardiographic and demographic data of the Grade Ia diastolic dysfunction were extracted and compared with that of Grades I and II in 515 patients. The mean of age of the cohort was 75 ± 9 years and body mass index did not differ significantly between the 3 groups (P = 0.45). Measurements of left atrial volume index (28.58 ± 7 mL/m(2) in I, 33 ± 10 mL/m(2) in Ia, and 39 ± 12 mL/m(2) in II P Ia, and 79 ± 15 msec in II P Ia, and 217 ± 57 msec in II P Ia, and 22 ± 8 in II), and lateral E/e' (8 ± 3 in I, 15 ± 6 in Ia, and 18 ± 9 in II P Ia compared with I and II. These findings remained significant even after adjusting for age, gender, diabetes, and smoking. Patients with echocardiographic characteristics of relaxation abnormality (E/A ratio of Ia group. © 2014, Wiley Periodicals, Inc.

  2. Quantitative grading of store separation trajectories

    CSIR Research Space (South Africa)

    Jamison, Kevin A

    2017-09-01

    Full Text Available . This paper describes the development of an automated analysis process and software that can run a multitude of separation scenarios. A key enabler for this software is the development of a quantitative grading algorithm that scores the outcome of each release...

  3. Geometry task sheets : grades 3-5

    CERN Document Server

    Rosenberg, Mary

    2009-01-01

    For grades 3-5, our Common Core State Standards-based resource meets the geometry concepts addressed by the NCTM standards and encourages the students to learn and review the concepts in unique ways. Each task sheet is organized around a central problem taken from real-life experiences of the students.

  4. Algebra task sheets : grades pk-2

    CERN Document Server

    Reed, Nat

    2009-01-01

    For grades PK-2, our Common Core State Standards-based resource meets the algebraic concepts addressed by the NCTM standards and encourages the students to learn and review the concepts in unique ways. Each task sheet is organized around a central problem taken from real-life experiences of the students.

  5. Geometry task sheets : grades pk-2

    CERN Document Server

    Rosenberg, Mary

    2009-01-01

    For grades PK-2, our Common Core State Standards-based resource meets the geometry concepts addressed by the NCTM standards and encourages the students to learn and review the concepts in unique ways. Each task sheet is organized around a central problem taken from real-life experiences of the students.

  6. Ferrite grade iron oxides from ore rejects

    Indian Academy of Sciences (India)

    Iron oxyhydroxides and hydroxides were synthesized from chemically beneficiated high SiO2/Al2O3 low-grade iron ore (57.49% Fe2O3) rejects and heated to get iron oxides of 96–99.73% purity. The infrared band positions, isothermal weight loss and thermogravimetric and chemical analysis established the chemical ...

  7. Elementary construction of graded lie groups

    International Nuclear Information System (INIS)

    Scheunert, M.; Rittenberg, V.

    1977-06-01

    We show how the definitions of the classical Lie groups have to be modified in the case where Grassmann variables are present. In particular, we construct the general linear, the special linear and the orthosymplectic graded Lie groups. Special attention is paid to the question of how to formulate an adequate 'unitarity condition'. (orig.) [de

  8. Developing Middle Grades Students' MP3

    Science.gov (United States)

    Tassell, Janet; Stobaugh, Rebecca; Sheffield, Linda

    2011-01-01

    Middle grades are a critical time for capturing the interest and imagination and developing the potential of mathematically promising students. This is a time for students to make sense of mathematics, build a solid foundation and enthusiasm, and set the course for the highest levels of mathematics in the future. This is a time to explore their…

  9. Osteoporosis Risk Factors in Eighth Grade Students.

    Science.gov (United States)

    Lysen, Victoria C.; Walker, Robert

    1997-01-01

    Presents findings from food frequency questionnaires and surveys of 138 Midwestern eighth-grade student-parent pairs. The study examined the incidence of modifiable and nonmodifiable osteoporosis risk factors and compared gender differences. Data analysis indicated that many adolescents possessed several modifiable and nonmodifiable risk factors…

  10. Whale Preservation. Grades Five to Nine.

    Science.gov (United States)

    Racicot, Darlene

    Dedicated to the conservation and preservation of whales, dolphins, and porpoises through public education, this instructional unit for grades 5-9 provides current (1993) facts, lesson plans, activities, and conservation and preservation techniques. Interdisciplinary activities involve students in debates, critical thinking, research, and…

  11. What Can Readers Read after Graded Readers?

    Science.gov (United States)

    McQuillan, Jeff

    2016-01-01

    Nation (2014) concluded that most of the vocabulary one needs to read challenging texts in English can be acquired incidentally through voluminous reading. This study examines possible texts that second language (L2) readers can use to move from controlled-vocabulary materials such as graded readers, which go up through approximately the…

  12. Comparison between two differential graded algebras in ...

    Indian Academy of Sciences (India)

    76

    A differential calculus on a “space” means the specification of a differential graded algebra (dga), often interpreted as space of forms. In classical geometry the “space” is a manifold and we have the de-Rham dga, whereas in noncommutative geometry a “space” is described by a triple called spectral triple. A spectral triple is ...

  13. Helping Your Kid Make the Grade.

    Science.gov (United States)

    Dornbusch, Sandy

    Research indicates that students' activities and relationships with their parents predict grades more surely than parental education, family income, ethnicity, sex, and family structure. Children with extremely permissive parents do not do well and children with extremely authoritarian parents do worse. Inconsistent parenting is even more strongly…

  14. Influence of Hydroxypropyl Methylcellulose Molecular Weight Grade ...

    African Journals Online (AJOL)

    Erah

    weight grades (K4M and K15M) on drug release from diclofenac sodium matrix tablets. Methods: Tablets containing diclofenac ... Keywords: Matrix, Diclofenac sodium, HPMC, Erosion, Water uptake. Received: 12 January 2011 .... incorporating the structure and geometric characteristics of the release device and n is.

  15. Graded-Lie-algebra cohomology and supergravity

    International Nuclear Information System (INIS)

    D'Auria, R.; Fre, P.; Regge, T.

    1980-01-01

    Detailed explanations of the cohomology invoked in the group-manifold approach to supergravity is given. The Chevalley cohomology theory of Lie algebras is extended to graded Lie algebras. The scheme of geometrical theories is enlarged so to include cosmological terms and higher powers of the curvature. (author)

  16. The Returns on Investment Grade Diamonds

    NARCIS (Netherlands)

    Renneboog, L.D.R.

    2013-01-01

    Abstract: This paper examines the risk-return characteristics of investment grade gems (white diamonds, colored diamonds and other types of gems including sapphires, rubies, and emeralds). The transactions are coming from gem auctions and span the period 1999-2012. Over our time frame, the annual

  17. 7 CFR 29.6018 - Grade.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Grade. 29.6018 Section 29.6018 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... to other characteristics when they are of sufficient importance to be treated separately. ...

  18. Examining Teacher Grades Using Rasch Measurement Theory

    Science.gov (United States)

    Randall, Jennifer; Engelhard, George, Jr.

    2009-01-01

    In this study, we present an approach to questionnaire design within educational research based on Guttman's mapping sentences and Many-Facet Rasch Measurement Theory. We designed a 54-item questionnaire using Guttman's mapping sentences to examine the grading practices of teachers. Each item in the questionnaire represented a unique student…

  19. Construction Industry Related Mathematics: Seventh Grade.

    Science.gov (United States)

    Mundell, Scott

    The field tested construction industry-related mathematics unit is intended to familiarize seventh grade students with various facets of the construction industry, including the various occupations available and the mathematical abilities and other skills and training necessary to pursue an occupation in the industry. The final set of activities…

  20. Communications and Media: Grade 7. Cluster II.

    Science.gov (United States)

    Calhoun, Olivia H.

    A curriculum guide for grade 7, the document is devoted to the occupational cluster "Communications and Media." It is divided into six units: advertising, film and photography, radio and television, journalism and publishing, library and periodicals, and transocean communications. Each unit is introduced by a statement of the topic, the…

  1. Environmental Education. Teacher's Handbook, Grade 5.

    Science.gov (United States)

    Nashville - Davidson County Metropolitan Public Schools, TN.

    Prepared for use in the 5th grade, this teacher's handbook consists of 19 science units dealing with environmental education. Topics are ecology, language arts, rocks and fossils, soil, noise pollution, Nashville pioneers and American Indians, conservation, waste and litter, water pollution, compass and mapping, plants and trees, use of the…

  2. Reliability Estimates for Undergraduate Grade Point Average

    Science.gov (United States)

    Westrick, Paul A.

    2017-01-01

    Undergraduate grade point average (GPA) is a commonly employed measure in educational research, serving as a criterion or as a predictor depending on the research question. Over the decades, researchers have used a variety of reliability coefficients to estimate the reliability of undergraduate GPA, which suggests that there has been no consensus…

  3. Grading Practices and Distributions Across Internal Medicine Clerkships.

    Science.gov (United States)

    Fazio, Sara B; Torre, Dario M; DeFer, Thomas M

    2016-01-01

    Clerkship evaluation and grading practices vary widely between U.S. medical schools. Grade inflation continues to exist, and grade distribution is likely to be different among U.S. medical schools. Increasing the number of available grades curtails "grade inflation." A national survey of all Clerkship Directors in Internal Medicine members was administered in 2011. The authors assessed key aspects of grading. Response rate was 76%. Among clerkship directors (CDs), 61% of respondents agreed that grade inflation existed in the internal medicine clerkship at their school, and 43% believed that it helped students obtain better residency positions. With respect to grading practices, 79% of CDs define specific behaviors needed to achieve each grade, and 36% specify an ideal grade distribution. In addition, 44% have a trained core faculty responsible for evaluating students, 35% describe formal grading meetings, and 39% use the Reporter-Interpreter-Manager-Educator (RIME) scheme. Grading scales were described as follows: 4% utilize a pass/fail system, 13% a 3-tier (e.g., Honors/Pass/Fail), 45% 4-tier, 35% 5-tier, and 4% 6+-tier system. There was a trend to higher grades with more tiers available. Grade inflation continues in the internal medicine clerkship. Almost half of CDs feel that this practice assists students to obtain better residency positions. A minority of programs have a trained core faculty who are responsible for evaluation. About one third have formal grading meetings and use the RIME system; both have been associated with more robust and balanced grading practices. In particular, there is a wide variation between schools in the percentage of students who are awarded the highest grade, which has implications for residency applications. Downstream users of clinical clerkship grades must be fully aware of these variations in grading in order to appropriately judge medical student performance.

  4. Histopathologic grading of anaplasia in retinoblastoma.

    Science.gov (United States)

    Mendoza, Pia R; Specht, Charles S; Hubbard, G Baker; Wells, Jill R; Lynn, Michael J; Zhang, Qing; Kong, Jun; Grossniklaus, Hans E

    2015-04-01

    To determine whether the degree of tumor anaplasia has prognostic value by evaluating its correlation with high-risk histopathologic features and clinical outcomes in a series of retinoblastoma patients. Retrospective clinicopathologic study. The clinical and pathologic findings in 266 patients who underwent primary enucleation for retinoblastoma were reviewed. The histologic degree of anaplasia was graded as retinocytoma, mild, moderate, or severe as defined by increasing cellular pleomorphism, number of mitoses, nuclear size, and nuclear hyperchromatism. Nuclear morphometric characteristics were measured. The clinical and pathologic data of 125 patients were compared using Kaplan-Meier estimates of survival. Fisher exact test and multivariate regression were used to analyze the association between anaplasia grade and high-risk histologic features. Increasing grade of anaplasia was associated with decreased overall survival (P = .003) and increased risk of metastasis (P = .0007). Histopathologic features that were associated with anaplasia included optic nerve invasion (P anaplasia grading as predictors of distant metastasis and death showed that high-risk histopathology was statistically significant as an independent predictor (P = .01 for metastasis, P = .03 for death) but anaplasia was not (P = .63 for metastasis, P = .30 for death). In the absence of high-risk features, however, severe anaplasia identified an additional risk for metastasis (P = .0004) and death (P = .01). Grading of anaplasia may be a useful adjunct to standard histopathologic criteria in identifying retinoblastoma patients who do not have high-risk histologic features but still have an increased risk of metastasis and may need adjuvant therapy. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Processing hot-dip galvanized AHSS grades: a challenging task

    Energy Technology Data Exchange (ETDEWEB)

    Pichler, A.; Hebesberger, T.; Tragl, E.; Traint, S.; Faderl, J.; Angeli, G.; Koesters, K. [voestalpine Stahl GmbH, Linz (Austria)

    2005-07-01

    High-strength thin sheet steel grades have gained a considerable market share. At present a very strong demand has been observed for DP (dual-phase), CP (complex phase) and TRIP grades, which are often summarized as advanced high-strength steel grades (AHSS). The potential benefits of applying AHSS grades were impressively demonstrated in the ULSAC-AVC project, in which a remarkable reduction in mass and an increase in stiffness and crash safety were achieved by using a very high share of AHSS steel grades. The present contribution concentrates on hot-dip galvanized AHSS thin sheet grades. The hot-dip galvanizeability of such grades is critically discussed after an overview is provided of the metallurgy of AHSS grades, including microstructure, mechanical properties, phase transformations and required alloy design. Based on these fundamentals, the processing of AHSS grades in the hot-dip galvanizing line is discussed and the resulting properties presented. (orig.)

  6. The effect of grades on the preference effect : Grading reduces consideration of disconfirming evidence

    NARCIS (Netherlands)

    Hayek, A.S.; Toma, C.; Oberlé, D.; Butera, F.

    2014-01-01

    The tendency to look for evidence that supports, rather than questions, one's viewpoint (preference effect) is a pervasive phenomenon. Although one important goal of education is developing critical thinking, the widespread practice of grading might discourage students in appreciating disconfirming

  7. A Comparison of Air Force Field Grade and Company Grade Officer Leadership

    National Research Council Canada - National Science Library

    Enrequez, Arnel

    1998-01-01

    ...), indicating that empirical development of a similar model for the USAF should be feasible. The purpose of this study was to determine differences in importance of leadership behaviors between AF company grade officers (CGOs), majors (O-4s...

  8. Will bottle-grade PET demand lure fiber-grade capacity?

    International Nuclear Information System (INIS)

    Coeyman, M.

    1993-01-01

    As demand for bottle-grade polyethylene terephthalate (PET) continues strong and new capacity hastens to meet it, some industry observers wonder if conversions to bottle-grade from fiber-grade capacity will become an industry trend. Taiwan's Nan Ya Plastics was recently said to be considering such a switch, but company sources say it has no such plans. Peter Driscoll, senior partner at PCI Fibres ampersand Raw Materials (Crawley, UK), says that while it is true that demand for the bottle-grade material remains unsatisfied, he doubts that many conversions will take place. You must remember, says Driscoll, that it is not always possible to switch, and that even where it is possible there are limitations

  9. High-grade and low-grade gliomas: differentiation by using perfusion MR imaging

    International Nuclear Information System (INIS)

    Hakyemez, B.; Erdogan, C.; Ercan, I.; Ergin, N.; Uysal, S.; Atahan, S.

    2005-01-01

    AIM: Relative cerebral blood volume (rCBV) is a commonly used perfusion magnetic resonance imaging (MRI) technique for the evaluation of tumour grade. Relative cerebral blood flow (rCBF) has been less studied. The goal of our study was to determine the usefulness of these parameters in evaluating the histopathological grade of the cerebral gliomas. METHODS: This study involved 33 patients (22 high-grade and 11 low-grade glioma cases). MRI was performed for all tumours by using a first-passage gadopentetate dimeglumine T2*-weighted gradient-echo single-shot echo-planar sequence followed by conventional MRI. The rCBV and rCBF were calculated by deconvolution of an arterial input function. The rCBV and rCBF ratios of the lesions were obtained by dividing the values obtained from the normal white matter of the contralateral hemisphere. For statistical analysis Mann-Whitney testing was carried out. A p value of less than 0.05 indicated a statistically significant difference. Receiver operating characteristic curve (ROC) analysis was performed to assess the relationship between the rCBV and rCBF ratios and grade of gliomas. Their cut-off value permitting discrimination was calculated. The correlation between rCBV and CBF ratios and glioma grade was assessed using Pearson correlation analysis. RESULTS: In high-grade gliomas, rCBV and rCBF ratios were measured as 6.50±4.29 and 3.32±1.87 (mean±SD), respectively. In low-grade gliomas, rCBV and rCBF ratios were 1.69±0.51 and 1.16±0.38, respectively. The rCBV and rCBF ratios for high-grade gliomas were statistically different from those of low-grade gliomas (p 0.05). The cut-off value was taken as 1.98 in the rCBV ratio and 1.25 in the rCBF ratio. There was a strong correlation between the rCBV and CBF ratios (Pearson correlation = 0.830, p<0.05). CONCLUSION: Perfusion MRI is useful in the preoperative assessment of the histopathologicalal grade of gliomas; the rCBF ratio in addition to the rCBV ratio can be incorporated

  10. Improving reading in the primary grades.

    Science.gov (United States)

    Duke, Nell K; Block, Meghan K

    2012-01-01

    Almost fifteen years have passed since the publication of the National Research Council's seminal report Preventing Reading Difficulties in Young Children, which provided research-based recommendations on what could be done to better position students in prekindergarten through third grade for success in grade four and above. This article by Nell Duke and Meghan Block first examines whether specific key recommendations from the report have been implemented in U.S. classrooms. They find that recommendations regarding increased access to kindergarten and greater attention to and improvement of students' word-reading skills have been widely adopted. Others have not. Vocabulary and comprehension, long neglected in the primary grades, still appear to be neglected. Contrary to the report's recommendations, attention to building conceptual and content knowledge in science and social studies has actually decreased in the past fifteen years. In other words, the easier-to-master skills are being attended to, but the broader domains of accomplishment that constitute preparation for comprehension and learning in the later grades--vocabulary knowledge, comprehension strategy use, and conceptual and content knowledge--are being neglected. Near stagnation in fourth-grade students' comprehension achievement is thus unsurprising. The authors then turn to research and reviews of research on improving primary-grade reading published since 1998, when Preventing Reading Difficulties was issued. They discuss several instructional approaches identified as effective in improving word-reading skill, vocabulary and conceptual knowledge, comprehension strategies, and reading outside of school; they discuss advances in interventions for struggling readers, and in whole-school literacy reform. Duke and Block then identify three key obstacles that have prevented widespread adoption of these best practices in teaching reading. The first obstacle is a short-term orientation toward instruction and

  11. INAA of polyacrylic hydrogels of pharmaceutical grade

    International Nuclear Information System (INIS)

    Ponta, C.; Salagean, M.; Pantelica, A.; Georgescu, I.I.

    1998-01-01

    Polyacrylic acid (PA) and its salts are promising biomaterials used in the pharmaceutical industry. They could be used as pharmaceutical additives, as a burn dressing and also in the slow released implants or trans-derma patch formulations. Polyacrylic acid of pharmaceutical grade can be obtained by gamma irradiation polymerization. The influence of the raw materials and of the technological procedure on the final product purity has been investigated by Instrumental Neutron Activation Analysis (INAA) method. The following materials have been analyzed by INAA: 1) acrylic acid of technical grade; 2) acrylic acid purified by double crystallisation; 3) NaOH of analytical grade; 4) CaCl-2·6H 2 O of pharmaceutical grade; 5) CaCl 2 ·2H 2 O of analytical grade; 6) granulated PANa; 7) ungranulated PANa; 8) ungranulated PANaCa; 9) PANaCa granulated by milling in IFIN-HH using the mill nr. 1; 10) PANaCa granulated by milling in Institute of Chemical and Pharmaceutical Research (ICPR); 11) PANaCa granulated by milling in IFIN-HH using the mill nr. 2. The first five samples, marked from 1 to 5, are raw materials and the other six samples, marked from 6 to 11, are the final polyacrylic structures processed by various technological procedures. The samples together with the appropriate reference materials have been irradiated at WWR-S reactor in a neutron flux of 2.5·10 12 cm -2 s -1 and the induced radioactivity was registered by a HPGe detector (EG/G ORTEC) of 30% efficiency and 2.1 keV resolution. The concentrations of As, Br, Ce, Co, Cr, Fe, La, Sb, Sc, Zn have been determined. For the final polyacrylic structures, except for granulated PANa (sample 6), only the elements Co, Cr, Fe, Sc, Zn were found at the following concentration levels: tens of ppm (Co), ppm (Zn), hundreds of ppb (Cr), tens of ppb (Co), ppb (Co, Sc), 10 -1 ppb (Sc). In the granulated PANa, in comparison with the other analyzed final products, similar concentration values were found for Fe, Sc and Zn

  12. Comparison of non-electrophoresis grade with electrophoresis grade BIS in NIPAM polymer gel preparation

    Science.gov (United States)

    Khodadadi, Roghayeh; Khajeali, Azim; Farajollahi, Ali Reza; Hajalioghli, Parisa; Raeisi, Noorallah

    2015-01-01

    Introduction:The main objective of this study was to investigate the possibility of replacing electrophoresis cross-linker with non-electrophoresis N, N′-methylenebisacrylamide (BIS) in N-isopropyl acrylamide (NIPAM) polymer gel and its possible effect on dose response. Methods: NIPAM polymer gel was prepared from non-electrophoresis grade BIS and the relaxation rate (R2) was measured by MR imaging after exposing the gel to gamma radiation from Co-60 source. To compare the response of this gel with the one that contains electrophoresis grade BIS, two sets of NIPAM gel were prepared using electrophoresis and non-electrophoresis BIS and irradiated to different gamma doses. Results: It was found that the dose–response of NIPAM gel made from the non-electrophoresis grade BIS is coincident with that of electrophoresis grade BIS. Conclusion:Taken all, it can be concluded that the non-electrophoresis grade BIS not only is a suitable alternative for the electrophoresis grade BIS but also reduces the cost of gel due to its lower price. PMID:26457250

  13. Comparison of cartilage thickness with radiologic grade of knee osteoarthritis

    International Nuclear Information System (INIS)

    Agnesi, Filippo; Amrami, Kimberly K.; Frigo, Carlo A.; Kaufman, Kenton R.

    2008-01-01

    To compare joint space width (JSW) measurements obtained from magnetic resonance imaging (MRI) with a semi-automated computer algorithm to the Kellgren and Lawrence grading of osteoarthritis (OA). Three hundred and six patients (234 female, 72 male) with a mean age of 56.7 years (range 31-81 years) underwent MRI of their knees with a fast oblique spiral spoiled gradient (SPGR) sequence. A board-certified musculoskeletal radiologist graded the OA of all the patients in accordance with the Kellgren and Lawrence OA scale. A previously validated computer algorithm was used to determine the minimum JSW for both the tibiofemoral joint and the patellofemoral joint. An analysis of variance (ANOVA) with the Student-Newman-Kuels post-hoc test was used to determine if there were differences in JSW as a function of OA grade. The radiologic grade of OA was inversely associated with the JSW. In the medial compartment the JSW did not change significantly between grade 1 and grade 2, but there was a significant decrease in JSW between grade 0 (normal) and grade 1 and for each OA grade above grade 2. In the lateral compartment no statistical differences were found till grade 2, while grade 3 was found to be statistically different from the previous one. The number of patients with a grade 4 patellofemoral OA was too low for the statistical significance to be assessed. In the patellofemoral joint the JSW did not change significantly until grade 2, while a statistically significant reduction was found for both grade 3 and grade 4. This study showed that an inverse non-linear relationship exists between radiologic grade and JSW. The relationship differs for the tibiofemoral and the patellofemoral joint. (orig.)

  14. Comparison of cartilage thickness with radiologic grade of knee osteoarthritis

    Energy Technology Data Exchange (ETDEWEB)

    Agnesi, Filippo [Mayo Clinic, Motion Analysis Laboratory, Division of Orthopedic Research, Rochester, MN (United States); Polytechnic of Milan, Department of Bioengineering, Milan (Italy); Amrami, Kimberly K. [Mayo Clinic, Department of Radiology, Rochester, MN (United States); Frigo, Carlo A. [Polytechnic of Milan, Department of Bioengineering, Milan (Italy); Kaufman, Kenton R. [Mayo Clinic, Motion Analysis Laboratory, Division of Orthopedic Research, Rochester, MN (United States); Mayo Clinic/Foundation, Motion Analysis Laboratory, Department of Orthopedic Surgery, Rochester, MN (United States)

    2008-07-15

    To compare joint space width (JSW) measurements obtained from magnetic resonance imaging (MRI) with a semi-automated computer algorithm to the Kellgren and Lawrence grading of osteoarthritis (OA). Three hundred and six patients (234 female, 72 male) with a mean age of 56.7 years (range 31-81 years) underwent MRI of their knees with a fast oblique spiral spoiled gradient (SPGR) sequence. A board-certified musculoskeletal radiologist graded the OA of all the patients in accordance with the Kellgren and Lawrence OA scale. A previously validated computer algorithm was used to determine the minimum JSW for both the tibiofemoral joint and the patellofemoral joint. An analysis of variance (ANOVA) with the Student-Newman-Kuels post-hoc test was used to determine if there were differences in JSW as a function of OA grade. The radiologic grade of OA was inversely associated with the JSW. In the medial compartment the JSW did not change significantly between grade 1 and grade 2, but there was a significant decrease in JSW between grade 0 (normal) and grade 1 and for each OA grade above grade 2. In the lateral compartment no statistical differences were found till grade 2, while grade 3 was found to be statistically different from the previous one. The number of patients with a grade 4 patellofemoral OA was too low for the statistical significance to be assessed. In the patellofemoral joint the JSW did not change significantly until grade 2, while a statistically significant reduction was found for both grade 3 and grade 4. This study showed that an inverse non-linear relationship exists between radiologic grade and JSW. The relationship differs for the tibiofemoral and the patellofemoral joint. (orig.)

  15. Production of nuclear grade zirconium: A review

    Energy Technology Data Exchange (ETDEWEB)

    Xu, L., E-mail: L.Xu-2@tudelft.nl [School of Materials Science and Metallurgy, Northeastern University, Shenyang 110004 (China); Department of Materials Science and Engineering, Delft University of Technology, Delft 2628 CD (Netherlands); Xiao, Y. [Department of Metallurgical Engineering, Anhui University of Technology, Ma' anshan 243002 (China); Zr-Hf-Ti Metallurgie B.V., Den Haag 2582 SB (Netherlands); Sandwijk, A. van [Zr-Hf-Ti Metallurgie B.V., Den Haag 2582 SB (Netherlands); Xu, Q. [School of Materials Science and Metallurgy, Northeastern University, Shenyang 110004 (China); Yang, Y. [Department of Materials Science and Engineering, Delft University of Technology, Delft 2628 CD (Netherlands)

    2015-11-15

    Zirconium is an ideal material for nuclear reactors due to its low absorption cross-section for thermal neutrons, whereas the typically contained hafnium with strong neutron-absorption is very harmful for zirconium as a fuel cladding material. This paper provides an overview of the processes for nuclear grade zirconium production with emphasis on the methods of Zr–Hf separation. The separation processes are roughly classified into hydro- and pyrometallurgical routes. The known pyrometallurgical Zr–Hf separation methods are discussed based on the following reaction features: redox characteristics, volatility, electrochemical properties and molten salt–metal equilibrium. In the present paper, the available Zr–Hf separation technologies are compared. The advantages and disadvantages as well as future directions of research and development for nuclear grade zirconium production are discussed.

  16. A low-grade extraskeletal osteosarcoma

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Kyoji; Ito, Hiroki; Miyakoshi, Naohisa; Itoi, Eiji [Department of Orthopedic Surgery, Akita University School of Medicine, 1-1-1 Hondo, Akita 010-8543 (Japan); Sageshima, Masato [Department of Clinical Pathology, Akita University Hospital, 1-1-1 Hondo, Akita 010-8543 (Japan); Nishida, Jun [Department of Orthopedic Surgery, Iwate Medical School, 19-1 Uchimaru, Morioka 020-8505 (Japan)

    2003-03-01

    The case of a 35-year-old woman with low-grade extraskeletal osteosarcoma of the left leg is presented. Radiographs showed peripheral ossification of the lesion, suggesting myositis ossificans. Most of the tumor was composed of cartilage, and the cellularity and cell atypia of the proliferating chondrocytes were mild to moderate. In the periphery, bone formation with a relatively clear margin and proliferation of spindle cells with minimal nuclear atypia were observed. The average percentage of cells positive for MIB-1 was 9.0%. A diagnosis of low-grade extraskeletal osteosarcoma was made on the basis of these histologic findings. The clinical course 47 months after a wide excision was uneventful. (orig.)

  17. Probabilistic Modeling of Graded Timber Material Properties

    DEFF Research Database (Denmark)

    Faber, M. H.; Köhler, J.; Sørensen, John Dalsgaard

    2004-01-01

    The probabilistic modeling of timber material characteristics is considered with special emphasis to the modeling of the effect of different quality control and selection procedures used as means for quality grading in the production line. It is shown how statistical models may be established...... on the basis of the same type of information which is normally collected as a part of the quality control procedures and furthermore, how the efficiency of different control procedures may be quantified and compared. The tail behavior of the probability distributions of timber material characteristics plays...... such that they may readily be applied in structural reliability analysis and their format appears to be appropriate for codification purposes of quality control and selection for grading procedures....

  18. Grading of vesicoureteral reflux by radionuclide cystography

    International Nuclear Information System (INIS)

    Fretzayas, A.; Karpathios, T.; Dimitriou, P.; Nicolaidou, P.; Matsaniotis, N.

    1984-01-01

    Thirty-six children with urinary tract infection aged 6 months to 14 years (mean age 4 1/2 years) were studied sequentially using direct radionuclide (RNC) and conventional voiding cystourethrography (VCU). Vesicoureteral reflux (VUR) was detected equally well by both methods. Twenty-seven refluxing ureters were found by RNC, 23 by VCU and 22 by both methods. Radiologic grade of reflux may be determined approximately with the isotope technique from the volume of regurgitating urine und duration of reflux, at a much decreased radiation exposure. Residual urine was also measured by RNC and found to be higher in children with VUR. RNC is a reliable method for detecting and grading VUR and should effectively replace VCU as the follow-up examination of choice. (orig.)

  19. Buckling Response of Thick Functionally Graded Plates

    Directory of Open Access Journals (Sweden)

    BOUAZZA MOKHTAR

    2014-11-01

    Full Text Available In this paper, the buckling of a functionally graded plate is studied by using first order shear deformation theory (FSDT. The material properties of the plate are assumed to be graded continuously in the direction of thickness. The variation of the material properties follows a simple power-law distribution in terms of the volume fractions of constituents. The von Karman strains are used to construct the equilibrium equations of the plates subjected to two types of thermal loading, linear temperature rise and gradient through the thickness are considered. The governing equations are reduced to linear differential equation with boundary conditions yielding a simple solution procedure. In addition, the effects of temperature field, volume fraction distributions, and system geometric parameters are investigated. The results are compared with the results of the no shear deformation theory (classic plate theory, CPT.

  20. Nanoscopic diffusion studies on III-V compound semiconductor structures: Experiment and theory

    Science.gov (United States)

    Gonzalez Debs, Mariam

    The electronic structure of multilayer semiconductor heterostructures is affected by the detailed compositional profiles throughout the structure and at critical interfaces. The extent of interdiffusion across these interfaces places limits on both the processing time and temperatures for many applications based on the resultant compositional profile and associated electronic structure. Atomic and phenomenological methods were used in this work through the combination of experiment and theory to understand the nanoscopic mechanisms in complex heterostructures. Two principal studies were conducted. Tin diffusion in GaAs was studied by fitting complex experimental diffusion profiles to a phenomenological model which involved the diffusion of substitutional and interstitial dopant atoms. A methodology was developed combining both the atomistic model and the use of key features within these experimentally-obtained diffusion profiles to determine meaningful values of the transport and defect reaction rate parameters. Interdiffusion across AlSb/GaSb multi-quantum well interfaces was also studied. The chemical diffusion coefficient characterizing the AlSb/GaSb diffusion couple was quantitatively determined by fitting the observed photoluminescence (PL) peak shifts to the solution of the Schrodinger equation using a potential derived from the solution of the diffusion equation to quantify the interband transition energy shifts. First-principles calculations implementing Density Functional Theory were performed to study the thermochemistry of point defects as a function of local environment, allowing a direct comparison of interfacial and bulk diffusion phenomena within these nanoscopic structures. Significant differences were observed in the Ga and Al vacancy formation energies at the AlSb/GaSb interface when compared to bulk AlSb and GaSb with the largest change found for Al vacancies. The AlSb/GaSb structures were further studied using positron annihilation spectroscopy (PAS) to investigate the role of vacancies in the interdiffusion of Al and Ga in the superlattices. The PL and PAS experimental techniques together with the phenomenological and atomistic modeling allowed for the determination of the underlying mass transport mechanisms at the nanoscale.

  1. Advances in High-Efficiency III-V Multijunction Solar Cells

    Directory of Open Access Journals (Sweden)

    Richard R. King

    2007-01-01

    Full Text Available The high efficiency of multijunction concentrator cells has the potential to revolutionize the cost structure of photovoltaic electricity generation. Advances in the design of metamorphic subcells to reduce carrier recombination and increase voltage, wide-band-gap tunnel junctions capable of operating at high concentration, metamorphic buffers to transition from the substrate lattice constant to that of the epitaxial subcells, concentrator cell AR coating and grid design, and integration into 3-junction cells with current-matched subcells under the terrestrial spectrum have resulted in new heights in solar cell performance. A metamorphic Ga0.44In0.56P/Ga0.92In0.08As/ Ge 3-junction solar cell from this research has reached a record 40.7% efficiency at 240 suns, under the standard reporting spectrum for terrestrial concentrator cells (AM1.5 direct, low-AOD, 24.0 W/cm2, 25∘C, and experimental lattice-matched 3-junction cells have now also achieved over 40% efficiency, with 40.1% measured at 135 suns. This metamorphic 3-junction device is the first solar cell to reach over 40% in efficiency, and has the highest solar conversion efficiency for any type of photovoltaic cell developed to date. Solar cells with more junctions offer the potential for still higher efficiencies to be reached. Four-junction cells limited by radiative recombination can reach over 58% in principle, and practical 4-junction cell efficiencies over 46% are possible with the right combination of band gaps, taking into account series resistance and gridline shadowing. Many of the optimum band gaps for maximum energy conversion can be accessed with metamorphic semiconductor materials. The lower current in cells with 4 or more junctions, resulting in lower I2R resistive power loss, is a particularly significant advantage in concentrator PV systems. Prototype 4-junction terrestrial concentrator cells have been grown by metal-organic vapor-phase epitaxy, with preliminary measured efficiency of 35.7% under the AM1.5 direct terrestrial solar spectrum at 256 suns.

  2. Deviations from Vegard’s law in ternary III-V alloys

    KAUST Repository

    Murphy, S. T.

    2010-08-03

    Vegard’s law states that, at a constant temperature, the volume of an alloy can be determined from a linear interpolation of its constituent’s volumes. Deviations from this description occur such that volumes are both greater and smaller than the linear relationship would predict. Here we use special quasirandom structures and density functional theory to investigate such deviations for MxN1−xAs ternary alloys, where M and N are group III species (B, Al, Ga, and In). Our simulations predict a tendency, with the exception of AlxGa1−xAs, for the volume of the ternary alloys to be smaller than that determined from the linear interpolation of the volumes of the MAs and BAs binary alloys. Importantly, we establish a simple relationship linking the relative size of the group III atoms in the alloy and the predicted magnitude of the deviation from Vegard’s law.

  3. Calculating the Curie temperature reliably in diluted III-V ferromagnetic semiconductors

    Czech Academy of Sciences Publication Activity Database

    Bouzerar, G.; Ziman, T.; Kudrnovský, Josef

    2005-01-01

    Roč. 69, č. 5 (2005), s. 812-818 ISSN 0295-5075 R&D Projects: GA AV ČR(CZ) IAA1010203; GA ČR(CZ) GA202/04/0583 Institutional research plan: CEZ:AV0Z10100520 Keywords : local RPA * Curie temperaure * ab-initio * Heisenberg model * magnetic percolation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.237, year: 2005

  4. All-optical XOR logic gate using intersubband transition in III-V quantum well materials.

    Science.gov (United States)

    Feng, Jijun; Akimoto, Ryoichi; Gozu, Shin-ichiro; Mozume, Teruo

    2014-06-02

    A monolithically integrated all-optical exclusive-OR (XOR) logic gate is experimentally demonstrated based on a Michelson interferometer (MI) gating device in InGaAs/AlAsSb coupled double quantum wells (CDQWs). The MI arms can convert the pump data with return-to-zero ON-OFF keying (RZ OOK) to binary phase-shift keying (BPSK) format, then two BPSK signals can interfere with each other for realizing a desired logical operation. All-optical format conversion from the RZ OOK to BPSK is based on the cross-phase modulation to the transverse electric (TE) probe wave, which is caused by the intersubband transition excited by the transverse magnetic (TM) pump light. Bit error rate measurements show that error free operation for both BPSK format conversion and XOR logical operation can be achieved.

  5. InGaAs focal plane array developments at III-V Lab

    Science.gov (United States)

    Rouvié, Anne; Reverchon, Jean-Luc; Huet, Odile; Djedidi, Anis; Robo, Jean-Alexandre; Truffer, Jean-Patrick; Bria, Toufiq; Pires, Mauricio; Decobert, Jean; Costard, Eric

    2012-06-01

    SWIR detection band benefits from natural (sun, night glow, thermal radiation) or artificial (eye safe lasers) photons sources combined to low atmospheric absorption and specific contrast compared to visible wavelengths. It gives the opportunity to address a large spectrum of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety) or industry (non destructive process control). InGaAs material appears as a good candidate to satisfy SWIR detection needs. The lattice matching with InP constitutes a double advantage to this material: attractive production capacity and uncooled operation thanks to low dark current level induced by high quality material. For few years, III-VLab has been studying InGaAs imagery, gathering expertise in InGaAs material growth and imaging technology respectively from Alcatel-Lucent and Thales, its two mother companies. This work has lead to put quickly on the market a 320x256 InGaAs module, exhibiting high performances in terms of dark current, uniformity and quantum efficiency. In this paper, we present the last developments achieved in our laboratory, mainly focused on increasing the pixels number to VGA format associated to pixel pitch decrease (15μm) and broadening detection spectrum toward visible wavelengths. Depending on targeted applications, different Read Out Integrated Circuits (ROIC) have been used. Low noise ROIC have been developed by CEA LETI to fit the requirements of low light level imaging whereas logarithmic ROIC designed by NIT allows high dynamic imaging adapted for automotive safety.

  6. Time Resolved Studies of Carrier Dynamics in III -v Heterojunction Semiconductors.

    Science.gov (United States)

    Westland, Duncan James

    Available from UMI in association with The British Library. Requires signed TDF. Picosecond time-resolution photoluminescence spectroscopy has been used to study transient processes in Ga _{.47}In_{.53 }As/InP multiple quantum wells (MQWs), and in bulk Ga_{.47}In _{.53}As and GaSb. To facilitate the experimental studies, apparatus was constructed to allow the detection of transient luminescence with 3ps time resolution. A frequency upconversion technique was employed. Relaxation of energetic carriers in bulk Ga _{.47}In_{.53 }As by optic phonons has been investigated, and, at carrier densities ~3 times 10^{18}cm ^{-3} is found to be a considerably slower process than simple theory predicts. The discrepancy is resolved by the inclusion of a non-equilibrium population of longitudinal optic phonons in the theoretical description. Slow energy loss is also observed in a 154A MQW under similar conditions, but carriers are found to relax more quickly in a 14A MQW with a comparable repeat period. The theory of non-equilibrium mode occupation is modified to describe the case of a MQW and is found to agree with experiment. Carrier relaxation in GaSb is studied and the importance of occupation of the L _6 conduction band valley in this material is demonstrated. The ambipolar diffusion of a photoexcited carrier plasma through an InP capping layer was investigated using an optical time-of-flight technique. This experiment also enables the efficiency of carrier capture by a Ga _{.47}In_{.53 }As quantum well to be determined. A capture time of 4ps was found.

  7. Near-thermal limit gating in heavily doped III-V semiconductor nanowires using polymer electrolytes

    Science.gov (United States)

    Ullah, A. R.; Carrad, D. J.; Krogstrup, P.; Nygârd, J.; Micolich, A. P.

    2018-02-01

    Doping is a common route to reducing nanowire transistor on-resistance but it has limits. A high doping level gives significant loss in gate performance and ultimately complete gate failure. We show that electrolyte gating remains effective even when the Be doping in our GaAs nanowires is so high that traditional metal-oxide gates fail. In this regime we obtain a combination of subthreshold swing and contact resistance that surpasses the best existing p -type nanowire metal-oxide semiconductor field-effect transistors (MOSFETs). Our subthreshold swing of 75 mV/dec is within 25 % of the room-temperature thermal limit and comparable with n -InP and n -GaAs nanowire MOSFETs. Our results open a new path to extending the performance and application of nanowire transistors, and motivate further work on improved solid electrolytes for nanoscale device applications.

  8. Exploring Cryogenic Focused Ion Beam Milling as a Group III-V Device Fabrication Tool

    Science.gov (United States)

    2013-09-01

    boiling, triple , and critical points of the elements” in CRC Handbook of Chemistry and Physics, 92nd ed., Boca Raton, FL: CRC press, 2011-2012, p. 4...The most widely used ion source in FIB instruments is a gallium (Ga) liquid metal ion source (LMIS) [4]. Gallium is attractive as an ion source...Figure 3b. EDS spectra were captured at different points across the patterned region of the room temperature milled sample, as indicated in Figure 4

  9. Theoretical Crystal-Field Calculations for Rare-Earth Ions in III-V semiconductor Compounds

    Science.gov (United States)

    1991-10-01

    22209 Director Director US Army Electronics Warfare Laboratory Defense Nuclear Agency Attn AMSEL-DD Attn Tech Library Attn AMSEL-DD, J. Charlton 6801...Washougal, WA 98671 Attn SLCHD-NW-TN, Chief Attn SLCHD-NW-TS, Chief Departmento Quimica Fundamental Attn SLCHD-PO, Chief Universidade Federal de

  10. Characterization of III-V nanowires for photovoltaic devices using advanced electron microscopy techniques

    DEFF Research Database (Denmark)

    Persson, Johan Mikael

    In this work, the crystal structure of epitaxially grown semiconductor nanowires has been analysed using electron microscopy and to some extent X-ray diffractometry. The goal of the EU project which this work was a part of was to build multi-junction solar cells with nanowires as the main building...... of the crystal structure at the junction. This thesis also comments on some unusual properties and _ndings of the examined nanowires: Some nanowires sported a droplet-like protrusion of the catalyst gold particle reaching into the solid center of the nanowire. This feature can be discussed in terms of nanowire...

  11. Growth and properties of low-dimensional III-V semiconductor nanowire heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Heiss, Martin

    2010-08-25

    In this work the properties of GaAs nanowire based heterostructures are investigated. The nanowires and their heterostructures are synthesized with Molecular Beam Epitaxy. The optical and structural properties are characterized by means of low temperature confocal micro-photoluminescence spectroscopy and Transmission Electron Microscopy. Molecular Beam Epitaxy is a versatile technique that allows to switch from radial to axial growth in order to cap the nanowires by an epitaxial prismatic AlGaAs/GaAs heterostructure. This can passivate surface states and improve the optical properties. The effect of such a passivation layer is studied by quantitative comparison of the diameter dependence of photoluminescence in passivated and unpassivated nanowires. The passivation is an important prerequisite for more complex axial heterostructures. Evidence for radial confinement effects is found in passivated nanowires with core diameters smaller than 70 nm. Furthermore, the polarization dependence of light absorption and emission is investigated. Two different types of axial heterostructures are studied that have the potential to further enhance the functionality of such nanowires. In a first step, the possibility of growth of axial InGaAs heterostructure in the Au-free Molecular Beam Epitaxy growth regime is investigated. Suitable growth conditions are identified and the growth temperature window for both GaAs and InGaAs nanowires is determined. At the optimum growth temperature for GaAs nanowires, the incorporation of indium in the structure is limited to a few percent. It is shown that by lowering the growth temperature the indium concentration in the structure can be increased up to 20%. The optical properties of the synthesized axial heterostructures are investigated by means of micro-photoluminescence spectroscopy and Transmission Electron Microscopy. The second type of axial nanowire heterostructure investigated in the present work is characterized by a change in crystal symmetry from cubic zinc-blende to hexagonal wurtzite structure, while the chemical composition of the material remains constant. The GaAs nanowires synthesized with the Au-free technique can be grown under conditions where a statistical wurtzite/zinc-blende polytypism occurs. A novel method for the direct correlation at the nanoscale of structural and optical properties of single GaAs nanowires is developed in order to characterize the resulting statistically distributed quantum heterostructures. Nanowires consisting of {approx}100% wurtzite and nanowires presenting zinc-blende/wurtzite polytypism are studied by photoluminescence spectroscopy and Transmission Electron Microscopy. The photoluminescence of wurtzite GaAs is found to be consistent with a bulk wurtzite band gap of 1.50 eV, slightly smaller compared to the zinc-blende GaAs band gap. In the polytypic nanowires, it is shown that the regions that are predominantly composed of either zinc-blende or wurtzite phase show photoluminescence emission close to the according bulk band gaps, while regions composed of a non periodic superlattice of wurtzite and zinc-blende phases exhibit a redshift of the photoluminescence spectra as low as 1.455 eV. The dimensions of the quantum heterostructures are correlated with the light emission, allowing us to estimate the band offsets of {delta}E{sub CB}=53{+-}20 meV and {delta}E{sub VB}=76{+-}12 meV between the two crystalline phases. These results are in excellent agreement with recent theoretical band structure calculations. (orig.)

  12. Investigation of Current Induced Spin Polarization in III-V Semiconductor Epilayers

    Science.gov (United States)

    Luengo-Kovac, Marta

    In the development of a semiconductor spintronics device, a thorough understanding of spin dynamics in semiconductors is necessary. In particular, electrical control of electron spins is advantageous for its compatibility with present day electronics. In this thesis, we will discuss the electrical modification of the electron g-factor, which characterizes the strength of the interaction between a spin and a magnetic field, as well as investigate electrically generated spin polarizations as a function of various material parameters. We report on the modification of the electron g-factor by an in-plane electric field in an InGaAs epilayer. We performed external magnetic field scans of the Kerr rotation of the InGaAs film in order to measure the g-factor independently of the spin-orbit fields. The g-factor increases from -0.4473(0.0001) at 0 V/cm to -0.4419( 0.0001) at 50 V/cm applied along the [110] crystal axis. A comparison of temperature and voltage dependent photoluminescence measurements indicate that minimal channel heating occurs at these voltages. Possible explanations for this g-factor modification are discussed, including an increase in the electron temperature that is independent of the lattice temperature and the modification of the donor-bound electron wave function by the electric field. The current-induced spin polarization and momentum-dependent spin-orbit field were measured in InGaAs epilayers with varying indium concentrations and silicon doping densities. Samples with higher indium concentrations and carrier concentrations and lower mobilities were found to have larger electrical spin generation efficiencies. Furthermore, current-induced spin polarization was detected in GaAs epilayers despite the absence of measurable spin-orbit fields, indicating that the spin polarization mechanism is extrinsic. Temperature-dependent measurements of the spin dephasing rates and mobilities were used to characterize the relative strengths of the intrinsic D'yakonov-Perel' and extrinsic Elliot-Yafet spin dephasing mechanisms. Proposed spin polarization mechanisms are discussed and compared with the experimental results.

  13. A new standardless quantitative electron probe microanalysis technique applied to III-V compound semiconductors

    International Nuclear Information System (INIS)

    Zangalis, K.P.; Christou, A.

    1982-01-01

    The present paper introduces a new standardless quantitative scheme for off-line electron microprobe analysis applications. The analysis is based on standard equations of the type Isub(i)=Csub(i)fsub(ZAF)βsub(i) and is specifically suitable for compound semiconductors. The roots to the resultant nth-degree polynomial are the unknown concentrations. Methods for computing Csub(i) when coefficients βsub(i) are unknown are also outlined. Applications of standardless analysis to GaAs and InP specimens are compared with results obtained by Auger electron spectroscopy and quantitative electron probe analysis with standards. (Auth.)

  14. Charge transport in non-polar and semi-polar III-V nitride heterostructures

    International Nuclear Information System (INIS)

    Konar, Aniruddha; Verma, Amit; Fang, Tian; Zhao, Pei; Jana, Raj; Jena, Debdeep

    2012-01-01

    Compared to the intense research focus on the optical properties, the transport properties in non-polar and semi-polar III-nitride semiconductors remain relatively unexplored to date. The purpose of this paper is to discuss charge-transport properties in non-polar and semi-polar orientations of GaN in a comparative fashion to what is known for transport in polar orientations. A comprehensive approach is adopted, starting from an investigation of the differences in the electronic bandstructure along different polar orientations of GaN. The polarization fields along various orientations are then discussed, followed by the low-field electron and hole mobilities. A number of scattering mechanisms that are specific to non-polar and semi-polar GaN heterostructures are identified, and their effects are evaluated. Many of these scattering mechanisms originate due to the coupling of polarization with disorder and defects in various incarnations depending on the crystal orientation. The effect of polarization orientation on carrier injection into quantum-well light-emitting diodes is discussed. This paper ends with a discussion of orientation-dependent high-field charge-transport properties including velocity saturation, instabilities and tunneling transport. Possible open problems and opportunities are also discussed. (paper)

  15. Bismuth containing III-V quaternary alloy InGaAsBi grown by MBE

    International Nuclear Information System (INIS)

    Feng, G.; Oe, K.; Yoshimoto, M.

    2006-01-01

    InGaAsBi epilayers were created on InP substrates by molecular beam epitaxy for the first time. The high crystalline quality of the InGaAsBi epilayer with smooth interface was confirmed by high resolution X-ray diffraction measurements. Up to 2.5% Bi was incorporated in the film based on Rutherford back scattering (RBS) results. The RBS channeling spectra give clear evidence that the Bi atoms were substitutionally located in the InGaAs zinc-blende lattice sites. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  16. Molecular beam epitaxy of Cd3As2 on a III-V substrate

    Directory of Open Access Journals (Sweden)

    Timo Schumann

    2016-12-01

    Full Text Available Epitaxial, strain-engineered Dirac semimetal heterostructures promise tuning of the unique properties of these materials. In this study, we investigate the growth of thin films of the recently discovered Dirac semimetal Cd3As2 by molecular beam epitaxy. We show that epitaxial Cd3As2 layers can be grown at low temperatures (110 °C–220 °C, in situ, on (111 GaSb buffer layers deposited on (111 GaAs substrates. The orientation relationship is described by ( 112 Cd 3 As 2 || (111 GaSb and [ 1 1 ¯ 0 ] Cd 3 As 2 || [ 1 ¯ 01 ] GaSb . The films are shown to grow in the low-temperature, vacancy ordered, tetragonal Dirac semimetal phase. They exhibit high room temperature mobilities of up to 19300 cm2/Vs, despite a three-dimensional surface morphology indicative of island growth and the presence of twin variants. The results indicate that epitaxial growth on more closely lattice matched buffer layers, such as InGaSb or InAlSb, which allow for imposing different degrees of epitaxial coherency strains, should be possible.

  17. Discrimination of defects in III-V semiconductors by positron lifetime distribution

    CERN Document Server

    Chen, Z Q; Wang, S J

    2000-01-01

    In this paper, the numerical Laplace inversion technique and maximum entropy method are utilized to extract continuous positron lifetime distribution in semiconductors. The result is used to discriminate the native vacancy-type defects in as-grown GaAs and In P with different conduction type. Direct evidence of shallow positron traps were also observed in ion-implanted p-In P. It is demonstrated that the lifetime distribution can give us more detailed information on the native defects.

  18. Theoretical modeling of a new structure of III-V tandem solar cells by ...

    African Journals Online (AJOL)

    junction solar cell is theoretically investigated by optimizing the thickness of GaAs and GaInPandusing a new optical model to separate the junction between the two solar cell in order to solve problems of tunnel junction and difficulties of fabrication.

  19. Structure of disordered alloys - II: self-consistent CCPA calculations for III-V semiconducting alloys

    International Nuclear Information System (INIS)

    Mookerjee, A.; Chaudhry, V.

    1980-09-01

    Using the chemical pseudopotential approach of Anderson and Bullett we have generated from first principles pseudo-Hamiltonians for heteropolar alloys. The one-electron density of states has been generated for Gasub(x)Insub(1-x)As using a self-consistent cluster CPA introduced earlier by one of us. Off-diagonal disorder has also been incorporated. (author)

  20. Optical characterisation of III-V nitride-based multiphase and diluted magnetic semiconductors

    International Nuclear Information System (INIS)

    Wegscheider, M.

    2009-01-01

    The present work is devoted to the investigation of the optical properties of transition metal doped Gallium nitride. The Gallium nitride layers are epitaxially grown in a full metalorganic chemical vapour deposition process whereas the transition metals iron or manganese as well as the n and p-type dopants silicon and magnesium are incorporated simultaneously. Background and driving force of the realization of such material systems is basically the evocation of ferromagnetic spin alignment where free carriers ensure the correspondence between the localized spin state provided by the metal ions. The production of completely new devices for semiconductor industries based on the possibility to switch on or off the ferrimagnetic alignment by changing the free carrier concentration can be expected in the near future. In this context photoluminescence studies in the ultraviolet and mid infrared spectral range at temperatures between the liquid helium point and room temperature at atmospheric pressure were made. These measurements basically provide information on optical transitions between the conduction and valence band and deep defects as well as on crystal field forced transitions within the d-orbitals of the metal ion involved. In this context valuable knowledge could have been gained on doping concentrations, growth fashions and parameters, formation of secondary phases as well as on the doping efficiency and incorporation sites of the metal atoms. (author) [de

  1. Temperature dependence Infrared and Raman studies of III-V/II-VI core-shell nanostructures

    Science.gov (United States)

    Manciu, Felicia S.; McCombe, Bruce D.; Lucey, Derrick

    2005-03-01

    The temperature dependence (8 K InP/ZnS sample. Raman scattering (457.9 nm excitation) features were determined without polarization selection in the backscattering geometry. Interesting T-dependent resonant Raman effect of the surface optical phonon modes has been discovered in InP/ZnSe sample. Reasonable agreement is obtained between the Raman and FIR results, as well as with theoretical calculations.

  2. Improved Ion Resistance for III-V Photocathodes in High Current Guns

    Energy Technology Data Exchange (ETDEWEB)

    Mulhollan, Gregory, A.

    2012-11-16

    The two photocathode test systems were modified, baked and recommissioned. The first system was dedicated to ion studies and the second to electron stimulated recovery (ESR) work. The demonstration system for the electron beam rejuvenation was set up, tested and demonstrated to one of the SSRL team (Dr. Kirby) during a site visit. The requisite subsystems were transferred to SSRL, installed and photoemission studies conducted on activated surfaces following electron beam exposure. Little surface chemistry change was detected in the photoemission spectra following the ESR process. The yield mapping system for the ion (and later, the electron beam rejuvenation) studies was implemented and use made routine. Ion species and flux measurements were performed for H, He, Ne, Ar, Kr and Xe ions at energies of 0.5, 1.0 and 2.0 kV. Gas induced photoyield measurements followed each ion exposure measurement. These data permit the extraction of photoyield induced change per ion (by species) at the measured energies. Electron beam induced rejuvenation was first demonstrated in the second chamber with primary electron beam energy and dependency investigations following. A Hiden quadrupole mass spectrometer for the electron stimulated desorption (ESD) measurements was procured. The UHV test systems needed for subsequent measurements were configured, baked, commissioned and utilized for their intended purposes. Measurements characterizing the desorption products from the ESD process and secondary electron (SE) yield at the surfaces of negative electron affinity GaAs photocathodes have been performed. One US Utility Patent was granted covering the ESR process.

  3. Deviations from Vegard’s law in ternary III-V alloys

    KAUST Repository

    Murphy, S. T.; Chroneos, Alexander; Grimes, R. W.; Jiang, C.; Schwingenschlö gl, Udo

    2010-01-01

    the linear relationship would predict. Here we use special quasirandom structures and density functional theory to investigate such deviations for MxN1−xAs ternary alloys, where M and N are group III species (B, Al, Ga, and In). Our simulations predict a

  4. Atomic scale study of intrinsic and Mn doped quantum dots in III-V semiconductors

    NARCIS (Netherlands)

    Bozkurt, M.

    2011-01-01

    In this thesis, a Cross Sectional Scanning Tunneling Microscope (X-STM) is used to investigate nanostructures in IIIV semiconductors and single Mn impurities in bulk GaAs. The atomic resolution which can be achieved with X-STM makes it possible to link structural properties of nanostructures to

  5. Controlling the emission wavelength in group III-V semiconductor laser diodes

    KAUST Repository

    Ooi, Boon S.; Majid, Mohammed Abdul; Afandy, Rami; Aljabr, Ahmad

    2016-01-01

    Methods are provided for modifying the emission wavelength of a semiconductor quantum well laser diode, e.g. by blue shifting the emission wavelength. The methods can be applied to a variety of semiconductor quantum well laser diodes, e.g. group III

  6. Ellipsometric study of metal-organic chemically vapor deposited III-V semiconductor structures

    Science.gov (United States)

    Alterovitz, Samuel A.; Sekula-Moise, Patricia A.; Sieg, Robert M.; Drotos, Mark N.; Bogner, Nancy A.

    1992-01-01

    An ellipsometric study of MOCVD-grown layers of AlGaAs and InGaAs in thick films and strained layer complex structures is presented. It is concluded that the ternary composition of thick nonstrained layers can be accurately determined to within experimental errors using numerical algorithms. In the case of complex structures, thickness of all layers and the alloy composition of nonstrained layers can be determined simultaneously, provided that the correlations between parameters is no higher than 0.9.

  7. Phase-coherent transport and spin-orbit-coupling in III/V-semiconductor nanowires

    International Nuclear Information System (INIS)

    Estevez Hernandez, Sergio

    2009-01-01

    Semiconductor nanowires fabricated by a bottom-up approach are not only interesting for the realization of future nanoscaled devices but also appear to be very attractive model systems to tackle fundamental questions concerning the transport in strongly confined systems. In order to avoid the problem connected with carrier depletion, narrowband gap semiconductors, i.e., InAs or InN, or core-shell Nanowires, i.e., GaAs/AlGaAs, are preferred. The underlying reason is that in InAs or InN the Fermi-level pinning in the conduction band results in a carrier accumulation at the surface. In fact, the tubular topology of the surface electron gas opens up the possibility to observe unconventional quantum transport phenomena. When the phase-coherence length in the nanowire is comparable to its dimensions the conductance fluctuates if a magnetic field is applied or if the electron concentration is changed by means of a gate electrode. These so-called universal conductance fluctuations being in the order of e 2 /h originate from the fact that in small disordered samples, electron interference effects are not averaged out. In this work are analyzed universal conductance fluctuations to study the quantum transport properties in InN, InAs and GaAs/AlGaAs nanowires. With the use of a magnetic field and a back-gate electrode the universal conductance fluctuations and localizations effects were analyzed. Since InN and InAs are narrow band gap semiconductors, one naturally expects spin-orbit coupling effects. Because this phenomena is of importance for spin electronic applications. However, owing to the cylindrical symmetry of the InN and InAs nanowires, the latter effect was observable and actually be used to determine the strength of spin-orbit coupling. In order to clearly separate the weak antilocalization effect from the conductance fluctuations, the averaging of the magnetoconductance at different gate voltages was essential. The low-temperature quantum transport properties of gated InN, InAs and GaAs/AlGaAs nanowires were investigated. Magnetic field-dependent as well as gate-dependent measurements of universal conductance fluctuations were performed to gain information on the phase coherence in the electron transport. In this work was found a pronounced decrease in the variance of the conductance by about a factor of 2 in gate-dependent fluctuation measurements if a magnetic field is applied. This effect is explained by the suppression of the Cooperon channel of the electron correlation contributing to the conductance fluctuations. Despite the fact that the diameter of the nanowire is less than 100 nm a clear weak antilocalization effect is found in the averaged magnetoconductance being in strong contrast to the suppression of weak antilocalization for narrow quantum wires based on planar two-dimensional electron gases. The unexpected robustness of the weak antilocalization effect observed here is attributed to the tubular topology of the surface electron gas in InN and InAs nanowires. (orig.)

  8. Modulation doping and delta doping of III-V compound semiconductors

    NARCIS (Netherlands)

    Hendriks, P.; Zwaal, E.A.E.; Haverkort, J.E.M.; Wolter, J.H.; Razeghi, M.

    1991-01-01

    The transport properties of the 2D electron gas produced by modulation doping of compound semiconductors are reviewed with attention given to the properties at high electric fields. Experimental studies are discussed in which the transport properties lead to insights into current instabilities and

  9. A model of gettering effects of rare-earth elements in III-V compounds

    Czech Academy of Sciences Publication Activity Database

    Šrobár, Fedor; Procházková, Olga

    2006-01-01

    Roč. 100, č. 8 (2006), s. 643-- ISSN 0009-2770. [Sjezd chemických společností /58./. Ústí nad Labem, 04.09.2006-08.09.2006] R&D Projects: GA ČR(CZ) GA102/06/0153 Institutional research plan: CEZ:AV0Z20670512 Keywords : semiconductor technology * rare earth metals * getters Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.431, year: 2006

  10. Study and characterization of III-V semiconductor materials for applications in ionizing radiation detection

    International Nuclear Information System (INIS)

    Moulin, H.

    1989-11-01

    The photoconduction in the bulk of the gallium arsenide (GaAs) and of the indium phosphide doped with iron (InP:Fe) is investigated. These semiconductor materials are to be applied in X rays detection. The photoconduction theory and the physical characteristics of those materials are reviewed. The computer simulation models for studying the photoconductor responses to the radiation pulses are described. The experimental results are discussed. They include the following aspects: the characterization of the GaAs and InP:Fe, in the obscurity, as a function of the polarized electric field and of the neutrons dose; the characterization under X ray. Continuous X rays and pulsed synchrotron radiation are applied [fr

  11. Growth and characterization of GaAs-GaSb III-V pseudo-binary nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Schamp, C.T. [Cerium Laboratories, Austin, TX 78741 (United States); Jesser, W.A. [Department of Materials Science and Engineering, 116 Engineer' s Way, University of Virginia, Charlottesville, VA 22904 (United States)

    2008-07-01

    The GaAs-GaSb pseudo-binary materials system presents an interesting challenge for growth because of 1) the existence of a miscibility gap in the solid-solid portion of the equilibrium phase diagram, and 2) the large differences in vapor pressure between the column III element, Ga, and the column V elements, As and Sb. To overcome these challenges in the growth of GaAs, GaSb, and Ga{sub 50}As{sub x}Sb{sub 50-x} alloy nanoparticles, single- and dual-target pulsed laser deposition (PLD) techniques were implemented using an Nd:YAG laser operated with a harmonic generator to utilize the second harmonic wavelength (532 nm) and a combination of the fundamental and the second harmonic wavelengths (1064 nm+532 nm). The nanoparticles were collected on amorphous carbon films for subsequent characterization by transmission electron microscopy. The analysis shows that single phase GaAs-rich Ga{sub 50}As{sub x}Sb{sub 50-x} (28>x>50) nanoparticles and nanocrystalline films have been formed through dual-target, single-wavelength (532 nm) pulsed laser ablation. Interestingly, through the ablation of the single component targets, two-phase particles were also found to form. These two phase particles resemble ''nano-ice cream cones'' with solid cones of either GaAs or GaSb with a spherical ''ice cream'' ball of Ga located at the wide portion of the cone, which is either an amorphous phase or liquid phase. Through an analysis by STEM-EDX spectroscopy, these particles are found to be consistant with this model. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. High Efficiency Quantum Dot III-V Multijunction Solar Cell for Space Power, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Quantum dots are nanoscale materials that have already improved the performance of optical sensors, lasers, and light emitting diodes. The unique properties of these...

  13. High Efficiency Quantum Dot III-V Thermophotovoltaic Cell for Space Power, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Quantum dots are nanoscale materials that have already improved the performance of optical sensors, lasers, light emitting diodes and solar cells. The unique...

  14. Silicon-photonics light source realized by III-V/Si grating-mirror laser

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper

    2010-01-01

    waveguide are made in the Si layer of a silicon-on-insulator wafer by using Si-electronics-compatible processing. The HCG works as a highly-reflective mirror for vertical resonance and at the same time routes light to the in-plane output waveguide. Numerical simulations show superior performance compared...... to existing silicon light sources....

  15. Theory of Anion-Substituted Nitrogen-Bearing III-V Alloys

    Science.gov (United States)

    1998-07-20

    was found by Zunger group). When more than 4% arsenic is incorporated into GaN in an ordered array, the band gap closes . Calculations of the...arsenic is incorporated into GaN in an ordered array, the band gap closes . Calculations of the properties of random alloys predict smaller bowing...BEARING lll-V ALLOYS Prepared by: M. A. Berding, Senior Research Physicist M. van Schilfgaarde, Senior Research Physicist A. Sher, Associate Director

  16. Investigation of proton damage in III-V semiconductors by optical spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yaccuzzi, E.; Giudici, P. [Departamento Energía Solar, Centro Atómico Constituyentes, Av. Gral. Paz 1499, 1650 San Martín (Argentina); CONICET, Godoy Cruz 2290 (C1425FQB), CABA (Argentina); Khachadorian, S.; Strittmatter, A.; Hoffmann, A. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Suárez, S. [Laboratorio de Colisiones Atómicas, Centro Atómico Bariloche, E. Bustillo 9500, 8400 Bariloche (Argentina); CONICET, Godoy Cruz 2290 (C1425FQB), CABA (Argentina); Reinoso, M. [Departamento Física Experimental, Centro Atómico Constituyentes, Av. Gral. Paz 1499, 1650 San Martín (Argentina); CONICET, Godoy Cruz 2290 (C1425FQB), CABA (Argentina); Goñi, A. R. [ICREA, Passeig Lluís Companys 23, 08010 Barcelona (Spain); Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra (Spain)

    2016-06-21

    We studied the damage produced by 2 MeV proton radiation on epitaxially grown InGaP/GaAs structure by means of spatially resolved Raman and photoluminescence (PL) spectroscopy. The irradiation was performed parallel to the sample surface in order to determine the proton penetration range in both compounds. An increase in the intensity of longitudinal optical phonons and a decrease in the luminescence were observed. We associate these changes with the creation of defects in the damaged region, also responsible for the observed change of the carrier concentration in the GaAs layer, determined by the shift of the phonon-plasmon coupled mode frequency. From the spatially resolved profile of the PL and phonon intensities, we obtained the proton range in both materials and we compared them with stopping and range of ions in matter simulations. The comparison between the experimentally obtained proton range and simulations shows a very good agreement for GaAs but a discrepancy of 20% for InGaP. This discrepancy can be explained in terms of limitations of the model to simulate the electronic orbitals and bonding structure of the simulated compound. In order to overcome this limitation, we propose an increase in 40% in the electronic stopping power for InGaP.

  17. Modeling Three-Terminal III-V/Si Tandem Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Emily L.; Deceglie, Michael G.; Stradins, Paul; Tamboli, Adele C.

    2017-06-27

    Three-terminal (3T) tandem cells fabricated by combining an interdigitated back contact (IBC) Si device with a wider bandgap top cell have the potential to provide a robust operating mechanism to efficiently capture the solar spectrum without the need to current match sub-cells or fabricate complicated metal interconnects between cells. Here we develop a two dimensional device physics model to study the behavior of IBC Si solar cells operated in a 3T configuration. We investigate how different cell designs impact device performance and discuss the analysis protocol used to understand and optimize power produced from a single junction, 3T device.

  18. Cutoff-mesa isolated rib optical waveguide for III-V heterostructure photonic integrated circuits

    Science.gov (United States)

    Vawter, G.A.; Smith, R.E.

    1998-04-28

    A cutoff mesa rib waveguide provides single-mode performance regardless of any deep etches that might be used for electrical isolation between integrated electrooptic devices. Utilizing a principle of a cutoff slab waveguide with an asymmetrical refractive index profile, single mode operation is achievable with a wide range of rib widths and does not require demanding etch depth tolerances. This new waveguide design eliminates reflection effects, or self-interference, commonly seen when conventional rib waveguides are combined with deep isolation etches and thereby reduces high order mode propagation and crosstalk compared to the conventional rib waveguides. 7 figs.

  19. Growth and Characterization of III-V Semiconductors for Device Applications

    Science.gov (United States)

    Williams, Michael D.

    2000-01-01

    The research goal was to achieve a fundamental understanding of the physical processes occurring at the surfaces and interfaces of epitaxially grown InGaAs/GaAs (100) heterostructures. This will facilitate the development of quantum well devices for infrared optical applications and provide quantitative descriptions of key phenomena which impact their performance. Devices impacted include high-speed laser diodes and modulators for fiber optic communications at 1.55 micron wavelengths and intersub-band lasers for longer infrared wavelengths. The phenomenon of interest studied was the migration of indium in InGaAs structures. This work centered on the molecular beam epitaxy reactor and characterization apparatus donated to CAU by AT&T Bell Laboratories. The material characterization tool employed was secondary ion mass spectrometry. The training of graduate and undergraduate students was an integral part of this program. The graduate students received a thorough exposure to state-of-the-art techniques and equipment for semiconductor materials analysis as part of the Master''s degree requirement in physics. The undergraduates were exposed to a minority scientist who has an excellent track record in this area. They also had the opportunity to explore surface physics as a career option. The results of the scientific work was published in a refereed journal and several talks were presented professional conferences and academic seminars.

  20. Photoluminescence Polarization Anisotropy in a Single Heterostructured III-V Nanowire with Mixed Crystal Phases

    International Nuclear Information System (INIS)

    Moses, A. F.; Hoang, T. B.; Ahtapodov, L.; Dheeraj, D. L.; Fimland, B. O.; Weman, H.; Helvoort, A. T. J. van

    2011-01-01

    Low temperature (10 K) micro-photoluminescence (μ-PL) of single GaAs/AlGaAs core-shell nanowires with single GaAsSb inserts were measured. The PL emission from the zinc blende GaAsSb insert is strongly polarized along the nanowire axis while the PL emission from the wurtzite GaAs nanowire is perpendiculary polarized to the nanowire axis. The result indicates that the crystal phase, through the optical selection rules, has significant effect on the polarization of the PL from NWs besides the dielectric mismatch. The analysis of the PL results based on the electronic structure of these nanowires supports the correlation between the crystal phase and the PL emission.

  1. Electron scattering by native defects in III-V nitrides and their alloys

    International Nuclear Information System (INIS)

    Hsu, L.; Walukiewicz, W.

    1996-03-01

    We have calculated the electron mobilities in GaN and InN taking into consideration scattering by short range potentials, in addition to all standard scattering mechanisms. These potentials are produced by the native defects which are responsible for the high electron concentrations in nominally undoped nitrides. Comparison of the calculated mobilities with experimental data shows that scattering by short range potentials is the dominant mechanism limiting the electron mobilities in unintentionally doped nitrides with large electron concentrations. In the case of Al x Ga 1-x N alloys, the reduction in the electron concentration due to the upward shift of the conduction band relative to the native defect level can account for the experimentally measured mobilities. Resonant scattering is shown to be important when the defect and Fermi levels are close in energy

  2. Polarization dependent femtosecond laser modification of MBE-grown III-V nanostructures on silicon

    OpenAIRE

    Zandbergen, Sander R.; Gibson, Ricky; Amirsolaimani, Babak; Mehravar, Soroush; Keiffer, Patrick; Azarm, Ali; Kieu, Khanh

    2017-01-01

    We report a novel, polarization dependent, femtosecond laser-induced modification of surface nanostructures of indium, gallium, and arsenic grown on silicon via molecular beam epitaxy, yielding shape control from linear and circular polarization of laser excitation. Linear polarization causes an elongation effect, beyond the dimensions of the unexposed nanostructures, ranging from 88 nm to over 1 um, and circular polarization causes the nanostructures to flatten out or form loops of material,...

  3. The influence of nitrogen on the photoluminescence of metastable III-V nitrides

    International Nuclear Information System (INIS)

    Hantke, K.

    2005-01-01

    The work presented here mainly summarizes experimental and theoretical results enlightening the material-specific, optical properties of (GaIn)(NAs). The primarily used experiment is the time-resolved photoluminescence spectroscopy. The comparison of experiment and theory yields a simple exponential form for the density of localized states. Furthermore it can be confirmed that the typical energy scale of the localization is diminished by the annealing step as well as by the hydrogenation process. In a next step, the investigation of (GaIn)(NAs) epitactical layers, that were optimized for solar cell application, reveals astonishing features: The minority-carrier diffusion-length of the p-doped layers is found to be slightly higher than for the n-doped material implying that (GaIn)(NAs) solar cells with a p-on-n structure should be preferred in terms of higher quantum efficiency. A new effect found during the investigations is the optimization of the internal quantum efficiency of the (GaIn)(NAs) structures after irradiation with intensive laser light attributed to the laser-induced annealing of defects. The final paragraph concentrates on the successful comparison of time-resolved photoluminescence, photo-modulated reflection measurements and a microscopic many-body theory. A profound understanding of the type-I type-II transition in (GaIn)As/Ga(NAs) heterostructures is achieved resulting in material-specific information as e.g. the temperature-dependent bandgap energies, the band offsets in Ga(NAs)/GaAs and (GaIn)As/Ga(NAs) respectively, as well as the interaction potential VN dependent on the nitrogen content. Finally, the fundamental dependence on excitation density investigated in the experiment is theoretically quantified not only for the photoluminescence intensity and but for the lifetimes, too. (orig.)

  4. Determination of stress distribution in III-V single crystal layers for heterogeneous integration applications

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, M.; Hayashi, S. [Dept. of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Goorsky, M.S.; Sandhu, R.; Chang-Chien, P.; Gutierrez-Aitken, A.; Tsai, R. [Northrop Grumman Space Technology, Redondo Beach, CA 90278 (United States); Noori, A.; Poust, B. [Dept. of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Northrop Grumman Space Technology, Redondo Beach, CA 90278 (United States)

    2007-08-15

    Double crystal X-ray diffraction imaging and a variable temperature stage are employed to determine the stress distribution in heterogeneous wafer bonded layers though the superposition of images produced at different rocking curve angles. The stress distribution in InP layers transferred to a silicon substrate at room temperature exhibits an anticlastic deformation, with different regions of the wafer experiencing different signs of curvature. Measurements at elevated temperatures ({<=}125 C) reveals that differences in thermal expansion coefficients dominate the stress and that interfacial particulates introduce very high local stress gradients that increase with increased temperature. For thinned GaAs substrates (100 {mu}m) bonded using patterned metal interlayers to a separate GaAs substrate at {approx}200 C, residual stresses are produced at room temperature due to local stress points from metallization contacts and vias and the complex stress patterns can be observed using the diffraction imaging technique. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Cognition Effects of Low-Grade Hypoxia

    Science.gov (United States)

    2016-07-01

    human short-term memory . Br J Anaesth. 1971; 43(6):548–552. 3. Crow TJ, Kelman GR. Psychological effects of mild acute hypoxia. Br J Anaesth. 1973; 45...Journal Article 3. DATES COVERED (From – To) Jan 2003 – Sep 2005 4. TITLE AND SUBTITLE Cognition Effects of Low-Grade Hypoxia 5a. CONTRACT NUMBER... cognitive function are reported in this paper. The study compared cognitive function during short exposures at four different altitudes. Ninety-one

  6. Fracture Analysis of Functionally Graded Materials

    International Nuclear Information System (INIS)

    Zhang, Ch.; Gao, X. W.; Sladek, J.; Sladek, V.

    2010-01-01

    This paper reports our recent research works on crack analysis in continuously non-homogeneous and linear elastic functionally graded materials. A meshless boundary element method is developed for this purpose. Numerical examples are presented and discussed to demonstrate the efficiency and the accuracy of the present numerical method, and to show the effects of the material gradation on the crack-opening-displacements and the stress intensity factors.

  7. Different grades MEMS accelerometers error characteristics

    Science.gov (United States)

    Pachwicewicz, M.; Weremczuk, J.

    2017-08-01

    The paper presents calibration effects of two different MEMS accelerometers of different price and quality grades and discusses different accelerometers errors types. The calibration for error determining is provided by reference centrifugal measurements. The design and measurement errors of the centrifuge are discussed as well. It is shown that error characteristics of the sensors are very different and it is not possible to use simple calibration methods presented in the literature in both cases.

  8. New examples of continuum graded Lie algebras

    International Nuclear Information System (INIS)

    Savel'ev, M.V.

    1989-01-01

    Several new examples of continuum graded Lie algebras which provide an additional elucidation of these algebras are given. Here, in particular, the Kac-Moody algebras, the algebra S 0 Diff T 2 of infinitesimal area-preserving diffeomorphisms of the torus T 2 , the Fairlie, Fletcher and Zachos sine-algebras, etc., are described as special cases of the cross product Lie algebras. 8 refs

  9. Vibration of Elastic Functionally Graded Thick Rings

    Directory of Open Access Journals (Sweden)

    Guang-Hui Xu

    2017-01-01

    Full Text Available The free vibration behaviors of functionally graded rings were investigated theoretically. The material graded in the thickness direction according to the power law rule and the rings were assumed to be in plane stress and plane strain states. Based on the first-order shear deformation theory and the kinetic relation of von Kárman type, the frequency equation for free vibration of functionally graded ring was derived. The derived results were verified by those in literatures which reveals that the present theory can be appropriate to predict the free vibration characteristics for quite thick rings with the radius-to-thickness ratio from 60 down to 2.09. Comparison between the plane stress case and the plane strain case indicates a slight difference. Meanwhile, the effects of the structural dimensional parameters and the material inhomogeneous parameter are examined. It is interesting that the value of the logarithmic form of vibration frequency is inversely proportional to the logarithmic form of the radius-to-thickness ratio or the mean radius.

  10. Uranium production from low grade Swedish shale

    International Nuclear Information System (INIS)

    Carlsson, O.

    1977-01-01

    In view of the present nuclear programmes a steep increase in uranium demand is foreseen which will pose serious problems for the uranium industry. The annual additions to uranium ore reserves must almost triple within the next 15 years in order to support the required production rates. Although there are good prospects for the discovery of further conventional deposits of uranium there is a growing interest in low grade uranium deposits. Large quantities of uranium exist in black shales, phosphates, granites, sea water and other unconventional sources. There are however factors which limit the utilization of these low grade materials. These factors include the extraction costs, the environmental constrains on mining and milling of huge amounts of ore, the development of technologies for the beneficiation of uranium and, in the case of very low grade materials, the energy balance. The availability of by-product uranium is limited by the production rate of the main product. The limitations differ very much according to types of ores, mining and milling methods and the surroundings. As an illustration a description is given of the Swedish Ranstad uranium shale project, its potential, constraints and technical solutions

  11. Automated Essay Grading using Machine Learning Algorithm

    Science.gov (United States)

    Ramalingam, V. V.; Pandian, A.; Chetry, Prateek; Nigam, Himanshu

    2018-04-01

    Essays are paramount for of assessing the academic excellence along with linking the different ideas with the ability to recall but are notably time consuming when they are assessed manually. Manual grading takes significant amount of evaluator’s time and hence it is an expensive process. Automated grading if proven effective will not only reduce the time for assessment but comparing it with human scores will also make the score realistic. The project aims to develop an automated essay assessment system by use of machine learning techniques by classifying a corpus of textual entities into small number of discrete categories, corresponding to possible grades. Linear regression technique will be utilized for training the model along with making the use of various other classifications and clustering techniques. We intend to train classifiers on the training set, make it go through the downloaded dataset, and then measure performance our dataset by comparing the obtained values with the dataset values. We have implemented our model using java.

  12. A vision of graded hemispheric specialization.

    Science.gov (United States)

    Behrmann, Marlene; Plaut, David C

    2015-11-01

    Understanding the process by which the cerebral hemispheres reach their mature functional organization remains challenging. We propose a theoretical account in which, in the domain of vision, faces and words come to be represented adjacent to retinotopic cortex by virtue of the need to discriminate among homogeneous exemplars. Orthographic representations are further constrained to be proximal to typically left-lateralized language-related information to minimize connectivity length between visual and language areas. As reading is acquired, orthography comes to rely more heavily (albeit not exclusively) on the left fusiform region to bridge vision and language. Consequently, due to competition from emerging word representations, face representations that were initially bilateral become lateralized to the right fusiform region (albeit, again, not exclusively). We review recent research that describes constraints that give rise to this graded hemispheric arrangement. We then summarize empirical evidence from a variety of studies (behavioral, evoked response potential, functional imaging) across different populations (children, adolescents, and adults; left handers and individuals with developmental dyslexia) that supports the claims that hemispheric lateralization is graded rather than binary and that this graded organization emerges dynamically over the course of development. Perturbations of this system either during development or in adulthood provide further insights into the principles governing hemispheric organization. © 2015 New York Academy of Sciences.

  13. Volume Equalization Method for Land Grading Design: Uniform ...

    African Journals Online (AJOL)

    muğla üniversitesi

    2011-05-23

    May 23, 2011 ... *Corresponding author. E-mail: ... Land grading has been in practice for a long time, but land-grading ... method was based on least-squares theory and he showed its ... Srinisava (1996) developed a nonlinear optimization.

  14. Comparative evaluation of six cytological grading systems in breast carcinoma

    Directory of Open Access Journals (Sweden)

    Kaushik Saha

    2013-01-01

    Conclusions: Robinson′s grading system is simple, more objective and reproducible, and demonstrated the best concordance with histological grading. So, Robinson′s system should be used routinely for breast carcinoma aspirates.

  15. Relation between grade and abundance of manganese nodules

    Digital Repository Service at National Institute of Oceanography (India)

    Sudhakar, M.

    Data from more than 1000 locations in the Central Indian Ocean Basin (CIOB) where both bulk nodule chemistry and abundance were determined and utilized to study the relationship between grade and abundance of manganese nodule deposits. Grade...

  16. A Quantitative Study on the Correlation between Grade Span Configuration of Sixth Grade Students in Private Florida Schools and Academic Achievement on Standardized Achievement Scores

    Science.gov (United States)

    Rantin, Deborah

    2017-01-01

    The applied dissertation was designed to investigate the three models of grade span configurations of sixth grade and the effects grade span configuration has on results of the standardized achievement scores of sixth grade students in private, Florida schools. Studies that have been conducted on sixth grade students and grade span configuration…

  17. Tumor grade-related thallium-201 uptake in chondrosarcomas

    International Nuclear Information System (INIS)

    Kaya, G.C.; Demir, Y.; Ozkal, S.

    2010-01-01

    Diagnosis of low-grade chondrosarcoma, especially discrimination between enchondroma and low-grade chondrosarcoma, may be difficult pathologically. The aim of this study was to evaluate the value of thallium-201 (Tl-201) scintigraphy in the diagnosis of chondrosarcoma and to investigate whether there was a correlation between Tl-201 uptake and tumor grade. We retrospectively evaluated 121 patients with pathologically proven bone and soft tissue tumors diagnosed between the years 1999 and 2007. All patients were followed by the Bone and Soft Tissue Tumor Working Group in our hospital. Twenty-three patients, mean age 44±15 (range 17-72) years, with a diagnosis of cartilaginous tumors were included. Increased Tl-201 uptake at the lesion sites greater than background was evaluated as malignant tumor. For the pathologic classification, a grading system (grade 1-3) based on the histopathologic findings was used. Pearson correlation coefficient was used to determine whether there was any correlation between Tl-201 uptake and tumor grade in chondrosarcoma. There were 7 enchondromas and 16 chondrosarcomas. Four of 16 patients with chondrosarcoma had lesions pathologically classified as grade 3, 5 as grade 2, and 7 had grade 1 chondrosarcoma. Increased Tl-201 uptake was observed in all patients with grade 3 chondrosarcoma and 2 patients with grade 2 chondrosarcoma. Of 10 patients with chondrosarcoma, 3 grade 2 chondrosarcomas and 7 grade 1 chondrosarcomas, there was no Tl-201 uptake in the tumor region. A significant correlation was found between Tl-201 uptake and tumor grade in chondrosarcoma (p=0.002, r=0.71). Only a few reports in literature have demonstrated false negative results in low-grade chondrosarcoma. Tl-201 uptake was related to tumor grade in chondrosarcoma. If there is a possibility of chondrosarcoma, Tl-201 scintigraphy should be reported with caution. (author)

  18. Determination of sieve grading curves using an optical device

    OpenAIRE

    PHAM, AM; DESCANTES, Yannick; DE LARRARD, François

    2011-01-01

    The grading curve of an aggregate is a fundamental characteristic for mix design that can easily be modified to adjust several mix properties. While sieve analysis remains the reference method to determine this curve, optical devices are developing, allowing easier and faster assessment of aggregate grading. Unfortunately, optical grading results significantly differ from sieve grading curves. As a consequence, getting full acceptance of these new methods requires building bridges between the...

  19. Grading options for western hemlock "pulpwood" logs from southeastern Alaska.

    Science.gov (United States)

    David W. Green; Kent A. McDonald; John Dramm; Kenneth Kilborn

    Properties and grade yield are estimated for structural lumber produced from No. 3, No. 4, and low-end No. 2 grade western hemlock logs of the type previously used primarily for the production of pulp chips. Estimates are given for production in the Structural Framing, Machine Stress Rating, and Laminating Stock grading systems. The information shows that significant...

  20. Preliminary work in developing sawbolt grading systems for white oak

    Science.gov (United States)

    Everette D. Rast; Everette D. Rast

    1971-01-01

    This paper is principally a description of one technique used in the development of white oak (Quercus alba L.) sawbolt grades--not a final sawbolt grading system for the species over its range. This technique can be used by anyone in developing other bolt-grade specifications or in refining the system presented in this paper.

  1. Extensive Graded Reading in the Liberal Arts and Sciences

    Science.gov (United States)

    Poulshock, Joseph

    2010-01-01

    For this research, learners did extensive graded reading (EGR) with traditional graded readers, and they also interacted with short graded stories in the liberal arts and sciences (LAS). This study describes the purpose and format of the LAS stories used by hundreds of university students and adult learners in Japan. It summarizes the results of…

  2. The Relationship between Attendance Policies and Student Grades

    Science.gov (United States)

    Aaron, Michael D.

    2012-01-01

    The relationship between attendance policies and student grades in college courses was investigated. Specifically, a calculated grade point average was determined for all academic classes taught at Shelton State Community College between 2000 and 2008. These grade point averages were compared descriptively and statistically in an effort to…

  3. 49 CFR 80.11 - Investment-grade ratings.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false Investment-grade ratings. 80.11 Section 80.11... § 80.11 Investment-grade ratings. (a) At the time a project sponsor submits an application, the DOT... investment-grade rating. (b) The full funding of a secured (direct) loan, loan guarantee, or line of credit...

  4. Collegiate Grading Practices and the Gender Pay Gap

    Directory of Open Access Journals (Sweden)

    Alicia C. Dowd

    2000-01-01

    Full Text Available Extending research findings by R. Sabot and J. Wakeman-Linn (1991, this article presents a theoretical analysis showing that relatively low grading quantitative fields and high grading verbal fields create a disincentive for college women to invest in quantitative study. Pressures on grading practices are modeled using higher education production functions.

  5. Collegiate Grading Practices and the Gender Pay Gap.

    Science.gov (United States)

    Dowd, Alicia C.

    2000-01-01

    Presents a theoretical analysis showing that relatively low grading quantitative fields and high grading verbal fields create a disincentive for college women to invest in quantitative study. Extends research by R. Sabot and J. Wakeman-Linn. Models pressures on grading practices using higher education production functions. (Author/SLD)

  6. 7 CFR 52.1855 - Grades of Sultana raisins.

    Science.gov (United States)

    2010-01-01

    ... § 52.1855 Grades of Sultana raisins. (a) “U.S. Grade A” is the quality of Sultana Raisins that have... in Table IV of this subpart. (b) “U.S. Grade B” is the quality of Sultana Raisins that have similar... than materially affected. Grit, sand, or silt None of any consequence may be present that affects the...

  7. Choosing the Adequate Level of Graded Readers--Preliminary Study

    Science.gov (United States)

    Prtljaga, Jelena; Palinkaševic, Radmila; Brkic, Jovana

    2015-01-01

    Graded readers have been used as second language teaching material since the end of the Second World War. They are an important source of simplified material which provides comprehensible input on all levels. It is of crucial importance for a successful usage of graded readers in the classroom and in studies which focus on graded readers, that an…

  8. The Effects of Framing Grades on Student Learning and Preferences

    Science.gov (United States)

    Bies-Hernandez, Nicole J.

    2012-01-01

    Two experiments examined whether framing effects, in terms of losses and gains, can be extended to student learning and grading preferences. In Experiment 1, participants rated psychology course syllabi to investigate preferences for differently framed grading systems: a loss versus gain grading system. The results showed a clear framing effect…

  9. Machine grading of lumber : practical concerns for lumber producers

    Science.gov (United States)

    William L. Galligan; Kent A. McDonald

    2000-01-01

    Machine lumber grading has been applied in commercial operations in North America since 1963, and research has shown that machine grading can improve the efficient use of wood. However, industry has been reluctant to apply research findings without clear evidence that the change from visual to machine grading will be a profitable one. For instance, mill managers need...

  10. The Causal Effects of Grade Retention on Behavioral Outcomes

    Science.gov (United States)

    Martorell, Paco; Mariano, Louis T.

    2018-01-01

    This study examines the impact of grade retention on behavioral outcomes under a comprehensive assessment-based student promotion policy in New York City. To isolate the causal effect of grade retention, we implement a fuzzy regression discontinuity (RD) design that exploits the fact that grade retention is largely determined by whether a student…

  11. Illusions of a Good Grade: Effort or Luck?

    Science.gov (United States)

    Buckelew, Susan P.; Byrd, Nikki; Key, Colin W.; Thornton, Jessica; Merwin, Michelle M.

    2013-01-01

    This study assessed the relationships among the accuracy of grade predictions, actual grades, self-enhancement bias, and attributions about academic performance. As a group, students anticipated higher grades than were earned. Individual differences in self-enhancement bias were measured using the discrepancy between anticipated and attained…

  12. Influence of "Halo" and "Demon" Effects in Subjective Grading.

    Science.gov (United States)

    Gibb, Gerald D.

    1983-01-01

    The phenomenon of "halo" effects in subjective grading was investigated. Two groups of three raters evaluated 20 term papers in introductory psychology. Term paper grades correlated significantly with course grades when information about previous academic performance was made available. When this information was not available, the…

  13. Grading Homework to Emphasize Problem-Solving Process Skills

    Science.gov (United States)

    Harper, Kathleen A.

    2012-01-01

    This article describes a grading approach that encourages students to employ particular problem-solving skills. Some strengths of this method, called "process-based grading," are that it is easy to implement, requires minimal time to grade, and can be used in conjunction with either an online homework delivery system or paper-based homework.

  14. Grading sacroiliitis with emphasis on MRI imaging; Grading der Sakroiliitis mit Betonung der MRT-Bildgebung

    Energy Technology Data Exchange (ETDEWEB)

    Jurik, A.G.; Egund, N. [The Department of Radiology R, Aarhus Kommunehospital (Denmark)

    2004-03-01

    Cross-sectional imaging techniques play a decisive role in identification, localization, and characterization of alterations in the sacroiliac joint during the early stage of seronegative spondylarthropathy (SpA). Although several studies showed that the diagnostic capabilities of MRI and CT are superior to those of conventional radiography, they have not yet become established and accepted as methods for evaluating the grade of ankylosing spondylitis (AS) in contrast to conventional radiography. The lack of acceptance for MRI and/or CT methods for evaluating and grading changes in the sacroiliac joint makes it difficult to include the results of these procedures in classifying the grade of SpA. Moreover, grading the changes in the sacroiliac joint in SpA with a method more sensitive than conventional radiography will be of prime importance in assessing treatment, e.g., the efficacy of new biological therapeutic agents directed against the tumor necrosis factor-alpha (TNF-{alpha}). An overview of the available grading methods is provided and MRI and CT techniques are presented. (orig.) [German] Schnittbildverfahren spielen bei der Identifizierung, Lokalisation und Charakterisierung von Veraenderungen des Sakroiliakalgelenks (SIG) im Fruehstadium der seronegativen Spondylarthropathie (SpA) eine entscheidende Rolle. Obwohl mehrere Studien zeigten, dass der diagnostische Wert der MRT und CT jenem der konventionellen Radiographie ueberlegen ist, hat sich das Schnittbildverfahren als Mittel zur Evaluierung des Grades der ankylosierenden Spondylitis (AS) im Gegensatz zur konventionellen Radiographie noch nicht etabliert und durchgesetzt. Dieses Fehlen eines akzeptierten MRT- und/oder CT-Verfahrens zur Evaluierung und zum Grading der Veraenderungen am SIG macht es schwierig, die Ergebnisse dieser Verfahren bei der Einstufung des Grades der AS-Veraenderungen und Erarbeitung von Diagnosekriterien fuer andere Formen der SpA einzubeziehen. Ausserdem wird das Grading der SIG

  15. Cognitive impairments in patients with low grade gliomas and high grade gliomas

    Directory of Open Access Journals (Sweden)

    Eliane C. Miotto

    2011-08-01

    Full Text Available OBJECTIVE: The relationship between brain tumors and cognitive deficits is well established in the literature. However, studies investigating the cognitive status in low and high-grade gliomas patients are scarce, particularly in patients with average or lower educational level. This study aimed at investigating the cognitive functioning in a sample of patients with low and high-grade gliomas before surgical intervention. METHOD: The low-grade (G1, n=19 and high-grade glioma (G2, n=8 patients underwent a detailed neuropsychological assessment of memory, executive functions, visuo-perceptive and visuo-spatial abilities, intellectual level and language. RESULTS: There was a significant impairment on verbal and visual episodic memory, executive functions including mental flexibility, nominal and categorical verbal fluency and speed of information processing in G2. G1 showed only specific deficits on verbal and visual memory recall, mental flexibility and processing speed. CONCLUSION: These findings demonstrated different levels of impairments in the executive and memory domains in patients with low and high grade gliomas.

  16. Working memory and individual differences in mathematics achievement: A longitudinal study from first grade to second grade

    OpenAIRE

    De Smedt, Bert; Janssen, Rianne; Bouwens, Kelly; Verschaffel, Lieven; Boets, Bart; Ghesquière, Pol

    2009-01-01

    This longitudinal study examined the relationship between working memory and individual differences in mathematics. Working memory measures, comprising the phonological loop, the visuospatial sketchpad, and the central executive, were administered at the start of first grade. Mathematics achievement was assessed 4 months later (at the middle of first grade) and 1 year later (at the start of second grade). Working memory was significantly related to mathematics achievement in both grades, show...

  17. Girls' Spatial Skills and Arithmetic Strategies in First Grade as Predictors of Fifth-Grade Analytical Math Reasoning

    Science.gov (United States)

    Casey, Beth M.; Lombardi, Caitlin McPherran; Pollock, Amanda; Fineman, Bonnie; Pezaris, Elizabeth

    2017-01-01

    This study investigated longitudinal pathways leading from early spatial skills in first-grade girls to their fifth-grade analytical math reasoning abilities (N = 138). First-grade assessments included spatial skills, verbal skills, addition/subtraction skills, and frequency of choice of a decomposition or retrieval strategy on the…

  18. HYPERGLYCEMIA IN GRADE III AND GRADE IV MALNUTRITION WITH DEHYDRATING GASTROENTERITIS

    Directory of Open Access Journals (Sweden)

    Mallesh

    2015-07-01

    Full Text Available OBJECTIVE OF THE STUDY: To study the incidence of hyperglycemia in grade III AND IV malnutrition with no signs and some signs of dehydration. SETTING: Tertiary care center located in north Karnataka. DESIGN: Prospective observational study involving 21 children. METHODS: All the children with grade III and grade IV malnutrition presenting with diarrhea of less than 14 days duration, having no signs to some signs of dehydration. RESULTS: Hyperglycemia was observed in three of 21 children hypoglycemia was observed in six children. CONCLUSION: Although hypoglycemia is common finding in moderate and severely malnourished children with dehydrating gastroenteritis, hyperglycemia should also be suspected and treated. Long term follow up of these children is needed involving larger number of people in multicenter studies.

  19. Clinical management of grade III oligodendroglioma

    Directory of Open Access Journals (Sweden)

    Simonetti G

    2015-07-01

    Full Text Available G Simonetti, P Gaviani, A Botturi, A Innocenti, E Lamperti, A Silvani Neurooncology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy Abstract: Oligodendrogliomas represent the third most common type of glioma, comprising 4%–15% of all gliomas and can be classified by degree of malignancy into grade II and grade III, according to WHO classification. Only 30% of oligodendroglial tumors have anaplastic characteristics. Anaplastic oligodendroglioma (AO is often localized as a single lesion in the white matter and in the cortex, rarely in brainstem or spinal cord. The management of AO is deeply changed in the recent years. Maximal safe surgical resection followed by radiotherapy (RT was considered as the standard of care since paramount findings regarding molecular aspects, in particular co-deletion of the short arm of chromosome 1 and the long arm of chromosome 19, revealed that these subsets of AO, benefit in terms of overall survival (OS and progression-free survival (PFS, from the addition of chemotherapy to RT. Allelic losses of chromosomes 1p and 19q occur in 50%–70% of both low-grade and anaplastic tumors, representing a strong prognostic factor and a powerful predictor of prolonged survival. Several other molecular markers have potential clinical significance as IDH1 mutations, confirming the strong prognostic role for OS. Malignant brain tumors negatively impacts on patients' quality of life. Seizures, visual impairment, headache, and cognitive disorders can be present. Moreover, chemotherapy and RT have important side effects. For these reasons, “health-related quality of life” is becoming a topic of growing interest, investigating on physical, mental, emotional, and social well-being. Understanding the impact of medical treatment on health-related quality of life will probably have a growing effect both on health care strategies and on patients. Keywords: anaplastic oligodendroglioma, radiotherapy, chemotherapy

  20. Low grade gastric MALT lymphoma: Radiographic findings

    International Nuclear Information System (INIS)

    Brown, J.A.; Carson, B.W.; Gascoyne, R.D.; Cooperberg, P.L.; Connors, J.M.; Mason, A.C.

    2000-01-01

    AIMS: Gastric MALT (mucosa-associated lymphoid tissue) lymphoma is now recognized as a distinct entity within extranodal non-Hodgkin's lymphoma. The purpose of this study was to describe the radiographic findings in low grade gastric MALT lymphoma. MATERIALS AND METHODS: We retrospectively reviewed the radiographic findings in 22 cases of low-grade gastric MALT lymphoma. The study group consisted of 15 men and seven women (median age 68 years, range 41-91 years). Lesions were designated as infiltrative or polypoid by consensus of two radiologists. Polypoid lesions were categorized by number and size. Anatomical site within the stomach and presence of transpyloric or oesophagogastric extension was determined for each case. The presence of abdominal lymphadenopathy was categorized as regional or distant. The presence of Helicobacter pylori was determined from endoscopic and surgical biopsies. RESULTS: Computed tomography (CT) revealed abnormalities of the stomach in 19 cases of the 21 in which it was performed. There were 14 infiltrative lesions and five polypoid lesions. Of the 14 infiltrative lesions, the mean gastric wall thickness was 2.2 cm (range 0.8-6.0 cm). There were three single and two multiple polypoid lesions (mean size 2.2 cm, range 1.5-2.7 cm). Transpyloric extension was observed in two cases and oesophagogastric extension in one. Abdominal lymphadenopathy was observed in 10 of 21 patients. Helicobacter pylori was found in 19 of 22 cases (86%). CONCLUSION: Low grade B cell gastric MALT lymphomas present with an infiltrative form on CT in about three-quarters of cases and a polypoid pattern in the remainder. Abdominal lymphadenopathy is seen in approximately one-half of cases. There is a high association with Helicobacter pylori. Brown, J.A. 2000. Clinical Radiology 55, 384-389