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Peer Reviewed

Predictors of Maximal Oxygen Consumption During Exercise, and Ecological and Behavioral Correlates in Lizards and Mammals

Lacerda De Albuquerque, Ralph
Advisor(s): Garland Jr., Theodore

UC Riverside Electronic Theses and Dissertations (2019)

The current paradigm in animal organismal biology links morphology, performance, behavior, and Darwinian fitness in a sequence of proximate causal relations. First, the combination of lower-level organismal traits (e.g., leg length, heart mass, muscle enzyme activities) generate the performance level observed (e.g., maximal sprint speed, maximal oxygen consumption during exercise [V̇O2max]), then maximal performance levels constrain behavioral options, and the consequences of behavioral choices influence fitness. Because behavior and performance are the last steps leading to fitness, selection acts most directly on them than on lower-level (subordinate) traits. Performance and behavior are, therefore, pivotal points in understanding animal adaptation. A primary determinant of an animal's aerobic performance capacity is V̇O2max which sets the limit to the intensity of physical effort that can be sustained over prolonged periods of time. Only during relatively rare occasions (e.g., during predator-prey interactions) do animals perform at levels above V̇O2max; therefore, most activities will be constrained by their capacity to consume oxygen. Many key events involve mostly aerobic levels of activity (e.g., foraging, patrolling territories), making V̇O2max a likely target for natural and sexual selection.

This dissertation investigated V̇O2max in two contexts. In chapters one and two I put V̇O2max in an evolutionary context, evaluating the coadaptation of V̇O2max and ecological traits among lizard and mammal species. These studies revealed that V̇O2max is weakly positively correlated with home range area among species of mammals, that viviparous lizards have lower V̇O2max than non-viviparous species, and that varanids, helodermatids, and skinks have higher V̇O2max than other groups of lizards.

In the third chapter, I use a mechanistic approach to elucidate the proximate causes and consequences of V̇O2max at the level of among-individual variation. I found that V̇O2max in adult male Sceloporus occidentalis lizards from Hampton Butte, OR during the breeding season is positively related to hematocrit (or hemoglobin) levels in the blood and that V̇O2max is positively related to territorial behaviors (number of push-ups using two or four legs per bout of push-ups).

Cover page: Predictors of Maximal Oxygen Consumption During Exercise, and Ecological and Behavioral Correlates in Lizards and Mammals

Article
Peer Reviewed

Magnetoresistance of the Kondo insulator Ce3Bi4Pt3

UC Irvine Previously Published Works (1993)

The magnetoresistance (MR) of the narrow-gap Kondo insulator Ce3Bi4Pt3 and its non-magnetic analog La3Bi4Pt3 have been measured in magnetic fields to 10 T and in the temperature range 2-300 K. Ce3Bi4Pt3 exhibits a large negative MR component below 7 K. At higher temperatures this negative component progressively decreases and a positive contribution becomes evident. Above 75 K the MR is positive at all fields and saturates to a value of a few percent. The non-magnetic analog La3Bi4Pt3 exhibits the same positive magnetoresistance present in Ce3Bi4Pt3 as well as a conventional positive H2 term at low temperatures. We discuss potential mechanisms for both the common positive effect and the large negative MR present in Ce3Bi4Pt3. © 1993.

Cover page: Magnetoresistance of the Kondo insulator Ce3Bi4Pt3

Creative Commons 'BY' version 4.0 license

Article
Peer Reviewed

Effects of doping on hybridization gapped materials

UC Irvine Previously Published Works (1992)

Doping studies are presented on three materials exhibiting hybridization gaps: Ce3Bi4Pt3, U3Sb4Pt3 and CeRhSb. In the case of trivalent La, Y, or Lu substituting for Ce or U, there is a suppression of the low temperature gap and an increase in the electronic specific heat, γ. In the case of tetravalent Th substitutions for U there is no change in γ and in the case of tetravalent Zr substitution for Ce in CeRhSb, there is an enhanced semiconductor-like behavior in the electrical resistance. These results are discussed in the light of a simple model of hybridization gapped systems. © 1992.

Cover page: Effects of doping on hybridization gapped materials

Article
Peer Reviewed

Low-temperature phase diagram of YbBiPt

UC Irvine Previously Published Works (1994)

Resistivity measurements are reported on the cubic heavy-fermion compound YbBiPt at ambient and hydrostatic pressures to ≊19 kbar and in magnetic fields to 1 T. The phase transition at Tc=0.4 K is identified by a sharp rise in resistivity. That feature is used to build low-temperature H-T and P-T phase diagrams. The phase boundary in the H-T plane follows the weak-coupling BCS expression remarkably well from Tc to T c/4, while small hydrostatic pressure of ≊1 kbar suppresses the low-temperature phase entirely. These effects of hydrostatic pressure and magnetic field on the phase transition are consistent with an spin-density-wave (SDW) formation in a very heavy electron band at T=0.4 K. Outside of the SDW phase at low temperature, hydrostatic pressure increases the T2 coefficient of resistivity, signaling an increase in heavy-fermion correlations with hydrostatic pressure. The residual resistivity decreases with pressure, contrary to trends in other Yb heavy-fermion compounds.

Cover page: Low-temperature phase diagram of YbBiPt

Article
Peer Reviewed

Fermi Surface Instability and Symmetry Breaking in Heavy-Fermion Compound YbBiPt

UC Irvine Previously Published Works (1994)

We report resistivity measurements on the cubic heavy-fermion compound YbBiPt at ambient and hydrostatic pressures to ≅6 kbar and in magnetic fields to 1 T. Resistivity anisotropy sets in below the phase-transition temperature Tc=0.4 K. We interpret a rise of resistivity below 0.4 K as due to partial gapping of the Fermi surface with the weak coupling energy gap of Δ0kBTc=1.65±0.15. Effects of hydrostatic pressure and magnetic field on the phase transition and heat capacity data are consistent with a spin density wave formation in a very heavy electron band at T=0.4 K. © 1994 The American Physical Society.

Cover page: Fermi Surface Instability and Symmetry Breaking in Heavy-Fermion Compound YbBiPt

Article
Peer Reviewed

Magnetic properties of the dense Kondo system CeB6 in high magnetic fields

UC Irvine Previously Published Works (2001)

This work reports on the phase diagram study of the dense Kondo system CeB6 by means of magnetization (M) and transverse magnetoresistance (MR) measurements in magnetic fields (B) to 1ST, in the temperature (T) range from 1.8 to 40 K. The zero field resistivity displays Kondo behavior in the paramagnetic P-phase, while two discontinuities at low T were observed at TQ ≈3.5 K and TN ≈ 2.3 K, the boundaries of the antiferro-quadrupolar (AFQ), and antiferromagnetic (AF) phases, respectively. The isothermal transverse MR is large and negative at low T, and it shows a distinct feature when the P-AFQ line of the B-T phase diagram is crossed. Similarly, the M vs. B curves at low temperatures show upward discontinuities at the phase boundary. Both the features in MR and M at the P-AFQ line correlate well in T, revealing the gradual increase of the T for the onset of AFQ ordering with B. No evidence for reentrant behavior could be observed in fields to 1ST. © 2001 Published by Elsevier Science B.V.

Cover page: Magnetic properties of the dense Kondo system CeB6 in high magnetic fields

Article
Peer Reviewed

Role of proenkephalin in the diagnosis of severe and subclinical acute kidney injury during the perioperative period of liver transplantation

UC San Diego Previously Published Works (2022)

In recent decades, clinical research on early biomarkers of renal injury has been frequent and intensive, with proenkephalin (PENK) being indicated as a promising filtration biomarker (BM). From a cohort of 57 patients, blood samples were collected preoperatively and 48 h after liver transplantation (LT). The following BMs were analyzed: PENK, cystatin-C (CYS-C), and serum creatinine (Scr). Diagnosis of AKI was based on the KDIGO criteria. Of the 57 patients undergoing LT, 50 (88%) developed acute kidney injury (AKI) and were categorized as follows: no-AKI/mild-AKI - 21 (36.8%) and severe-AKI 36 (63.2%). During the preoperative period, only PENK was significantly higher in patients with severe AKI, with an AUC of 0.69 (CI 0.54-0.83), a cutoff of 55.30 pmol/l, a sensitivity of 0.86, a specificity of 0.52, and an accuracy of 0.75. In addition, subclinical AKI was determined preoperatively in 32 patients. Forty-eight hours after LT, PENK maintained its performance in determining severe AKI, with an AUC of 0.83 (CI 0.72-0.94), a cutoff of 119.05 pmol/l, a sensitivity of 0.81, a specificity of 0.90, and an accuracy of 0.84. PENK detected AKI 48 h earlier than serum creatinine. In a multivariate linear regression analysis, PENK was an independent predictor of severe AKI. This small study suggests that the filtration biomarker PENK shows promise for detecting AKI in patients undergoing LT, revealing greater accuracy and an earlier rise in patients with severe AKI. The combination of kidney functional and filtration BMs may aid in the management and prevention of AKI progression.

Cover page: Role of proenkephalin in the diagnosis of severe and subclinical acute kidney injury during the perioperative period of liver transplantation

Article
Peer Reviewed

Low-temperature thermal expansion of SmB6: Evidence for a single energy scale in the thermodynamics of Kondo insulators

UC Irvine Previously Published Works (1994)

We have measured the thermal expansion of the Kondo insulator SmB6 from 5 to 80 K using a sensitive capacitance dilatometer. There is a pronounced negative anomaly in the linear expansion coefficient α, of electronic origin, which achieves a local minimum of -5×10-6 K-1 at 45 K. We interpret this anomaly as a Schottky-like contribution arising from transitions across a semiconducting energy gap Eg140 K. Although there are several energy scales in the problem, a Grüneisen analysis indicates that the thermodynamics is driven by a single energy, which we identify as the gap energy. © 1994 The American Physical Society.

Cover page: Low-temperature thermal expansion of SmB6: Evidence for a single energy scale in the thermodynamics of Kondo insulators

Article
Peer Reviewed

Magnetism and heavy fermion-like behavior in the RBiPt series

UC Irvine Previously Published Works (1991)

Members of the RBiPt (R=Ce-Lu with the exceptions of Pm and Eu) series have been grown as single crystals. Magnetic susceptibility and electrical resistance have been measured on all members of the series, and specific heat measurements have been performed on representatives. The high temperature resistance uniformly changes from that of a small-gap semiconductor or semimetal seen in NdBiPt to that of a heavy-fermion metal seen in YbBiPt, which shows a linear coefficient of specific heat at low temperatures of 8 J/K2 mole. Further, the lighter rare earth members show an unusually sharp increase in their resistance associated with antiferromagnetic ordering at low temperatures.

Cover page: Magnetism and heavy fermion-like behavior in the RBiPt series

Article
Peer Reviewed

Absence of antiferromagnetic order in UBe13

UC Irvine Previously Published Works (1992)

The linear magnetostriction (λ{norm of matrix} and λ⊥) of a single-crystalline sample of the heavy-fermion compound UBe13 has been measured for fields B < 8 T (B{norm of matrix}[100]) in the temperature interval 0.3 < T < 12 K. We find neither evidence for the antiferromagnetic order (TN = 8.8 K) nor for the magnetostrictive oscillations, that were reported recently. Instead λ varies proportional to B2 as expected for a normal paramagnetic metal. © 1992.

Cover page: Absence of antiferromagnetic order in UBe13