10,000 publications from this institution
Experimental manipulations of fish in a Northern California river during summer base flow reveal that they have large effects on predators, herbivores, and plants in river food webs. California roach and juvenile steelhead consume predatory insects and fish fry, which feed on algivorous chironomid larvae. In the presence of fish, filamentous green algae are reduced to low, prostrate webs, infested with chironomids. When the absence of large fish releases smaller predators that suppress chironomids, algal biomass is higher, and tall upright algal turfs become covered with diatoms and cyanobacteria. These manipulations provide evidence that the Hairston, Smith, Slobodkin–Fretwell theory of trophic control, which predicts that plants will be alternately limited by resources or herbivores in food webs with odd and even numbers of trophic levels, has application to river communitics.
A molecular beam surface scattering apparatus designed for the study of corrosion and catalytic surface reactions is described. The apparatus incorporates two molecular or atomic beams aimed at a surface characterized by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES), a rotatable, differentially pumped quadrupole mass spectrometer, and a versatile manipulator. Angular distributions and energy distributions as a function of angle and independent of the surface residence time can be measured. Typical data for the oxidation of deuterium to D2O on a Pt(111) crystal surface are presented.
Form follows function . . . has been misunderstood. Form and function should be one, joined in a spiritual union.Frank Lloyd Wright, protégé of Louis Henri Sullivan and architect
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
This article spotlights four transversal principles that animate Pierre Bourdieu’s research practice and can fruitfully guide inquiry on any empirical front: the Bachelardian imperative of epistemological rupture and vigilance; the Weberian command to effect the triple historicization of the agent (habitus), the world (social space, of which field is but a subtype), and the categories of the analyst (epistemic reflexivity); the Leibnizian–Durkheimian invitation to deploy the topological mode of reasoning to track the mutual correspondences between symbolic space, social space, and physical space; and the Cassirer moment urging us to recognize the constitutive efficacy of symbolic structures. I also flag three traps that Bourdieusian explorers of the social world should exercise special care to avoid: the fetishization of concepts, the seductions of “speaking Bourdieuse” while failing to carry out the research operations Bourdieu’s notions stipulate, and the forced imposition of his theoretical framework en bloc when it is more productively used in kit through transposition. These principles guiding the construction of the object are not theoretical slogans but practical blueprints for anthropological inquiry. This implies that mimesis and not exegesis should guide those social scientists who wish to build on, revise, or challenge the scientific machinery and legacy of Pierre Bourdieu.
ABSTRACTA positive correlation between massive red meat consumption with colorectal cancer had been reported. Given the complexity of meat components, we focused on investigating the role of Neu5Gc in human healthy. Two groups, either feeding with normal and overdose concentration of Neu5Gc for two weeks, to mimic the normal and overconsumption of red meat conditions in human, respectively. The colorectal transcriptomes revealed that Neu5Gc promotes intestinal immune response and identified the hub genes positively correlated with colorectal cancer such as Tnf, Cd19, Muc13, and Nso2,. The colorectal cancer patients have a 25–30% chance of developing liver metastases, thus we sequenced the liver and revealed the role of Neu5Gc in regulating cell metabolism. Moreover, we found that Neu5Gc negatively regulates the expression of Cmah. We conclude that high Neu5Gc intake promotes colorectal inflammatory responses in ApcMin/+ mice, and suppresses colorectal and hepatic metabolic and digestive processes through Cmah inhibition.
Ao assumir um papel central no governo pós-keynesiano da divisão racial e da pobreza, o crescente sistema carcerário tornou-se uma força preeminente na (re)for mação da raça e da cidadania nos Estados Unidos da América. Não só significa mas também reforça a negritude através da sua fusão prática da cor com criminalidade e violência desviada. Da mesma maneira que a escravatura resultou na "morte social" dos cativos africanos importados e dos seus descendentes, o encarceramento massivo dos Afro-Americanos induz a morte cívica daqueles que enreda através da sua exclusão do contrato social. Os reclusos são o alvo de um triplo movimento de fechamento excludente que lhes nega o acesso a capital cultural institucionalizado, que os afasta da redistribuição social e que os incapacita da participação politica. Os estatutos da privação criminal dos direitos de voto que proíbem este ultimo a quase 2 milhões de americanos (re)colocam-nos no papel histórico de antítese viva do "modelo americano". A estreita relação entre a retórica e a politica de expurgação politica dos condenados no fim do seculo e as da exclusão dos Negros em épocas mais remotas sugere que a negritude e mais bem compreendida como o crime cívico primevo da América, de acordo com a concepão durkheimiana do crime enquanto "um acto" que "ofende estados fortes da consciência colectiva" - neste caso, a representação idealizada que a América tem de si própria como a terra prometida da liberdade, da igualdade e da auto-determinação. Ao reactivar e ao actualizar a lógica da infâmia racializada, a excomunhão criminal lembra-nos que a divisão de casta e um traço constitutivo e não o teratológico do republicanismo americano. Da testemunho da compleição estratificada e restritiva da cidadania americana no limiar do novo milénio.
Antigenic stimulation of T cells gives rise to short-lived effector cells and long-lived memory cells. We used two stable isotope-labeling techniques to identify kinetically distinct subpopulations of T cells and to determine the effect of advanced infection with HIV-1. Long-term deuterated water ((2)H(2)O) incorporation into DNA demonstrated biphasic accrual of total and of memory/effector (m/e)–phenotype but not naive-phenotype T cells, consistent with the presence of short-lived and longer-lived subpopulations within the m/e-phenotype T cell pool. These results were mirrored by biphasic die-away kinetics in m/e- but not naive-phenotype T cells after short-term (2)H-glucose labeling. Persistent label retention was observed in a subset of m/e-phenotype T cells (presumably memory T cells), confirming the presence of T cells with very different life spans in humans. In advanced HIV-1 infection, much higher proportions of T cells were short-lived, compared to healthy controls. Effective long-term anti-retroviral therapy restored values to normal. These results provide the first quantitative evidence that long-lived and quiescent T cells do indeed predominate in the T cell pool in humans and determine T cell pool size, as in rodents. The greatest impact of advanced HIV-1 infection is to reduce the generation of long-lived, potential progenitor T cells.
We have located a T-cell receptor variable (V) delta gene segment immediately 3' of the delta constant (C) region gene and 5' to the known joining (J) alpha gene segments. This V delta gene is in the opposite transcriptional polarity to C delta and has rearranged to C delta by inversion in a gamma/delta-expressing hybridoma, DN7.3. This V delta gene is commonly rearranged in adult but not fetal gamma/delta-expressing thymocytes and has not been observed among alpha gene rearrangements reported to date. The reciprocal joining sequence isolated from this cell line contains N region nucleotides between the recombination signal sequences, in contrast to previously analyzed reciprocal joints. The results are discussed in the context of models accounting for ordered V gene usage during lymphocyte development.
Atypical femoral fractures (AFFs) have been well defined clinically and epidemiologically. Less clear are the underlying mechanisms responsible. This commentary points out the likely sources of decreased resistance to fracture using lessons from bone material studies and biomechanics. We hypothesize that the key element in the cascade of events leading to failure of the largest and strongest bone in the human body is long-term suppression of normal bone turnover caused by exposure to potent anti-remodeling agents, most notably the bisphosphonates (BPs). Suppressed bone turnover produces changes in bone that alter its material quality and these changes could lead to adverse effects on its mechanical function. At the submicroscopic [<1μm] level of collagen fibrils, suppression of bone turnover allows continued addition of non-enzymatic cross links that can reduce collagen's plasticity and this in turn contributes to reduced bone toughness. Further, adverse changes in hydroxyapatite crystalline structure and composition can occur, perhaps increasing collagen's brittleness. At the microscopic level [~1–500μm] of the bone-matrix structure, suppressed bone turnover allows full mineralization of cortical bone osteons and results in a microstructure of bone that is more homogeneous. Both brittleness and loss of heterogeneity allow greater progression of microscopic cracks that can occur with usual physical activity; in crack mechanical terms, normal mechanisms that dissipate crack tip growth energy are greatly reduced and crack progression is less impeded. Further, the targeted repair of cracks by newly activated BMUs appears to be preferentially suppressed by BPs. We further hypothesize that it is not necessary to have accumulation of many cracks to produce an AFF, just one that progresses — one that is not stopped by bone's several protective mechanisms and is allowed to penetrate through a homogeneous environment. The remarkable straight transverse fracture line is an indicator of the slow progression of a “mother crack” and the failure of usual mechanisms to bridge or deflect the crack. Research in AFF mechanisms has been focused at the organ level, describing the clinical presentation and radiologic appearance. Although today we have not yet connected all the dots in the pathophysiology of BP-induced AFF, recent advances in measuring bone mechanical qualities at the submicroscopic and tissue levels allow us to explain how spontaneous catastrophic failure of the femur can occur.
From a pedagogical point of view, the memristor is defined in this tutorial as any 2-terminal device obeying a state-dependent Ohm's law. This tutorial also shows that from an experimental point of view, the memristor can be defined as any 2-terminal device that exhibits the fingerprints of 'pinched' hysteresis loops in the v-i plane. It also shows that memristors endowed with a continuum of equilibrium states can be used as non-volatile analog memories. This tutorial shows that memristors span a much broader vista of complex phenomena and potential applications in many fields, including neurobiology. In particular, this tutorial presents toy memristors that can mimic the classic habituation and LTP learning phenomena. It also shows that sodium and potassium ion-channel memristors are the key to generating the action potential in the Hodgkin-Huxley equations, and that they are the key to resolving several unresolved anomalies associated with the Hodgkin-Huxley equations. This tutorial ends with an amazing new result derived from the new principle of local activity, which uncovers a minuscule life-enabling 'Goldilocks zone', dubbed the edge of chaos, where complex phenomena, including creativity and intelligence, may emerge. From an information processing perspective, this tutorial shows that synapses are locally-passive memristors, and that neurons are made of locally-active memristors.
