bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comprehensive Review on Protected Cultivation of Horticultural Crops: Advances and Sustainability
Authors: Tiwari Nimisha Jain , Dubey Saket , Kumar Ashutosh , Amala Ediga , Sangmesh Panchal , Yadav Anju , Jain R.C , Giri Bishnupada
Published: February 2025

Horticultural crop growing under protection has become a vital method in contemporary agriculture, providing several advantages like improved quality, higher yield, and defence against pests and unfavourable weather. The purpose of this thorough research is to outline the present state of protected cultivation methods and investigate their potential in horticulture going forward. The examination starts out by going over the many kinds of protected cultivation structures as well as their benefits and drawbacks, such as shade houses, high tunnels, and greenhouses. It then emphasizes how important protected farming is in tackling the issues of global food security by guaranteeing crop output all year round and lowering reliance on seasonal fluctuations. The review goes on to examine how protected cultivation methods, such as enhanced crop morphogenesis, better precipitation control, and the optimization of environmental parameters like temperature, humidity, and carbon dioxide levels, affect the growth and development of horticultural crops. Additionally, the use of cutting-edge technologies such as vertical farming, hydroponics, and aeroponics in protected growing systems is investigated, with a focus on how they might maximize crop output while consuming the fewest resources possible. The study also explores the difficulties and limitations associated with putting protected cultivation into practice, such as financial concerns, energy needs, and the need for artificial inputs. It talks about eco-friendly and sustainable ways to lessen these problems and support ecological balance, like using renewable energy sources and switching to organic farming methods. The paper concludes by outlining some potential future developments and trends in protected cultivation, such as the application of artificial intelligence, precision agriculture methods, and smart farming technology. In the end, these developments could result in higher yield and quality improvements in the production of horticulture crops by further optimizing resource use, enhancing automation, and improving crop monitoring and management.
Effect of Different Levels of Boron for Improving the Yield and Concentration of Boron in Wheat Crop (Triticum aestivum L.)
Authors: Dwivedi Anshuman , Kumar Vinay , Dwivedi Deepak Kumar
Published: February 2025

A field experiment was conducted to study the “Effect of Different Levels of Boron for Improving the Yield and concentration of Boron in wheat Crop (Triticum aestivum L.) during the Winter (Rabi) Season of 2012-2013 at the Research Farm of the Department of Agricultural Chemistry and Soil Science, Udai Pratap Autonomous College, Varanasi, Uttar Pradesh, India. Six treatments, viz. T0: Control (no input), T1: B @ 0.5 kg ha-1, T2: B @ 1.0 kg ha-1, T3: B @ 1.5 kg ha-1, T4: B @ 2.0 kg ha-1, T5: B @ 2.5 kg ha-1, and N, P2O5, and K2O were applied at the recommended dose @ 120: 80: 60 kg ha-1, respectively, were comprised in a randomized block design (RBD) with the three replications. The results revealed that different levels of boron significantly improved the yield and yield-attributing characters of wheat. Maximum grain yield (37.70 q ha-1), straw yield (47.13 q ha-1), total dry matter (84.48 q ha-1) and dry weight of root g-3 plant at 60 DAS (0.318) were recorded with Boron @ 2 kg ha-1. Moreover, maximum dry weight of shoot-3 plant at 60 DAS (1.91) was observed with boron at 2.5 kg ha-1). Maximum B concentration in 3rd leaf (40.63 mg kg-1) B concentration in grain (25.37 mg kg-1) B concentration in straw (30.87 mg kg-1) B concentration in root (160.20 mg kg-1) was recorded under Boron @ 2.0 kg ha-1.
Characterization and Evaluation of the Biological Activities of Ulvan Extracted from Ulva lactuca with a Focus on the Antiviral Activity Against Herpes Simplex Virus Type 1
Authors: Franco Maria Syndel Caroline Ribeiro , Silva Fyama Araujo da , Santos Luma Brisa Pereira dos , Araujo Thais Danyelle Santos , Lima Laís Ramos Monteiro de , Dourado Bianca Maria de Sousa , Paula Regina Célia Monteiro de , Rodrigues Klinger Antonio da Franca , Ferreira Gustavo Portela , Araújo-Nobre Alyne Rodrigues de , Silva Durcilene Alves da , Pereira Anna Carolina Toledo da Cunha
Published: February 2025

Aims: Physicochemical characterization and evaluation of the cytotoxic, antioxidant, antibacterial and antiviral activities of the ulvan polysaccharide, extracted from Ulva lactuca, with emphasis on its action against herpesvirus type 1 (HSV-1).
Study Design: The study followed an experimental design focusing on the bioactive properties of ulvan, involving tests against the HSV-1 virus, in addition to the evaluation of its cytotoxic, antioxidant and antibacterial properties.
Place and Duration of Study: This research was conducted at the Laboratory of Biochemistry and Molecular Biology of Microorganisms and Plants (BIOMIC) in conjunction with the Center for Research in Biodiversity and Biotechnology (BIOTEC), located at the Federal University of Delta do Parnaíba, state of Piauí, Brazil.
Methodology: Ulvan was obtained from the macroalgae Ulva lactuca collected on Coqueiro beach, in the city of Luis Correia, state of Piauí. The polysaccharide was characterized and evaluated for its biological activities. The antioxidant capacity was evaluated by the ABTS (2,2'-azinobis(3-ethylbenzenethiazoline-6-sulfonic acid)) radical scavenging assay, the cytotoxicity was evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test, and the antibacterial activity was evaluated by the minimum inhibitory concentration (MIC) technique. The percentage of HSV-1 inhibition was verified by titrations of the pretreatment assays of cells (PTC) and viral particles (PTV) with ulvan. The atomic force microscopy (AFM) technique was used to observe possible changes that ulvan could cause in the structure of HSV-1, in addition to verifying the dimensions of the particles between the control and the viral treatment with ulvan.
Results: Ulvan did not show antibacterial activity against the tested strains. However, it showed ABTS radical scavenging and reducing activity, in addition to low cytotoxicity with CC50 above 8,805 µg/mL and viral inhibition percentages of 65% and 88%. Through AFM images, a decrease in HSV-1 particles was observed after treatment with ulvan, which decreased from 150 nm to 79 nm, indicating that there was possible damage to the viral envelope.
Conclusion: This study provided valuable information into the biological activities of ulvan, providing unique insights into the mechanism of action of the polysaccharide against HSV-1. These results help advance knowledge on the use of marine polysaccharides as biomaterials, while contributing to new advances in the discovery of antiviral materials.
Effect of Salinity Levels on Root and Shoot Growth of Brinjal Varieties Grafted on Solanum torvum
Authors: Jyothi Motapalukula , Tambe T.B. , Khandare V.S. , Shinde V.N. , Ismail Syed , Shinde G.U.
Published: February 2025

A study was conducted to know the effect of different salinity levels on root and shoot attributes of brinjal varieties grafted on Solanum torvum under pot experiment and laid out in Factorial Randomized Block Design (FRBD) at College of Agriculture, Department of Horticulture, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani (Maharashtra) during the year 2020 and 2021. Experiment replicated twice with two factors, i.e., brinjal grafts at four levels (Phule Arjun, Phule Harit, Krishna and Manjari Gota grafted on Solanum torvum by cleft grafting method) and salinity levels at five levels (0/control, 2, 3, 4 and 5 dS m-1 were imposed with sodium chloride). Among the different varieties grafted on Solanum torvum Phule Harit showed significantly superior performance for shoot dry weight (129.83 g), primary roots (54.05), root fresh (139.67 g) and dry weight (67.33 g), root to shoot ratio (0.497). However, shoot fresh weight (463.45 g), secondary roots (2699.85) and root length (50.45 cm) were recorded in Phule Arjun. Among the different salinity levels, majority of the characters were noted to be significantly maximum in control (0.00 dS m-1). All together Phule Arjun and Phule Harit grafted on Solanum torvum was found significantly maximum values for majority parameters at heigher salinity levels (3.00 and 5.00 dS m-1). Phule Arjun and Phule Harit grafted onto Solanum torvum at salinity levels of 3.00, 4.00 and 5.00 dS m-1 was found significantly maximum values for different shoot and root parameters.
Crystallization and preliminary X‐ray analysis of outer membrane phospholipase A fromEscherichia coli
Authors: Blaauw Mieke , Dekker Niek , Verheij Hubertus M. , Kalk Kor H. , Dijkstra Bauke W.
Published: July 2002

The outer membrane phospholipase A (OMPLA) ofEscherichia coliis one of the few integral outer membrane proteins displaying enzymatic activity. It is encoded as a mature protein of 269 amino acids preceded by a signal sequence of 20 amino acids. There is no sequence homology with water‐soluble lipases and phospholipases. Crystals of the mature enzyme were obtained at 22°C from 24–28% (vlv) 2‐methyl‐2,4‐pentanediol in Bis‐Tris buffer, pH 5.9–6.0, with 1 mM calcium chloride and 1.5% (w/v) β‐octylglucoside. They have the symmetry of the trigonal spacegroup P3121 (or P3221) with cell dimensions of). Native crystals diffract to a resolution of 2.6 Å.
Differential incorporation of 1‐β‐D‐arabinofuranosylcytosine and 9‐β‐D‐arabinofuranosylguanine into nuclear and mitochondrial DNA
Authors: Zhu Chaoyong , Johansson Magnus , Karlsson Anna
Published: July 2002

The anti‐leukemic nucleoside analogs 1‐β‐D‐arabinofuranosylcytosine (araC) and 9‐β‐D‐arabinofuranosylguanine (araG) are dependent on intracellular phosphorylation for pharmacological activity. AraC is efficiently phosphorylated by deoxycytidine kinase (dCK). Although araG is phosphorylated by dCK in vitro, it is a preferred substrate of mitochondrial deoxyguanosine kinase. We have used autoradiography to show that araC was incorporated into nuclear DNA in Molt‐4 and CEM T‐lymphoblastoid cells as well as in Chinese hamster ovary cells. In contrast, araG was predominantly incorporated into mitochondrial DNA in the investigated cell lines, without detectable incorporation into nuclear DNA. These data suggest that the molecular targets of araG and araC may differ.
The role of mild uncoupling and non‐coupled respiration in the regulation of hydrogen peroxide generation by plant mitochondria
Authors: Casolo Valentino , Braidot Enrico , Chiandussi Elisa , Macrì Francesco , Vianello Angelo
Published: July 2002

The roles of mild uncoupling caused by free fatty acids (mediated by plant uncoupling mitochondrial protein (PUMP) and ATP/ADP carrier (AAC)) and non‐coupled respiration (alternative oxidase (AO)) on H2O2 formation by plant mitochondria were examined. Both laurate and oleate prevent H2O2 formation dependent on the oxidation of succinate. Conversely, these free fatty acids (FFA) only slightly affect that dependent on malate plus glutamate oxidation. Carboxyatractylate (CAtr), an inhibitor of AAC, completely inhibits oleate‐ or laurate‐stimulated oxygen consumption linked to succinate oxidation, while GDP, an inhibitor of PUMP, caused only a 30% inhibition. In agreement, CAtr completely restores the oleate‐inhibited H2O2 formation, while GDP induces only a 30% restoration. Both oleate and laurate cause a mild uncoupling of the electrical potential (generated by succinate), which is then followed by a complete collapse with a sigmoidal kinetic. FFA also inhibit the succinate‐dependent reverse electron transfer. Diamide, an inhibitor of AO, favors the malate plus glutamate‐dependent H2O2 formation, while pyruvate (a stimulator of AO) inhibits it. These results show that the succinate‐dependent H2O2 formation occurs at the level of Complex I by a reverse electron transport. This generation appears to be prevented by mild uncoupling mediated by FFA. The anionic form of FFA appears to be shuttled by AAC rather than PUMP. The malate plus glutamate‐dependent H2O2 formation is, conversely, mainly prevented by non‐coupled respiration (AO).
Identification of interaction partners of the cytosolic polyproline region of CD95 ligand (CD178)1
Authors: Ghadimi Markus Philipp , Sanzenbacher Ralf , Thiede Bernd , Wenzel Jennifer , Jing Qian , Plomann Markus , Borkhardt Arndt , Kabelitz Dieter , Janssen Ottmar
Published: July 2002

The CD95/Fas/Apo‐1 ligand (CD95L, CD178) induces apoptosis through the death receptor CD95. CD95L was also described as a co‐stimulatory receptor for T‐cell activation in mice in vivo. The molecular basis for the bidirectional signaling capacity and directed expression of CD95L is unknown. In the present study we identify proteins that precipitate from T‐cell lysates with constructs containing fragments of the CD95L cytosolic tail. The determined peptide mass fingerprints correspond to Grb2, actin, β‐tubulin, formin binding protein 17 (FBP17) and PACSIN2. Grb2 had been identified as a putative mediator of T‐cell receptor‐to‐CD95L signaling before. FBP17 and PACSIN2 may be associated with expression and trafficking of CD95L. When overexpressed, CD95L co‐precipitates with FBP17 and PACSIN. Protein–protein interactions are mediated via Src homology 3 (SH3) domain binding to the polyproline region of CD95L and can be abolished by mutation or deletion of the respective SH3 domain.
Solution conformational study of Scyliorhinin I analogues with conformational constraints by two‐dimensional NMR and theoretical conformational analysis
Authors: Rodziewicz‐Motowidło S. , Łegowska A. , Qi X.‐F. , Czaplewski C. , Liwo A. , Rolka K. , Sowiński P. , Mozga W. , Olczak J. , Zabrocki J.
Published: July 2002

Two analogues of Scyliorhinin I (ScyI), a tachykinin with N‐MeLeu in position 8 and a 1,5‐disubstituted tetrazole ring between positions 7 and 8, introduced in order to generate local conformational constraints, were synthesized using the solid‐phase method. Conformational studies in water and DMSO‐d6 were performed on these peptides using a combination of the two‐dimensional NMR technique and theoretical conformational analysis. The algorithm of conformational search consisted of the following three stages: (i) extensive global conformational analysis in order to find all low‐energy conformations; (ii) calculation of the NOE effects and vicinal coupling constants for each of the low energy conformations; (iii) determining the statistical weights of these conformations by means of a nonlinear least‐squares procedure, in order to obtain the best fit of the averaged simulated spectrum to the experimental one. In both solvents the three‐dimensional structure of the analogues studied can be interpreted only in terms of an ensemble of multiple conformations. For [MeLeu8]ScyI, the C‐terminal 6–10 fragment adopts more rigid structure than the N‐terminal one. In the case of the analogue with the tetrazole ring in DMSO‐d6 the three‐diemnsional structure is characterized by two dominant conformers with similar geometry of their backbones. They superimpose especially well (RMSD = 0.28 Å) in the 6–9 fragments. All conformers calculated in both solvents superimpose in their C‐terminal fragments much better than those of the first analogue. The results obtained indicate that the introduction of the tetrazole ring into the ScyI molecule rigidifies its structure significantly more than that of MeLeu.
How do visual status and age impact on driving performance as measured on a closed circuit driving track?
Authors: Wood Joanne M.
Published: July 2002

The aim of this study was to determine the effects of age and visual impairment on driving performance as measured on a closed circuit course. Sixty two subjects were tested, including young (<30 years) visual normals, old (>60 years) visual normals and old (>60 years) subjects with early visual impairment. All subjects had a binocular visual acuity of 6/12 or better and were legally eligible to drive in Australia. Driving performance was assessed for sign detection and recognition, driving reaction times, speed estimation, and driving time.

Age and early visual impairment had significant (P<0.05) effects on sign detection and recognition, peripheral reaction times and driving time. This is of significance because all of the drivers drove regularly and were legally eligible to do so. The results also demonstrate that high contrast visual acuity is a poor predictor of the driving performance skills measured for this range of licensed drivers.
Guillain‐Barré syndrome occurring in two women after ketoacidosic comatose state disclosing an insulin‐dependent diabetes mellitus
Authors: Rouanet‐Larriviere Marie , Vital Claude , Arne Pierre , Favarel‐Garrigues Jean‐Claude , Gin Henry , Vital Anne
Published: July 2002

Abstract  We report two women who presented with a Guillain‐Barré syndrome just after a ketoacidosic comatose state disclosing an insulin‐dependent diabetes mellitus. One had characteristic clinical signs and the other had major motor involvement. At neurophysiologic investigations, one had typical demyelinating neuropathy whereas the second had mainly axonal degeneration. At ultrastructural examination of a peripheral nerve biopsy, features of macrophage‐associated demyelination were present in both nerve specimens, thus confirming the diagnosis of acute inflammatory demyelinating polyneuropathy, i.e., Guillain‐Barré syndrome. Prominent axonal involvement was also present in the motor nerves of the second patient. Insulin therapy had to be permanently continued and these two cases are quite different from the transient diabetes sometimes observed in certain cases of Guillain‐Barré syndrome. Both the latter and insulin‐dependent diabetes mellitus probably have auto‐immune mechanisms. It is likely that in our two patients both auto‐immune diseases were triggered by a common event. Such cases of Guillain‐Barré syndrome have to be distinguished from other acute diabetic neuropathies.
SUB‐CLINICAL PERIPHERAL NERVE INVOLVEMENT IN PSORIATIC ARTHRITIS
Authors: Di Girolamo C. , Massini R. , Lullo F. , Crisci C.
Published: July 2002

Immunological studies document the role of HLA in psoriasis and the correlation between neuropeptides, psoriasis, and related arthritis. Some anecdotal case reports, moreover, describe a noncasual association between peripheral neuropathy and psoriatic manifestations. To verify a possible subclinical peripheral nerve involvement in this disimmune pathology, we started a pilot study in twenty patients with psoriatic arthritis and in whom other common causes of peripheral neuropathies had been ruled out.

We performed a complete clinical neurological examination and a neurophysiological examination (orthodromic sensory and motor nerve conduction velocity in median and tibial nerves; antidromic sensory nerve conduction velocity in sural nerve).

In 40% of the patients there was a mild but definite “glove‐stocking” hypoesthesia, while hypopallesthesia was detected in only 20%. Electrophysiologic examinations were less informative borderline distal conduction velocities in 30% of patients.

These preliminary data suggest a peripheral nerve involvement in this pathology, mainly affecting the small nerve fibres.
A NOVEL MYELIN PROTEIN ZERO MUTATION ASSOCIATED WITH CHARCOT‐MARIE‐TOOTH TYPE II DISEASE
Authors: D.  , P.  , F.  , L.  , F.  , P.  , E.
Published: July 2002

Charcot‐Marie‐Tooth type II disease (CMT2) is a typical peroneal muscular atrophy syndrome and is characterised by normal or slightly reduced nerve conduction velocities with signs of axonal degeneration. CMT2 is genetically heterogeneous: linkage to 1p35–p36 (CMT2A; KIF1B gene), 3q13–q22 (CMT2B), 7p14 (CMT2D) and 8p21 (CMT2E; NF‐L gene) loci has been reported for the autosomal dominant disease; however, the majority of CMT2 families do not link to any of the reported loci. Mutations of the myelin protein zero (MPZ) gene were found associated with demyelinating forms of hereditary neuropathies such as CMT1B, Dejerine‐Sottas syndrome and congenital hypomyelination. So far, few CMT2 cases (CMT2F) were found to be caused by point mutations in the MPZ (see CMT Mutation Database, http://molgen‐www.uia.ac.be/CMTMutations/) in 1q22 region.

We report a family in which three members are affected with a late‐onset peripheral neuropathy. The index patient is a 68‐year‐old male who presents with pronounced distal muscle weakness of inferior limbs, bilateral pes cavus and absence of deep tendon reflexes. Electrophysiological findings were suggestive of an axonal form of peripheral neuropathy, thus allowing the diagnosis of CMT type 2. At the clinical and electrophysiological examination, two other family members (first cousins of the proband) resulted to be affected. MPZ gene direct sequencing revealed a heterozygous T/A transversion in the exon 3 of the gene, predicting an Asp103Glu aminoacid substitution in the extracellular domain of the protein. This variant was not found in unaffected relatives and in 100 normal chromosomes. This finding confirms the role of protein zero in axonal neuropathies and the phenotypic heterogeneity associated with MPZ mutations.

(The laboratory is a member of the European CMT Consortium; partially granted by Ministero della Sanitá to PM, MURST to FA)
Preparation of Y2Ba4Cu8O20−x thin films by thermal coevaporation
Authors: Berkley D. D. , Kim D. H. , Johnson B. R. , Goldman A. M. , Mecartney M. L. , Beauchamp K. , Maps J.
Published: July 2002

We report on the preparation of Y2Ba4Cu8O20−x (‘‘248’’) thin films by coevaporation using a combination of electron beam and Knudsen cell vapor sources. Our best film shows a superconducting onset at 80 K and zero resistance at 72 K. The x-ray diffraction patterns show nearly single phase ‘‘248’’ with a small YBa2Cu3O7−x (‘‘123’’) impurity. It has been our experience that films can be annealed at least twice without displaying any shift in diffraction peak position.
Effect of processing on the structure of the Si/SiO2 interface
Authors: Ourmazd A. , Rentschler J. A. , Bevk J.
Published: July 2002

Starting from atomically smooth and characterized (100)Si/SiO2 interfaces, we use lattice imaging techniques to investigate the effect of annealing temperature and processing steps on the interfacial structure. Our results show that a c-SiO2 layer is present under all conditions we have investigated.
Electrical transport properties in epitaxial codeposited CoSi2 layers on 〈111〉 Si
Authors: Duboz J. Y. , Badoz P. A. , Rosencher E. , Henz J. , Ospelt M. , von Känel H. , Briggs A.
Published: July 2002

Electrical measurements (resistivity, Hall effect, and superconducting critical temperature) are performed in epitaxial CoSi2 layers obtained by room-temperature codeposition of Co and Si on 〈111〉 Si subsequently annealed between 250 and 650 °C. On the one hand, the CoSi2 layers annealed at low temperature (250–350 °C) exhibit poorer electrical characteristics than the films realized by solid phase epitaxy at 650 °C, because of both a lack of carriers and a degraded mobility. A possible origin of this fact could be the presence of unreacted Co atoms in the metal layer. On the other hand, the films annealed ex situ at 700 °C show excellent electrical characteristics, together with mirror-like surfaces and extremely smooth Si/CoSi2 interfaces, for silicide thicknesses ranging from 35 up to 500 Å. Furthermore, by comparing the films obtained by the solid phase epitaxy and the codeposition techniques, we show that the long-range roughness (few hundreds of angstroms) has no major influence on the steep increase of resistivity with decreasing film thicknes observed in ultrathin CoSi2 layers.
Grain growth of rapid-thermal-annealed Y-Ba-Cu oxide superconducting thin films
Authors: Hamdi A. H. , Mantese J. V. , Micheli A. L. , Waldo R. A. , Chen Y. L. , Wong C. A.
Published: July 2002

A study of the microstructure of Cu-rich and stoichiometric Y-Ba-Cu oxide thin-film superconductors is presented. The films were deposited on 〈100〉 SrTiO3 by the nonvacuum technique of metalorganic deposition followed by rapid thermal annealing in oxygen. Analysis showed that for annealing temperatures below 900 °C, grain size increased with increased annealing temperature, with an enhancement in grain growth for the Cu-rich films. Annealing near or above the melting point of the 1-2-3 phase causes only a slight increase in the rate of grain growth and no detectable effects of the excess Cu. Annealing above 920 °C produces segregated CuO islands 5–10 μm in size in the Cu-rich films. Oriented grain growth was found for the 1-2-3 grains with their c axis perpendicular and parallel to the SrTiO3 substrates. Sheet resistivity measurements were correlated with grain size, phase separation, and oriented grain growth. An anomalous behavior in the resistance-temperature plot at 220–240 K of the Cu-rich films is shown to be related to the presence of the excess Cu.
Cavity length dependence of threshold current for quantum well lasers
Authors: Shieh C. , Engelmann R. , Mantz J. , Alavi K. , Shu C.
Published: July 2002

The cavity length dependence of the threshold current for separate confinement quantum well lasers with a single well, three wells, and six wells is studied. Only the single quantum well laser showed the anomalous increase of threshold current at short cavity length. Comparison of the experimental results with theoretical calculations concludes that the polarization enhancement of the oscillator strength in a quantum well has to be taken into account in the gain spectrum calculation of the quantum well laser.
Growth of indium phosphide by metalorganic vapor phase epitaxy using dimethyl (3-dimethylaminopropyl) indium as a new indium source
Authors: Molassioti A. , Moser M. , Stapor A. , Scholz F. , Hostalek M. , Pohl L.
Published: July 2002

Dimethyl (3-dimethylaminopropyl) indium was synthesized and used for the first time as an indium source for the growth of InP layers by metalorganic vapor phase epitaxy at atmospheric pressure. This compound is liquid at room temperature with a vapor pressure of 30–40 Pa at 30 °C, which enables its use at low source temperatures. The layers were grown at a bubbler temperature of 30 °C. The growth temperature was varied between 580 and 660 °C. Hall measurements revealed good electrical data with carrier mobilities up to 49 900 cm2 /V s at 77 K. Temperature-dependent photoluminescence experiments confirmed these results and indicated that zinc was the main residual acceptor impurity.
Inelastic tunneling in (111) oriented AlAs/GaAs/AlAs double-barrier heterostructures
Authors: Luo L. F. , Beresford R. , Wang W. I. , Mendez E. E.
Published: July 2002

AlAs/GaAs/AlAs double-barrier heterostructures grown along the (111) crystal axis show a factor of two improvement in the peak-to-valley ratio compared to samples grown in the (100) orientation. A structure consisting of 2.8 nm barriers and an 8 nm well shows a peak-to-valley ratio much better than any published results on (100) oriented structures with similar well and barrier layers. This result is interpreted in terms of the increased effective mass for carriers tunneling inelastically via the AlAs X-point barrier. An increased mass leads to a reduction in the barrier transmission probability and, therefore, a decrease in the leakage current due to inelastic tunneling.
Nonthermal optical response of Y-Ba-Cu-O thin films
Authors: Kwok H. S. , Zheng J. P. , Ying Q. Y. , Rao R.
Published: July 2002

Separate fast and slow components were observed in the electrical response to optical excitation of an Y-Ba-Cu-O thin film prepared by laser deposition. The temperature dependence of these two components indicated different thermal and nonthermal behavior. The speed of the nonthermal component is limited by the 6 ns laser pulse duration used in the excitation. It was also demonstrated that thin films that were optically semitransparent were crucial in the observation of the fast nonthermal response.
Hot-carrier Coulomb effects in GaAs investigated by femtosecond spectroscopy around the band edge
Authors: Gong T. , Nighan W. L. , Fauchet P. M.
Published: July 2002

We report the first femtosecond measurements of carrier-induced changes in the absorption and refractive index of GaAs thin films. Absorption measurements in the vicinity of the band edge indicate instantaneous band-gap renormalization as well as instantaneous plasma screening of electron-hole interactions. Band filling and plasma screening appear to be the dominant contributions to the changes of refractive index.
Luminescent porous silicon synthesized by visible light irradiation
Authors: Noguchi Nobuaki , Suemune Ikuo
Published: July 2002

Photosynthesis of porous silicon is reported for the first time with visible-light irradiation in a hydrofluoric acid solution, which does not need any electrodes for anodization. The photosynthesized porous layer consisted of microparticles, and the photoluminescence spectra were very close to those of anodized porous silicons. The formation of the porous layer was dependent on the wavelength of the incident light, and the simultaneous irradiation of an ultraviolet light did not form the porous layer. The mechanism is discussed with the quantum confinement model of the porous layer.
Passive mode locking of monolithic semiconductor ring lasers at 86 GHz
Authors: Hohimer J. P. , Vawter G. A.
Published: July 2002

We report the development of monolithic passively mode-locked semiconductor ring lasers. These direct-waveguide-coupled lasers with a ring radius of 150 μm emit a continuous train of 1.3 ps transform-limited lasing pulses at 86 GHz repetition rate with a peak power of 10 mW/pulse at the laser output facet. We also observe, under certain conditions, the presence of a second pulse in the ring cavity doubling the pulse repetition rate to 172 GHz.
Selective growth of InGaAs on nanoscale InP islands
Authors: Ahopelto J. , Lipsanen H. , Sopanen M. , Koljonen T. , Niemi H. E.-M.
Published: July 2002

The formation of an InGaAs quantum well on nanoscale InP islands by selective growth using metalorganic vapor phase epitaxy is demonstrated. The structures show intense low-temperature photoluminescence at 1.35 eV. The blueshift of the emission peak by increasing the excitation intensity suggests that the carriers are three-dimensionally confined. The insertion of quantum well into the islands allows a better control of the properties of structures fabricated by the self-organizing growth, a novel technique to realize nanoscale structures without using any lithographical process steps.
Original technique for third-harmonic-generation measurements in liquids
Authors: Kajzar F. , Messier J.
Published: July 2002

An original technique, with a special design of liquid cell, is proposed for third-harmonic generation in liquids. The technique is based on a principle of harmonic generation in an infinite medium by focused laser beam applied for liquid cell windows and uses a thin wedge-shaped liquid compartment. The measurements can be performed in air, and a high precision in cubic susceptibility and refractive index dispersion determination can be obtained. The technique also allows measurements to be made on liquids absorbing at harmonic and fundamental frequencies and in function of external parameters like temperature, pressure, and electric or magnetic fields. Some results for organic solvents are presented and compared with those obtained by other methods.
Calibration of pulsed bremsstrahlung spectra with photonuclear reactions of 77Se and 79Br
Authors: Anderson J. A. , Collins C. B.
Published: July 2002

A new method is reported for calibrating bremsstrahlung spectra in the 200–1000-keV range with x-ray activation techniques. This approach is particularly significant for pulsed sources that cannot be characterized with conventional spectroscopy methods.
High-resolution bent-crystal spectrometer for the ultrasoft x-ray region
Authors: Beiersdorfer P. , von Goeler S. , Bitter M. , Hill K. W. , Hulse R. A. , Walling R. S.
Published: July 2002

A multichannel vacuum Bragg-crystal spectrometer has been developed for high-resolution measurements of the line emission from tokamak plasmas in the wavelength region between 4 and 25 Å. The spectrometer employs a bent crystal in Johann geometry and a microchannel-plate-intensified photodiode diode array. The instrument is capable of measuring high-resolution spectra (λ/Δλ≊3000) with fast time resolution (4 ms per spectrum) and good spatial resolution (3 cm). The spectral bandwidth is Δλ/λ0=15% at λ0=8 Å. A simple tilt mechanism allows access to different wavelength intervals. In order to illustrate the utility of the new spectrometer, time- and space-resolved measurements of the n=3–2 spectrum of selenium from the Princeton Large Torus tokamak plasmas are presented. The data are used to determine the plasma transport parameters and to infer the radial distribution of fluorinelike, neonlike, and sodiumlike ions of selenium in the plasma. The new ultrasoft x-ray spectrometer has thus enabled us to demonstrate the utility of high-resolution L-shell spectroscopy of neonlike ions as a fusion diagnostic.
On p-type doping in GaN—acceptor binding energies
Authors: Fischer S. , Wetzel C. , Haller E. E. , Meyer B. K.
Published: July 2002

Photoluminescence investigations on undoped n-type GaN layers grown on 6H-SiC and sapphire reveal the presence of residual acceptors with a binding energy of 230 meV. Their presence in high temperature vapor phase epitaxy grown layers is strongly correlated with the graphite susceptor containing the Ga. Mg as a contamination can be ruled out. In metal organic vapor phase epitaxially grown layers, the metal organic are probably the source of the carbon contamination. It is concluded that carbon on nitrogen sites introduces the most shallow acceptor in GaN. The experimental observations are supported by an estimate of the acceptor binding energy using effective-mass-theory.
Chemical trends of S-, Se-, and Te-related DX centers in InGaP
Authors: Kwon S. D. , Kwon Ho Ki , Choe Byung-Doo , Lim H.
Published: July 2002

Deep level properties of S-, Se-, and Te-doped In1−xGaxP layers grown by liquid phase epitaxy are studied by deep level transient spectroscopy and capacitance-temperature measurements. From the dependence of deep level properties on the impurity species and also from the existence of persistent photoconductivity, these impurity-related deep levels are attributed to the DX centers. The emission activation energies of these centers are observed to decrease as their atomic number increases.
Effects of spatial resolution and spectral purity on transvenous coronary angiography images
Authors: Chapman D. , Thomlinson W. C. , Gmür N. F. , Dervan J. P. , Stavola T. , Giacomini J. , Gordon H. , Rubenstein E. , Lavender W. , Schulze C. , Thompson A. C.
Published: July 2002

Measurements have been made on the National Synchrotron Light Source Coronary Angiography X17B2 beamline under ideal and real imaging conditions to investigate the optimal imaging conditions for spatial resolution and spectral purity.
A survey of the signal-induced noise in photomultiplier detection of wide dynamics luminous signals
Authors: Cairo F. , Congeduti F. , Poli M. , Centurioni S. , Di Donfrancesco G.
Published: July 2002

In the LIDAR sounding of wide atmospheric ranges, as in middle atmospheric probing, signal-induced noise (SIN) from the photomultiplier (PMT) has been known since long time as a challenging problem for scientists. In this article the results of investigations on SIN are reported and strategies to minimize its amount proposed. Three different types of PMTs have been tested and their response to pulsed light signals of various duration and amplitude, comparable with close range LIDAR return, have been studied. An analysis of the time properties and spectral characteristics of SIN has been performed, and a method to reduce SIN effects in photon counting acquisition has been proposed. The method is based on a careful choice of discriminator threshold level settings, and exploits differences observed between SIN and signal cumulative pulse height distributions. The method shows dependency on single PMT behavior.
Plasma driven superpermeation and its possible applications to ion sources and neutral beam injectors
Authors: Bacal M. , El Balghiti-Sube F. , Livshits A. I. , Notkin M. E. , Riz D. , Soloviev M. N. , Kuroda T. , Tanaka M. Y.
Published: July 2002

A metal membrane of macroscopic thickness can, under certain conditions, become superpermeable to hydrogen particles whose energy (kinetic, internal, or chemical) exceeds 1 eV. Such a membrane can transfer the energetic hydrogen almost like an opening of the same area. Superpermeable membranes can also compress the permeating gas by orders of magnitude and clean it from any impurities. Due to these characteristics superpermeable membranes could be employed in ion sources and neutral beam injectors: (a) for pumping and recycling hydrogen from ion sources, (b) for pumping hydrogen gas from the extraction area and recycling the gas into the ion source, (c) for pumping deuterium or hydrogen in the plasma neutralizer of a negative ion based neutral beam injector. We will describe the possible use of superpermeable membranes in these devices, the experiments which we effected demonstrating this new technique, and projects for its future use.
Neural network evaluation of reflectometry density profiles for control purposes
Authors: Santos J. , Nunes F. , Manso M. , Nunes I.
Published: July 2002

Broadband reflectometry is a diagnostic that is able to measure the density profile with high spatial and temporal resolutions, therefore it can be used to improve the performance of advanced tokamak operation modes and to supplement or correct the magnetics for plasma position control. To perform these tasks real-time processing is needed. Here we present a method that uses a neural network to make a fast evaluation of radial positions for selected density layers. Typical ASDEX Upgrade density profiles were used to generate the simulated network training and test sets. It is shown that the method has the potential to meet the tight timing requirements of control applications with the required accuracy. The network is also able to provide an accurate estimation of the position of density layers below the first density layer which is probed by an O-mode reflectometer, provided that it is trained with a realistic density profile model.
Intrinsic strain and temperature characteristics of Yb-doped silica-based optical fibers
Authors: Sun T. , Zhang Z. Y. , Grattan K. T. V. , Palmer A. W.
Published: July 2002

An investigation of strain and temperature characteristics of Yb-doped fibers has been carried out in this article. Results obtained are compared with those reported on Nd-doped fibers, showing that the lifetime variation rate of the single mode Yb-doped fiber with increasing strain is temperature independent, and within experimental error similar to that of Nd, although in each case, the fiber modes, the dopant concentration level, and the rare earth ion itself are different. Their stable behavior may form the basis of a dual element sensor with which to obtain stress and temperature information independently in so-called “smart structures.”
Spatial distribution of electron cloud footprints from microchannel plates: Measurements and modeling
Authors: Tremsin A. S. , Siegmund O. H. W.
Published: July 2002

The measurements of the electron cloud footprints produced by a stack of microchannel plates (MCPs) as a function of gain, MCP-to-readout distance and accelerating electric field are presented. To investigate the charge footprint variation, we introduce a ballistic model of the charge cloud propagation based on the energy and angular distribution at the MCP output. We also simulate the Coulomb repulsion in the electron cloud, which is likely to cause the experimentally observed increase in the cloud size with increasing MCP gain. Calculation results for both models are compared to the charge footprint sizes measured both in our experiments with high rear-field values (∼200–900 V/mm) and in the experiments of Edgar et al. [Rev. Sci. Instrum. 60, 3673 (1989)] (accelerating electric field ∼30–130 V/mm).
Influence of doping on sensitivity and response time of TiO2 oxygen gas sensor
Authors: Sharma Rajnish K. , Bhatnagar M. C. , Sharma G. L.
Published: July 2002

The recent trend in gas sensor research is to achieve higher gas sensitivity and shorter response time at low operating temperatures. In the present study, titanium dioxide was studied as an oxygen gas sensor at different chromium (Cr) dopant concentrations. The sensitivity and response time measurements were carried out as a function of operating temperature and oxygen partial pressure. A higher sensitivity and shorter response time was observed at 700 °C in 0.40 wt % Cr doped sensor as compared to an undoped sensor, which showed higher sensitivity at 800 °C. The 0.40 wt % Cr doped sensor shows 13 times higher sensitivity as compared to undoped sensor. The porosity of the material decreases as Cr concentration increases. A large number of operation cycles were performed on the sensor, which shows the stability of the device over long period. The sensitivity and response time of the sensor were also correlated with electronic structure results obtained from x-ray photoelectron spectroscopy.
Enhanced nonlinear absorption and optical limiting in semiconducting polymer/methanofullerene charge transfer films
Authors: Cha M. , Sariciftci N. S. , Heeger A. J. , Hummelen J. C. , Wudl F.
Published: July 2002

Nonlinear optical absorption in solid films of poly(3-octylthiophene) (P3OT) sensitized with methanofullerene was investigated for wavelengths from 620 to 960 nm. The nonlinear absorption is enhanced over that in either of the component materials by more than two orders of magnitude at 760 nm. The large nonlinearity results from efficient photoinduced intermolecular charge transfer from P3OT to methanofullerene, followed by absorption in the charge separated excited state. P3OT/fullerene films are promising as optical limiters; the transmission clamps at an average fluence of approximately 0.1 J/cm2. The damage threshold was 15 μJ/pulse (≊1 J/cm2 in average fluence), above which there is a permanent change in the linear transmission.
Analysis of reverse current–voltage characteristics of Ti/6H–SiC Schottky diodes
Authors: Schröder Chr. , Heiland W. , Held R. , Loose W.
Published: July 2002

Investigations on electrical properties of as fabricated and annealed titanium 6H–SiC Schottky contacts were performed by current–voltage (I–V) and capacitance–voltage (C–V) measurements in a temperature range of 100–460 K. Both the Schottky barrier height (SBH) Φb and the ideality factor n were found to depend on temperature and voltage. In addition, a systematic discrepancy between barrier heights extracted from I–V and C–V curves was observed. An explanation is given for the high leakage currents which are still a general problem of SiC Schottky diodes. On the basis of two analytical models we are able to describe this behavior assuming the formation of a very thin inhomogeneous interfacial layer between metal and semiconductor.
The role of atomic size asperities in the mechanical deformation of nanocontacts
Authors: Mann A. B. , Pethica J. B.
Published: July 2002

The processes leading to permanent deformation when two bodies make contact are important in adhesion, wear, and tribology. We present nanoindentation results for GaAs showing that impact kinetic energies of only a few eV can lead to a dramatic reduction in the load required to cause permanent deformation when compared to the load required for impact energies of less than 1 eV. We explain this extreme sensitivity to the initial contact in terms of atomic size asperities which must be deformed if defects are to be generated on impact. Lower kinetic energies do not destroy the asperities, and dislocations must be nucleated later in the indentation cycle.
Nanometer scale surface clustering on ZnSe epilayers
Authors: Smathers J. B. , Kneedler E. , Bennett B. R. , Jonker B. T.
Published: July 2002

We have used atomic force microscopy to investigate the surface morphology of ZnSe films grown on GaAs(001) by molecular beam epitaxy. We report the observation of nanometer scale surface clusters 400–1200 Å in diameter and 60–200 Å in height. The clusters form ex situ as the result of the initial exposure of the ZnSe to atmosphere, and undergo Ostwald ripening at room temperature. Our observations, combined with the relevant literature, suggest that the cluster composition is SeO2. We propose that the oxidation of the ZnSe epilayers produces a thin layer of SeO2 which migrates to form surface clusters on a stable, zinc-related oxide surface. These findings should facilitate greater control of surface morphologies during ZnSe based device fabrication processes.
2e
2
/h
to e2/h switching of quantum conductance associated with a change in nanoscale ferromagnetic domain structure
Authors: Ono Teruo , Ooka Yutaka , Miyajima Hideki , Otani Yoshichika
Published: July 2002

We demonstrate the electrical conductance quantization in a Ni nanowire formed in a break junction between a ferromagnetic Ni wire and a Ni plate in applied magnetic fields. The conductance of the nanowire is clearly quantized in units of 2e2/h in a zero magnetic field, but it is switched to e2/h by applying magnetic fields above 60 Oe. This switching behavior seems closely related to a ferromagnetic domain formation in the vicinity of a nanowire, suggesting that nanoscale magnetic domain walls play an important role in determining nanoscale spin-dependent transport. The effect offers the possibility of a new device, a nanoscale colossal magnetoresistive sensor.
Size-dependent second-harmonic generation by nanocrystals prepared by plasma-enhanced chemical-vapor deposition
Authors: Milovzorov D. , Suzuki T.
Published: July 2002

The second-harmonic generation (SHG) from silicon nanocrystallites in polycrystalline films prepared by low-temperature plasma-enhanced chemical-vapor deposition has been studied. We observed an increase in the SHG signal due to the quantum-size effect and shape distortion by decrease in the sizes of crystallites. It was shown that the resonant SHG spectra have a size-dependent fine structure. Also, the power dependence of the SHG response from polycrystalline silicon films was investigated.
Direct synthesis of silicon nanowires, silica nanospheres, and wire-like nanosphere agglomerates
Authors: Gole J. L. , Stout J. D. , Rauch W. L. , Wang Z. L.
Published: July 2002

Elevated temperature synthesis has been used to generate virtually defect free SiO2 sheathed crystalline silicon nanowires and silica (SiO2) nanospheres which can be agglomerated to wire-like configurations impregnated with crystalline silicon. The SiO2 passivated (sheathed) crystalline silicon nanowires, generated with a modified approach using a heated Si–SiO2 mix, with their axes parallel to 〈111〉 are found to be virtually defect free. Modifications to the system allow the simultaneous formation of SiO2 nanospheres (d∼10–30 nm) as virtually monodisperse gram quantity powders which form large surface area catalysts for the selective conversion of ethanol to acetaldehyde.
Strain relief via trench formation in Ge/Si(100) islands
Authors: Chaparro S. A. , Zhang Y. , Drucker Jeff
Published: July 2002

Trenches formed at Ge/Si(100) island bases become an effective strain-relief mechanism at high growth temperatures. Trenches result from diffusion of the most highly strained material to regions of lower strain. The trench depth self-limits, scaling linearly with island diameter. A simple atomistic model of island elasticity indicates that this self-limiting behavior is of kinetic rather than energetic origin.