Semiclassical Mechanics of the Wigner 6j-Symbol

The semiclassical mechanics of the Wigner 6j-symbol is examined from the standpoint of WKB theory for multidimensional, integrable systems, to explore the geometrical issues surrounding the Ponzano-Regge formula. The relations among the methods of Roberts and others for deriving the Ponzano-Regge formula are discussed, and a new approach, based on the recoupling of four angular momenta, is presented. A generalization of the Yutsis-type of spin network is developed for this purpose. Special attention is devoted to symplectic reduction, the reduced phase space of the 6j-symbol (the 2-sphere of Kapovich and Millson), and the reduction of Poisson bracket expressions for semiclassical amplitudes. General principles for the semiclassical study of arbitrary spin networks are laid down; some of these were used in our recent derivation of the asymptotic formula for the Wigner 9j-symbol.Comment: 64 pages, 50 figure

Convective self-aggregation in numerical simulations: a review

Organized convection in the Tropics occurs across a range of spatial and temporal scales and strongly influences cloud cover and humidity. One mode of organization found is “self-aggregation”, in which moist convection spontaneously organizes into one or several isolated clusters despite spatially homogeneous boundary conditions and forcing. Self-aggregation is driven by interactions between clouds, moisture, radiation, surface fluxes, and circulation, and occurs in a wide variety of idealized simulations of radiative-convective equilibrium. Here we provide a review of convective self-aggregation in numerical simulations, including its character, causes, and effects. We describe the evolution of self-aggregation including its time and length scales and the physical mechanisms leading to its triggering and maintenance, and we also discuss possible links to climate and climate change

The Lunar Instrumentation for Subsurface Thermal Exploration with Rapidity (LISTER) on Blue Ghost Mission 1 to Mare Crisium. I. Pneumatic Excavation of Regolith

The Lunar Instrumentation for Subsurface Thermal Exploration with Rapidity (LISTER) is the first robotically deployed subsurface thermal probe that actively excavates lunar regolith and makes scientific measurements at multiple depths. It was deployed in Mare Crisium on Blue Ghost Mission 1 in 2025 March, reached 1 m depth, and measured the temperature and thermal conductivity of the regolith at eight different depths. The previous depth record for robotic in situ thermal measurements of the Moon was 8 cm. LISTER utilizes the pneumatic excavation technique, blowing a jet of pressurized nitrogen gas, as it pushes its thermal probe into the regolith. The gas expands rapidly in the lunar vacuum and lofts regolith clumps and clasts out of the hole. When the probe reaches one of the depths targeted for thermal measurements, LISTER stops blowing gas and pushes the probe into the yet-to-be-excavated bottom-hole regolith. It completes the necessary thermal measurements in 2 hr and then resumes excavation to the next targeted depth. LISTER detects obstacles on its way by monitoring the weight on bit (WOB). When the WOB exceeds a programmable threshold, LISTER attempts to dislodge the obstacle by automatically performing a piston-like vibratory movement (“dithering”), while it keeps blowing gas. Finally, video-monitoring the ejecta from LISTER’s excavation operations is useful in studying the stratigraphy of the regolith

Merchant-kings and Everymen: Narratives of the South Asian Diaspora of East Africa

The building of the Uganda railway at the turn of the nineteenth century brought about radical shifts in the notion of territory and the conception of time within East Africa. A sense of Indian Ocean continuity and cosmopolitanism signified by the pace of the dhow and the seaward perspective of coastal communities was substantially replaced by a new sense of time and territory determined by the speed of the train and the inland focus of colonial ambition. This paper explores this long moment of transition through a number of texts: the first year of the East African Standard (1902-03), the journal of Ebrahimji Noorbhai Adamji (1902-05) and three recent novels. These texts delineate the role of the South Asian diaspora in both the expansion of the colonial economy and the maintenance of an older sensibility. The founder of the African Standard, Alibhai Mulla Jeevanjee, held the contract for the recruitment of indentured labourers for the building of the railway and financed the establishment of Nairobi. While his newspaper displays complicity with colonial projects, it also reveals the disparity between the overtly expansive ideals and the narrowly national/racial aims of the empire. In Adamji's journal, the oscillation between the use of British time and Arbi - the Arabic Swahili system of time - is a notable imprecision that signifies the writer's position on a cusp between the world of coastal trade and life under colonial rule. Beneath the biographies of businessmen like Jeevanjee and Adamji, the history of the Asian presence in East Africa figures labourers, discarded wives, unsuccessful traders and children of mixed racial parentage: people whose position in the racial hierarchy of colonial East Africa becomes ever more obscure. The paper concludes by tracing the way in which three writers use the novel form to tell the relationship between class complicity and racial hierarchy which defined the Asian East African position during the period of British colonial rule

Prescription Opioid Injection Among HIV-Positive People Who Inject Drugs in a Canadian Setting

Prescription opioids (POs) are commonly prescribed to patients living with HIV/AIDS, while the illicit use of POs remains a major public health concern throughout Canada and the United States. We sought to identify the prevalence and correlates of PO injection among HIV-positive people who inject drugs (PWID) in Vancouver, Canada, where HIV/AIDS treatment and care is offered at no cost. We examined data from 634 individuals from an ongoing prospective cohort of HIV-positive PWID. Between December 2005 and November 2013, the median prevalence of recent PO injection was 24.2 % [interquartile range (IQR): 21.5–25.8 %]. In a multivariable generalized estimating equation model, Caucasian ethnicity, heroin injection, and drug dealing were positively associated with PO injection, while older age and methadone maintenance treatment were negatively associated with PO injection (all p < 0.05). Engagement on antiretroviral therapy was inversely associated with PO injection in a bivariable analysis, but did not remain significant after adjusting for heroin injection. These findings describe a particularly vulnerable sub-group of PWID who may benefit from targeted efforts to both minimize drug-related risk behaviors and support HIV/AIDS treatment