The Effect of Prior Heavy Exercise On Progressive Exercise To Fatigue [MEDICINE]

At the onset of constant-load exercise in healthy humans, the rate of muscle metabolism increases to a steady state. However, when exercise is preceded by a bout of high-intensity or 'heavy exercise' several minutes prior, steady state is typically achieved more quickly. The aim of the present study was to study the metabolic effects of prior heavy exercise on a progressive exercise protocol, in which steady state is not achieved.

Scientific Abstract:

At the onset of constant-load exercise, the rate of muscle metabolism increases to a steady state. When exercise is preceded by a bout of heavy intensity (HVY) exercise, steady state is typically achieved more quickly. The effects of a prior HVY bout on a progressive exercise protocol, in which a steady state is not achieved, are unknown. The present study, therefore, was designed to study the effects of a prior HVY bout on a progressive plantar flexion exercise protocol in healthy humans. Subjects (n=5 males, age 25 ± 4 years) completed two randomized exercise protocols that included a progressive exercise protocol (RAMP) and a progressive exercise protocol preceded 6 min prior by 6 min of HVY (HVY-RAMP). Exercise involved repeated isotonic plantar flexion (0.5 Hz, ~ 40° ROM) against an incremental resistance (~1.0 W/min) and was performed inside a 3.0 Tesla magnet for data collection using 31P-MRS (15s time acquisition per spectrum). All subjects had previously completed at least one familiarization RAMP trial, from which the steady state workload in HVY was calculated as the power output halfway between the onset of intracellular acidification and volitional fatigue. Our findings were, compared to the RAMP protocol, HVY-RAMP resulted in an increased (p <>

HVY exercise, the onset of the rapid fall in pHi is delayed, but once initiated, occurs at the same rate as in the RAMP protocol. This delay may be the result of an increased contribution of xidative metabolism suggested by the delayed onset of rapid increases in [Pi]/[PCr].

Ion Chamber Dosimetry: Accuracy in Small X-Ray Field Measurements [MEDICINE]

Modern radiation therapy techniques, such as stereotactic radiotherapy and tomotherapy, deliver the total treatment dose to the patient using many small fields. This helps to construct a dose distribution which delivers a high dose to the tumour, while minimizing the dose to normal tissue. When considering a single small field, the dose resulting from that small field is usually reported as a relative dose factor (RDF). The RDF is the percentage of dose in a small field as compared to a large reference field. Task group report #51 from the American Association of Physicists in Medicine (AAPM) provides the protocol according to which absolute dose measurements using an ion chamber must be taken, all with respect to measurements at a reference point in a large reference field. In the case of RDF measurements several assumptions are made which allows for the simplification of the TG-51 protocol, but attention is not necessarily paid to the fact that the conditions in a large reference field differ considerably from those ina small field. In this study we have used experimental measurements with plane-parallel ion chambers and theoretical simulations (Monte Carlo BEAMnrc code) to investigate the validity of the assumptions made in the determination of RDFs for small fields. Four custom-made plane parallel ion chambers, as well as other common high resolution radiation dosimeters, were used to measure the dose response in circular 6MV stereotactic radiotherapy fields. BEAMnrc was then used to simulate the experimental conditions and determine the validity of the assumptions mentioned previously. The assumptions were determined to be invalid for use in small radiation fields. Corrections

were calculated from Monte Carlo results and applied to the experimental measurements. Care needs to be taken when applying existing protocols to non-reference conditions.

Longitudinal 31P Magnetic Resonance Spectroscopy Study of Schizophrenia [MEDICINE]

Schizophrenia affects one in a hundred Canadians at some point in their life. This disorder is characterized by auditory hallucinations, delusions, lack of motivation and thought disorder. Antipsychotic drugs improve some of these symptoms, but there is no cure and the cause of schizophrenia is still unknown. Current models suggest that a brain lesion in-utero, in conjunction with neurodegeneration, may result in the symptoms of the disease. These processes may result in abnormal brain function, manifested as changes in brain metabolism.

In our past studies of first-episode and chronic schizophrenia, we used 31P MRS, a noninvasive technique, to measure the changes in brain metabolism. These studies revealed significant changes between patients and normals in several regions, including the thalamus, and the anterior cingulate. In order to determine the location of significant changes in metabolites as the disease progresses, more measurements between the initial and chronic stages of the disease are required.

In this longitudinal study of schizophrenia, the same subjects undergo 2 separate scans, the first at disease onset and the second at 30 months. Presently 24 schizophrenic patients and 15 matched controls have undergone the initial scan at disease onset and 6 schizophrenic patients and 6 controls have undergone the 30 month scan. Once complete, this study may reveal locations where significant membrane abnormalities occur in the early progression of the disease. This information will help to confirm that degeneration continues after schizophrenia is diagnosed clinically and may also help to target drug treatments to prevent this degeneration.

Babbitt metal [MECH]

Babbitt metal, also called white metal, is an alloy used to provide the bearing surface in a plain bearing. It was invented in 1839 by Isaac Babbitt in Taunton, Massachusetts, USA. The term is used today to describe a series of alloys used as a bearing metal. Babbit metal is characterized by its resistance to gall.

Common compositions for Babbitt alloys:

• 90% tin 10% copper
• 89% tin 7% antimony 4% copper
• 80% lead 15% antimony 5% tin

Originally used as a cast in place bulk bearing material, it is now more commonly used as a thin surface layer in a complex, multi metal structure.

Babbitt metal is soft and easily damaged, and seems at first sight an unlikely candidate for a bearing surface, but this appearance is deceptive. The structure of the alloy is made up of small hard crystals dispersed in a matrix of softer alloy. As the bearing wears the harder crystal is exposed, with the matrix eroding somewhat to provide a path for the lubricant between the high spots that provide the actual bearing surface.

BlueTec [mech]

BlueTec is DaimlerChrysler's name for its two nitrogen oxide (NO_x) reducing systems, for use in their Diesel automobile engines. One is a urea catalyst called AdBlue, the other is called DeNO_x and uses an oxidising catalytic converter and particular filter combined with other NO_x introduced the systems in the reducing systems. Both systems were designed to slash emissions further than ever before. Mercedes-BenzE-Class (using the 'DeNO_x' system) and GL-Class (using 'AdBlue') at the 2006 North American International Auto Show as the E 320 and GL 320 Bluetec. This system makes these vehicles 45-state and 50-state legal respectively in the United States, and is expected to meet all emissions regulations through 2009. It also makes DaimlerChrysler the only car manufacturer in the the US committed to selling diesel models in the 2007 model year.

CVCC [mech]

CVCC is a trademark by the Honda Motor Company for a device used to reduce automotive emissions called Compound Vortex Controlled Combustion. This technology allowed Honda's cars to meet the 1970s US Emission requirements without a catalytic converter, and first appeared on the 1975 ED1 engine. It is a form of stratified charge engine.

Honda CVCC engines have normal inlet and exhaust valves, plus a small auxiliary inlet valve which provides a relatively rich air / fuel mixture to a volume near the spark plug. The remaining air / fuel charge, drawn into the cylinder through the main inlet valve is leaner than normal. The volume near the spark plug is contained by a small perforated metal plate. Upon ignition flame fronts emerge from the perforations and ignite the remainder of the air / fuel charge. The remaining engine cycle is as per a standard four stroke engine.

This combination of a rich mixture near the spark plug, and a lean mixture in the cylinder allowed stable running, yet complete combustion of fuel, thus reducing CO (carbon monoxide) and hydrocarbon emissions.

stratified charge engine [mech]

The stratified charge engine is a type of internal-combustion engine, similar in some ways to the Diesel cycle, but running on normal gasoline. The name refers to the layering of fuel/air mixture, the charge inside the cylinder.

In a traditional Otto cycle engine the fuel and air are mixed outside the cylinder and are drawn into it during the intake stroke. The air/fuel ratio is kept very close to stoichiometric, which is defined as the exact amount of air necessary for a complete combustion of the fuel. This mixture is easily ignited and burns smoothly.

The problem with this design is that after the combustion process is complete, the resulting exhaust stream contains a considerable amount of free single atoms of oxygen and nitrogen, the result of the heat of combustion splitting the O₂ and N₂ molecules in the air. These will readily react with each other to create NO_x, a pollutant. A catalytic converter in the exhaust system re-combines the NO_x back into O₂ and N₂ in modern vehicles.

A Diesel engine, on the other hand, injects the fuel into the cylinder directly. This has the advantage of avoiding premature spontaneous combustion—a problem known as detonation or ping that plagues Otto cycle engines—and allows the Diesel to run at much higher compression ratios. This leads to a more fuel-efficient engine. That is why they are commonly found in applications where they are being run for long periods of time, such as in trucks.

E85 [mech]

E85 is an alcohol fuel mixture of 85% ethanol and 15% gasoline, by volume. ethanol derived from crops (bioethanol) is a biofuel.

E85 as a fuel is widely used in Sweden and is becoming increasingly common in the United States, mainly in the Midwest where corn is a major crop and is the primary source material for ethanol fuel production.

E85 is usually used in engines modified to accept higher concentrations of ethanol. Such flexible-fuel engines are designed to run on any mixture of gasoline or ethanol with up to 85% ethanol by volume. The primary differences from non-FFVs is the elimination of bare magnesium, aluminum, and rubber parts in the fuel system, the use of fuel pumps capable of operating with electrically-conductive (ethanol) instead of non-conducting dielectric (gasoline) fuel, specially-coated wear-resistant engine parts, fuel injection control systems having a wider range of pulse widths (for injecting approximately 30% more fuel), the selection of stainless steel fuel lines (sometimes lined with plastic), the selection of stainless steel fuel tanks in place of terne fuel tanks, and, in some cases, the use of acid-neutralizing motor oil. For vehicles with fuel-tank mounted fuel pumps, additional differences to prevent arcing, as well as flame arrestors positioned in the tank's fill pipe, are also sometimes used.

FADEC - Full Authority Digital Engine Control.[mech]

FADEC is the acronym for Full Authority Digital Engine Control. It is a system consisting of a digital computer (called EEC /Electronic Engine Control/ or ECU /Electronic Control Unit/) and its related accessories which control all aspects of aircraft engine performance. FADECs have been produced for both piston engines and jet engines, their primary difference due to the different ways of controlling the engines.

Electronics' superior accuracy led to early generation analogue electronic control first used in Concorde's Rolls-Royce Olympus 593 in the 1960s. Later in the 1970s NASA and Pratt and Whitney experimented with the first experimental FADEC, first flown on an F-111 fitted with a highly modified Pratt & Whitney TF-30 left engine. The experiments led to Pratt & Whitney F100 and Pratt & Whitney PW2000 being the first military and civil engines respectively fitted with FADEC and later the Pratt & Whitney PW4000 as the first commercial 'Dual FADEC' engine.

The aircraft's thrust lever sends electrical signals (pilot's command, may also be the autothrottle) to the FADEC. The FADEC digitally calculates and precisely controls the fuel flow rate to the engines giving precise thrust. In addition to the fuel metering function, the FADEC performs numerous other control and monitoring functions such as Variable Stator Vanes (VSV's) and Variable Bleed Valves (VBV's) control, cabin bleeds and power off-takes control, control of starting and re-starting, turbine blade and vane cooling and blade tip clearance control, thrust reversers control, engine health monitoring, oil debris monitoring and vibration monitoring. The inputs come from various aircraft and engine sensors. Apart from the key parameters that are monitored for a safe thrust control (shaft rotational speeds, pressures and temperatures at various points along the gas path) the FADEC also monitors hundreds of various analog, digital and discrete data coming from the engine subsystems and related aircraft systems, providing a fully redundant and fault tolerant engine control.

Hybrid Synergy Drive (HSD)

Hybrid Synergy Drive (HSD) is a set of hybrid car technologies developed by Toyota and used in that company's Prius, Highlander Hybrid, Camry Hybrid, Lexus RX 400h, and Lexus GS 450h automobiles. It combines the characteristics of an electric drive and a continuously variable transmission, using electricity and transistors in place of toothed gears. The Synergy Drive is a drive-by-wire system with no direct mechanical connection between the engine and the engine controls: both the gas pedal and the gearshift lever in an HSD car merely send electrical signals to a control computer.

HSD is a refinement of the original Toyota Hybrid System (THS) used in the 1997–2003 Toyota Prius. As such it is occasionally referred to as THS II. The name was changed in anticipation of its use in vehicles outside the Toyota brand (Lexus).

When required to classify the transmission type of an HSD vehicle (such as in standard specification lists or for regulatory purposes), Toyota describes HSD-equipped vehicles as having E-CVT (Electronically-controlled Continuously Variable Transmission).

regenerative brake

A regenerative brake is an apparatus, a device or system which allows a vehicle to recapture part of the kinetic energy that would otherwise be lost to heat when braking and make use of that power either by storing it for future use or feeding it back into a power system for other vehicles to use.

It is similar to an electromagnetic brake, which generates heat instead of electricity and is unable to completely stop a rotor.

Regenerative brakes are a form of dynamo generator, originally discovered in 1832 by Hippolyte Pixii. The dynamo's rotor slows as the kinetic energy is converted to electrical energy through electromagnetic induction. The dynamo can be used as either generator or brake by converting motion into electricity or be reversed to convert electricity into motion.

Using a dynamo as an regenerative brake was discovered co-incident with the modern electric motor. In 1873, Zénobe Gramme attached the wires from two dynamos together. When one dynamo rotor was turned as a regenerative brake, the other became an electric motor.

It is estimated that regenerative braking systems in vehicles currently reach 31.3% electric generation efficiency, with most of the remaining energy being released as heat; the actual efficiency depends on numerous factors, such as the state of charge of the battery, how many wheels are equipped to use the regenerative braking system, and whether the topology used is parallel or serial in nature.^{[citation needed]} The system is no more efficient than conventional friction brakes, but reduces the use of contact elements like brake pads, which eventually wear out. Traditional friction-based brakes must also be provided to be used when rapid, powerful braking is required.