Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 44
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Science ; 379(6633): 646-648, 2023 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-36795826

RESUMO

Copyleft AI with Trusted Enforcement (CAITE) can support an adaptable so ft law approach for ethics in AI.

2.
Sci Rep ; 13(1): 1597, 2023 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-36709384

RESUMO

The intermetallic compound Eu[Formula: see text]In[Formula: see text]Sb[Formula: see text], an antiferromagnetic material with nonsymmorphic crystalline structure, is investigated by magnetic, electronic transport and specific heat measurements. Being a Zintl phase, insulating behavior is expected. Our thermodynamic and magnetotransport measurements along different crystallographic directions strongly indicate polaron formation well above the magnetic ordering temperatures. Pronounced anisotropies of the magnetic and transport properties even above the magnetic ordering temperature are observed despite the Eu[Formula: see text] configuration which testify to complex and competing magnetic interactions between these ions and give rise to intricate phase diagrams discussed in detail. Our results provide a comprehensive framework for further detailed study of this multifaceted compound with possible nontrivial topology.

3.
Pneumologie ; 75(4): 268-275, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32820488

RESUMO

OBJECTIVES: The assessment of pulmonary single-breath diffusing capacity is a frequently performed diagnostic procedure and considered as an important tool in medical surveillance examinations of pulmonary diseases.The aim of this study was to establish reference equations for pulmonary single-breath diffusing capacity parameters in a representative adult-population across a wide age range and to compare the normative values from this sample with previous ones. METHODS: Diffusing capacity measurement was carried out in 3566 participants (1811 males) of a cross-sectional, population-based survey ("Study of Health in Pomerania - SHIP"). RESULTS: Individuals with cardiopulmonary disorders and current smoking habits were excluded, resulting in 1786 healthy individuals (923 males), aged 20 - 84 years. Prediction equations for both sexes were established by quantile regression analyses, taking into consideration the influence of age, height, weight and former smoking. CONCLUSION: The study provides a novel set of prediction equations for pulmonary single-breath diffusing capacity in an adult Caucasian population. The results are comparable to previously reported equations, underline their importance and draw attention to the need for up-to-date reference equations that adequately take into account both the subjects' origin, age, anthropometric characteristics and the equipment used.


Assuntos
Pneumopatias , Capacidade de Difusão Pulmonar , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Valores de Referência , Fumar , Adulto Jovem
4.
Sci Rep ; 8(1): 3595, 2018 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-29483577

RESUMO

Rare-earth (R)-iron alloys are a backbone of permanent magnets. Recent increase in price of rare earths has pushed the industry to seek ways to reduce the R-content in the hard magnetic materials. For this reason strong magnets with the ThMn12 type of structure came into focus. Functional properties of R(Fe,T)12 (T-element stabilizes the structure) compounds or their interstitially modified derivatives, R(Fe,T)12-X (X is an atom of hydrogen or nitrogen) are determined by the crystal-electric-field (CEF) and exchange interaction (EI) parameters. We have calculated the parameters using high-field magnetization data. We choose the ferrimagnetic Tm-containing compounds, which are most sensitive to magnetic field and demonstrate that TmFe11Ti-H reaches the ferromagnetic state in the magnetic field of 52 T. Knowledge of exact CEF and EI parameters and their variation in the compounds modified by the interstitial atoms is a cornerstone of the quest for hard magnetic materials with low rare-earth content.

5.
J Phys Condens Matter ; 29(24): 24LT01, 2017 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-28465498

RESUMO

We report the attainment of the ferromagnetic state in an interstitially modified heavy rare-earth-iron intermetallic compound in an external magnetic field. The starting composition is RE2Fe17, which is the RE-Fe binary richest in iron. We concentrate on the Tm-Fe compound, which is the most sensitive to magnetic field. The maximum possible amount of hydrogen (5 at.H/f.u.) is inserted into a Tm2Fe17 single crystal. We demonstrate that in a magnetic field of 57 T Tm2Fe17H5 reaches the ferromagnetic state with an enviably high polarization of 2.25 T.

6.
Phys Rev Lett ; 115(17): 177203, 2015 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-26551139

RESUMO

A combination of phenomenological analysis and Mössbauer spectroscopy experiments on the tetragonal Fe(1+y)Te system indicates that the magnetic ordering transition in compounds with higher Fe excess, y≥0.11, is unconventional. Experimentally, a liquidlike magnetic precursor with quasistatic spin order is found from significantly broadened Mössbauer spectra at temperatures above the antiferromagnetic transition. The incommensurate spin-density wave order in Fe(1+y)Te is described by a magnetic free energy that violates the weak Lifshitz condition in the Landau theory of second-order transitions. The presence of multiple Lifshitz invariants provides the mechanism to create multidimensional, twisted, and modulated solitonic phases.

7.
Sci Rep ; 4: 7003, 2014 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-25384532

RESUMO

In the scientific description of unconventional transport properties of oxides (spin-dependent transport, superconductivity etc.), the spin-state degree of freedom plays a fundamental role. Because of this, temperature- or magnetic field-induced spin-state transitions are in the focus of solid-state physics. Cobaltites, e.g. LaCoO3, are prominent examples showing these spin transitions. However, the microscopic nature of the spontaneous spin crossover in LaCoO3 is still controversial. Here we report magnetostriction measurements on LaCoO3 in magnetic fields up to 70 T to study the sharp, field-induced transition at Hc ≈ 60 T. Measurements of both longitudinal and transversal magnetostriction allow us to separate magnetovolume and magnetodistortive changes. We find a large increase in volume, but only a very small increase in tetragonal distortion at Hc. The results, supported by electronic energy calculations by the configuration interaction cluster method, provide compelling evidence that above Hc LaCoO3 adopts a correlated low spin/high spin state.

8.
J Phys Condens Matter ; 22(22): 226005, 2010 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-21393756

RESUMO

The magnetic structure of GdMn2Ge2 (tetragonal I4/mmm) has been studied by hot neutron powder diffraction and x-ray resonant magnetic scattering techniques. These measurements, along with the results of bulk experiments, confirm the collinear ferrimagnetic structure with moment direction parallel to the c-axis below T(C) = 96 K and the collinear antiferromagnetic phase in the temperature region T(C) < T < T(N) = 365 K. In the antiferromagnetic phase, x-ray resonant magnetic scattering has been detected at Mn K and Gd L2 absorption edges. The Gd contribution is a result of an induced Gd 5d electron polarization caused by the antiferromagnetic order of Mn-moments.

9.
Rev Sci Instrum ; 79(6): 063902, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-18601412

RESUMO

To simultaneously perform magnetization and magnetostriction measurements in high magnetic fields, a miniaturized device was developed that combines an inductive magnetometer with a capacitive dilatometer and, therefore, it is called "dilamagmeter." This combination of magnetic and magnetoelastic investigations is a new step to a complex understanding of solid state properties. The whole system can be mounted in a 12 mm clear bore of any cryostat usually used in nondestructive pulsed high field magnets. The sensitivity of both methods is about 10(-5) A m(2) for magnetization and 10(-5) relative changes in length for striction measurements. Measurements on a GdSi single crystal, which are corrected by the background signal of the experimental setup, agree well with the results of steady field experiments. All test measurements, which are up until now performed in the temperature range of 4-100 K, confirm the perfect usability and high stability in pulsed fields up to 50 T with a pulse duration of 10 ms.

10.
J Econ Entomol ; 98(5): 1630-40, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16334333

RESUMO

This 3-yr study examined the use of two different apple, Malus domestica Borkhausen, pest management programs based on horticultural mineral oil. Whereas oil provided some additional control of codling moth, Cydia pomonella (L.), when targeting eggs of both generations (Oil/Direct Pest program, typically six applications per season), the additional benefit was difficult to detect when densities were high. With moderate densities, oil reduced the number of fruit infestations, but not stings (unsuccessful entries). There also were some measurable benefits to leafroller, Pandemis pyrusana Kearfott control. Oil was most useful, however, in suppression of secondary pests. White apple leafhopper, Typhlocyba pomaria McAtee, was the primary target of oil applications in the Oil/Indirect Pest program (typically three applications per season). However, leafhopper suppression in the Oil/Direct Pest program was generally greater because of the higher number of applications. Phytophagous tetranychid and eriophyid mites also were suppressed by more oil applications. Predatory mite populations were lower in both oil programs than in the check, but it is difficult to determine whether direct toxicity or reduction of prey was responsible for lower predator populations. There also was some evidence that oil suppressed woolly apple aphid, Eriosoma lanigerum Hausman. The six-spray oil program largely prevented a woolly apple aphid outbreak that occurred in July and August 1998 in the check, although the three-spray program seemed to provide some suppression despite the nonspecific spray timing.


Assuntos
Controle de Insetos/métodos , Malus/crescimento & desenvolvimento , Óleo Mineral/administração & dosagem , Estações do Ano , Animais , Afídeos , Larva/crescimento & desenvolvimento , Ácaros , Mariposas , Densidade Demográfica
11.
J Insect Sci ; 5: 14, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16341246

RESUMO

Three neonicotinyl insecticides, acetamiprid, thiacloprid and clothianidin, were evaluated for their impact on four species of lepidopteran pests of apple in Washington, the codling moth, Cydia pomonella (L.), the Pandemis leafroller, Pandemis pyrusana Kearfott, and the obliquebanded leafroller, Choristoneura rosaceana (Harris), and Lacanobia subjuncta (Grote & Robinson). None of the neonicotinyl insecticides demonstrated sufficient activity against P. pyrusana, C. rosaceana, or L. subjuncta to warrant field trials. Conversely, all had some activity against one or more stages of C. pomonella. Acetamiprid was highly toxic to larvae in laboratory bioassays, and had relatively long activity of field-aged residues (21 days). It also showed some toxicity to C. pomonella eggs (via topical exposure) and adults. Acetamiprid provided the highest level of fruit protection from C. pomonella attack in field trials conducted over five years in experimental orchards with extremely high codling moth pressure. Thiacloprid performed similarly in bioassays, but fruit protection in field trials was slightly lower than acetamiprid. Clothianidin showed moderate to high toxicity in bioassays, depending on the C. pomonella stage tested, but poor fruit protection from attack in field trials. None of the neonicotinyl insecticides were as toxic to larvae or effective in protecting fruit as the current standard organophosphate insecticide used for C. pomonella control, azinphosmethyl. However, both acetamiprid and thiacloprid should provide acceptable levels of C. pomonella control in commercial orchards where densities are much lower than in the experimental orchards used for our trials. The advantages and disadvantages of the neonicotinyl insecticides as replacements for the organophosphate insecticides and their role in a pest management system for Washington apple orchards are discussed.


Assuntos
Inseticidas , Lepidópteros , Malus/parasitologia , Agricultura/métodos , Animais , Azinfos-Metil , Bioensaio/métodos , Relação Dose-Resposta a Droga , Guanidinas , Controle de Insetos/métodos , Larva/efeitos dos fármacos , Dose Letal Mediana , Neonicotinoides , Óvulo/efeitos dos fármacos , Piridinas , Tiazinas , Tiazóis , Fatores de Tempo , Washington
12.
J Insect Sci ; 5: 16, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16341248

RESUMO

The effect of neonicotinyl insecticides on integrated mite control in Washington apple was examined from 0 In a series of 20 field trials (54 treatments) designed primarily to look at efficacy against the codling moth, Cydia pomonella, nearly half of the treatments using four or more applications of acetamiprid had peak mite densities exceeding the economic threshold of 5 mites per leaf. Overall, acetamiprid treatments had 4.6-fold higher mite densities than the standard organophosphate insecticide treatment. Of the treatments with high mite populations, Panonychus ulmi, the European red mite, and Tetranychus urticae, the twospotted spider mite, were the dominant species in roughly equal numbers of cases. Only 11.1% of the thiacloprid treatments exceeded 5 mites per leaf; these experimental treatments included eight applications, whereas the current label restricts the number of applications at the rate for C. pomonella to two applications. One out of six clothianidin treatments caused a significantly higher mite density than the standard treatment; however, this material appeared to suppress predatory mites. Neonicotinyl insecticides did not eliminate predatory mites, but they inhibited their ability to respond normally to increasing prey populations. In field trials designed specifically to examine mite population densities where neonicotinyl insecticides were used, significantly higher levels of tetranychid mites occurred in one or more acetamiprid treatments (one, two or four applications) in five out of six trials. In the sixth trial (in a commercial orchard), only two acetamiprid applications were made, and mite populations were low in all treatments. While elevated mite densities were more likely to occur with four applications, in one case it occurred following a single application. The predominant tetranychid mite species (either P. ulmi or T. urticae) varied from trial to trial; however, there was no apparent bias regarding stimulation of the two species. Horticultural mineral oil was used with acetamiprid in some trials in an attempt to mitigate mite outbreaks. However, the addition of oil did not counteract the tendency of acetamiprid to increase tetranychid mite populations, and in one trial, had a negative effect on predatory mite densities. Seasonal tetranychid mite density was positively related to the total grams AI (or number of applications) of acetamiprid, thus reducing the number of applications per season should lower the probability of mite outbreaks.


Assuntos
Anabasina/análogos & derivados , Controle de Insetos , Inseticidas , Lepidópteros , Malus , Animais , Bioensaio , Relação Dose-Resposta a Droga , Guanidinas , Larva , Dose Letal Mediana , Óleo Mineral , Neonicotinoides , Óvulo , Densidade Demográfica , Piridinas , Estações do Ano , Tiazinas , Tiazóis , Fatores de Tempo , Washington
13.
Phys Rev Lett ; 95(8): 086403, 2005 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-16196877

RESUMO

We report on a field-induced change of the electronic band structure of CeBiPt as evidenced by electrical-transport measurements in pulsed magnetic fields. Above approximately 25 T, the charge-carrier concentration increases nearly 30% with a concomitant disappearance of the Shubnikov-de Haas signal. These features are intimately related to the Ce 4f electrons since for the non-4f compound LaBiPt the Fermi surface remains unaffected. Electronic band-structure calculations point to a 4f-polarization-induced change of the Fermi-surface topology.

14.
J Econ Entomol ; 94(5): 1075-84, 2001 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11681668

RESUMO

Pesticides were evaluated for their effect on two parasitoid species, Colpoclypeus flouts and Trichogramma platneri, that are potential biological control agents of leafrollers in apple orchards. Organophosphate and carbamate insecticides were highly toxic to both parasitoids in topical applications, but foliar residues of some products were nontoxic after 7 d. At reduced rates, topically applied pyrethroids were low in toxicity to C. florus were highly toxic to T. platneri, and foliar residues were nontoxic after about 7 d. Imidacloprid and abamectin were highly toxic when applied topically to both parasitoids but were not toxic as 1-d-old residues. Insect growth regulators did not cause mortality either as topical applications or residues; however, diflubenzuron caused severe sublethal effects, completely blocking the production of C. florus offspring. Biorational pesticides, such as soap, oil, and B. thuringiensis products, caused no toxicity to C. florus but had a direct impact on T. platneri as topical applications through physical immobilization. The potential to integrate different pesticides with biological control of leafrollers and the need for a step-wise approach to evaluate the impact of pesticides against natural enemies is discussed.


Assuntos
Controle de Insetos/métodos , Mariposas/parasitologia , Praguicidas/toxicidade , Vespas/efeitos dos fármacos , Animais , Resíduos de Praguicidas , Washington
16.
J Econ Entomol ; 94(6): 1500-5, 2001 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11777055

RESUMO

The attraction of the stink bug Euschistus conspersus Uhler to sources of the synthetic pheromone component methyl (2E,4Z)-decadienoate was investigated in a series of field experiments in native vegetation surrounding commercial apple orchards in Washington. In experiments with pheromone lures placed inside two different tube-type traps, stink bugs were attracted to the immediate area around traps in large numbers, but very few were caught in the traps. Pheromone lures attached directly to the host plant mullein, Verbascum thapsus L., demonstrated that these 'baited" plants attracted significantly more E. conspersus than unbaited plants. Spring (reproductive) and summer (reproductively diapausing) E. conspersus adults, both males and females, were attracted to pheromone-baited plants. There was no significant difference in the number of male or female E. conspersus attracted to pheromone-baited traps or plants in any of the experiments, further characterizing methyl (2E,4Z)-decadienoate as an aggregation, and not a sex pheromone. Stink bug aggregations formed within 24-48 h of lure placement on mullein plants and remained constant until the lure was removed after which aggregations declined over 3-4 d to the level of unbaited plants. The implications of these studies for E. conspersus monitoring and management are discussed.


Assuntos
Decanoatos/química , Hemípteros , Controle de Insetos/métodos , Controle Biológico de Vetores , Feromônios/química , Animais , Feminino , Masculino , Malus , Controle Biológico de Vetores/métodos
17.
Opt Express ; 6(5): 111-6, 2000 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-19401752

RESUMO

The time-dependent Schrodinger equation is solved for a 1Dx1D two-electron model helium atom subject to a low-frequency short, intense laser pulse. A half-cycle pulse leads to strong single but no double ionization. A full-cycle pulse leads to double ionization which begins precisely at the classical return time for the first ejected electron. When the excursion range for the first electron is truncated, the double ionization at later times, corresponding to longer excursions, disappears. When the field near the nucleus is turned off during the return of the first electron, double ionization persists.

18.
Anal Chem ; 70(9): 1788-96, 1998 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-9599579

RESUMO

Solid-phase microextraction (SPME) is applied to the determination of cannabidiol, delta 8-tetrahydrocannabinol (delta 8-THC), delta 9-tetrahydrocannabinol (delta 9-THC), and cannabinol in pure water and human saliva. The inherent extraction behavior of the cannabinoids in pure water is evaluated along with optimization of the method in human saliva. The commercially available poly(dimethylsiloxane) (PDMS) SPME fibers were found to be the best class for the cannabinoid analysis. Partition coefficients were found to be extremely large for all of the cannabinoids (log K > 4.0). Equilibrium times for the 7- and 30-micron PDMS fibers were 50 and 240 min, respectively. A shorter extraction time of 10 min with the 30-micron PDMS fiber may be used for multiple extractions from the same vial, thus conserving the sample necessary for analysis and speeding up the total analysis time. Recoveries for the cannabinoids in saliva, relative to pure water, were dramatically improved by a method developed in our laboratory involving addition of glacial acetic acid to the sample vial prior to performing SPME. Using this method, recoveries relative to SPME in pure water ranged from 21 to 47% depending on the cannabinoid. The linear range for spiked saliva samples was established at 5-500 ng/mL (r2 > 0.994) with precisions between 11 and 20% RSD. The ultimate level of detection by SPME for the cannabinoids in saliva was 1.0 ng/mL, with signal-to-noise values of > or = 12. A saliva sample collected 30 min after marijuana smoking was subject to SPME and traditional liquid-liquid extraction analysis. Internal standard quantitation results for delta 9-THC by both methods yielded comparable results, indicating that the SPME method of analysis is highly accurate and precise. The level of delta 9-THC by SPME was found to be 9.54 ng/mL for the saliva sample.


Assuntos
Canabinoides/análise , Saliva/química , Água/análise , Dronabinol/análise , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Fumar Maconha/metabolismo , Detecção do Abuso de Substâncias
19.
J Biol Chem ; 271(5): 2443-7, 1996 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-8576205

RESUMO

The effects of insulin-like growth factor I (IGF-I) on the migration of two human breast cancer cell lines, MCF-7 and MDA-231, were examined using a modified Boyden chamber. 10 ng/ml was the optimal IGF-I concentration for stimulation of migration. The majority of IGF-I-stimulated migration in both cell types was due to chemotaxis. MCF-7 cells failed to migrate on membranes coated with gelatin or fibronectin and migrated only in small numbers on laminin. In contrast, when vitronectin- or type IV collagen-coated membranes were used, the MCF-7 cells migrated in large numbers specifically in response to IGF-I but not to 10% fetal calf serum, epidermal growth factor, fibroblast growth factor, or platelet derived growth factor-BB. An IGF-I receptor-blocking antibody inhibited IGF-I-stimulated migration in both cell types. In addition, a blocking antibody to the alpha v beta 5 integrin (a vitronectin receptor) inhibited migration of MCF-7 cells in response to IGF-I through vitronectin but not through type IV collagen. Similarly, blocking antibodies specific for alpha 2 and beta 1 integrins significantly inhibited migration of both cell types through type IV collagen-coated membranes but not through vitronectin-coated membranes. We conclude that: 1) IGF-I stimulates migration of these two cell types through the IGF-I receptor; 2) interaction of vitronectin with the alpha v beta 5 integrin or collagen with the alpha 2 beta 1 integrin is necessary for the complete IGF-I response in MCF-7 cells, and 3) because migration represents an in vitro model for metastatic spread, integrins, extracellular matrix proteins, and IGF-I may play coordinated roles in the metastasis of breast cancer in vivo.


Assuntos
Neoplasias da Mama/patologia , Quimiotaxia/fisiologia , Proteínas da Matriz Extracelular/fisiologia , Fator de Crescimento Insulin-Like I/farmacologia , Integrinas/fisiologia , Anticorpos Monoclonais/imunologia , Quimiotaxia/efeitos dos fármacos , Humanos , Receptor IGF Tipo 1/imunologia , Células Tumorais Cultivadas
20.
Magn Reson Imaging ; 13(4): 641-4, 1995.
Artigo em Inglês | MEDLINE | ID: mdl-7674861

RESUMO

Adrenocorticotropic hormone (ACTH) secreting islet cell tumors of the pancreas are extremely rare. A case of an ACTH producing islet cell tumor with multiple liver metastases is reported and the magnetic resonance imaging (MRI) findings are described.


Assuntos
Adenoma de Células das Ilhotas Pancreáticas/diagnóstico , Hormônio Adrenocorticotrópico/metabolismo , Meios de Contraste , Gadolínio , Hormônios Ectópicos/metabolismo , Imageamento por Ressonância Magnética , Neoplasias Pancreáticas/diagnóstico , Adenoma de Células das Ilhotas Pancreáticas/metabolismo , Adulto , Humanos , Masculino , Neoplasias Pancreáticas/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...