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The Prime Extragalactic Areas for Reionization and Lensing Science, a James Webb Space Telescope (JWST) GTO program, obtained a set of unique NIRCam observations that have enabled us to significantly improve the default photometric calibration across both NIRCam modules. The observations consisted of three epochs of 4-band (F150W, F200W, F356W, and F444W) NIRCam imaging in the Spitzer IRAC Dark Field (IDF). The three epochs were six months apart and spanned the full duration of Cycle 1. As the IDF is in the JWST continuous viewing zone, we were able to design the observations such that the two modules of NIRCam, modules A and B, were flipped by 180° and completely overlapped each other’s footprints in alternate epochs. We were therefore able to directly compare the photometry of the same objects observed with different modules and detectors, and we found significant photometric residuals up to ∼0.05 mag in some detectors and filters, for the default version of the calibration files that we used (jwst_1039.pmap). Moreover, there are multiplicative gradients present in the data obtained in the two long-wavelength bands. The problem is less severe in the data reduced using the latest pmap (jwst_1130.pmapas of 2023 September), but it is still present, and is non-negligible. We provide a recipe to correct for this systematic effect to bring the two modules onto a more consistent calibration, to a photometric precision better than ∼0.02 mag.

A broad continuum excess in the near-infrared, peaking in the rest frame at 2-5 mm, is detected in a spectroscopic sample of 88 galaxies at 0.5 < z < 2.0 taken from the Gemini Deep Deep Survey. Line emission from polycyclic aromatic hydrocarbons (PAHs) at 3.3 mm alone cannot explain the excess, which can be fit by a spectral component consisting of a template of PAH emission lines superposed on a modified blackbody of temperature T [?] 850 K. The luminosity of this near-infrared excess emission at 3 mm is found to be correlated with the star formation rate of the galaxy. The origin of the near-infrared excess is explored by examining similar excesses observed locally in massive star-forming regions, reflection and planetary nebulae, post-asymptotic giant branch stars, and in the galactic cirrus. We also consider the potential contribution from dust heated around low-luminosity active galactic nuclei. We conclude that the most likely explanation for the 2-5 mm excess is the contribution from circumstellar disks around massive young stellar objects seen in the integrated light of high-redshift galaxies. Assuming circumstellar disks extend down to lower masses, as they do in our own Galaxy, the excess emission presents us with an exciting opportunity to measure the formation rate of planetary systems at cosmic epochs before our own solar system formed.

We present the results of Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) imaging of a sample of 19 high-mass passively evolving galaxies with 1.2 < z < 2, taken primarily from the Gemini Deep Deep Survey (GDDS). Around 80% of galaxies in our GDDS sample have spectra dominated by stars with ages [?]1 Gyr. Our rest-frame R-band images show that most of these objects have compact regular morphologies which follow the classical R 1/4 law. These galaxies scatter along a tight sequence in the size versus surface brightness parameter space which defines the Kormendy relation. Around one-third (3/10) of the massive red objects in the GDDS sample are extraordinarily compact, with effective radii under 1 kpc. Our NICMOS observations allow the detection of such systems more robustly than is possible with optical (rest-frame UV) data, and while similar systems have been seen at z [?] 2, this is the first time such systems have been detected in a rest-frame optical survey at 1.2 < z < 2. We refer to these compact galaxies as "red nuggets," and note that similarly compact massive galaxies are completely absent in the nearby universe. We introduce a new "stellar mass Kormendy relation" (stellar mass density versus size) which we use to single out the effects of size evolution from those of luminosity and color evolution in stellar populations. The 1 < z < 2 passive galaxies have mass densities that are an order of magnitude larger then early-type galaxies today and are comparable to the compact distant red galaxies at 2 < z < 3. We briefly consider mechanisms for size evolution in contemporary models focusing on equal-mass mergers and adiabatic expansion driven by stellar mass loss. Neither of these mechanisms appears to be able to transform the high-redshift Kormendy relation into its local counterpart, leaving the origin and fate of these compact "red nuggets" unresolved.

Using a set of deep imaging data obtained by the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) shortly after its deployment, Yan, Windhorst, & Cohen found a large number of F775W-band dropouts (i-dropouts), which are consistent with being galaxies at z [?] 6. The surface density of i-dropouts thus derived, however, is an order of magnitude higher than those subsequent studies found in other deep ACS fields, including the Hubble Ultra Deep Field (HUDF). Here we revisit this problem, using both existing and new data. We confirm that the large overdensity of i-dropouts does exist in this field, and that their optical-to-IR colors are similar to those in the HUDF. However, we have discovered that the i-dropout overdensity is accompanied by an even larger excess of faint field objects in this region and its vicinity. This large excess of field objects is most likely caused by the fact that we have resolved the faint diffuse light extending from an interacting galaxy pair in the Virgo Cluster, M60/NGC 4647, which lies several arcminutes away from the region where the excess is found. The i-dropouts in this field are within the magnitude range where this excess of field objects occurs, and their spatial distribution seems to follow the same gradient as the entire excess field population. This excess population is also red in color, and the red wing of its color distribution continuously extends to the regime where the i-dropouts reside. While we still cannot completely rule out the possibility that the overdensity of i-dropouts might be a genuine large-scale structure of galaxies at z [?] 6, we prefer the interpretation that most of them are part of the excess stellar population related to M60/NGC 4647.

We have used the Hubble Space Telescope's Advanced Camera for Surveys (Ford et al. 2003) to measure the cumulative mass density in morphologically selected early-type galaxies over the redshift range 0.8 < z < 1.7. Our imaging data set covers four well-separated sight lines and is roughly intermediate (in terms of both depth and area) between the GOODS/GEMS imaging data and the images obtained in the Hubble Deep Field campaigns. Our images contain 144 galaxies with ultradeep spectroscopy obtained as part of the Gemini Deep Deep Survey. These images have been analyzed using a new purpose-written morphological analysis code, which improves the reliability of morphological classifications by adopting a "quasi-Petrosian" image thresholding technique. We find that at z ~ 1 about 80% of the stars living in the most massive galaxies reside in early-type systems. This fraction is similar to that seen in the local universe. However, we detect very rapid evolution in this fraction over the range 0.8 < z < 1.7, suggesting that over this redshift range the strong morphology-mass relationship seen in the nearby universe is beginning to fall into place. By comparing our images to published spectroscopic classifications, we show that little ambiguity exists in connecting spectral classes to morphological classes for spectroscopically quiescent systems. However, the mass density function of early-type galaxies is evolving more rapidly than that of spectroscopically quiescent systems, which we take as further evidence that we are witnessing the formation of massive early-type galaxies over the 0.8 < z < 1.7 redshift range.

Using the deep Spitzer Infrared Array Camera (IRAC) observations of the Great Observatories Origins Deep Survey (GOODS), we study the stellar masses and star formation histories of galaxies at z [?] 6 based on the i775-band dropout sample selected from the GOODS fields. In total, we derive stellar masses for 53 i775-band dropouts that have robust IRAC detections. These galaxies have typical stellar masses of ~1010 M and typical ages of a couple of hundred million years, consistent with earlier results based on a smaller sample of z [?] 6 galaxies. The existence of such massive galaxies at z [?] 6 can be explained by at least one set of N-body simulations of the hierarchical paradigm. We also study 79 i775-band dropouts that are invisible in the IRAC data and find that they are typically less massive by a factor of 10. These galaxies are much bluer than those detected by the IRAC, indicating that their luminosities are dominated by stellar populations with ages [?]40 Myr. Based on our mass estimates, we derive a lower limit to the global stellar mass density at z [?] 6, which is 1.1-6.7 x 106 M Mpc-3. The prospect of detecting the progenitors of the most massive galaxies at yet higher redshifts is explored. We also investigate the implication of our results for reionization and find that the progenitors of the galaxies comparable to those in our sample, even in the most optimized (probably unrealistic) scenario, cannot sustain the reionization for a period longer than ~2 Myr. Thus most of the photons required for reionization must have been provided by other sources, such as the progenitors of the dwarf galaxies that are far below our current detection capability.

We use data from the first epoch of observations with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope for the Great Observatories Origins Deep Survey (GOODS) to detect and study a collection of Lyman break galaxies at z [?] 6-5 in the Hubble Ultra Deep Field (HUDF), six of which have spectroscopic confirmation. At these redshifts, IRAC samples rest-frame optical light in the range 0.5-0.8 mm, where the effects of dust extinction are smaller and the sensitivity to light from evolved stars is greater than at shorter, rest-frame ultraviolet wavelengths observable from the ground or with the Hubble Space Telescope. As such, it provides useful constraints on the ages and masses of these galaxies' stellar populations. We find that the spectral energy distributions for many of these galaxies are best fitted by models of stellar populations with masses of a few times 1010 M and with ages of a few hundred million years, values quite similar to those derived for typical Lyman break galaxies at z [?] 3. When the universe was only 1 Gyr old, some galaxies had already formed a mass of stars approaching that of the present-day Milky Way, and they started forming those stars at z > 7 and in some cases much earlier. We find that the lower limits to the space density for galaxies in this mass range are consistent with predictions from recent hydrodynamic simulations of structure formation in a LCDM universe. All objects in our samples are consistent with having solar metallicity, suggesting that they might have already been significantly polluted by metals and thus are not comprised of "first stars." The values for dust reddening derived from the model fitting are low or zero, and we find that some of the galaxies have rest-frame UV colors that are even bluer than those predicted by the stellar population models to which we compare them. These colors might be attributed to the presence of very massive stars (>100 M) or weaker intergalactic H I absorption than what is commonly assumed.

We have discovered an extended Lya plume (UDF 5225) associated with a compact source at redshift z [?] 5.4 in slitless spectroscopic data from the Grism ACS Program for Extragalactic Science (GRAPES) project. The spatial extent of the emission is about 6 x 1.5 kpc (1'' x 0.''25). Combining our grism data and the broadband images from the Hubble Ultra Deep Field (UDF) images, we find a Lya line flux of ~2.2 x 10-17 ergs cm-2 s-1 and surface brightness ~7 x 10-17ergs cm-2 s-1 arcsec-2. The UDF images show diffuse continuum emission associated with UDF 5225, including three embedded knots. The morphology of UDF 5225 is highly suggestive of a galaxy in assembly. It is possible that the prominent Lya emission from this object is due to an active nucleus, and that we are seeing the simultaneous growth through accretion of a galaxy and its central black hole. Follow-up observations at higher spectral resolution could test this hypothesis.

Using early data from the Infrared Array Camera (IRAC) on the Spitzer Space Telescope, taken for the Great Observatories Origins Deep Survey (GOODS), we identify and study objects that are well detected at 3.6 mm but are very faint (and in some cases, invisible) in the Hubble Ultra Deep Field (HUDF) ACS and NICMOS images and in very deep VLT Ks-band imaging. We select a sample of 17 objects with fn(3.6 mm)/fn(z850) > 20. The analysis of their spectral energy distributions (SEDs) from 0.4 to 8.0 mm shows that the majority of these objects cannot be satisfactorily explained without a well-evolved stellar population. We find that most of them can be well fitted by a simple two-component model, where the primary component represents a massive, old population that dominates the strong IR emission, while the secondary component represents a low-amplitude, on-going star formation process that accounts for the weak optical fluxes. Their estimated photometric redshifts (zp) range from 1.6 to 2.9 with the median at zp = 2.4. For the simple star formation histories considered here, their corresponding stellar masses range from (0.1-1.6)x1011 M for a Chabrier initial mass function (IMF). Their median rest-frame Ks-band absolute magnitude is -22.9 mag in the AB system, or 1.5 x L*(K) for present-day elliptical galaxies. In the scenario of pure luminosity evolution, such objects may be direct progenitors for at least 14%-51% of the local population of early type galaxies. Because of the small cosmic volume of the HUDF, however, this simple estimate could be affected by other effects, such as cosmic variance and the strong clustering of massive galaxies. A full analysis of the entire GOODS area is now under way to assess such effects.

This article discusses a research done on the weak-link morphology and tensile behavior of wool and high-modulus polyethylene terephthalate (PET) in situ. Although the characterization is difficult for fiber structural weak-link, the complex method of the tensile behavior and the fracture-end morphology of the tensile behavior and the fracture-end morphology in situ of a fiber established in this present paper can be used effectively and accurately to identify the structure and properties of fiber structural weak-links. The weak structures of wool fibers are mainly the concentrated defects in fiber cross-section, weak neck, mechanical damage and dispersed flaws in a certain range, and have a high correlation with the tensile behavior and the morphological weak-link of the fiber. For the weak structure with dispersed flaws, the fluctuation on the end part of the specific stress strain curve, or the critical specific work of rupture should be considered as a judging rule. The breaking ends of PET fibers differ from those of wool fibers, and result in the linear crack and its propagation. The dispersed defects with a low interaction between the micro-structural elements can also develop into a fiber structural weak-link. The weak-link characteristics of PET fibers represent low stress, low strain and low work rupture.

The variance of fiber morphology along a fiber and the natural and artificial flaws in the fiber structure represent the primary reasons for the weak link of fibers. Accordingly, the fiber weak link can be divided into two types, that is, the geometrical thinnest part and the structural weak point. Scanning electron microscopic observation was used to characterize the morphological features of the fiber weak points whose forms are the normal thin sections, natural flaws, and artificial damage. Both the fiber profile morphology and the tensile behavior of wool fibers have been measured using a single-fiber analyzer (SIFAN) and an optical microscope with a CCD camera plus an XQ-1 fiber tensile tester (OM + XQ). The results from the SIFAN and OM+XQ methods indicate that the fibers breaking at their minimum diameters represent only one part of the broken fibers. The percentage of this kind of breakage is in the range of 40–60%. A new approach is presented to identify the weak-point breakage relying on the fiber tensile behavior. The experimental results show that the probabilities of weak-point, normal, and thinnest-part breakage evaluated by these methods approximate 40, 60, and slightly more than 80%, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1206–1212, 2003

The Chandra Deep Field-South (CDF-S) 1 Ms exposure produced a catalog of 346 X-ray sources, of which 59 were not visible on the Very Large Telescope (VLT)/FORS1 and the ESO-MPI/WFI deep R-band images to a limit of Rvega = 26.1-26.7 mag. Using the first release of the ESO VLT/ISAAC JHKs data on the CDF-S, we identified six of the 12 such objects that were within the coverage of these IR observations. The VLT/FORS1 I-band data further confirm that five of these six objects are undetected in the optical. The photometric properties of these six counterparts are compared against those of the optically brighter counterparts of Chandra sources in the same field. We found that the location of these optically brighter Chandra sources in the near-IR color space was bifurcated, with the color of one branch being consistent with that of E/S0 galaxies at 0 [?] z [?] 1.5, and the other branch being consistent with that of unreddened active galactic nuclei/quasi-stellar objects (AGNs/QSOs) at 0 [?] z [?] 3.5. The six counterparts that we identified seemed to lie on the E/S0 branch and its extension, suggesting that these X-ray source hosts are mostly luminous E/S0 galaxies (MV ~ -20 mag in the AB system) at 1 [?] z [?] 2.5. On the other hand, some of them can also be explained by AGNs/QSOs over a wide redshift range (0 [?] z [?] 5), if a range of internal extinction (AV = 0-1 mag) is allowed. However, the later interpretation requires fine-tuning extinction together with redshift for these objects individually. If they are indeed AGNs/QSOs, the most luminous of them is just barely qualified for being a QSO. Finally, we point out that neither high-redshift (z > 5) star-forming galaxies nor irregular galaxies at lower redshift can be a viable explanation to the nature of these six counterparts.

Systematic surveys are being proposed to discover a significant number of galaxies at z [?] 6, which is now suggested as the epoch at which the reionization era of the universe ends. To plan such surveys, we need a reasonable expectation of the surface density of high-redshift galaxies at different flux limits. Here we present a simple prediction of the surface density of 5.5 [?] z [?] 6.5 galaxies in the optical regime, extrapolating from what is already known about galaxies at z [?] 3. This prediction is consistent with the results of nearly all known searches for objects at z [?] 6, giving confidence that we may use it to plan optimal combination of survey depth and sky coverage in searching for such objects. We suggest that the most efficient strategy with existing ground-based facilities is to do medium-depth (mAB [?] 24.0-24.5 mag), wide-field (a couple of square degrees) survey using a wide-field camera at a 4 m class telescope. As the predicted surface density at this brightness level is very sensitive to the value of L*, the result of such a survey can be easily used to constrain the luminosity evolution from z [?] 3 to 6.

In this paper, we propose a new method for measuring fabric wrinkling based on integrating photometric stereo and image analysis techniques. In the traditional method. wrinkled fabrics are evaluated subjectively according to the grades of replica plates supplied by the American Association of Textile Chemists and Colorists (AATCC). But due to the disadvantages of subjective methods. which are tedious, time-consuming, subjective, and so on. image analysis techniques are used in this work as an objective method. However, serious problem occur when colored and patterned fabrics are tested with conventional images and processing techniques, although they work for tests of solid fabrics. In this paper, a photometric stereo method is used to extract three-dimensional surfaces of fabrics and successfully eliminate the influence of color and pattern. Image analysis techniques are furthered to extract wrinkling features of these reconstructed 3D images, and there is a good linear correlation between objective parameters and subjective AATCC grades.

The influence of repeated freeze–thawing on pore structural characteristics and physical properties of porous silk fibroin materials prepared by freeze drying were studied. It showed that when quick‐frozen silk fibroin solution was repeatedly thawed and frozen before being vacuum dried, thus pore size of prepared porous silk fibroin materials increased from 67 µm to about 120 µm, and pore density decreased from 80 per square millimeter to about 28 per square millimeter; at the same time compression ratio and moisture permeability increased from 22.7% and 230 g/m2hr to about 33.7% and 308 g/m2hr, respectively, tensile strength and dissolvability in hot water decreased from 20.2 N/cm2and 42.7% to about 12.5 N/cm2and 26.1%, respectively. Both the times of repeated thawing and the thawing temperature had a certain influence on the above‐mentioned pore characteristic parameters and physical properties. Copyright © 2001 John Wiley & Sons, Ltd.

Porous silk fibroin materials, with average pore size 10 ~ 300 μm, pore density 1 ~ 2000/mm², and porosity 35 ~ 70%, were prepared by freeze drying aqueous solution of silk fibroin obtained by dissolving silk fibroin in ternary solvent CaCl2 · CH3CH2OH · H2O. Pore size distribution of such materials mostly accorded with logarithmic normal distribution. It is possible to control the aforementioned structural parameters and the physical properties of moisture permeability, compressibility, strength, elongation, etc., by adjusting freezing temperature and concentration of silk fibroin solution. Above glass transition zone (−34 ~ −20°C) of silk fibroin, the freezing temperature has more significant effect on the structure and properties of porous silk fibroin materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2192–2199, 2001

Silk fibroin solution was prepared by dissolving the silk fibroin in triad solvent CaCl2 · CH3CH2OH · H2O. In this article we tested and analyzed the state of frozen silk fibroin solution and fine structure of freeze dried porous silk fibroin materials. The results indicated that the glass transition temperature of frozen silk fibroin solution ranges from −34 to −20°C, and the initial melting temperature of ice in frozen solution is about −8.5°C. When porous silk fibroin materials are prepared by means of freeze drying, if freezing temperature is below −20°C, the structure of silk fibroin is mainly amorphous with a little silk II crystal structure, and if freezing temperature is above −20°C, quite a lot of silk I crystal structure forms. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2185–2191, 2001

We describe in detail the extinction correction procedures used for the Beijing-Arizona-Taiwan-Connecticut Sky Survey (BATC Survey). The survey covers the spectral range 3200-9900 ? by utilizing a set of 15 intermediate-band filters. These filters are specifically designed to exclude most of the bright and variable night-sky emission lines. We also present extinction coefficients for the filter passbands for typical photometric nights at the Xinglong Observing Station, Beijing Astronomical Observatory (where the observations of the survey are being carried out). Time-dependent, low-amplitude (?1%), nightly extinction variation has been observed. Such variation is demonstrably independent of filter bandpass and air mass, with amplitudes ranging from ?0.01 to ?0.03 mag. The variation is plausibly caused by slowly varying (at ?1%) atmospheric extinction, possibly related to changes in air pressure/temperature/humidity that occur during the night. An iterative fitting scheme has been developed to take this time-varying component into account. We conclude that the survey can achieve its stated observational goal, namely, an absolute photometric calibration that is tied to the AB?system to an accuracy of 1% in all filters.

In the paper, the influence of temperature on PU asymmetric mem branes was investigated. The expermental results showed that the microstructure and physical properties of PU films containing various additives are appreciably affected by changing the temperature of the condensation bath. A possible mecharusm for these findings is also explained.

Application of polyurethanes (PU) is extending into various fields, such as artificial leather, microfiltration, moisture-permeable water-proof material, and osmosis membranes. The polyurethane coated films are a porous material with dense surface backed by a porous substructure; they possess an excellent adsorption and permeability, a useful strength and toughness. These properties are closely related with their microstructure. The microstructure of PU film may be altered dur ing its formation. The investigation of the formation mechanism of microstructure of leather type PU films made from different PU/DMF/additive systems is reported in this paper. The microstructure of the different PU films is also elucidated and ana lysed on the triangular phase diagram consisting of PU/DMF/H2O additive system and precipitation values.