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Surface-emitting diode lasers have recently made significant advances because of the emergence of a variety of applications such as optical interconnects, optical computing, communications or diode-pumped solid-state lasers. These devices can be roughly grouped into three types based on their cavity configurations. The paper will examine the concepts, fabrication techniques and operating characteristics associated with each type of laser. The performance of monolithic arrays of surface-emitting diode lasers will also be discussed.

Mesoscopic self-collimation (MSC) in mesoscopic photonic crystals with high reflectivity is exploited to realize a novel high Q-factor cavity by means of mesoscopic PhC planar mirrors. These mirrors efficiently confine a mode inside a planar Fabry–Perot-like cavity, that results from a beam focusing effect that stabilizes the cavity even for small beam sizes, resembling the focusing behavior of curved mirrors. Moreover, they show an improved reflectivity with respect to their standard distributed Bragg reflector counterparts that allows higher compactness. A Q-factor higher than 10^4 has been achieved for an optimized 5-period-long mirror cavity. The optimization of the Q-factor and the performances in terms of energy storage, field enhancement, and confinement are detailed.

We propose a simple, fast, and accurate method to design complex layered photonic crystal structures that exhibit mesoscopic self-collimation. We apply this method to the control of the overall reflectivity of such structures, and we numerically demonstrate high-transmissivity (>99%) self-collimating waveguides and high-reflectivity (>99%) self-collimating Bragg mirrors.

Planar 2D photonic crystals are of tremendous interest for integrated optics applications. In the last years, several possible laser cavities have been proposed in that prospect. In this paper, we review our work on 2D photonic crystal second order DFB lasers. We will show that an affine deformation of the photonic crystal allows the fabrication of closely spaced arrays of high Q DFB lasers. Combining waveguide and photonic crystal affine deformations, we demonstrate arrays of optically pumped single mode DFB lasers with controlled wavelength spacing. Potential extension of this scheme will be discussed, altogether with potential for electrical pumping implementation.

We report the measurement of a polarization-independent guided-mode resonant filter with a Q factor of ∼2200 functioning near normal incidence in the near infrared (850?nm). Besides this remarkable performance, we provide a detailed optical and structural characterization of the component, which points out the origins of the limitation of the experimental performance. We conclude that the defaults in question can be corrected by improving the lithography process, and we are confident that even greater performance will be obtained in future realizations.

Expanded polytetrafluoroethylene ePTFE is used as a support for artificial corneas. Implanted in corneas, most of the time this polymer is colonized by corneal host cells. The absence of colonization often coincides with extrusion of the polymer. Therefore, we decided to introduce keratocytes into ePTFE in vitrobefore implantation. Because keratocytes do not spontaneously enter ePTFE, we used several chemoattractants, separately and in a mixture, to stimulate the penetration of cultured keratocytes into the polymer. The influence of the passage number on cell penetration was also studied. No significant differences were observed up to the seventh passage, although seventhpassage cells penetrated somewhat more slowly than younger cells. Satisfactory results were obtained with four of the tested chemotactic factors: IL6, type alpha transforming growth factor TGFα, platelet derived growth factor isoform BB PDGFBB, and fibroblast growth factor2 FGF2. Under our experimental conditions, two to more than six million keratocytes entered the polymer discs with a volume of 706.5 mm3in the presence of these four chemoattractants. TGFα was the most efficient and was selected for further in vitroand in vivostudies. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res 56: 487–493, 2001

Strained InAs1−xSbx(0

Most modern aircraft engines rely on the use of high Bypass Ratios (BPR) turbofans to achieve both high thrust and low specific fuel consumption. However, such configurations are prone to the formation of ground vortices during low-speed operations. This phenomenon arises under specific combinations of wind direction, velocity or inlet air speed, generating engine vibrations and leading to the suction of damaging abrasive particles. Its characterization in early design stages is crucial. In this work, a joint experimental and numerical exploration of operating conditions leading to ground vortex presence is carried out on a scaled wind tunnel configuration. Flow details are investigated for several working points obtained from a specific set of input parameters (intake speed, wind speed, ground clearance). A methodology suitable for both experimental and Computational Fluid Dynamics (CFD) works is developed to extract vortex characteristic quantities, based on a local pressure minimum and Q-criterion contours topology. A very good agreement is obtained when comparing vortex predictions stemming from CFD and experiments. This database shall be used to transpose experimental data probed outside of the nacelle to data within the nacelle using data analytics techniques, paving the way for future data driven predictive models.

Alignment of 15 vertebrate alpha1,3-fucosyltransferases revealed one arginine conserved in all the enzymes employing exclusively type 2 acceptor substrates. At the equivalent position, a tryptophan was found in FUT3-encoded Lewis alpha1,3/1,4-fucosyltransferase (Fuc-TIII) and FUT5-encoded alpha1,3/1,4-fucosyltransferase, the only fucosyltransferases that can also transfer fucose in alpha1, 4-linkage. The single amino acid substitution Trp111 --> Arg in Fuc-TIII was sufficient to change the specificity of fucose transfer from H-type 1 to H-type 2 acceptors. The additional mutation of Asp112 --> Glu increased the type 2 activity of the double mutant Fuc-TIII enzyme, but the single substitution of the acidic residue Asp112 in Fuc-TIII by Glu decreased the activity of the enzyme and did not interfere with H-type 1/H-type 2 specificity. In contrast, substitution of Arg115 in bovine futb-encoded alpha1, 3-fucosyltransferase (Fuc-Tb) by Trp generated a protein unable to transfer fucose either on H-type 1 or H-type 2 acceptors. However, the double mutation Arg115 --> Trp/Glu116 --> Asp of Fuc-Tb slightly increased H-type 1 activity. The acidic residue adjacent to the candidate amino acid Trp/Arg seems to modulate the relative type 1/type 2 acceptor specificity, and its presence is necessary for enzyme activity since its substitution by the corresponding amide inactivated both Fuc-TIII and Fuc-Tb enzymes.

The thermogenic capacity of brown adipose tissue has been investigated in I-strain mice to determine whether this tissue could play a role in the lower efficiency of food utilization reported in this strain of mice. (1) As compared with C57BL mice (a control strain), interscapular-brown-adipose-tissue weight and lipid percentage were decreased by 40% and 13% respectively in I-strain mice. (2) Mitochondrial protein content and cytochrome c oxidase activity were similar in the two strains, but the number of mitochondrial GDP-binding sites and uncoupling-protein content were increased by 2-fold in I-strain mice. (3) Fatty acid synthetase and citrate-cleavage enzyme (units/mg of protein) were 3-fold higher in the brown adipose tissue of I-strain mice. These results indicate that I-strain mice possess a very active brown adipose tissue. This enhanced capacity of energy dissipation in brown adipose tissue could contribute to the decreased capacity of I-strain mice to store adipose tissue.

This study was undertaken to determine whether receptor and non-receptor components of the adenylate cyclase (AC) cascade were altered in brown adipose tissue (BAT) of 14-day-old pre-obese (fa/fa) rats, before endocrine status is strongly modified by fa gene expression. Activity of the AC catalytic subunit did not differ between the two genotypes. In fa/fa rats compared with control Fa/fa rats, there was a 50% decrease in the activity of alpha Gs (stimulated by NaF or guanosine 5′-[gamma-thio]triphosphate) but no change in protein content (Western blotting). alpha Gi function, assessed by the inhibitory action of low concentrations of guanosine 5′-[beta gamma-imido]triphosphate upon 10(-4) M forskolin-stimulated AC activity, was equally low in both genotypes. Analysis of dose-response curves for different beta-agonists revealed that (i) both the basal and the maximally stimulated activity of AC were 2-fold lower in fa/fa rats than in Fa/fa rats; (ii) BRL37344 and CGP12177 (beta 3 agonists) were less potent in fa/fa than in Fa/fa rats (Kact. multiplied by 2); (iii) noradrenaline and isoprenaline (Iso), at the low-affinity site (beta 3-AR), were less potent in fa/fa than in Fa/fa pups (Kact. increased by 30 and 20% respectively). At the high-affinity site (mainly beta 1) these two agonists were more potent in fa/fa than in Fa/fa rats (Kact. decreased by 40 and 80% respectively). In good agreement with the latter result, the beta 1-adrenergic receptor (beta 1-AR)-selective antagonist CGP20712A had more effect on the Iso-stimulated AC activity in pre-obese than in lean pups (2-fold decreased in IC50). Binding experiments with [3H]CGP12177 show that in BAT of suckling rats, beta 3-ARs represent 80% of the total beta-ARs. Bmax values for the two sites were not affected by the genotype, although the beta 3-AR mRNA concentration in BAT (quantitative reverse-transcriptase PCR) was 3-fold lower in fa/fa rats than in Fa/fa pups. In conclusion, these results provide evidence for alterations in beta 1- and beta 3-AR signalling in BAT of 14-day-old suckling pre-obese Zucker rats with a decreased activity of alpha Gs. The impaired AC responsiveness to catecholamines might be a primary contributor to the development of this genetic obesity.

Recently 980 nm separate confinement heterostructure (SCH) InGaAs/GaInAsP/GaInP lasers have become of great interest because of potential improvements in threshold current and optical far field divergence over SCH InGaAs/GaAs/GaInP lasers. The authors report the first theoretical study on the influence of barrier composition on threshold current density and the optical far field of GaInAs/GaAs/GaInP and GaInAs/GaInAsP/GaInP SCH lasers. The paper presents the CADILAC model for computer-aided design of aluminium-free GaInAs strained quantum well lasers taking into account in particular the effects of strain on modification of the well band structure. A comparison between theoretical and experimental results is reported. The variations of the threshold current density and the transverse far field divergence versus energy bandgap of the SCH layer in multiple quantum well GaInAs/GaAs/GaInP and GaInAs/GaInAsP/GaInP SCH laser emitting at 980 nm are analysed. It is found that the increase of the bandgap energy of the barrier layer causes only a slight degradation of the radiative current density and a reduction of the far field divergence due to the refraction index decrease of the GaInAsP material and to well broadening in order to allow for the emission at 980 nn. Expecting the decrease in barrier current resulting from better confinement of the carriers in GaInAs/GaInAsP wells, these results tend to confirm the superiority of the InGaAs/GaInAsP/GaInP laser as a candidate for the pump sources of erbium-doped fibre optic amplifiers.

Rats were overfed during the suckling period by litter size manipulation in order to investigate the possible contribution of preadipocytes from the stromavascular compartment of adipose tissue to the development of obesity. Rats raised in litters of four pups were overfed; for normal feeding we assigned eight pups per litter. As early as 10 d of age, overfed rats became fatter than controls, and showed an increase in both plasma insulin and triacylglycerol levels. At this age, adipose tissue overdevelopment arose only from adipocyte hypertrophy, since hyperplasia occurred only at 15 d of age. Concurrently, compared to normal feeding, overfeeding led to significantly higher activities of lipoprotein lipase (LPL), glycerophosphate dehydrogenase (GPDH) and glycerophosphate acyltransferase (GPAT) in mature fat cells; 10-d-old overfed pups exhibited a higher stromal cell number. Further separation of this heterogeneous fraction by density gradient centrifugation showed a higher preadipocyte number as compared to that of controls. In stromal cells, LPL, GPDH, GPAT and acyl CoA ligase activities were detected during the suckling period. As compared to controls, overfeeding induced an increase in both LPL and GPDH activities in 10-d-old pups. Results indicate that overfeeding in early life induced an excess of fat storage capacity through a simultaneous increase in proliferation and differentiation rates of adipocyte precursors.

In 16-day-old conscious Zucker rats, at a time when pre-obese fa/fa rats were not yet hyperinsulinaemic compared with their lean Fa/fa littermates, the whole-body glucose-metabolism rate was decreased by 10% in pre-obese compared with lean pups. The markedly decreased glucose utilization found in brown adipose tissue (BAT) of pre-obese compared with lean pups accounted for at least 70% of the difference in whole-body glucose metabolism observed between the two genotypes. In pre-obese fa/fa rats, the 20% decrease in noradrenaline content of BAT reported in this study is consistent with the diminished glucose utilization by this tissue, and further supports the hypothesis of a defect in the sympathetic-nervous-system regulation of BAT metabolism as one of the primary causes for this genetic obesity.

Rats were fed diets containing various amounts of added thiram, a dithiocarbamate fungicide. As thiram feeding resulted in decreased appetite, control rats not receiving thiram were pair-fed to the experimental ones. On d 30 of the experiment the animals were weighed and sacrificed, and the following organs were weighed: liver, kidneys, heart, epididymal and perirenal fat pads, testes, seminal vesicles, tibia, adrenals, and thyroid. Liver concentrations of lactate, pyruvate, β-hydroxybutyrate, acetoacetate, ATP, and ADP were determined by enzymatic-spec trofluorimetric assay.For each parameter studied and each thiram dosage, values for treated rats were compared to those for control rats and the proability under the null hypothesis was computed. These probabilities were transformed into probits, logits, or “Weibull transforms” and plotted against the logarithms of the respective doses. Models were fitted to the data by linear regression techniques. Finally, the dose inducing the least significant difference (LSD dose), and the dose considered “safe” at P = 0.95, 0.99, and 0.999 were calculated. Significant pesticide-induced changes in the following parameters were found: food intake; weights of the whole body, kidneys, epididymal and perirenal fat pads, testes, and seminal vesicles; and liver β-hydroxybutyrate/ acetoacetate and lactate/pyruvate ratios.As the models did not differ in fit to the experimental data or in computed LSD doses, they were discriminated on the grounds of their underlying theoretical assumptions and their prediction of safe doses in a long-term study. The log-probit model was rejected for the former reason, and it was shown that the Weibull model foresees a nonnegligible risk of change, with thiram feeding at low doses, for too many parameters. The analysis resulted in the selection of the log-probit model for further use. Weight of fatty tissues was the most sensitive parameter and, using the log-probit model, the predicted no-effect dose at the 95 percent confidence level was 38 ppm thiram in the diet.

Les spectres de fluorescence directe et retardée du cristal de naphtalène ont été étudiés entre 77° K et 300° K, sous différentes excitations. Le naphtalène soumis à des traitemen ts mécaniques (broyage de l'échantillon), fait apparaitre de nouvelles raies et bandes attribuées à des traces de pyrène et aux déformations du réseau qu'elles provoquent.Prompt and delayed fluorescence of naphthalene in crystal state differently excited are investigated from 77 to 300° K. The naphthalene mechanically treated (grinding) shows new lines and bands we may attribute to pyrene traces and to the lattice perturbations induced.

The present study was undertaken to determine whether the capacity for 3,5,3′,5′-tetraiodothyronine (T4) conversion into 3,5,3′-tri-iodothyronine (T3), as measured by the activity of thyroxine type II 5′-monodeiodinase (T4-5′D), was altered in the brains of young Zucker fa/fa rats during the period of intense maturation of the central nervous system (i.e. from 10 to 20 days of life). From 7 to 14 days of age, no difference in brain T4-5′D activity could be detected between lean and pre-obese rats; serum free T4 was not affected by the fa gene. During the suckling to weaning transition, T4-5′D reached a plateau in brains of lean rats, while it increased by 50% in brains of pre-obese rats; concurrently, serum free T4 increased in Fa/fa rats, whereas it did not change in fa/fa rats. The increased capacity for conversion of T4 into T3 observed in brains of pre-obese compared with lean rats could not be ascribed to a variation in the amount of T4-5′D, since Vmax. did not differ between the two genotypes; however, it could be totally accounted for by an increased affinity of the enzyme for T4. This change may represent an adaptive response to low serum free T4 in order to maintain the cerebral T3 concentration in pre-obese rats. These results show that the alteration in T4 metabolism in brains of fa/fa rats is not an early event and thus cannot interfere with maturation of the central nervous system. However, the decreased serum free T4 which was observed in pre-obese rats after suckling might play a secondary role in development of this genetic obesity.

The letter reports short wavelength emission (7205 A˚) from MBE AlGaAs GRINSCH single Quantum well lasers. Visible emission is obtained with a 60 A˚ AlGaAs well containing ⋍ 18% aluminium and both design optimisation and growth conditions lead to low-threshold operation. Broad area Fabry-Perot diodes have threshold current densities as low as 390 A/cm2 and 670 A/cm2 for cavity lengths of 500 µm and 250 µm, respectively.

O-Fucose has been described on both epidermal growth factor-like (EGF-like) repeats and Thrombospondin type 1 repeats (TSRs). The enzyme adding fucose to EGF-like repeats, protein O-fucosyltransferase 1 (Pofut1), is a soluble protein located in the lumen of endoplasmic reticulum (ER). A second protein O-fucosyltransferase, Pofut2, quite divergent from its homolog Pofut1, has recently been shown to O-fucosylate TSRs but not EGF-like repeats. To date, Pofut1 genes have only been characterized in human, mouse, and fly, and Pofut2 in mouse, fly, and partially in the nematode Caenorhabditis elegans. Here, we report cDNA sequences and genomic structures of bovine Pofut1 and Pofut2 genes and describe for the first time five alternative spliced transcripts for each gene. Only one transcript for both Pofut1 and Pofut2 encodes an active bovine O-fucosyltransferase. Variant transcript distribution was examined in 13 bovine tissues. Transcripts encoding active forms are ubiquitous, whereas other forms possess a more restricted tissue-expression profile. Sequence comparison and phylogenetic analyses revealed that both Pofut genes are present as a single copy in animal genomes, and their exon–intron organizations are conserved among vertebrates. The last common ancestor of all analyzed bilaterian species would be predicted to possess polyexonic Pofut genes in their genome.