Comments on the global constraints in light-cone string and membrane theories

In the light-cone closed string and toroidal membrane theories, we associate the global constraints with gauge symmetries. In the closed string case, we show that the physical states defined by the BRS charge satisfy the level-matching condition. In the toroidal membrane case, we show that the Faddeev-Popov ghost and anti-ghost corresponding to the global constraints are essentially free even if we adopt any gauge fixing condition for the local constraint. We discuss the quantum double-dimensional reduction of the wrapped supermembrane with the global constraints.Comment: 12 pages, typos corrected, to appear in JHE

The role of mesoscale hydrography on microbial dynamics in the northeast Atlantic: Results of a spring bloom experiment

During RV Meteor cruise No. 10 from May to June 1989 (JGOFS pilot study) bacterial and picocyanobacterial abundance, biomass, and bacterial production were estimated at two drift stations close to 47N, 20W and 58N, 20W in the northeast Atlantic. At 47N two different mesoscale hydrographic structures were sampled which divided the drift experiment into a cyclonic and an anticyclonic circulation phase. Transition from one phase to the next was clearly reflected by changes of the biological structure in the upper water column. Phytoplankton stocks maintained during the cyclonic phase were about 1.8 times higher than those of the anticyclonic phase (1552 mg C m−2 and 880 mg C m−2, resp., integrated over the mixed layer, Deckers, 1991). Integrated stocks of bacteria showed an opposite pattern of distribution. Picocyanobacterial biomass (PCB) was 3.4 times higher during the anticyclonic phase than during the cyclonic phase (96 mg C m−2 and 28 mg C m−2, resp.), and the respective factor for total bacterial biomass (TBB) was 3.7 (830 mg C m−2 and 225 mg C m−2, resp.). Our analysis indicates that the combined bacterial biomass dominated within the mixed layer during the anticyclonic phase, while the cyclonic phase was clearly dominated by eucaryotic phytoplankton. Additional evidence for a shift of biology toward the microbial food web was indicated by a strong increase of bacteria during the anticyclonic phase. Thus, simultaneously and side by side, an autotrophic and a heterotrophic system were supported by the prevailing hydrographic conditions. At 58N within an anticyclonic mesoscale hydrographic structure the phytoplankton bloom was at a developing stage, characterized by low biomass (730 mg C m−2 in the mixed layer, Deckers, 1991) but relatively high primary production. In contrast, bacterial stocks were quite high, but bacterial production was low in comparison to the anticyclonic phase at 47N (90 mg C m−2 d−1 and 153 mg C m−2 d−1, resp., integrated from 0–300 m). It was calculated that bacterial gross production averaged 42% (47N, anticyclonic phase) and 25% (58N) of primary production. These results suggest that within a specific type of hydrographic structure either a heterotrophic or an autotrophic system can be established, depending on the stage of bloom development. In conclusion: Depending on their origin and age, mesoscale hydrographic structures can be correlated with different stages of biological development. This leads to the mesoscale patchiness of biological measurements, which is a characteristic feature of the northeast Atlantic

Fractionation of sulfur isotopes during heterogeneous oxidation of SO₂ on sea salt aerosol: a new tool to investigate non-sea salt sulfate production in the marine boundary layer

The oxidation of SO₂ to sulfate on sea salt aerosols in the marine environment is highly important because of its effect on the size distribution of sulfate and the potential for new particle nucleation from H₂SO₄ (g). However, models of the sulfur cycle are not currently able to account for the complex relationship between particle size, alkalinity, oxidation pathway and rate – which is critical as SO₂ oxidation by O₃ and Cl catalysis are limited by aerosol alkalinity, whereas oxidation by hypohalous acids and transition metal ions can continue at low pH once alkalinity is titrated. We have measured ³⁴S/³²S fractionation factors for SO₂ oxidation in sea salt, pure water and NaOCl aerosol, as well as the pH dependency of fractionation. <br><br> Oxidation of SO₂ by NaOCl aerosol was extremely efficient, with a reactive uptake coefficient of ≈0.5, and produced sulfate that was enriched in ³²S with &alpha;_OCl = 0.9882±0.0036 at 19 °C. Oxidation on sea salt aerosol was much less efficient than on NaOCl aerosol, suggesting alkalinity was already exhausted on the short timescale of the experiments. Measurements at pH = 2.1 and 7.2 were used to calculate fractionation factors for each step from SO₂(g) → multiple steps → SO_OCl^2&minus;. Oxidation on sea salt aerosol resulted in a lower fractionation factor than expected for oxidation of SO₃^2&minus; by O₃ (&alpha;_seasalt = 1.0124±0.0017 at 19 °C). Comparison of the lower fractionation during oxidation on sea salt aerosol to the fractionation factor for high pH oxidation shows HOCl contributed 29% of S(IV) oxidation on sea salt in the short experimental timescale, highlighting the potential importance of hypohalous acids in the marine environment. <br><br> The sulfur isotope fractionation factors measured in this study allow differentiation between the alkalinity-limited pathways – oxidation by O₃ and by Cl catalysis (&alpha;₃₄ = 1.0163&plusmn;0.0018 at 19 °C in pure water or 1.0199&plusmn;0.0024 at pH = 7.2) – which favour the heavy isotope, and the alkalinity non-limited pathways – oxidation by transition metal catalysis (&alpha;₃₄ = 0.9905±0.0031 at 19 °C, Harris et al., 2012a) and by hypohalites (&alpha;₃₄ = 0.9882±0.0036 at 19 °C) – which favour the light isotope. In combination with field measurements of the oxygen and sulfur isotopic composition of SO₂ and sulfate, the fractionation factors presented in this paper may be capable of constraining the relative importance of different oxidation pathways in the marine boundary layer

On a Matrix Model of Level Structure

We generalize the dimensionally reduced Yang-Mills matrix model by adding d=1 Chern-Simons term and terms for a bosonic vector. The coefficient, \kappa of the Chern-Simons term must be integer, and hence the level structure. We show at the bottom of the Yang-Mills potential, the low energy limit, only the linear motion is allowed for D0 particles. Namely all the particles align themselves on a single straight line subject to \kappa^2/r^2 repulsive potential from each other. We argue the relevant brane configuration to be D0-branes in a D4 after \kappa of D8's pass the system.Comment: 1+6 pages, No figure, LaTeX; Minor changes; To appear in Class. Quant. Gra

A INFLUÊNCIA DA LEGISLAÇÃO URBANA NA ILUMINAÇÃO NATURAL DE EDIFÍCIOS: UM ESTUDO DE CASO EM DOMINGOS MARTINS - ES

A crise no âmbito social, econômico e ambiental têm apontado para a necessidade de se buscar práticas mais sustentáveis no processo de projeto e planejamento urbano. No que tange aos aspectos ambientais, a busca pela eficiência energética nas edificações, associada à adoção de estratégias bioclimáticas no projeto, mostra-se como uma forma adequada para se atingir parte desse objetivo. Nesse sentido, a iluminação natural desempenha um importante papel visto que o seu aproveitamento contribui para o conforto ambiental e redução no consumo de energia elétrica. Entretanto, a disponibilidade de luz natural no ambiente interno depende, dentre outros fatores, da geometria urbana, sendo esta normalmente resultante dos parâmetros estabelecidos pelas regulamentações urbanas. Sendo assim, o objetivo principal desta pesquisa é investigar a influência da legislação urbana, por meio de seus principais parâmetros urbanísticos, na disponibilidade de iluminação natural no ambiente interno, adotando como objeto de estudo a cidade de Domingos Martins ES. A principal estratégia para obtenção dos dados foram as simulações computacionais no programa Troplux, adotando-se três tipos de céu padrão da CIE (3, 7 e 12). A pesquisa dividiu-se em duas etapas, sendo que na primeira buscou-se verificar a adequabilidade da legislação vigente e da legislação anterior tendo como base a ocupação urbana existente; e na segunda fase, analisou-se a interferência dos parâmetros largura da via, altura das edificações e afastamento lateral, tendo em vista as áreas de expansão urbana e futuros loteamentos. A partir dos resultados, pôde-se constatar que apesar de não ter sido considerada nenhuma metodologia específica relacionada ao conforto ambiental na elaboração da atual regulamentação urbana de Domingos Martins-ES, o Plano Diretor Municipal, por meio do estabelecimento de parâmetros urbanos mais restritivos, contribui com o aumento da disponibilidade de iluminação natural no ambiente interno. Adicionalmente, percebeu-se também que o Código de Obras, regulamentação que vigorava até a aprovação do PDM e que propunha índices mais permissivos, não era pernicioso em relação ao potencial de aproveitamento da luz natural no interior das edificações. Pôde-se constatar, inclusive, que, dentre os parâmetros urbanos analisados, a altura das edificações obstruidoras é o índice que exerce maior influência para a variação dos níveis lumínicos e dos percentuais de UDI, entretanto, o efeito das obstruções pode ser minorado mediante a adoção de uma maior largura de via, reforçando a relevância da vinculação entre a altura das edificações e afastamentos entre as mesmas. Além disso, confirmou-se também a importância de se considerar as características climáticas de cada contexto e as orientações das vias e edificações na definição dos índices urbanísticos, visto que para cada tipo de céu e orientação uma determinada geometria urbana apresenta melhor desempenho para o aproveitamentos da luz natural. Palavras-chave: iluminação natural, legislação urbana, simulação computacional

A Rapid Method for Observing the Internal Morphology of Amphibian Embryos

A simple, rapid method for visualizing the internal morphology of amphibian embryos is described. Fixed embryos of Ambystoma mexicanum are surrounded with commercial embedding material and are frozen. Internal structure is revealed by cutting the embryos with a cooled scalpel or razor blade, removing the frozen embedment with an aqueous buffer, and processing the halved embryos for scanning electron microscopy (SEM). This technique allows the internal anatomy of the embryo to be viewed but is much simpler and more rapid than previously described techniques. It should therefore prove useful for understanding and teaching the three-dimensional relationship between tissues in developing embryos. In addition, we believe that this technique could be used, with minor changes, as a rapid method for viewing the internal morphology of a variety of specimens

Detection of very-high-energy gamma-ray emission from the vicinity of PSR B1706-44 with H.E.S.S

The energetic pulsar PSR B1706-44 and the adjacent supernova remnant (SNR) candidate G 343.1-2.3 were observed by H.E.S.S. during a dedicated observational campaign in 2007. A new source of very-high-energy (VHE; E > 100 GeV) gamma-ray emission, HESS J1708-443, was discovered with its centroid at RA(J2000) = 17h08m10s and Dec(J2000) = -44d21', with a statistical error of 3 arcmin on each axis. The VHE gamma-ray source is significantly more extended than the H.E.S.S. point-spread function, with an intrinsic Gaussian width of 0.29 +/- 0.04 deg. Its energy spectrum can be described by a power law with a photon index Gamma = 2.0 +/- 0.1 (stat) +/- 0.2 (sys). The integral flux measured between 1-10 TeV is ~17% of the Crab Nebula flux in the same energy range. The possible associations with PSR B1706-44 and SNR G343.1-2.3 are discussed.Comment: 4+ pages, 2 figures; v1 submitted to ICRC Proceedings on 15 May 2009; v2 has additional references and minor change

The nucleus pulposus microenvironment in the intervertebral disc: the fountain of youth?

The intervertebral disc (IVD) is a complex tissue, and its degeneration remains a problem for patients, without significant improvement in treatment strategies. This mostly age-related disease predominantly affects the nucleus pulposus (NP), the central region of the IVD. The NP tissue, and especially its microenvironment, exhibit changes that may be involved at the outset or affect the progression of IVD pathology. The NP tissue microenvironment is unique and can be defined by a variety of specific factors and components characteristic of its physiology and function. NP progenitor cell interactions with their surrounding microenvironment may be a key factor for the regulation of cellular metabolism, phenotype, and stemness. Recently, celltransplantation approaches have been investigated for the treatment of degenerative disc disease, highlighting the need to better understand if and how transplanted cells can give rise to healthy NP tissue. Hence, understanding all the components of the NP microenvironment seems to be critical to better gauge the success and outcomes of approaches for tissue engineering and future clinical applications. Knowledge about the components of the NP microenvironment, how NP progenitor cells interact with them, and how changes in their surroundings can alter their function is summarised. Recent discoveries in NP tissue engineering linked to the microenvironment are also reviewed, meaning how crosstalk within the microenvironment can be adjusted to promote NP regeneration. Associated clinical problems are also considered, connecting bench-to-bedside in the context of IVD degeneration