Designing building skins

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1992.Includes bibliographical references (p. 55).This thesis involves framing criteria and discerning issues to be considered in the design of building skins in an urban environment. The 'information age' has paradoxically seen the demise of the facade as an important signifier of cultural meaning. Homogeneous and minimally articulated skins have become silent and passive masks, creating anonymous and unresponsive urban environments. In contrast, the decorated facades of post-modem architecture have failed to address questions of meaning and representation in a serious and satisfactory way. Perhaps the problem is not solely one of economic constraints and misguided construction practices, but a lack of understanding and evaluation of the role of the skin, both as an architectural element, and as a social and cultural phenomenon. This thesis will use the ethnographic theories of Gottfried Semper as a basis for establishing themes that have persisted in the understanding and construction of closure elements since the earliest shelters of man. The issue of transparency and spatial depth will then be addressed as a modem social and architectural dilemma, inseparable from the problem of designing building facades. Thirdly, this thesis will be concerned with skins that have a high degree of operability, allowing them to adapt to a dynamic and ever changing environment. The vehicle for exploring the problem of building skins will be the design of a market building in the Haymarket area of Boston.by Arjun Desai.M.Arch

Ultrasound-Guided Popliteal Nerve Block in a Patient with Malignant Degeneration of Neurofibromatosis 1

A 41-year-old female patient with neurofibromatosis 1 presented with new neurologic deficits secondary to malignant degeneration of a tibial lesion. Ultrasound mapping of the popliteal nerve revealed changes consistent with an intraneural neurofibroma. Successful popliteal nerve blockade was achieved under ultrasound guidance

The Spectral Energy Distribution and Infrared Luminosities of z ≈ 2 Dust-obscured Galaxies from Herschel and Spitzer

Dust-obscured galaxies (DOGs) are a subset of high-redshift (z ≈ 2) optically-faint ultra-luminous infrared galaxies (ULIRGs, e.g., L_(IR) > 10^(12) L_☉). We present new far-infrared photometry, at 250, 350, and 500 μm (observed-frame), from the Herschel Space Telescope for a large sample of 113 DOGs with spectroscopically measured redshifts. Approximately 60% of the sample are detected in the far-IR. The Herschel photometry allows the first robust determinations of the total infrared luminosities of a large sample of DOGs, confirming their high IR luminosities, which range from 10^(11.6) L_☉ 10^(13) L_☉. The rest-frame near-IR (1-3 μm) spectral energy distributions (SEDs) of the Herschel-detected DOGs are predictors of their SEDs at longer wavelengths. DOGs with "power-law" SEDs in the rest-frame near-IR show observed-frame 250/24 μm flux density ratios similar to the QSO-like local ULIRG, Mrk 231. DOGs with a stellar "bump" in their rest-frame near-IR show observed-frame 250/24 μm flux density ratios similar to local star-bursting ULIRGs like NGC 6240. None show 250/24 μm flux density ratios similar to extreme local ULIRG, Arp 220; though three show 350/24 μm flux density ratios similar to Arp 220. For the Herschel-detected DOGs, accurate estimates (within ~25%) of total IR luminosity can be predicted from their rest-frame mid-IR data alone (e.g., from Spitzer observed-frame 24 μm luminosities). Herschel-detected DOGs tend to have a high ratio of infrared luminosity to rest-frame 8 μm luminosity (the IR8 = L_(IR)(8-1000 μm)/νL_ν(8 μm) parameter of Elbaz et al.). Instead of lying on the z = 1-2 "infrared main sequence" of star-forming galaxies (like typical LIRGs and ULIRGs at those epochs) the DOGs, especially large fractions of the bump sources, tend to lie in the starburst sequence. While, Herschel-detected DOGs are similar to scaled up versions of local ULIRGs in terms of 250/24 μm flux density ratio, and IR8, they tend to have cooler far-IR dust temperatures (20-40 K for DOGs versus 40-50 K for local ULIRGs) as measured by the rest-frame 80/115 μm flux density ratios (e.g., observed-frame 250/350 μm ratios at z = 2). DOGs that are not detected by Herschel appear to have lower observed-frame 250/24 μm ratios than the detected sample, either because of warmer dust temperatures, lower IR luminosities, or both

Thermally Comfortable Affordable Housing: A Study on Residential Building Code In India

On an average, India has more than 3000 Cooling Degree Days (CDD). The multifamily public housing being constructed under India’s Prime Minister Awas Yojana (PMAY) is aimed at providing formal housing to the society’s Economic Weaker Section (EWS). It is essential that this housing delivers thermally comfortable in-doors to the occupants. This study mapped the design and construction practices followed under PMAY Urban (PMAY-U) against India’s Residential Energy Building Code, Eco Niwas Samhita (ENS). The metric prescribed in ENS is Residential Envelope Transmittance Value (RETV). For 80 PMAY-U projects, information related to spatial design, and walling assemblies was collated. 30 projects were short-listed for detailed analysis. The RETV for selected projects was calculated. The analysis demonstrated that walling assemblies and technologies having a lower thermal transmittance value (U-value) resulted in meeting the ENS prescribed RETV numbers, hence, code compliance. The study further extended to assess the energy performance of the housing unit by exploring the change in walling assemblies. The change in thermally comfortable hours were reported in the range of 4145 and 6034, and Energy Performance Index (EPI) of the dwelling units were reported between 64 and 68 kWh/m2/year for the various walling assemblies

High-Redshift Dust Obscured Galaxies: A Morphology-Spectral Energy Distribution Connection Revealed by Keck Adaptive Optics

A simple optical to mid-IR color selection, R – [24]>14, i.e., f_ν(24 μm)/f_ν(R) ≳ 1000, identifies highly dust obscured galaxies (DOGs) with typical redshifts of z ~ 2 ± 0.5. Extreme mid-IR luminosities (L_(IR) > 10^(12-14)) suggest that DOGs are powered by a combination of active galactic nuclei (AGNs) and star formation, possibly driven by mergers. In an effort to compare their photometric properties with their rest-frame optical morphologies, we obtained high-spatial resolution (0."05-0."1) Keck Adaptive Optics K'-band images of 15 DOGs. The images reveal a wide range of morphologies, including small exponential disks (eight of 15), small ellipticals (four of 15), and unresolved sources (two of 15). One particularly diffuse source could not be classified because of low signal-to-noise ratio. We find a statistically significant correlation between galaxy concentration and mid-IR luminosity, with the most luminous DOGs exhibiting higher concentration and smaller physical size. DOGs with high concentration also tend to have spectral energy distributions (SEDs) suggestive of AGN activity. Thus, central AGN light may be biasing the morphologies of the more luminous DOGs to higher concentration. Conversely, more diffuse DOGs tend to show an SED shape suggestive of star formation. Two of 15 in the sample show multiple resolved components with separations of ~1 kpc, circumstantial evidence for ongoing mergers

The Star Formation Histories of z ~ 2 Dust-obscured Galaxies and Submillimeter-selected Galaxies

The Spitzer Space Telescope has identified a population of ultraluminous infrared galaxies (ULIRGs) at z ~ 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses (M_*) of two populations of Spitzer-selected ULIRGs that have extremely red R – [24] colors (dust-obscured galaxies, or DOGs) and compare our results with submillimeter-selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-infrared (mid-IR) spectral energy distribution (SED) at rest frame 1.6 μm associated with stellar emission ("bump DOGs"), while the other set of 51 DOGs have power-law mid-IR SEDs that are typical of obscured active galactic nuclei ("power-law DOGs"). We measure M_* by applying Charlot & Bruzual stellar population synthesis models to broadband photometry in the rest-frame ultraviolet, optical, and near-infrared of each of these populations. Assuming a simple stellar population and a Chabrier initial mass function, we find that power-law DOGs and bump DOGs are on average a factor of 2 and 1.5 more massive than SMGs, respectively (median and inter-quartile M_* values for SMGs, bump DOGs, and power-law DOGs are log(M_*/M_☉) = 10.42^(+0.42)_(–0.36), 10.62^(+0.36)_(–0.32), and 10.71^(+0.40)_(–0.34), respectively). More realistic star formation histories drawn from two competing theories for the nature of ULIRGs at z ~ 2 (major merger versus smooth accretion) can increase these mass estimates by up to 0.5 dex. A comparison of our stellar masses with the instantaneous star formation rate (SFR) in these z ~ 2 ULIRGs provides a preliminary indication supporting high SFRs for a given M_*, a situation that arises more naturally in major mergers than in smooth accretion-powered systems

CO J=2-1 line emission in cluster galaxies at z~1: fueling star formation in dense environments

We present observations of CO J=2-1 line emission in infrared-luminous cluster galaxies at z~1 using the IRAM Plateau de Bure Interferometer. Our two primary targets are optically faint, dust-obscured galaxies (DOGs) found to lie within 2 Mpc of the centers of two massive (>10^14 Msun) galaxy clusters. CO line emission is not detected in either DOG. We calculate 3-sigma upper limits to the CO J=2-1 line luminosities, L'_CO < 6.08x10^9 and < 6.63x10^9 K km/s pc^2. Assuming a CO-to-H_2 conversion factor derived for ultraluminous infrared galaxies in the local Universe, this translates to limits on the cold molecular gas mass of M_H_2 < 4.86x10^9 Msun and M_H_2 < 5.30x10^9 Msun. Both DOGs exhibit mid-infrared continuum emission that follows a power-law, suggesting that an AGN contributes to the dust heating. As such, estimates of the star formation efficiencies in these DOGs are uncertain. A third cluster member with an infrared luminosity, L_IR < 7.4x10^11 Lsun, is serendipitously detected in CO J=2-1 line emission in the field of one of the DOGs located roughly two virial radii away from the cluster center. The optical spectrum of this object suggests that it is likely an obscured AGN, and the measured CO line luminosity is L'_CO = (1.94 +/- 0.35)x10^10 K km/s pc^2, which leads to an estimated cold molecular gas mass M_H_2 = (1.55+/-0.28)x10^10 Msun. A significant reservoir of molecular gas in a z~1 galaxy located away from the cluster center demonstrates that the fuel can exist to drive an increase in star-formation and AGN activity at the outskirts of high-redshift clusters.Comment: 22 pages, 4 figures; accepted for publication in Ap

Clustering of Dust-Obscured Galaxies at z ~ 2

We present the angular autocorrelation function of 2603 dust-obscured galaxies (DOGs) in the Bootes field of the NOAO Deep Wide-Field Survey. DOGs are red, obscured galaxies, defined as having R-[24] \ge 14 (F_24/F_R \ga 1000). Spectroscopy indicates that they are located at 1.5 \la z \la 2.5. We find strong clustering, with r_0 = 7.40^{+1.27}_{-0.84} Mpc/h for the full F_24 > 0.3 mJy sample. The clustering and space density of the DOGs are consistent with those of submillimeter galaxies, suggestive of a connection between these populations. We find evidence for luminosity-dependent clustering, with the correlation length increasing to r_0 = 12.97^{+4.26}_{-2.64} Mpc/h for brighter (F_24 > 0.6 mJy) DOGs. Bright DOGs also reside in richer environments than fainter ones, suggesting these subsamples may not be drawn from the same parent population. The clustering amplitudes imply average halo masses of log M = 12.2^{+0.3}_{-0.2} Msun for the full DOG sample, rising to log M = 13.0^{+0.4}_{-0.3} Msun for brighter DOGs. In a biased structure formation scenario, the full DOG sample will, on average, evolve into ~ 3 L* present-day galaxies, whereas the most luminous DOGs may evolve into brightest cluster galaxies.Comment: ApJL in press; 4 pages, 3 figures, 1 tabl

Spitzer Mid-Infrared Spectroscopy of 70um-Selected Distant Luminous Infrared Galaxies

We present mid-infrared spectroscopy obtained with the Spitzer Space Telescope of a sample of 11 optically faint, infrared luminous galaxies selected from a Spitzer MIPS 70um imaging survey of the NDWFS Bootes field. These are the first Spitzer IRS spectra presented of distant 70um-selected sources. All the galaxies lie at redshifts 0.3<z<1.3 and have very large infrared luminosities of L_IR~ 0.1-17 x 10^12 solar luminosities. Seven of the galaxies exhibit strong emission features attributed to polycyclic aromatic hydrocarbons (PAHs). The average IRS spectrum of these sources is characteristic of classical starburst galaxies, but with much larger infrared luminosities. The PAH luminosities of L(7.7) ~ 0.4 - 7 x 10^11 solar luminosities imply star formation rates of ~ 40 - 720 solar masses per year. Four of the galaxies show deep 9.7um silicate absorption features and no significant PAH emission features (6.2um equivalent widths < 0.03um). The large infrared luminosities and low f70/f24 flux density ratios suggests that these sources have AGN as the dominant origin of their large mid-infrared luminosities, although deeply embedded but luminous starbursts cannot be ruled out. If the absorbed sources are AGN-dominated, a significant fraction of all far-infrared bright, optically faint sources may be dominated by AGN.Comment: 8 Pages, ApJ accepte