Relationships of drought and biotic interactions to crayfish assemblage structure in Gulf coastal headwater streams

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 55-62).Issued also on microfiche from Lange Micrographics.Relationships between environmental variability and natural communities have been extensively studied. However the relative strengths of abiotic and biotic factors in structuring stream communities continues to be debated. Although North American crayfish are taxonomically diverse, occur across a variety of habitats, and are important components of stream ecosystems, when compared to other invertebrates or fish, factors influencing their distribution are poorly studied. Crayfishes may respond differently to disturbance and predators or competitors. In intermittent streams of East Texas, fishes that may influence the distribution of crayfish are rare or absent, so crayfish assemblages may differ between hydrologically variable and stable streams. In order to understand abiotic and biotic factors structuring native crayfish assemblages, environmental variables and densities of fishes and crayfishes were quantified simultaneously in 16 East Texas streams during June and October 1999, and February and April 2000. Three crayfish species, Procambarus clarkii, Orconectes palmeri, and Procambarus kensleyi, and several fishes were collected. Although fish and crayfish assemblages were similar in all streams during June before drought occurred, relative densities varied across intermittent and perennial streams following drought. After flow resumed in intermittent streams, densities of juvenile P. kensleyi were higher, but predatory fishes and adult O. palmeri were reduced, whereas in perennial streams, the opposite pattern occurred. These results suggest that P. kensleyi could tolerate abiotic stress, exploit resources, and maintain higher densities in intermittent streams where predators were reduced, but its smaller size may have facilitated higher predation by fish in perennial streams. Assemblages in perennial streams suggested interactions among crayfishes and fishes favored O. palmeri and P. clarkii, which appeared to be superior competitors and resistant to predators. Procambarus clarkii was not strongly correlated with either abiotic or biotic factors measured in this study, including stressful conditions associated with drought. These results are consistent with life history trade-offs among stress tolerance, resistance to disturbance and predation, and competitive ability. The occurrence of both perennial and intermittent streams within a drainage provides a range of habitats that maintains more crayfish species from among those in the regional species pool than would either habitat alone

The T-shaped “axe” from Northeast Honduras: Observations on chronology and function of a pre Columbian stone tool

This paper provides a description and analysis of a distinctive type of pre-Columbian stone tool, usually termed a T-shaped axe, found almost exclusively in Northeast Honduras, Central America. There have been very few detailed or technical studies of lithics from Honduras. Early archaeological research and the current understanding of the regional prehistory are included, with Northeast Honduras viewed as a frontier zone located between the Mesoamerican and Isthmo-Columbian culture areas. Our study examines, in particular, a collection of these tools curated today at the Cambridge University Museum of Archaeology and Anthropology (CUMAA). The 39 (whole and fragmentary) specimens were collected between 1937 and 1939, from the Bay Islands, Northeast Honduras, but have never been published. This paper classifies the collection specimens into five varieties, based on morphology, with sample statistics, form dimensions, and illustrations provided for each. Manufacturing technology is primarily percussion flaking. The tool type is compared with similar specimens excavated and described from the Bay Islands and adjacent Honduran mainland, and with similar appearing implements from elsewhere in Central America. Insights about the possible age and function of these unusual, and distinctive, lithics are included. Based on preliminary macroscopic and microscopic analyses, it is concluded that the tools may have been employed as agricultural implements (hoes or spades), primarily for digging activities, rather than as axes or weapons used for cutting and slicing. It is most likely that these implements first appeared about 800 CE, and continued in use until at least 1400 CE. The tool type is most probably a local (not imported) product. More functional analysis is encouraged

Economical Litigation Agreements: The Civil Litigation Prenup Need, Basis, and Enforceability

This article identifies the basis and limits of the parties\u27 abilities to define and enforce discovery in an ex ante contract. Despite the deficiencies of litigation, the free, public dispute resolution forum of the civil justice system provides significant value in commercial disputes. That value can be used to maximum mutual advantage only if parties replace the infinite discovery permitted in conventional litigation with the finite discovery contracted in Economical Litigation Agreement (ELA) litigation. This article will help parties to understand the benefit and enforceability of the ELA

AT 2023prq: A Classical Nova in the Halo of the Andromeda Galaxy

The classical nova, AT 2023prq, was discovered on 2023 August 15 and is located at a distance of 46 kpc from the Andromeda Galaxy (M 31). Here we report photometry and spectroscopy of the nova. The 'very fast' ($t_{2,r^{\prime}}\sim3.4$ d) and low luminosity ($M_{r^{\prime}}\sim-7.6$) nature of the transient along with the helium in its spectra would indicate that AT 2023prq is a 'faint-and-fast' He/N nova. Additionally, at such a large distance from the centre of M 31, AT 2023prq is a member of the halo nova population.Comment: 3 pages, 1 figure; Published in Research Notes of the American Astronomical Societ

Population Pharmacokinetics and Pharmacodynamics of Extended-Infusion Piperacillin and Tazobactam in Critically Ill Children

The study objective was to evaluate the population pharmacokinetics and pharmacodynamics of extended-infusion piperacillintazobactam in children hospitalized in an intensive care unit. Seventy-two serum samples were collected at steady state from 12 patients who received piperacillin-tazobactam at 100/12.5 mg/kg of body weight every 8 h infused over 4 h. Population pharmacokinetic analyses were performed using NONMEM, and Monte Carlo simulations were performed to estimate the piperacillin pharmacokinetic profiles for dosing regimens of 80 to 100 mg/kg of the piperacillin component given every 6 to 8 h and infused over 0.5, 3, or 4 h. The probability of target attainment (PTA) for a cumulative percentage of the dosing interval that the drug concentration exceeds the MIC under steady-state pharmacokinetic conditions (TMIC) of\u3e50% was calculated at MICs ranging from 0.25 to 64 mg/liter. The mean ± standard deviation (SD) age, weight, and estimated glomerular filtration rate were 5 ± 3 years, 17 ± 6.2 kg, and 118 ± 41 ml/min/1.73m2, respectively. A one-compartment model with zero-order input and first-order elimination best fit the pharmacokinetic data for both drugs. Weight was significantly associated with piperacillin clearance, and weight and sex were significantly associated with tazobactam clearance. Pharmacokinetic parameters (mean ± SD) for piperacillin and tazobactam were as follows: clearance, 0.22 ± 0.07 and 0.19 ± 0.07 liter/h/kg, respectively; volume of distribution, 0.43 ± 0.16 and 0.37 ± 0.14 liter/kg, respectively. All extended-infusion regimens achieved PTAs of\u3e90% at MICs of/liter. Only the 3-h infusion regimens given every 6 h achieved PTAs of\u3e90% at an MIC of 32 mg/liter. For susceptible bacterial pathogens, piperacillin-tazobactam doses of\u3e80/10 mg/kg given every 8 h and infused over 4 h achieve adequate pharmacodynamic exposures in critically ill children

Detection of Fetomaternal Genotype Associations in Early-Onset Disorders: Evaluation of Different Methods and Their Application to Childhood Leukemia

Several designs and analytical approaches have been proposed to dissect offspring from maternal genetic contributions to early-onset diseases. However, lack of parental controls halts the direct verification of the assumption of mating symmetry (MS) required to assess maternally-mediated effects. In this study, we used simulations to investigate the performance of existing methods under mating asymmetry (MA) when parents of controls are missing. Our results show that the log-linear, likelihood-based framework using a case-triad/case-control hybrid design provides valid tests for maternal genetic effects even under MA. Using this approach, we examined fetomaternal associations between 29 SNPs in 12 cell-cycle genes and childhood pre-B acute lymphoblastic leukemia (ALL). We identified putative fetomaternal effects at loci CDKN2A rs36228834 (P = .017) and CDKN2B rs36229158 (P = .022) that modulate the risk of childhood ALL. These data further corroborate the importance of the mother's genotype on the susceptibility to early-onset diseases