WHY DO FARMERS FORWARD CONTRACT IN FACTOR MARKETS?

This study investigated farmers' incentives to forward purchase inputs. A model of farmer decision making was used to derive an optimal forward contracting rule. Explicit in the model was the tradeoff between the quantity of input to be purchased in advance, and the remaining portion to be purchased later on the spot market. Results indicated that the primary reasons farmers contract inputs are to reduce risk and to speculate on favorable price moves. A numerical example of fertilizer used in corn production indicated that the size of the price discount was the dominant factor in forward contracting decisions.Farm Management,

Strengthening of reinforced concrete beams in shear with fiber reinforced cementitious matrix

The development of cement-based composites has been fruitful in the recent years. It is important to examine the new materials and technologies so they can fulfill repairing and strengthening applications in the structural engineering fields. An experimental study on the behavior of reinforced concrete beams strengthened in shear using an externally applied fiber reinforced cementitious matrix (FRCM) is presented. The PBO-FRCM system consists of two components: the reinforcing mesh is Polyparaphenylene benzobisoxazole – PBO fiber composite and the bonding agent is cementitious matrix. The test variables included two different configurations of U-wrapped systems and the PBO reinforcement’s ratio. The aims of this study were to investigate the effectiveness and the shear performance of the PBO-FRCM system for strengthening reinforced concrete beams in shear. All the beams were instrumented and tested under four-points loading. The test results included the observed shear contribution of the PBO-FRCM system and the failure mode of the strengthened beams

Effects of neutral gas release on current collection during the CHARGE-2 rocket experiment

Observations of current collection enhancements due to cold nitrogen gas control jet emissions from a highly charged rocket payload in the ionosphere are reported. These observations were made during the second cooperative high altitude rocket gun experiment (CHARGE-2) which was an electrically tethered mother/daughter payload system. The current collection enhancement was observed at the daughter payload located 100 to 400 m away from the mother which was firing an energetic electron beam. The authors interpret these results in terms of an electrical discharge forming in close proximity to the daughter during the short periods of gas emission. The results indicate that it is possible to enhance the electron current collection capability of positively charged vehicles by means of deliberate neutral gas releases into an otherwise undisturbed space plasma. These results can also be compared with recent laboratory observations of hollow cathode plasma contactors operating in the ignited mode. Experimental observations of current collection enhancements due to cold nitrogen gas control jet emissions from a highly charged, isolated daughter payload in the nighttime ionosphere were made. These observations were derived from the second cooperative high altitude rocket gun experiment (CHARGE-2) which was an electrically tethered mother-daughter payload system. The rocket flew from White Sands Missile Range (WSMR) in December, 1985. The rocket achieved an altitude of 261 km and carried a 1 keV electron beam emitting up to 48 mA of current (Myers, et al., 1989a). The mother payload, carried the electron beam source, while the daughter acted as a remote current collection and observation platform and reached a distance of 426 m away from the main payload. Gas emissions at the daughter were due to periodic thruster jet firings to maintain separation velocity between the two payloads

Als3 is a Candida albicans invasin that binds to cadherins and induces endocytosis by host cells.

Candida albicans is the most common cause of hematogenously disseminated and oropharyngeal candidiasis. Both of these diseases are characterized by fungal invasion of host cells. Previously, we have found that C. albicans hyphae invade endothelial cells and oral epithelial cells in vitro by inducing their own endocytosis. Therefore, we set out to identify the fungal surface protein and host cell receptors that mediate this process. We found that the C. albicans Als3 is required for the organism to be endocytosed by human umbilical vein endothelial cells and two different human oral epithelial lines. Affinity purification experiments with wild-type and an als3delta/als3delta mutant strain of C. albicans demonstrated that Als3 was required for C. albicans to bind to multiple host cell surface proteins, including N-cadherin on endothelial cells and E-cadherin on oral epithelial cells. Furthermore, latex beads coated with the recombinant N-terminal portion of Als3 were endocytosed by Chinese hamster ovary cells expressing human N-cadherin or E-cadherin, whereas control beads coated with bovine serum albumin were not. Molecular modeling of the interactions of the N-terminal region of Als3 with the ectodomains of N-cadherin and E-cadherin indicated that the binding parameters of Als3 to either cadherin are similar to those of cadherin-cadherin binding. Therefore, Als3 is a fungal invasin that mimics host cell cadherins and induces endocytosis by binding to N-cadherin on endothelial cells and E-cadherin on oral epithelial cells. These results uncover the first known fungal invasin and provide evidence that C. albicans Als3 is a molecular mimic of human cadherins

Improvement of Soil and Rock Properties for Foundation Support for Missouri Interchange Project

Expansion and growth in the southwestern region of Missouri necessitated the expansion of State Route 249 and the construction of a new interchange to provide service to the Joplin, Missouri area. The project is located above a former lead and zinc mine in Jasper County, Missouri and includes a five bridge interchange connecting State Route 249 and US Route 171. The variable subsurface conditions, both natural and manmade prompted the design team to use ground improvement via grouting and small diameter micropiles to provide support for several of the bridge foundations on the project. The scope of work included mine shaft closures, 17,070 m (56,000 ft) of overburden and rock drilling, 3,400 m (11,155 ft) of micropiles, 400 m³ (524 cy) of balanced/stabilized high mobility grouts, and over 6,800 m³ (8,900 cy) of low mobility grout. The selection of the grout used was based on the actual subsurface conditions. Low mobility grout (LMG) was used in voided conditions and for closure of the mine shafts encountered during the excavation. High mobility grout (HMG) was used in fractured rock with the goal of improving the mechanical properties of the rock underneath the future bridge footings and controlling grout volumes during micropile installation. The split spacing method was utilized for both LMG and HMG holes. Geology of the project consisted of extremely variable bedrock with strong to very strong limestone, chert, breccia, extremely weak shale, and weak to strong sandstone in conjunction with the activities associated with the mining disturbance (such as partial filled vertical mine shafts, shallow and deep mine horizons, modified hydrology including artesian conditions). Real time monitoring and recording of all drilling and grouting parameters was conducted to assist in the evaluation of in-situ geological properties of the site in order to modify the ground improvement and micropile program as necessary. This paper will discuss the design and execution of the ground improvement and micropile program. The project is an excellent example of the use of multiple ground improvement and foundation support techniques combined with real time data analysis to provide a foundation support solution for a complex geological environment

Actin capping protein regulates postsynaptic spine development through CPI-motif interactions

Dendritic spines are small actin-rich protrusions essential for the formation of functional circuits in the mammalian brain. During development, spines begin as dynamic filopodia-like protrusions that are then replaced by relatively stable spines containing an expanded head. Remodeling of the actin cytoskeleton plays a key role in the formation and modification of spine morphology, however many of the underlying regulatory mechanisms remain unclear. Capping protein (CP) is a major actin regulating protein that caps the barbed ends of actin filaments, and promotes the formation of dense branched actin networks. Knockdown of CP impairs the formation of mature spines, leading to an increase in the number of filopodia-like protrusions and defects in synaptic transmission. Here, we show that CP promotes the stabilization of dendritic protrusions, leading to the formation of stable mature spines. However, the localization and function of CP in dendritic spines requires interactions with proteins containing a capping protein interaction (CPI) motif. We found that the CPI motif-containing protein Twinfilin-1 (Twf1) also localizes to spines where it plays a role in CP spine enrichment. The knockdown of Twf1 leads to an increase in the density of filopodia-like protrusions and a decrease in the stability of dendritic protrusions, similar to CP knockdown. Finally, we show that CP directly interacts with Shank and regulates its spine accumulation. These results suggest that spatiotemporal regulation of CP in spines not only controls the actin dynamics underlying the formation of stable postsynaptic spine structures, but also plays an important role in the assembly of the postsynaptic apparatus underlying synaptic function

NSTAR Ion Thruster and Breadboard Power Processor Functional Integration Test Results

A 2.3 kW Breadboard Power Processing Unit (BBPPU) was developed as part of the NASA Solar Electric Propulsion Technology Application Readiness (NSTAR) Program. The NSTAR program will deliver an electric propulsion system based on a 30 cm xenon ion thruster to the New Millennium (NM) program for use as the primary propulsion system for the initial NM flight. The final development test for the BBPPU, the Functional Integration Test, was carried out to demonstrate all aspects of BBPPU operation with an Engineering Model Thruster. Test objectives included: (1) demonstration and validation of automated thruster start procedures, (2) demonstration of stable closed loop control of the thruster beam current, (3) successful response and recovery to thruster faults, and (4) successful safing of the system during simulated spacecraft faults. These objectives were met over the specified 80-120 VDC input voltage range and 0.5-2.3 output power capability of the BBPPU. Two minor anomalies were noted in discharge and neutralizer keeper current. These anomalies did not affect the stability of the system and were successfully corrected

Characterization of Shewanella oneidensis MtrC: a cell-surface decaheme cytochrome involved in respiratory electron transport to extracellular electron acceptors

MtrC is a decaheme c-type cytochrome associated with the outer cell membrane of Fe(III)-respiring species of the Shewanella genus. It is proposed to play a role in anaerobic respiration by mediating electron transfer to extracellular mineral oxides that can serve as terminal electron acceptors. The present work presents the first spectropotentiometric and voltammetric characterization of MtrC, using protein purified from Shewanella oneidensis MR-1. Potentiometric titrations, monitored by UV–vis absorption and electron paramagnetic resonance (EPR) spectroscopy, reveal that the hemes within MtrC titrate over a broad potential range spanning between approximately +100 and approximately -500 mV (vs. the standard hydrogen electrode). Across this potential window the UV–vis absorption spectra are characteristic of low-spin c-type hemes and the EPR spectra reveal broad, complex features that suggest the presence of magnetically spin-coupled low-spin c-hemes. Non-catalytic protein film voltammetry of MtrC demonstrates reversible electrochemistry over a potential window similar to that disclosed spectroscopically. The voltammetry also allows definition of kinetic properties of MtrC in direct electron exchange with a solid electrode surface and during reduction of a model Fe(III) substrate. Taken together, the data provide quantitative information on the potential domain in which MtrC can operate