Ple Model Research Articles

Bolstering employee relations in a public sector undertaking: validation of CODE and PLE model

PurposeThe purpose of this research is to examine the relationship between employer and employees in a public power sector undertaking through the validation of CODE (compensation, organizational justice, dispute resolution and employee empowerment) and PLE (workforce productivity, employee loyalty and employee engagement) model.Design/methodology/approachA hypothesized research model was developed and validated by using structural equation modeling (AMOS 20). In total, 303 responses were accumulated by administering a structured questionnaire among the employees of a state-owned power sector.FindingsThe results revealed that a harmonious climate of employee relations is prevailing in the public power utility. Additionally, the findings suggest that the CODE and PLE model of employee relations are found to be positive and significant by investigating the impact of compensation, organizational justice, dispute resolution and employee empowerment as the predictors; and workforce productivity, employee loyalty and employee engagement as the critical outcomes of employee relations.Practical implicationsThe study recommends some plausible insights for practitioners, decision-makers and policy formulators to develop strategies and policies for nurturing congenial employee relations and also to cultivate a facilitative work environment for generating contented and competent manpower.Originality/valueValidation of CODE and PLE model of employee relations in the new perspective of power sector undertaking is an epoch-making and novel contribution that offers significant empirical evidence to the extant literature. Moreover, the exploration of employer–employee relations in this context is a unique and innovative effort toward existing research.

New methods of coalbed methane production analysis based on the generalized gamma distribution and field applications

Decline curve analysis is a simple and fast regression method of estimating recoverable reserves and future performance, but it is challenged when applied to unconventional reservoirs. Based on a generalized Gamma distribution in the real number field, a theoretical forecasting model describing the whole-process change of coalbed methane well production was constructed, that is, the gas production can be estimated by the early rising section data and a few declining section data, or even just the early rising section data. Furthermore, a generalized production decline analysis model was proposed, which can match all flow regimes in coalbed methane reservoirs as well as in shale gas and tight gas reservoirs. Particularly, the Arps exponential decline model, Duong model, and SEPD model are some of its special forms. By analyzing the production of typical wells in the Zhengzhuang-Fanzhuang block of China, it has demonstrated that the generalized production forecasting model performs significantly better than the Duong model in terms of data fitting accuracy and prediction accuracy, and in comparison to the Arps model, PLE model, SEPD model and Duong model, the generalized production decline model has also demonstrated greater scientific validity and field applicability for predicting coalbed methane production. The MAPE value between the predicted and actual gas production ranges from 4.46% to 8.82%, with an average of 5.75%, and the RRMSE between them ranges from 6.24% to 9.74%, with an average of 7.53%, which are both significantly lower than those provided by the Arps model, PLE model, SEPD model, and Duong model.

A Bimodal Spike and Slab Model for Variable Selection and Model Exploration

We have developed an enhanced spike and slab model for vari- able selection in linear regression models via restricted nal prediction error (FPE) criteria; classic examples of which are AIC and BIC. Based on our proposed Bayesian hierarchical model, a Gibbs sampler is developed to sam- ple models. The special structure of the prior enforces a unique mapping between sampling a model and calculating constrained ordinary least squares estimates for that model, which helps to formulate the restricted FPE crite- ria. Empirical comparisons are done to the lasso, adaptive lasso and relaxed lasso; followed by a real life data example.

Emissivity model of steel 430 during the growth of oxide layer at 800–1100 K and 1.5 μm

This work studied the variation in spectral emissivity with growth of oxide layer at the different temperatures. For this reason, we measured the normal spectral emissivity during the growth of oxide layer on the sample surface at a wavelength of 1.5 μm over a temperature range 800–1100 K. In the experiment, the temperature was measured by the two thermocouples, which were symmetrically welded onto the front surface of specimens. The average of their readings was regarded as the true temperature. The detector should be perpendicular to the specimen surface as accurately as possible. The variation in spectral emissivity with growth of oxide layer was evaluated at a certain temperature. Altogether 11 emissivity models were evaluated. The conclusion was gained that the more the number of parameters used in the models was, the better the fitting accuracy became. On the whole, all the PEE models, the four-parameter LEE model and the five-parameter PFE, PLE and LEE models could be employed to well fit this kind of variation. The variation in spectral emissivity with temperature was determined at a certain thickness of oxide film. Almost all the models studied in this paper could be used to accurately evaluate this variation. The approximate models of spectral emissivity as a function of temperature and oxide-layer thickness were proposed. The strong oscillations of spectral emissivity were observed, which were affirmed to arise from the interference effect between the two radiations stemming from the oxide layer and from the substrate. The uncertainties in the temperature of steel 430 generated only by the surface oxidization were approximately 4.1–10.7 K in this experiment.

Benchmarking EUR estimates for hydraulically fractured wells with and without fracture hits using various DCA methods

Various decline curve analysis (DCA) methods can be applied to forecast the production performance of hydrocarbon wells, including horizontal wells stimulated with hydraulic fracturing. Yet, which method is more preferable remains in doubt. The objective of this study is to evaluate various DCA methods by history matching and hindcasting both synthetic and field production data in order to assess for each method the reliability of production forecasts and the estimated ultimate recovery (EUR). Five DCA methods have been evaluated because of their computational simplicity and broad application. These methods are the Modified Hyperbolic Decline model (MHD), Duong model, Logistic Growth Analysis Model (LGM), and the Power Law Exponential (PLE, with D∞=0 and D∞=∞) Decline models. Each method was evaluated using three data sets: synthetic shale oil production rates based on a CMG reservoir model using Eagle Ford reservoir characteristics, data from producing Eagle Ford wells and from Austin Chalk wells. The hindcast method was applied to the Eagle Ford synthetic wells to establish the EUR deviation between the synthetic reservoir model production forecast and the various DCA methods. The weighted residuals of history matched production rates for Eagle Ford indicate that the MHD and Duong models give the lowest matching errors (as low as 1.32%) and the highest EUR estimations (as high as 3,447,609 stb). The PLE model (with D∞≠0) gives the most conservative EUR estimation, and also the least reliable history matching method (on our Eagle Ford data sets), which therefore is the least preferable DCA method. For the Austin Chalk wells in our study, all methods generate fairly similar EUR predictions with similar matching errors (from 13% to 15%) so that the DCA method preference becomes indifferent. This study also touches upon the relationship between DCA results when well interference occurs due to various hydraulic fracture hits. Shale wells that primarily contain hydraulic fractures and few natural fractures (Eagle Ford) give the most reliable forecasts using the MHD and Duong DCA methods. However, wells in the Austin Chalk, a naturally fractured reservoir, show little difference between the forecast accuracy from the various DCA methods.

“The Coast” is Complicated: A Model to Consistently Describe the Nation’s Coastal Population

Our nation's coast is a complicated management area where no single delineation provides all of the demo- graphic statistics needed to address the full range of policy and management issues. As a result, several different coastal delineations are currently being used, yielding a variety of US coastal population statistics. This paper proposes a sim- ple model for generating and applying coastal population statistics at the national and regional level to increase con- sistency in coastal policy discussions and improve public understanding of coastal issues. The model includes two major components. The first component is "the population that most directly affects the coast," represented by the permanent US population that resides in a standard suite of Coastal Watershed Counties, where land use and water quality changes most directly impact coastal ecosystems. The second component is "the population most directly affected by the coast," represented by the permanent US population that resides in a standard suite of Coastal Shore- line Counties that are directly adjacent to the open ocean, major estuaries, and the Great Lakes, which due to their proximity to these waters, bear a great proportion of the full range of effects from coastal hazards and host the majority of economic production associated with coastal and ocean resources.

Novel synthesis of various orthogonally protected Cα-methyllysine analogues and biological evaluation of a Vapreotide analogue containing (S)-α-methyllysine

Prochiral malonic diesters containing a quaternary carbon center have been successfully transformed into a diverse set of (t)Boc-Fmoc-α(2,2)-methyllysine-OH analogues through chiral malonic half-ester intermediates obtained via enzymatic (Pig Liver Esterase, PLE) hydrolysis. The variety of chiral half-ester intermediates, which vary from 1 to 6 methylene units in the side chain, are achieved in moderate to high optical purity and in good yields. The PLE hydrolysis of malonic diesters with various side chain lengths appears to obey the Jones's PLE model according to the stereochemical configurations of the resulting chiral half-esters. The established synthetic strategy allows the construction of both enantiomers of α(2,2)-methyllysine analogues, and a (S)-β(2,2)-methyllysine analogue from a common synthon by straightforward manipulation of protecting groups. Two different straightforward and cost effective synthetic strategies are described for the synthesis of α(2,2)-methyllysine analogues. The described strategies should find significant usefulness in preparing novel peptide libraries with unnatural lysine analogues. A Vapreotide analogue incorporating (S)-α(2,2)-methyllysine was prepared. However, the Vapreotide analogue with (S)-α-methyl-α-lysine is found to lose its specific binding to somatostatin receptor subtype 2 (SSTR2).

Do all QSOs have the same black hole mass?

QSOs from SDSS, 2QZ and 2SLAQ covering an order of magnitude in luminosity at fixed redshift exhibit similar amplitudes of clustering. In addition, QSO clustering evolution at z>0.5 is well fitted by a model that assumes a fixed host halo mass, implying that QSOs may occur in a relatively narrow range of halo and BH mass. We argue that the slow evolution of early-type galaxies out to z~1-2 may also provide support for a slow evolution of QSO host BH masses. The result would mean that if high-z QSOs radiate at Eddington rates then low-z SyI must radiate at ~100x less than Eddington. We conclude that models where QSOs radiate at L_Edd require M_BH and M_halo to be decoupled to circumvent the clustering results. While single BH mass and flickering models fit the z>0.5 clustering results, they appear to be rejected by the z~0, M_BH-L relation from reverberation mapping. We find that the inclusion of z<0.5 QSO clustering data improves the fit of a long-lived QSO model and suggest that the predictions of a PLE model for QSO BH masses agree reasonably with UV-bump and reverberation estimates (abridged).

Optically faint X-ray sources in the Chandra deep field North:Spitzerconstraints

We investigate the properties of the most optically faint sources in the GOODS-N area (R > 26.5 AB). Such extremely optically faint populations present an uncharted territory despite the fact that they represent an appreciable fraction of the X-ray sources in the GOODS-N field. They are believed to contain either red AGN at moderate redshifts or possibly QSO at very high redshift. We compile our sample by first finding the 3.6um IRAC counterparts of the X-ray sources and searching for the optical counterparts of the IRAC sources. 35 sources do not have counterparts in the R-band Subaru optical images. Of these, 18 have HST-ACS counterparts while the remaining have no optical counterparts. The vast majority of our 35 sources are classified as Extremely Red Objects (EROs) on the basis of their V-K lower limits. Their photometric redshifts show that these populate moderate redshifts (median z~2.8), being markedly different from the already spectroscopically identified population which peaks at z~0.7. The Spitzer-IRAC mid-IR colours of the sources which have no HST counterparts tend to lie within the mid-IR colour diagram AGN "wedge", suggesting either QSO, ULIRG (Mrk231), or early-type galaxy templates at z>3. A large fraction of our sources (17/35), regardless of whether they have HST counterparts, can be classified as mid-IR bright/optically faint sources (Dust Obscured Galaxies) a class which is believed to include many heavily absorbed AGN. The co-added X-ray spectrum of the optically faint sources is very flat having a spectral index of Gamma~0.87, significantly flatter than the spectrum of the X-ray background. The optically faint R>26.5 X-ray sources constitute more than 50% of the total X-ray population at redshifts z>2 bearing important implications for the luminosity function and its evolution; considering X-ray sources with 2<z<4 we find good agreement with a modified PLE model.

The VVDS type-1 AGN sample: the faint end of the luminosity function

In a previous paper (Gavignaud et al. 2006, A&A, 457, 79), we presented the type-1 Active Galactic Nuclei (AGN) sample obtained from the first epoch data of the VIMOS-VLT Deep Survey (VVDS). The sample consists of 130 faint, broad-line AGN with redshift up to and , selected on the basis of their spectra. The sample is thus free of the morphological and color selection biases, that lead to significant incompleteness in the optical surveys of faint AGN. In this paper we present the measurement of the Optical Luminosity Function up to derived from this sample, we compare our results with previous results from brighter samples both at low and at high redshift and finally, through the estimate of the bolometric luminosity function, we compare them also with the results from X-ray and mid-IR selected samples. Our data, more than one magnitude fainter than previous optical surveys, allow us to constrain the faint part of the luminosity function up to high redshift. A comparison of our data with the 2dF sample at low redshift () shows that the VVDS data can not be well fitted with the PLE models derived by previous samples. Qualitatively, this appears to be due to the fact that our data suggest the presence of an excess of faint objects at low redshift () with respect to these models. By combining our faint VVDS sample with the large sample of bright AGN extracted from the SDSS DR3 (Richards et al. 2006b, AJ, 131, 2766) and testing a number of different evolutionary models, we find that the model which better represents the combined luminosity functions, over a wide range of redshift and luminosity, is a luminosity dependent density evolution (LDDE) model, similar to those derived from the major X-surveys. Such a parameterization allows the redshift of the AGN space density peak to change as a function of luminosity and explains the excess of faint AGN that we find at . On the basis of this model we find, for the first time from the analysis of optically selected samples, that the peak of the AGN space density shifts significantly towards lower redshift going to lower luminosity objects. The position of this peak moves from for to for . This result, already found in a number of X-ray selected samples of AGN, is consistent with a scenario of “AGN cosmic downsizing”, in which the density of more luminous AGN, possibly associated to more massive black holes, peaks earlier in the history of the Universe (i.e. at higher redshift), than that of low luminosity ones, which reaches its maximum later (i.e. at lower redshift).

The K20 survey

We present the results of VLT optical spectroscopy of a complete sample of 78 EROs with over a field of 52 arcmin2. About 70% of the 45 EROs with have been spectroscopically identified with old passively evolving and dusty star-forming galaxies at . The two classes are about equally populated and for each of them we present and discuss the average spectrum. From the old ERO average spectrum and for we derive a minimum age of ~3 Gyr, corresponding to a formation redshift of zf ≳ 2.4. PLE models with such formation redshifts well reproduce the density of old EROs (consistent with being passively evolving ellipticals), whereas the predictions of the current hierarchical merging models are lower than the observed densities by large factors (up to an order of magnitude). From the average spectrum of the star-forming EROs we estimate a substantial dust extinction with ≳ 0.5. The star formation rates, corrected for the average reddening, suggest a significant contribution from EROs to the cosmic star-formation density at .

Titan, Mars and Earth : Entropy production by latitudinal heat transport

Temperature contrasts between warm tropics and cool high latitudes depends on how efficiently heat is transported by the atmosphere (and oceans) from the tropics. This heat transport is generally assumed to be proportional to atmospheric pressure, but we show with a simple model that this prediction fails by orders of magnitude for Mars and Titan. However, a basic principle, previously postulated for the Earth, does successfully predict the heat flows and zonal temperatures of Mars and Titan. The circulation predicted by this Maximum Entropy Production (MEP) principle is consistent with Titan's observed zonal structure and the winds and CO2 frost cycle on Mars. The principle makes powerful predictions where detailed information is lacking, such as on the early Earth and on possibly habitable extrasolar planets.

Differences in the dense gas between type 1 and type 2 Seyferts

We have used observations of the CO J =1 ! 0 transition in a sample of 20 Seyfert galaxies in order to test the result of Heckman et al. (1989), who nd that type 2 Seyferts have a higher molecular gas content than type 1 Seyferts. From our observational results alone, we possibly nd that LCO=LFIR (Sy2) LCO=LFIR (Sy1) for LFIR 10 11 L Seyferts, but LCO=LFIR (Sy2) 3LCO=LFIR (Sy1), when we use all of our sample (LFIR 10 10 10 11 L). The results suggest that star-burst ac- tivity is most dominant in the (LFIR 10 10 L )t ype 2 Seyferts, and the relative contribution of this activity to the FIR flux (compared to the AGN) may decrease with increasing LFIR. Also, in order to test whether the Seyfert classes dier in their molecular gas distributions, we have used a sim- ple model to estimate the inclination of the sub-kpc scale molecular ring, and, upon comparison with the observed spectra, conclude that the ring is generally aligned with the galactic disc, with the largest deviations from this be- ing exhibited by the type 1 Seyferts. With regard to the nucleus, for most of the sample, the pc-scale obscuring torus appears to be approximately (within 30) aligned with the molecular ring for both Seyfert classes.

Galaxy number counts--IV. Surveying the Herschel Deep Field in the near-infrared

We present results from two new near-infrared imaging surveys. One survey covers 47.2 arcmin2 to K(3σ)=20 mag whilst a second, deeper catalogue covers a subarea of 1.8 arcmin2 to K(3σ)=22.75 mag. Over the entire area we have extremely deep optical photometry in four bandpasses (UBRI), allowing us to track the colour evolution of galaxies to very faint magnitude limits. Our K-band number counts are consistent with the predictions of non-evolving models with 0q00.5. The K-selected (B−K) galaxy colour distributions from our surveys move sharply bluewards fainter than K∼20. At brighter magnitudes (K 4 and 19 4 galaxies at K∼20 are lower than the predictions of passively evolving models or PLE models with a low level of continuing star formation, suggesting that at least part of the larger deficiency observed in (B−K) at K∼20 may be caused by star formation rather than dynamical merging. As we and others have noted, the number redshift distribution at 18 1. Dynamical merging is one possible solution to reduce the numbers of these galaxies but (as we have suggested previously) a dwarf-dominated initial mass function for early-type galaxies could offer an alternative explanation; we show here that such a model reproduces well the optical–infrared colour distributions and K-band galaxy counts.

Slengo kultūra : sociologinis tyrimas

Qualitative research on subculture groups of youth in Lithuania, based on the theory and methodology of contemporary culture (including the works of I. Hassan, J.Fornäs, R.Laermans, J.Huizinga, V.Kavolis, P. Alasuutari and others) is presented in this article. Expressions of youth culture, a phe nomena known as the underground culture (applica bly coined undergrounds in Lithuanian), which has been increasingly proliferating over the last decade of this century, have been investigated. Spe cifically, during this time period, the cultural mi lieu has been refuting ideological bolts, as opportu nities for free individual expression have become possible. This study has been treated as a subcul ture phenomena, because an increasing individual ity in orientation of values among young people has been revealed. The analysis highlights the appearance of traits of the late modern culture (the term first used by J.Fornäs, 1987), otherwise known as post-modern, in Lithuania. Life experience in the world of the youth subculture is defined as a created virtual re ality. The fundamental aspect of virtual reality in volve the formation of new and meaningful struc tures of ethics and aesthetics. It is a type of exper imentation on the playing field. It is characteristic of youth to create organizational structures, vital personages, and artistic forms of self-expression, and seek individualistic aesthetic and mystical ex periences, and to develop a world outlook. Three of the main experiments of youth under ground culture are presented in this article. The first, named stage of underground culture, empha sizes the various genres of world of youth subcul ture, such as skinheads, punks, hardcore, bikers (rockers), techno culture, football fans and others. The most popular and more active of them is the musically inclined metal subculture, which subdi vides into numerous different styles. The cultural identity of the member of the underground person is also analyzed. The problem of interaction be tween external image and world outlook is raised, and characteristics of real versus pseudo members of the underground, discussed. The second experiment involves the organization and activities of the underground music culture. The organizational structure of a music underground is analyzed. Although the structure seems like the model of the official culture, it operates on an op posing set of principles. Among them are principles over pragmatism and commercialism of mass soci ety, and the desire to rebel against official culture. Such an analysis probes the problems of under ground culture within the culture in common, par ticularly the influence of developments in popular culture, and its impact on the subculture. The third experiment of youth analysed is the creation of models for cultural identity. Young peo ple model their perspective of the world from con temporary cultural fragments, as well as those of the past, and the meaningfulness and origins of symbolic expression. Among members of the un derground culture, a so-called Pagan world view has been evolving. It has been forming both from myths found in literary sources, as well as those imagined, regarding the feats of ancient Lithua nians, and the struggles and victories of their ances tors. It is also formed of the numerous ideas about Paganism, or even Satanism, which have come from the culture of Western Europe. Expressions of such a world view include avante-garde art forms and stylized arrangements, such as metal music, and the projection of an everyday and a stage image. By considering themselves to be carrying forth their ethnic cultural traditions, members of the under ground culture deny the continuation of traditional thinking. The spiritual state of being during the time under analysis is indicated by more and more widespread ideas, regarding the denial of principles which op erate in contemporary society, and formation of an alternative world in which to live. It is also marked by the search for meaning in the culture of the past, and a cultural niche for spiritual comfort. Empirical data suggests an opposite tendency in the youth culture, the need to accept the cultural forms of the West. On the other hand, there is the need to form cultural individuality, by employing interpreted meanings of traditional culture. Young people accept new ideas from Western culture, how ever the sense of one's immediate world is gained in the here and now. Thus, it would be one sided to consider this cultural phenomena as a borrower of culture. It is far more likely to be an expression of changes occurring in the social and cultural life of Lithuania.

Surface potential studies using Kelvin force spectroscopy

A home-built Kelvin force microscope combined with a spectroscopic method is dedicated to local measure- ments of topography and contact potential differences (CPD). This technique is based on a simple modification of a non- contact atomic force microscopy (nc-AFM), where a bias voltage is applied between the sample and tip during the CPD measurement. The changes in CPD between the tip and vari- ous sample materials have been measured. Kelvin force spec- tra of Pd=Si and of self-assembling monolayer films (SAMs) are presented. The Kelvin method (1) is a well-established technique for measuring the contact potential differences (CPD) between a reference electrode and a sample. The CPD for clean metal surfaces is given by the difference in the work functions of the two materials. A common method of measuring the con- tact potential difference is the vibrating capacitor method or Kelvin method. In this method, the probe, which is made of a material with a known work function (commonly tungsten or platinum), is arranged close to the surface to be measured as a parallel plate capacitor with small spacing. In a sim- ple model, the contact potential between the two materials is VCPDD 1=e.2 1/ ,w here 1 and 2 are the work func- tions of the conductors, including changes due to adsorption layers on the surface. A periodic vibration between the two plates at frequency ! with amplitude d1 results in a current i.t/ given by i.t/D @C

The QSO Evolution Derived from the HBQS and Other Complete QSO Surveys

An ESO Key programme dedicated to an Homogeneous Bright QSO Survey (HBQS) has been completed. 327 QSOs (Mb<-23, 0.3<z<2.2) have been selected over 555 deg^2 with 15<B<18.75. For B<16.4 the QSO surface density turns out to be a factor 2.2 higher than what measured by the PG survey, corresponding to a surface density of 0.013+/-.006 deg^{-2}. If the Edinburgh QSO Survey is included, an overdensity of a factor 2.5 is observed, corresponding to a density of 0.016+/-0.005 deg^{-2}. In order to derive the QSO optical luminosity function (LF) we used Monte Carlo simulations that take into account of the selection criteria, photometric errors and QSO spectral slope distribution. The LF can be represented with a Pure Luminosity Evolution (L(z)\propto(1+z)^k) of a two power law both for q_0=0.5 and q_0=0.1. For q_0=0.5 k=3.26, slower than the previous Boyle's (1992) estimations of k=3.45. A flatter slope beta=-3.72 of the bright part of the LF is also required. The observed overdensity of bright QSOs is concentrated at z<0.6. It results that in the range 0.3<z<0.6 the luminosity function is flatter than observed at higher redshifts. In this redshift range, for Mb<-25, 32 QSOs are observed instead of 19 expected from our best-fit PLE model. This feature requires a luminosity dependent luminosity evolution in order to satisfactorily represent the data in the whole 0.3<z<2.2 interval.

The clustering of blue and red galaxies at B 25.5 mag

Deep CCD imaging at the Isaac Newton Telescope provided a sample of ∼7000 faint galaxies, with B – R colours, to faint limits of B ≃ 25.5 mag and R≃ 24.5 mag. The number counts of these galaxies are consistent with the previous galaxy number counts of Metcalfe et al. and Tyson, showing at faint magnitudes an excess above non-evolving predictions, consisting of galaxies with moderately blue colours of 0.0≤B;— R≤1.5. The number of redder (B — R> 1.5) galaxies did not exceed the non-evolving prediction. We calculate the angular correlation function, co(8), of these faint galaxies, and compare with the predictions of new models which take into account the observed dependence of galaxy clustering properties on morphology and luminosity. In agreement with previous studies (e.g., by Roche et al.), the ω (θ) amplitude of faint galaxies in our data set is found to fall well below the predictions of models in which galaxy clustering remains stable in proper coordinates and the redshift distribution N(z) has a non-evolving form, suggesting that the faint galaxyN(z) is more extended than this and includes a high proportion of z > 1 galaxies. We find that a pure luminosity evolution model, with a steep luminosity function for late-type galaxies, a significant increase with redshift in the star-forming activity of Sab and Sbc spirals, and mild dust-reddening, gives a good fit to both the galaxy number counts and the ω (θ) results, as obtained from this data set and from other published CCD surveys. However, the peak in the faint galaxy colour distribution is closer to B Ȕ R≃0.8 than to the bluer colour of B — R≃0.4 predicted by our model (the reason for this discrepancy remains unclear). The ω (θ) amplitude of the redder (B 2014 R > 1.5) galaxies in our sample appears to be higher than that of the bluer (B 2014 R> 1.5) galaxies, in agreement with Roche et al. and Neuschaefer et al. We also find very little cross-correlation between red and blue galaxies. The lower ω (θ ) amplitude of the bluer galaxies suggests that the steep fall in galaxy ω (θ ) amplitudes at B > 23 is caused by the same blue galaxies that produce the excess in the number counts at these magnitudes. The colour dependence of ω (θ ) is well fitted by our PLE model, in which, at B∼25, almost all of the redder galaxies would lie at z< 1, while the bluer galaxy subsample would consist of both dwarf late-type galaxies at low/moderate redshifts and evolving L∼L* galaxies widely distributed in redshift from z∼ 0.5 out to z∼3, giving a much more extended N(z), and consequently a lower ω (θ) amplitude, for bluer galaxies. The stronger clustering of the redder galaxies suggests that galaxy clustering is approximately stable (ε = 0) out to at least z ∼ 0.6, and therefore that the low ω (θ ) amplitude of the full sample does not result simply from very rapid evolution of the clustering of all galaxies. These results may argue against models, such as merging-dominated models, in which the excess blue galaxies are confined to lower redshifts. The excess blue galaxies could only lie within a no-evolution N(z) if they belong to a separate population of dwarf starburst galaxies which is intrinsically very weakly clustered. However, there is evidence (e.g., Cole et al.) that dwarf starburst galaxies are normally clustered. This would leave significant L⋆ evolution, with a redshift distribution extending to z ∼ 3 at B ∼ 25, as the most plausible explanation of the low ω (θ) amplitude of B ∼ 25 galaxies.

X-ray topographic observation of dislocation structure in sapphire single crystal grown by temperature gradient technique

The characteristic triangular cross-grid dislocation structure in sapphire single crystals grown in [0001] direction by temperature gradient technique (TGT) has been investigated by means of X-ray diffraction topography. Dislocations lie on (0001) basal planes and primarily appear as three parallel groups of straight dislocation lines. At high temperature these dislocation lines can move easily on the slip planes and form different dislocation configurations due to pinning, climbing and interacting. The analysis of Burgers vector and image width of dislocation lines confirmed that three parallel groups of straight dislocation lines are pure edge type having 〈11 2 0〉 type Burgers vector, and a few dislocation reactions are of the type of [11 2 0] + [1 2 10] + [ 2 110] = 0. A sim ple model of basal slip of the type of (0001)〈11 2 0〉 is used to explain these dislocations.