STUDYING HERBICIDE RESISTANCE USING TREATMENT AREA DYNAMICS MODEL

Repeated use of a herbicide or herbicides with the same mode of action on a particular crop over a number of years may cause the selection of herbicide resistant weed populations. As a result effective weed control is lost which can seriously affect crop yield and quality. The selection of herbicide resistant weed populations is a concern not only for crop-growers, but also the manufacturers of the affected herbicides. In the present paper a two-step procedure is developed to identify the herbicide resistant activity in a particular crop growing region by estimating the resistant areas (in acres/hectares) in a given year of herbicide continued treatment along with percent risk of detecting herbicide resistance. A computer aided treatment area dynamics model (TADM) for estimating resistant areas, and a multistage model for estimating risk of herbicide resistance are discussed. An example is presented at the end to illustrate the two-step procedure

Analysis of Dislocation Mechanism for Melting of Elements: Pressure Dependence

In the framework of melting as a dislocation-mediated phase transition we derive an equation for the pressure dependence of the melting temperatures of the elements valid up to pressures of order their ambient bulk moduli. Melting curves are calculated for Al, Mg, Ni, Pb, the iron group (Fe, Ru, Os), the chromium group (Cr, Mo, W), the copper group (Cu, Ag, Au), noble gases (Ne, Ar, Kr, Xe, Rn), and six actinides (Am, Cm, Np, Pa, Th, U). These calculated melting curves are in good agreement with existing data. We also discuss the apparent equivalence of our melting relation and the Lindemann criterion, and the lack of the rigorous proof of their equivalence. We show that the would-be mathematical equivalence of both formulas must manifest itself in a new relation between the Gr\"{u}neisen constant, bulk and shear moduli, and the pressure derivative of the shear modulus.Comment: 19 pages, LaTeX, 9 eps figure

Case Report: Ischial Stress Fracture Non-Union in a College Football Player

Stress fractures are common injuries associated with repetitive high-impact activities, often in high-level athletes and military recruits. Although predominantly occurring in the lower extremities, stress fractures may occur wherever there is a sudden increase in frequency or intensity of activity, thereby overloading the yield point of the local bone environment. Ischial stress fractures are a rarely diagnosed cause of pain around the hip and pelvis. Often, patients present with buttock pain with activity, which can be misdiagnosed as proximal hamstring tendonitis or avulsion. Here, we report a case of a college football player who was diagnosed with an ischial stress fracture which went on to symptomatic non-union after extensive conservative management. We treated his ischial non-union with open reduction internal fixation utilizing a tension band plate and screws. This interesting case highlights an uncommon cause of the relatively common presentation of posterior hip pain and describes our technique for addressing a stress fracture non-union in the ischium

Sex-Specific Correlations of Individual Heterozygosity, Parasite Load, and Scalation Asymmetry in a Sexually Dichromatic Lizard

Heterozygosity-fitness correlations (HFCs) provide insights into the genetic bases of individual fitness variation in natural populations. However, despite decades of study, the biological significance of HFCs is still under debate. In this study, we investigated HFCs in a large population of the sexually dimorphic lizard Takydromus viridipunctatus (Lacertidae). Because of the high prevalence of parasitism from trombiculid mites in this lizard, we expect individual fitness (i.e., survival) to decrease with increasing parasite load. Furthermore, because morphological asymmetry is likely to influence individuals\u27 mobility (i.e., limb asymmetry) and male biting ability during copulation (i.e., head asymmetry) in this species, we also hypothesize that individual fitness should decrease with increasing morphological asymmetry. Although we did not formally test the relationship between morphological asymmetry and fitness in this lizard, we demonstrated that survival decreased with increasing parasite load using a capture-mark-recapture data set. We used a separate sample of 140 lizards to test the correlations between individual heterozygosity (i.e., standardized mean d2 and HL based on 10 microsatellite loci) and the two fitness traits (i.e., parasite load and morphological asymmetry). We also evaluated and excluded the possibility that single-locus effects produced spurious HFCs. Our results suggest male-only, negative correlations between individual heterozygosity and parasite load and between individual heterozygosity and asymmetry, suggesting sex-specific, positive HFCs. Male T. viridipunctatus with higher heterozygosity tend to have lower parasite loads (i.e., higher survival) and lower asymmetry, providing a rare example of HFC in reptiles

Time-resolved impulse response of the magnetoplasmon resonance in a two-dimensional electron gas

We have used optically excited ultrashort electrical pulses to measure the magnetoplasmon resonance of a two-dimensional electron gas formed in an AlGaAs/GaAs heterostructure at frequencies up to 200 gigahertz. This is accomplished by incorporating the sample into a guided wave probe operating in a pumped (^{3}He) system. We are able to detect the resonance by launching a stimulus pulse in the guide, and monitoring the system response in a time resolved pump-probe arrangement. Data obtained from measurements yield resonant frequencies that agree with the magnetoplasmon dispersion relation.Comment: 4 pages, 4 figure