Life Sciences Commons^™

Thermal Links For The Implementation Of An Optical Refrigerator, John Parker, David Mar, Steven Von Der Porten, John Hankinson, Kevin Byram, Chris Lee, Michael K. Mayeda, Richard C. Haskell, Qimin Yang, Scott R. Greenfield, Richard I. Epstein

All HMC Faculty Publications and Research

Optical refrigeration has been demonstrated by several groups of researchers, but the cooling elements have not been thermally linked to realistic heat loads in ways that achieve the desired temperatures. The ideal thermal link will have minimal surface area, provide complete optical isolation for the load, and possess high thermal conductivity. We have designed thermal links that minimize the absorption of fluoresced photons by the heat load using multiple mirrors and geometric shapes including a hemisphere, a kinked waveguide, and a tapered waveguide. While total link performance is dependent on additional factors, we have observed net transmission of photons with …

An Undescribed Gecko (Gekkonidae: Cyrtodactylus) From Deer Cave, Gunung Mulu National Park, Sarawak, With Comments On The Distribution Of Bornean Cave Geckos, Donald A. Mcfarlane, Joyce Lundberg, Keith Christenson

WM Keck Science Faculty Papers

Geckos of the genus Cyrtodactylus are a speciose group in Southeast Asia, with at least nine species known from the island of Borneo (Das & Ismail, 2001; Das, 2006). Of these species, Cyrtodactylus cavernicolus has the smallest known range and is therefore the most vulnerable, a status that is reflected in the species having been designated a Totally Protected Species in Sarawak. Confirmed records of C. cavernicolus are known only from Niah Cave, located in an isolated limestone block known as the Gunung Subis massif, approximately 13 km² in extent. The Niah Cave Gecko is presumed to be dependent on …

Bats And Bell Holes: The Microclimatic Impact Of Bat Roosting, Using A Case Study From Runaway Bay Caves, Jamaica, Joyce Lundberg, Donald A. Mcfarlane

WM Keck Science Faculty Papers

The microclimatic effect of bats roosting in bell holes (blind vertical cylindrical cavities in cave roofs) in Runaway Bay Caves, Jamaica, was measured and the potential impact of their metabolism on dissolution modelled. Rock temperature measurements showed that bell holes with bats get significantly hotter than those without bats during bat roosting periods (by an average of 1.1 °C). The relationship is clearest for bell holes with more than about 300 g aggregate bat body mass and for bell holes that are moderately wide and deep, of W:D ratio between 0.8 and 1.6. Measurement of temperature decay after abandonment showed …

A Note On The Thermal Ecology And Foraging Behaviour Of The Egyptian Fruit Bat, Rousettus Aegyptiacus, At Mt. Elgon, Kenya, Donald A. Mcfarlane, Joyce Lundberg

WM Keck Science Faculty Papers

The Egyptian fruit bat, Rousettus aegyptiacus, is an abundant and widely distributed African pteropid (Nowak, 1999). The species is unusual amongst pteropids in being an obligate cave-dweller (Kwiecinski & Griffiths, 1999), sometimes reaching colony sizes in the thousands (Kingdon, 1974). In the caves of Mt. Elgon National Park, western Kenya (1° 08′N, 34° 39′E), precision temperature loggers placed in major Rousettus roosts and intervening passages have allowed us to precisely monitor bat emergence and return times.

The major caves of Mt. Elgon National Park consist of geophagically modified tunnels and collapse chambers cut into Miocene-aged pyroclastic strata (Lundberg & …

Compensatory Evolution Of Gene Regulation In Response To Stress By Escherichia Coli Lacking Rpos, Daniel M. Stoebel, Karsten Hokamp, Michael S. Last, Charles J. Dorman

All HMC Faculty Publications and Research

The RpoS sigma factor protein of Escherichia coli RNA polymerase is the master transcriptional regulator of physiological responses to a variety of stresses. This stress response comes at the expense of scavenging for scarce resources, causing a trade-off between stress tolerance and nutrient acquisition. This trade-off favors non-functional rpoS alleles in nutrient-poor environments. We used experimental evolution to explore how natural selection modifies the regulatory network of strains lacking RpoS when they evolve in an osmotically stressful environment. We found that strains lacking RpoS adapt less variably, in terms of both fitness increase and changes in patterns of transcription, than …