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JOS - Josephson Junction
Josephson Junction Description (JOS)
- Note that there is NO eating or drinking in the 111-Lab anywhere, except in rooms 282 & 286 LeConte on the bench with the BLUE stripe around it. Thank You the Staff.
Superconducting phenomena are among the most fascinating features in physics, and the Josephson effect is the most interesting of all. In 1962, Brian Josephson predicted that electron pairs could tunnel without resistance through an insulating barrier between two superconductors. Here we use a point contact between niobium wire with a thin oxide layer and a niobium block. Both the DC and AC Josephson effects are observed and measured. A DC current can flow through the junction with no potential difference, but when a DC voltage is applied together with a small alternating voltage, the I-V curve shows a characteristic step structure. From this step structure the value of 2e/h can be calculated easily and accurately, an exciting consequence of the properties of the junction. The ratio e/h appears throughout atomic and condensed matter physics.
In this experiment you will learn some low temperature techniques which are used in many research laboratories. You will also learn some practical and often frustrating electronics, together with manual skills in making niobium points and adjusting them to produce a useful electronic signal.
- Pre-requisites: Physics 137A (may be taken concurrently)
- Days Alloted for the Experiment: 8
All pages in this lab. Note To print Full Lab Write-up click on each link below and print separately
I. Josephson Junction
II. How to use the digital oscilloscope
This lab will be graded 40% on theory, 40% on technique, and 20% on analysis. For more information, see the Advanced Lab Syllabus.
Comments: E-mail Don Orlando
Josephson Effect Photos
Josephson Experiment with the Computer Click here to see larger picture
Liquid Helium Dewar Click here to see larger picture
Josephson Probes & Liquid level testers Storage Location Click here to see larger picture
Hot Plate for heating points and IR Temperature meter Click here to see larger picture
Wear Your Eye Safety Glasses
Before the 1st Day of Lab
Complete the following before your experiment's scheduled start date:
- View the Josephson Junction video.
- Complete the JOS Pre Lab and Evaluation sheets. Print, fill it out, then turn in your answers with the report. The Pre-Lab must be printed separately. Discuss the experiment and pre-lab questions with any faculty member or GSI and get it signed off by that faculty member or GSI. Turn in the signed pre-lab sheet with your lab report.
- Read before handling of Cryogenics: Read the Cryogenic Liquids information from the campus Environmental Health and Safety (EH&S) department Cryogenic Liquids.
- Notify the staff/GSI to fill the liquid helium tank one (1) day before you begin the experiment.
- Check points are examination points that are placed in this lab where you must STOP and call a GSI or professor to make sure you understand what's expected. There could be multiple check points throughout your lab so make sure you don't skip them since there is a sign off sheet that must be turned in with your lab report. There are 3 Checkpoints in this lab.
Suggested Reading:
- †Clarke, John, "The Josephson Effect and e/h," American Journal of Physics, Vol. 38, No. 9, September 1970, pp. 1071-1095. Searchable Page
- †Feynman, R.P., Leighton, R.B., and Sands, M. The Feynman Lectures on Physics.. Vol. III. Menlo Park: Addison-Wesley, 1966.
- †Langenberg, D.N., Scalapion, D.J., and Taylor, B.N. "The Josephson Effects," Scientific American, Vol.214, p.30, May, 1966. Published article APS site
- †Richards, P.I., Shapiro, S., and Grimes, C.C. "Student Laboratory Demonstration of Flux Quantization and the Josephson Effect in Superconductors," American Journal of Physics, Vol. 36, No. 8, August 1968, pp. 690-697. Searchable Page
- Anderson, Philip W. "How Josephson Discovered His Effect"; Physics Today: November, 1970, pp. 23-29. (PAGES 26 & 28 ARE INTENTIONALLY MISSING.)
- Four Wire Measurements
- Josephson Reprints on Physics 111-Lab Library site
- Last day of the experiment please fill out the Experiment Evaluation
More References
You should keep a laboratory notebook. The notebook should contain a detailed record of everything that was done and how/why it was done, as well as all of the data and analysis, also with plenty of how/why entries. This will aid you when you write your report.
- Learn what real experimental physics is about
- Learn the synergy between experimental and theoretical work
- Learn to use pieces of equipment that are commonly used in research
- Learn how measurements are performed, analyzed, and interpreted.
- Learn how to present your work and results
- Learn problem solving strategies
- Learn how to manage and organize your time
- Understand what is superconductivity and how it relates to the Josephson Junction effect.
- Deeply explore and understand what are the DC and AC Josephson effect.
- Learn how the experiment works and how to use the equipment properly as well as mastering the experiment's procedure.
- Analyze any data you take and argue why does that data make sense or doesn't.(Demonstrate the steps you take to get to these conclusions.)
Intent and scope of this laboratory manual
This manual is intended to provide general guidance for the lab. It is not designed to explain all the physics necessary for understanding this experiment. Nor is it a "cook-book" telling you exactly which buttons to press, etc. It is up to the student to become familiar with the necessary material in the reprints, and to figure out the exact procedure necessary for completion of the assignments in the lab. Talk with an instructor often, but not until you have given the physics and procedures some thought first. We are here to instruct and help, but not to do your thinking for you.
In this experiment you will construct a Josephson junction, use it to observe the DC and AC Josephson effects, and measure the ratio of fundamental constants
$\Large \frac{2e}{h}\cong483.60MHz/{\mu}V $
You will learn the techniques in Low Temperature four wire measurements and handling Liquid Helium.
The junction
The central component of this experiment is the point-contact junction (PCJ), shown in Figure 1. It is a niobium needle that is delicately pressed against a niobium screw. Both pieces have oxide layers that form a barrier to electrical conduction between the niobium pieces. The thin oxide layers and the small contact area between the needle's point and the screw provide the weak-link necessary to observe Josephson tunneling.
The junction assembly
The junction is mounted in an assembly shown in Figure 2. To adjust the pressure in the junction, we use a mechanism called a differential screw (D), which moves the niobium needle point towards the niobium base screw (FB) with a great deal of control. The needle (A) fits into a hole in a form (B) made of a kind of fiberglass called "G10." The needle is held in place by two screws (not shown in figure 2 \[see figure 9\]). The body piece (B) can slide up and down on the two stainless steel rods (C). The flat base (FB) of the junction is held rigidly in place in G10 and cannot slide up or down. The differential screw (D) has pitch of 72 threads per inch at the top and a pitch of 80 threads per inch at the tip fixed in (B).
When the differential screw (D) is advanced one turn, it moves down 1/72". But part (B), which cannot rotate, moves up 1/80". The net motion of the needle with respect to the Nb base is thus only 1/720" (= 1/72" - 1/80"). Even with this effective pitch of 720 turns per inch, the screw must be turned very slowly to prevent damaging the needle point.
The Cryogenic Probe assembly
The junction assembly is mounted in a probe, manufactured from a ~three foot length of 1/2" diameter Stainless Steel Tubing (SST), as shown in Figure 3. This tube serves as a holder for the junction assembly and as a waveguide for the microwaves used in the observation of the AC effect.
The junction end of the probe is inserted into a cryostat filled with liquid helium. The other end remains outside the cryostat and provides the electrical connections (not shown), radio-frequency (RF) coupling port, and differential screw manipulator (labeled Hand adjustment). The junction is held in the probe by set screws (F). When the screws are turned counterclockwise (advancing them outward), the screw heads engage in a retaining hole in the SST wall, locking the assembly in place. (Note that as the screw holes in the assembly were not drilled 180 degrees apart, while the retaining holes were, both set screws cannot be engaged simultaneously. One screw goes through a retaining hole, the other can be adjusted to keep the fit secure.)
I-V Measurements
All of your measurements will be made by examining the current-voltage (I-V) characteristic of the junction. The I-V curve is traced by measuring the voltage that develops across the junction as the current is swept by a low frequency (~60 Hz) oscillator SRS DS 345. Since the impedance of the junction is small, a standard four-terminal measurement must be used. Four Wire Measurement . This is a very important way of measurement for this experiment. You will get a resistive measurement instead of a I/V curve measurement.
The electronic hookup is shown in Figure 4. The parts in the dashed area are physically located below in the small gray box next to the power meter. The four electrical connections to the junction are labeled P1, P2, and B1, B2 on the side of the box.
The Radio-Frequency electromagnetic radiation (RF)
The RF is generated by a Hewlett-Packard model 8350B sweep oscillator running in continuous-wave (CW) mode, outputting maximum power of ~20 dBm. The oscillator output is connected to an active doubler, a semiconductor device which amplifies the output by ~ 20 dBm (up to a maximum of ~ 29 dBm) and doubles the frequency. For example, setting the HP to 11 GHz and 5 dBm will result in ~25 dBm of 22 GHz RF out of the doubler. The doubler is mounted to a heat sink and to the wave guide. The wave guide connects through an isolator, a power splitter (directional coupler), an attenuator, and finally to the cryogenic probe. The isolator prevents potentially damaging reflections from returning to the doubler. The power splitter picks off a fraction of the RF power and sends it to an RF frequency measurement instrument consisting of a variably-tuned absorption cavity and a crystal RF power detector. The output of the crystal detector is an electrical signal that is proportional to the RF power incident on the detector. RF frequency measurement is achieved by tuning the absorption cavity until a reduction in the magnitude of the detector output is observed on the oscilloscope. The frequency is then read off the graduated scale on the absorption cavity. Its accuracy is much better than that of the RF source.
Cryogenics Safety
The liquid helium is contained in a ~ 5 foot tall insulated vessel called a cryostat. You must notify the lab staff at least once day in advance that you will need liquid helium for your lab and before it is near empty (about 4 liters remaining).
Read before handling of Cryogenics: Read the Cryogenic Liquids information from the campus Environmental Health and Safety (EH&S) department Cryogenic Liquids
Prep and Clean-up
There are many little parts and tools associated with the apparatus.You must keep the area clean! When you leave for the day, assemble the probe and put it back in its holder, get the cables off of the floor, and collect the tools. Keeping the area clean and organized will not only save you a great deal of time but also will serve you as practice when working in future experiments that involve a whole lot of equipment.
Making a point
Grab a pair disposable gloves to avoid any extra impurities on the Nb tip.Take a short Nb wire (around 5/8 of an inch long) and shape it with a file (See GSI or professor to cut for you 6 Inches of Nb wire). It is best to use the pen vice at your station to hold the point. File evenly around the point by rotating the vise so you get a conical shape, with sides at roughly 45 degrees to the axis of the point. (Significantly smaller angles will weaken the point, while significantly larger angles may make for a messy contact.) After shaping it with the file, smooth the surface of the tip with emery paper, or fine sandpaper. (There should be a variety of grades of sand paper under the table.) Check the appearance of the point by eye or with a microscope. The appearance should be something like Figure 7. Holding the point over a white surface, like a sheet of paper, can make it easier to see its shape.
By far the best results are obtained by leaving the point out in air to oxidize overnight. You can get a working point right away by using a hot plate, but it is extremely difficult to get the desired amount of oxidation and avoid introducing impurities. If you absolutely need a working point right away, preheat the hot plate. Then put your point on the plate for approximately 25 seconds to a minute, or until the point achieves a nice brassy color. Don't have high expectations for this hot plate point, though.
It is recommended that you spend the first day of this experiment making the points that you will use in the succeeding days. You should make at least five right away. Once you've done this, take some time to familiarize yourself with the equipment; you don't have to take data your first day. Make sure that once your done with your experiment you throw your tips away, you don't want someone else to benefit from your hard work while they do nothing.
Remove the junction assembly from the probe
This is the most delicate part of the lab. Please work over a clean surface, exercise caution, use your good judgment, and consult the lab staff if you have any uncertainty about what to do. Please refer to Figure 2, repeated here for your reference, as well as photographs of the junction assembly in Figure 8.
Two tiny set screws (F), which are not on opposite ends of the diameter, hold the junction in the probe. To remove the junction, one of the set screws must be turned in (clockwise) to the fiberglass housing, so that it will clear the holes in the stainless steel tubing. Using an allen head wrench, gently turn the set screw clockwise until it clears. Check to see that the wire leads are free at the upper end of the probe, (i.e., the rubber cork should be out). Then gently pull the junction out of the tube. A slight twisting action helps.
When reinstalling the assembly, the crucial point is that there should be no resistance to backing out the set screw. The hole must be lined up exactly and the set screw backed out only far enough to hold the junction in place. No attempt should be made to tighten it.
Installing a point in the assembly
There are many tiny parts (screws, etc.) in this assembly that can be easily lost or damaged. When disassembling the apparatus, please do it directly over a clutter-free bench top, so that when the little parts do fall, they don't make it to floor to roll around and get lost. Get a container in which to put the parts. Take all the disassembled parts and store them in a safe spot where you will be able to find them when you are ready to reassemble the apparatus. Use a minimum of force and don't be afraid to ask for help if anything seems stuck.
To install a new point, you will have to first remove the existing one.
Steps to remove the old point:
- First back off the differential screw (D) until it comes out of the housing.
- Loosen the nuts associated with the screws (See Figures 8 and 9) which have solder lugs attached to them, in piece (G10). You usually don't need to remove the nuts entirely (and its easier if you don't).
- Using small needle-nose pliers, gently pull the needle out of the housing (B). You can prevent the screws from falling off by placing two fingers on opposite sides of the assembly applying a slight amount of pressure on the screws with each finger to still be able to remove the old point. Keep your fingers held in place with your fingers until you install the new point. If the screws come off, worry not, instructions on how to install them back and fast will be provided to you below. Do this over a clean surface because the screws will probably fall out as you remove the needle.
- Throw the old needle away.
Steps to install the new point when screws still in place:
- Use emery paper (or light sand paper) to remove the oxide layer from the back end of the point (the last 3/8" or so), where it will meet the electrical contacts. Be careful you don't disturb the oxide layer on the tip of the point.
- Thread the new point through the lower screw shaft, making sure the solder lug corresponding to P1 is properly attached (see figure 9; note that the wires are color coded).
- Then thread the point through the upper screw shaft, with the lug for P2 properly secured. Tighten the nuts tight enough to make good electrical and mechanical contact, but not too tight. Too much tightening will bend the needle making it nearly impossible to remove. While holding the point close to the Nb base, but not touching it, replace the differential screw. Be careful that the tip of the differential screw does not touch the back end of the niobium needle, inadvertently grounding it. When the junction assembly is inserted into the tube, the screws and solder lugs may come in contact with the tube's inner wall, shorting them; it may be desirable to place insulating material, such as small strips of electrical tape, over these exposed connections (don't use very much; in the tube, space is limited)
Steps to install the new point when screws fell off:
- Use emery paper (or light sand paper) to remove the oxide layer from the back end of the point (the last 3/8" or so), where it will meet the electrical contacts. Be careful you don't disturb the oxide layer on the tip of the point.
- Grab your new point with the black pliers, this will provide with a better grip, but make sure not to squeeze it too hard. Then insert the point through the same whole in the assembly until you reach the point before lower hole for the P1 screw.
- Pick up one of the screws and adjust the nut just enough so the screw barely clears the hole in the nut, this is approximately the length necessary to match the level at which the point will be threading through the hole in the middle of the screws. Do the same for the other screw.
- Choose either screw and align the hole axis with the point and insert the screw in the aperture for the lower screw P1 (you need not to hook your cables just yet). While holding the screw in place so it won't move out of alignment, use your other hand to grab the pliers and thread your point through the hole in the screw until it reaches the point before the upper screw aperture. If aligned properly or close to alignment the point will make its way through the point, otherwise if after a couple of tries it doesn't go through you may have to adjust the level of the whole a little; you can do this loosening your nut just a little so it will be just below the point the screw clears the whole aperture of the nut. (Do this with the other screw as well) Repeat step 4 again until you are able to thread the point.
- Pick up the last screw and do the same thing as in step 4 but this time for the upper screw. Be careful that the tip of the differential screw does not touch the back end of the niobium needle, inadvertently grounding it.
- Now that the screws and point are in place start by loosening the lower screw nut and attaching the cable with the soldered lug corresponding to P1 and tighten back the nut after (Note that the wires are color coded and labeled at the top of the probe). Do the same for the upper screw which correspond to P2. Make sure your lugs are tight enough so they won't wiggle around. When the junction assembly is inserted into the tube, the screws and solder lugs may come in contact with the tube's inner wall, shorting them; it may be desirable to place insulating material, such as small strips of electrical tape, over these exposed connections (don't use very much; in the tube, space is limited).
Replace the junction assembly in the probe tube. As you do this, make sure that the socket in the top of the differential screw mates securely with the drive shaft running the length of the probe. It also helps to have your partner gently take up the slack that develops in the wires as you move the assembly into the probe. Secure the assembly by backing out the retaining set-screw.
After you get everything hooked up, be careful with the probe; lay it flat on the table when its not in the cryostat (you don't want to loose all your hard work to a drop or a kick).
Check for proper electrical continuity
After installing the junction in the probe, check to see that an infinite resistance separates each output (B1, B2, P1, and P2) from ground (the metal body of the probe tube). B1-B2 as well as P1-P2 should show continuity. With an open junction, P1-B1, P2-B1, P1-B2, P2-B2 should show infinite resistance. You should do these checks before every immersion in liquid helium.
Make contact between the point and the base
Connect an analog Ohm meter (e.g., the 3478A Multimeter) between P1 and B1. Set it to a scale that would display 50 Ohms easily (You may have to mess with the range). It should show an open circuit. Slowly tighten the screw at the top of the probe. Don't over-tighten the screw or you will scrape off your oxide layer and have to start all over. After a few turns, the VOM ought to suddenly show a small resistance, approximately a few Ohms, or tens of Ohms. If you can't get this behavior your point may need to be replaced.
Connect the probe to the I-V curve electronics
Connect the probe to the electronics box on the side of the power meter, here you will see 4 connections. Follow the diagram in Figure 4 to properly connect the current oscillator, preamp, scope, P1, B1, P2, B2 to the probe. Good initial settings for the electronics are...
- Scope: Set the scope for X-Y mode with 1 V/division for both axes and DC coupling.
- Low-frequency oscillator: Frequency = 60 Hz, Amplitude = ~ 5 to 8 Volts peak-to-peak (so that the trace fills the vertical scale).
- Preamp: Gain = 500, Bandwidth 0.03 Hz - 30 KHz, DC coupling for both channels.
You should see a straight line on the scope with the preamp turned off. You may have to play with a number of the above settings; every point is different. The Low-Frequency oscillator is set to 60 Hz to match any 60 cycle pick up, but the wall current may vary (20 mHz, so you may need to adjust the frequency slightly to get a signal on the scope that doesn't oscillate. By using the slope of the I-V line, calculate the room-temperature resistance of the junction. It should be the same as what you measured on the VOM.
$\checkmark$This is a checkpoint and a great time to stop and think about the physics at play. Discuss the following questions with you partner and once you feel you have a better understanding of what is happening, call over a GSI to sign you off:
Will matching the Low-Frequency oscillator to the wall current frequency affect the conclusions you will be drawing? What systematic error could occur?
Before you Insert the probe into the cryostat
Liquid helium is expensive. So you must be careful in order not to waste it. As mentioned, each time you go to cool the probe, you should check for shorts, proper continuity, and proper junction resistance. Only if everything checks out and is working properly, may you proceed to insert the probe into the cryostat. You should only need to immerse each point once. As most of the helium boil-off occurs with the cool down, it is the number of immersions, not the length of time the sample is immersed, that will determine how much LHe is used.
Liquid helium has a low heat capacity. So you must be gentle when handling the cryostat. You can boil off a lot of extra helium just by shaking the cryostat or making excess turbulence inside it. To avoid excessive boil off during insertion, it is useful to know how much LHe is in the cryostat.Follow safety precautions before starting handling this cryogenic liquid (He). You will want to first check the pressure in the tank is marking around zero, if this is not the case then check if the flow valve directly position opposite to the pressure valve (180 degrees) is open; if not contact Don Orlando or a professor immidiately. This valve regulates the pressure of the tank and should always be kept open!. If the pressure is close to zero then you shall proceed. Open the valve at the top of the cryostat. It will vent for a few seconds. There should be a long, thin (< 1 cm) metal tube with a latex membrane over one end located at your station. Hold a finger over the membrane and lower the tube into the cryostat; note when it touches the bottom. As LHe boils off, He vapor traveling up the tube should cause the membrane to vibrate. Lift the tube and note its height when you feel the vibration change; this gives you the depth of the LHe.
Before you cool the probe, check that it is completely dry; any leftover condensation from previous cooling cycles on the exterior of the probe could quickly form dangerous, neck clogging ice, while and liquid in the point assembly could ruin the experiment. Remove all the electrical connections from the probe, and check that the rubber plug (R) and RF coupling port cap are securely in place.
Carefully insert the probe into the cryostat, turning it back and forth as you go to prevent sticking. When the probe is an inch above the surface to the LHe, as you measured it, slow up its descent. Helium will rush out past the sides of the probe as you immerse it. Don't go too fast. The sound of the rushing helium should be soft and quiet, if it gets too loud (if you can hear it above the din in the 111-lab, it probably is) stop lowering the probe until it subsides, but don't stop turning it. The probe is more likely to freeze to the cryostat during excessive outflow. If the probe freezes into the storage vessel neck such that it cannot be turned or removed, call a staff member immediately. This is potentially quite dangerous as pressure in the vessel could build up.
Every day, before you go home, you should remove the probe from the cryostat; if the probe is left unattended overnight, the neck could freeze closed and there could be an explosion. You should make sure you close the cryostat valve after the probe is removed to avoid wasting LHe. Whenever the probe is taken out of the liquid helium, it should be dried. There is a heat gun on the lab table; use it to remove any condensation and heat the entire probe, including the point assembly, until it is warm to the touch (not hot: you don't want to melt anything). Even if you are leaving the probe overnight, it is important to dry it, as you some condensed water may not evaporate.
$\checkmark$This is a checkpoint and a great time to stop and think about the physics at play. Discuss the following questions with you partner and once you feel you have a better understanding of what is happening, call over a GSI to sign you off:
Explain the steps and why you must follow these instructions before inserting the probe into the cryostat, when lowering the probe down the cryostat, and after the probe has been removed.
Observe the DC effect
Connect the probe outputs to the electronics and observe the I-V curve displayed on the scope. Gently turn the screw to obtain the DC effect. You may very quickly see an I-V curve that looks like the DC effect (see Figure 10). Test whether this is a true DC Josephson effect or a supershort by bringing the large permanent magnet near the cryostat. If you have the DC effect, you should see fluctuations in the maximum current that flows without a voltage drop as you move the magnet around. If you do not observe these fluctuations, keep adjusting. You should find that the DC Effect is not too difficult to get, although it takes patience. If you don't get a good effect, try subtly raising and lowering the point with the screw; each time you do this, you make the contact at a slightly different location (were talking Angstroms here) with potentially different properties at the same time, with each contact, some of the oxide layer is removed (which may or may not be a good thing).
First you should use the analog scope to see all of your data DC and AC effects, then use the Josephson junction VI accessible from the desktop to acquire more data (This is a LabView program). You will have to switch your leads from the oscilloscope to the DAQ on your work station table. Once you open your JSO LabView program on the top tab you can select the input ports where you will now connect your leads. You should be saving your data collected.
Observe the AC effect
Once you have a good DC effect, you are ready to get the AC effect by applying the microwaves. First turn on the RF Oscillator (Figure 11) and the Microwaves doubler power supply. Then measure the RF power. Set the attenuator to 20 dB, then attach the power meter to the waveguide like this (You may have to unscrew the waveguide connection to the probe before). Set the power meter's scale to 10 mW and the mount resistance to 200 Ohms (We do this merely to make sure there is power coming out of the waveguide, don't spend too much time here). You must keep the attenuation at a value that gives a power reading without overloading the meter. The thermistor detector, connected to the waveguide, may be damaged if you apply it more than 15 mW power (15mW maximum), so be careful. That is why the microwave attenuator is set to 20dB to start.
You will vary the RF source to a frequency in the 9 - 13 GHz range( this is sent to the frequency doubler to get 18-26 Ghz). A good place to start is around the middle of the range by pressing the "CW" button followed by the frequency on the Data Entry pad press 1, 1, GHz for 11 GHz (It is usually set to this value when the RF Oscillator is turned on). The display should look like the picture below (Figure 11). You can adjust the frequency with the knob below the display, and it's a good idea to do so when you search for the AC effect.
Because the doubler doesn't precisely double the frequency of the RF Oscillator, practice measuring the output frequency by tuning the absorption cavity. Start by tuning the absorption cavity in the neighborhood of twice the displayed frequency of the RF source. Probe the crystal detector with the oscilloscope in channel 1 and set it to DC mode; you should see a line on the scope if triggered correctly. Once you get a steady DC voltage you can start varying the cavity. When you observe the highest increase in the DC signal, the cavity is tuned to the RF frequency, which may be read off of the cavity's scale (finding the cavity requires a finite tuning due to the small signal, proceed slowly). If you have trouble finding the RF frequency you can also feed your signal the Pre-Amp to amplify it by setting it to DC coupling,SOURCE A, not filter cutoffs, and a gain of 100.
The RF system will generate about 50 to 350 mW of power (The power can be more and that's okay). Record how much power you're getting (based on the power meter readings and the attenuation, as well as the frequency). Then connect the waveguide to the probe.
To find the AC effect, you really only have three variables at your disposal: RF power, RF frequency, and junction pressure. To vary the power, either use the attenuator, or the power output knob on the RF source (the former is probably best). Tweak the pressure of the point contact as you watch for faint steps. Most probably you will need to vary the microwave power and the pre-amp / scope settings to see the effect. The best advice is to play with everything at your disposal to obtain the effect. When you have as many clear steps as you can find, take a photo of the scope display for analysis. The AC effect is a little more difficult to achieve, but everyone does get it after some adjustments; have patience and be gentle. Once you have the AC effect, leave the RF frequency set-up undisturbed; you will want to make a precise frequency measurement after you have calibrated the PRE-AMP and scope.
First you should use the analog scope to see all of your data DC and AC effects.
As you might imagine, the accuracy of your results depends critically on the calibration of the voltage axis of the I-V curve. One method of calibration would be to measure the gain of each individual piece of the signal chain (junction to pre-amp to scope) and multiply them together. But that becomes impractical as the number of signal chain elements grows, and is more prone to error than the alternative. So, although the signal chain in this experiment is not too complex, you are going to use the technique of measuring end-to-end gain. Replace the Josephson junction, two wire cables, with a voltage box about 517 µV. Measure the box voltage with the DVM and hook it up to replace the point contact voltage. Measure the limits of the excursion of the trace on the scope and use this to calibrate your equipment setup. See pictures below.
Voltage Reference Box 517 µVolts
Click to enlarge
Voltage Reference Hookup
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Zero Reference on Meter- Note zero
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Read voltage on Meter + zero reading
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- Determine the number of divisions that the dot spans on the scope.
- Using the digital volt-meter (DVM)at the lab setup, measure the RMS amplitude of the signal that you are applying to the pre-amp.
Be sure to record estimates of your measurement uncertainties. Calculate the end to end gain.
Make a precise measurement of the RF frequency using the absorption cavity and make an estimate of 2e/h. What do you trust more the synthesizer reading or the cavity measurement? As with all experiments, you should be calculating and checking results in lab, as you go through the experiment. Don't take data and expect that it will all work out later.
- Be sure that your report includes the oscilloscope pictures with the axes clearly labeled and scaled for quick identification.
- Compare your value for 2e/h with that obtained by Parker, Taylor and Langenberg The Josephson Effects (Phys. Rev. Letters 18, 287 (1967)) of (483.5912 + 0.0012) MHz/microvolt. Explain any major discrepancies between your results and theirs. What are the errors on your measurements? Are your errors consistent with the quality of your data?
- When displaying the I-V characteristic, which of the axes needs high band-width. Why do we not need high band-with for the other axis?
- What physical significance does an accurate measurement of the ratio e/h have?
- What do the microwaves do in this experiment?
- Why not use another frequency range like 100 MHz?
- Last day of the experiment please fill out the Experiment Evaluation
- Richards, P.L. "The Josephson Junction as a Detector of Microwave and Far Infrared Radiation"; UCRL-19035, Lawrence Radiation Lab, pp. 1-35.
- Maglich B. "Observation of Josephson Effect and Measurement of e/h," Adventures in Experimental Physics - gamma volume, Chapter 2.
- Kittel, Charles. "Josephson Superconductor Tunneling Effect." Introduction to Solid State Physics. Third ed. New York: John Wiley and Sons, 1969. Pp. 737-743.
- Eisberg, R. and Resnick R. "Ch. 14: Solids -- Superconductors and Magnetic Properties." Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles. Pp 532. New York: John Wiley and Sons, 1974.
- Taylor, Pointon "Microwave Ultrasonics"; Contemporary Physics, Vol. 10, No.2, 1969, pp 159-178
Other reprints and reference materials can be found on the Physics 111 Library Site


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Legal experts: Cannon's lawyers possibly already met with U.S. attorney
by: Jim Bradley Updated:
CHARLOTTE - Nearly a week after former Charlotte Mayor Pat Cannon was arrested, neither his attorney nor federal prosecutors are taking publicly about the case. However, local legal experts say Cannon's team has likely already met with the U.S. attorney's office and could already be testing the waters for a possible plea deal.
The criminal complaint filed in the case against Cannon lists three charges related to public corruption, bribery and fraud. But prosecutors could seek even more charges when they take the case to a grand jury, which is expected to happen later this month.
"Their investigation may involve many other matters, many other individuals and many other incidents," said Charlotte attorney James Wyatt.
Wyatt says Cannon's attorney, James Ferguson, may already be trying to minimize the potential for more charges by working with federal prosecutors toward a potential plea in the case.
"There could be what's called 'charge bargaining,' where you would attempt to convince a prosecutor to bring a certain charge but not another," said Wyatt.
In order to get cooperation from prosecutors, though, multiple legal experts Eyewitness News has spoken with suggest that Cannon would likely need to offer something himself.
They said Cannon would have to tell prosecutors if there are other incidents of bribery or illegal activity beyond the current allegations that he accepted thousands of dollars in bribes from undercover FBI agents posing as developers.
"The government may look to see if Mr. Cannon is willing to cooperate and to testify against people who may be involved in those transactions or other transactions," Wyatt said. "They'll want to pursue every avenue. They'll look for him to be completely truthful with them and if not that could cause big problems."
So far Cannon has not indicated how he might plead to the charges he faces. They carry a maximum penalty of 50 years in prison.


text:
Follow Harriet on Twitter
About Harriet
- The Poetry Foundation's blog for poetry and related news.
- More about Harriet
- Contributors
- Archive
Poetry News
The White Cliffs of Dover's First Writer in Residence
The White Cliffs of Dover, made poem-famous by Matthew Arnold, have their first writer in residence.
From CBS:
Philosopher Julian Baggini has a high-altitude new assignment — pondering the significance and symbolism of the White Cliffs of Dover, landmarks he likens to Britain's Statue of Liberty.
The National Trust, guardian of the chalk cliffs on England's southeast coast, has appointed Baggini the cliffs' first writer in residence.
Starting Monday, he will spend a week living in a cliff-top lighthouse, writing and speaking about the cliffs and talking to local residents.
Baggini said he hoped to learn "what the white cliffs of Dover mean for British people, including those for whom the cliffs were the first sight of the country which would become their adopted home."
The cliffs loom above the English Channel at its narrowest point, and so have been the first sight of Britain for centuries of visitors, immigrants and invaders.
"For millions of Britons living across the world, the white cliffs is a clear symbol of Britain, in much the same way that the Statue of Liberty has defined America," said Baggini, whose mother is from Dover and whose father came to Britain from Italy in the 1960s.
"Even if we've never been to or seen the white cliffs of Dover, there is a collective sense that they matter."
Full article here.
Posted in Poetry News on Monday, August 27th, 2012 by Harriet Staff.


text:
massage and bodywork professionals
a community of practitioners
596 members
141 members
269 members
211 members
67 members
Can massage therapists bill CPT code 97110 - Theraputic exercise? Sometimes, with the right client, I teach a few simple exercises in order to aid their recovery between sessions.
Started this discussion. Last reply by Gary W Addis, LMT Mar 20.
All the industry leaders, or some of them anyway... Come in here to sell their continiuing education deals for credit in order to maintain your license.. And I understand that, and it makes sense.…Continue
Started this discussion. Last reply by Gordon J. Wallis Dec 16, 2015.
I was debating weather to put this on the Typical Experience thread or make it a new thread. I decided to make it a new thread because its a bit different. Rightly or wrongly it shows the way I think…Continue
Started this discussion. Last reply by Gordon J. Wallis May 25, 2015.
Diane Lake LMT, NCTMB asked me, after I'd made a chat coment. "Gordon, how does paying for continuing education restrict your freedom to learn?" In the past I've made lots of coments in here about…Continue
Started Feb 18, 2015
Email me some videos at firstname.lastname@example.com
Hello Gordon! Just wanted to check in, hope all is well with you!
Hi Gordon,
I enjoy your "down to earth" posts!
Hey, buddy.
I just stumbled into a forum thread "Flat Back Syndrome".
Your thoughts? The MT could use your advice, I think. Was posted on the 10th, and only two comments. I suggested TPs in the iliopsoas and abs pulling the hips into anterior tilt. Any advice yo ucan give the MT?
Hi Gordon, just saw your friend request. Thanks!
Hi Gordon, Thanks for the friend request. I just discovered this site and became fascinated with your thread "Just Dumping" on the how the Massage/Bodywork profession is perceived by the general public and other health professionals. It's a subject about which I have much to say. As one who has been doing this work for over 25 years but who just finally jumped through the hoops for the license I am experiencing a very rude awakening as to the realities of this field as a business and as a profession. I shall expand my thoughts as time goes on. I especially welcome the input of successful male MTs as I am discovering that obtaining bread and butter work in this field may not be in my cards. Spas and health clubs are not even responding to my resume, or if they do then it doesn't even progress to the practical part of working on someone to experience my skills.
I gather you're a martial artist. Me too: 1st Degree Black Belt in Kendo, Training in Chi Gong, Bagwa, Tai Chi and some Aikido.
Thanks for connecting!
© 2017 Created by Lara Evans Bracciante. Powered by


text: I carry a 40 cal. Sub compact as my EDC. I would like to remove the decocker on the right side. The decocker protrudes and prints in my IWB Crossbred holster. Can anyone tell me if there is someway to replace it or do I just need to grind it down so it is not so proud. Thanks


text:
|Patriots Look Poised For Another Super Bowl Run
|Bruins Trade For Drew Stafford
|Black and Gold Bruins Turn Yellow On Parade Day
|Inconsistency Will Continue For Bruins Unless A Change Is Made
Things are hot, with both conferences' 8 seeds leading their closets contenders by half a game. The West is once again making its case for the elite conference, with not one team below .500 team in sight of a playoff spot. Speaking of which, the Nets actually won last week. Twice. And they're only 15.5 games back of the 1 seed and 7.5 back of the 8 seed, so there's still plenty of room and time for them to move up. Not likely. But enough bashing the league's patsy team; there's been plenty of movement in the seeding in the past week, so let's look at what would happen if the playoffs started as of Wednesday December 9 at 11:15pm (sans the late game):
LA has now won a league-best nine straight, making them undefeated since the return of Pau Gasol. With the Lakers playing the way they are, does anyone really expect them to not sweep a team like the Thunder?
Denver lost to Charlotte of all teams Tuesday, while Houston beat Cleveland of all teams Wednesday. The Rockets are looking pretty decent, and even though the Nuggets should win, the Rockets have everything they need to knock off Denver if Denver isn't careful; Houston even took the Lakers to seven games last year.
Dallas won a one-point squeaker over Phoenix Tuesday, while Utah was locked in a close late match on the road against the Lakers Wednesday. The Mavericks have struggled in the playoffs ever since losing the NBA Finals, while the Jazz haven't made much of an impact since they opposed Michael Jordan and the Bulls. Actually leading their division again, the Mavericks have done very well for themselves this season, and have the home record to trounce Utah.
Phoenix has been slipping ever since their strong start, losing two straight, while Portland took a game in Indiana Wednesday. Still, Phoenix remains unbeaten at home. Phoenix should be able to use this to pick up the win, and has the match-up to take a game in Portland as insurance.
Detroit has won three straight, but remains at 9-12. Orlando has won six straight, though, and has a vastly superior advantage in the home/away match-up, in both categories. Detroit has had a tough time in recent years, and this year looks to be no different.
Do we really need to mention anything here? After 33 and18-point victories, will the Celtics really run into problems? Charlotte is not Atlanta, here.
Atlanta's 9-2 home record against Milwaukee's 2-8 road record leaves no question who the winner will be here. Even at the 6 seed, Milwaukee is still under .500 at 10-11. This is just another example of a sub-par team getting into the playoffs because the East needs to send eight teams, especially after the Hawks have won against Dallas and Chicago to feel better after losing to the Knicks.
After a tough loss in Houston, Cleveland slips a spot, giving us a look at what might have been if Miami had won game seven in Atlanta last year. Cleveland has lost two straight, but LeBron can only lose for so long before picking things up again, especially with Shaq having his back. Miami will have to charge forward with much vigor if they want to win this one. Cleveland has already lost to Charlotte, so that might not be too much of a stretch.
Tags: Atlanta Hawks, Boston Celtics, Charlotte Bobcats, Cleveland Cavaliers, Dallas Mavericks, Denver Nuggets, Detroit Pistons, Houston Rockets, Los Angeles Lakers, Miami Heat, Milwaukee Bucks, NBA Playoffs, Oklahoma City Thunder, Orlando Magic, Phoenix Suns, Portland Trailblazers, Utah Jazz


text:
Should your preferred language not be available, contents will be displayed in English.
Ate de Jong, director of 'The Blitz' ('Het Bombardement' in Dutch), predicts that Auro 11.1 will become the new standard for cinema audio. 'The Blitz' tells the story of a young boxer and a wealthy socialite whose quest for love is overshadowed by the German invasion and subsequent bombing of Rotterdam in 1940. "As the movie is filled with dramatic flyovers and enveloping war scenery, the sound format helps to bring the story in a better way," explains Ate de Jong.
Watch the exclusive interview with Ate de Jong and Gareth Llewellyn, re-recording mixer for 'The Blitz', and discover how Auro 11.1 contributes to the ultimate movie experience.
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text:
|Patriots Look Poised For Another Super Bowl Run
|Bruins Trade For Drew Stafford
|Black and Gold Bruins Turn Yellow On Parade Day
|Inconsistency Will Continue For Bruins Unless A Change Is Made
Perhaps the guys who are in limbo the most are the guys who saw little to no time. Carlos Arroyo, Troy Murphy and Sasha Pavlovic were all mid-season pick-ups and all three will most likely not be returning to the Celtics next year.
Von Wafer, on the other hand, has a chance to be back in Boston. Wafer showed at times that he can come in and provide a spark off the bench.
Arroyo only appeared in 15 games for the Celtics averaging 2.4 points in just over 12 minutes of play. Arroyo's contract was dirt cheap at $407,772. Despite the fact that the Celtics could sign Arroyo for little to no money, I don't expect him to return. The first reason being they have to resign Delonte West who is also a free agent. The second reason being Avery Bradley will be on the Celtics roster this season and grab some minutes. The Celtics are not going to sign a guy who would be their fourth point guard.
Probability of return: 0%
A lot was made when Troy Murphy decided to sign with the Celtics instead of the Heat. Looking back on it now, we see that Troy Murphy was a non-factor on the Celtics. Murphy only appeared in 17 games, averaging 2.6 points and 2.2 rebounds in 10 minutes of play. Troy Murphy hasn't had a good season since 2009 when he was with the Pacers and more importantly, he has only played in 35 games the past two years.
Probability of return: 0%
Sasha Pavlovic will not be returning to the Celtics. He played in only 17 games and averaged 1.8 points a game. Celtic fans have a better chance seeing Troy Murphy back than Sasha Pavlovic.
Probability of return: 0%
Von Wafer appeared in 58 games for the Celtics averaging 3.2 points a game. Von Wafer is a decent bench player who can provide a spark for them from time-to-time. Unfortunately for Wafer, most people remember him for missing a dunk against the Wizards and then posing afterwards. With that said, the Celtics could bring him back for around $1 million a year.
Probability of return: 30%
Tags: Carlos Arroyo, Celtics, Sasha Pavlovic, Troy Murphy, Von Wafer


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text: The Brian Lehrer Show Published by The Brian Lehrer Show Listener Call In Download this audio Want to embed this player? Use the code below. More info. <iframe frameborder="0" scrolling="no" height="130" width="100%" src="https://www.wnyc.org/widgets/ondemand_player/wnyc/#file=/audio/json/24575/&share=1"></iframe> Share on Facebook Share on Twitter Email a Friend Listeners weigh in on Mitt Romney: has he flip flopped on issues like abortion, gun control, and gay rights--or have his positions evolved?


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Thread: Browns Running back Injured?
Browns Running back Injured?
The Crazy Newshound has found a new Ravens article.
Cleveland Browns running back Peyton Hillis is not practicing because of an unspecified injury.
The Browns (5-9) host the Ravens (10-4) this week.
Hillis has 252 carries and 59 catches in his first season with the Browns, who acquired him in a trade with Denver. Coach Eric Mangini doesn't believe Hillis, who has 1,129 rushing yards, is wearing down and said the workhorse back's injury "is nothing that I'm that concerned about."
Hillis rushed for 144 yards and a touchdown in the previous matchup between the teams.
Link to the full story.]


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|More images
Ganguly has met with moderate success at the start of his country's first full tour of Pakistan since 1989, but he knows the time has come for him to stand and be counted.
"Yes, I must get good runs in this important game," the Indian captain said ahead of Friday's third One-day International in this Northwestern city.
With both sides locked 1-1 in the five-match series, the victor on Friday will have a clear edge going into the last two games in Lahore on March 21 and 24.
Both the matches so far at Karachi and Rawalpindi produced in excess of 300 runs in each innings, so Ganguly's contributions of 45 and 15 were meagre by his lofty standards.
The stylish left-hander is one of the most prolific batsmen in Limited Overs cricket with 9,204 runs from 246 games. His 22 centuries are only second behind teammate Sachin Tendulkar's world record tally of 37.
Most of those hundreds came as an opening batsman, but Ganguly now bats in the middle-order to give the in-form duo of Tendulkar and Virender Sehwag the opportunity to make aggressive starts.
"I had the luxury to play more overs when I opened, but I have tried to adjust in the middle-order," he said. "It is not an excuse. I have to get runs in any position."
The pressure of touring Pakistan, where cricketers' movements are restricted by the tight security both at the team hotels and outside, would test the patience of even the most hardened tourist.
But Ganguly remains unconcerned. "The security does become stifling at times, but we have taken it in our stride," he said.
"There is no room to complain. We have been looked after very well on the tour so far."
Ganguly's worries are centred more on his depleted bowling attack, trying to contain without much success the free-stroking Pakistanis on beautiful batting wickets.
The Indians, already without three injured frontline bowlers, Harbhajan Singh, Anil Kumble and Ajit Agarkar, were hit further when left-arm seamer Ashish Nehra was sent home with a hand injury.
The tourists have called up two-match rookie Amit Bhandari as a back-up for the Lahore One-dayers, making young Irfan Pathan an almost certain starter on Friday in Nehra's place.
"It's obvious the batsmen have to deliver every time," Ganguly said. "We have to put up enough runs on the board, because containing the opposition is not going to be easy on such good wickets."
The outspoken Indian captain, a master at playing mind games, has already taken a swipe at Pakistan's fiery paceman Shoaib Akhtar, whose controversial action has been a hot topic in world cricket.
Asked at a press conference if Akhtar's deliveries were legal, Ganguly shot back: "What do you think watching on TV? I think we all know the answer, don't we?"
Pakistan have so far refrained from joining issues with the Indian skipper, but his comments are certain to add spice to the last three One-dayers and the three Tests to follow.


text:
How often should fluids be changed on 323I 2008
how often should I change my fuilds, for example bmw dealer told me I should change my oil every year or 25,000km. My buddy has a 2006 5 series and he does his every 6mth or 6000km to avoid any problems. any advice would be great thank you.
15 years of history and millions of BMW show clearly that there isn't any problem with every year or 25 000km, assuming the right oil and OEM filter.
The car will tell you when to change oil.
6000km or 12 months for me
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My '07 335i is super low mileage weekend/summer car. I stick to the once a year oil change. If mileage were to suddenly increase, I doubt I would go longer than 6000-8000km in between changes.
Thats just my opinion; your mileage may vary *grin*
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Scores Arrested At North Carolina 'Moral Mondays' Protest Against Austerity
Police arrested 151 people who were taking part in a peaceful demonstration Monday outside the North Carolina Legislative Building in Raleigh. The demonstration drew more than 1,000 people for a fifth consecutive week as part of the "Moral Monday" movement, a protest against proposed cuts to education and social programs.
The protests, organized by the NAACP and faith-based groups, began a little more than a month ago. They continue to grow as more residents call for an end to a Republican-led proposal for spending cuts that protest leaders claim will harm middle- and low-income residents.
"Don't ask us when we'll stop. Ask Tillis and Berger and the man in the governor's mansion. When will they stop?" said Rev. William Barber, NAACP state president, according to a North Carolina Public Radio recording of the demonstration. "When will they stop hurting children? When will they stop hurting the sick? When will they stop hurting our public schools? When will they stop hurting our economics? Because if they stop, we'll stop. But we can't stop as long as people are being hurt."
Barber was joined by faith leaders, community organizers and professors who say they are fed up with the proposals of their elected representatives
The Raleigh News & Observer reports that some protesters attempted to walk into the Legislative Building, prompting the largest number of arrests in the series of Moral Monday protests.
North Carolina Public radio reports that the group is protesting the Republican-led legislature, demanding that it not pass bills that they say would restrict voting rights, shorten unemployment benefits and cut funding for education.
In February, the North Carolina General Assembly approved a 35 percent cut to unemployment benefits, dropping the weekly sum from $535 to $350. Some elected officials believe that this proposal will hurt middle-class families struggling to make ends meet.
"Families struggling to secure their place in the middle class will suffer a grievous blow, and the state's economy will lose $780 million in federal funds that are vital to reducing North Carolina's high unemployment rate," said Seth D. Harris, the acting U.S. labor secretary, in a press release.
The state legislature is also considering a proposal to give taxpayer dollars to private schools through vouchers, as well as a voter ID law that opponents say is designed to curb Democratic votes.
There are no reports of Republican legislators meeting with protest leaders, but some have commented that they intend to maintain their support for the policies that have riled thousands.
"I think of it like Carolina playing at Duke," Republican Rep. John Blust told the Charlotte Observer. "I'm not going to let the Cameron Crazies throw off my game."
Stories published in our Hot Topics section are chosen based on the interest of our readers. They are republished from a number of sources, and are not produced by MintPress News. The views expressed in these articles are the author's own and do not necessarily reflect Mint Press News editorial policy.
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text:
For the first time in my life, I have bought an older home.
Jenn and I have owned three other houses – two of them brand new and one was four years old.
Now we have purchased a home that is 28 years old.
Yeah, that wood paneling with wallpaper over it that looked like wedding cake was beautiful. The two different leaks in the roof were nice. The discovery of a pile of trash underneath the house was great.
With the work that we wanted to accomplish on the house, we decided to delay moving in until we had addressed many of the known issues. We have worked tirelessly for almost two months to get the house ready, and we finally moved in last weekend.
We're tired! It has been nearly a full-time job getting this house ready. I spoke four times at NewSpring Church on Sunday, February 25th, and when I finished the fourth message, I got into the car and drove to the house to work on the house. My days that I have taken off from my crusade have been spent at the house. As we worked on repairing the roof, I managed to smash my thumb to oblivion using a 22 oz Estwing hammer.
You may be considering buying and fixing up a house. You may be wondering if it would be worth the effort. I will tell you this – I am the son of a home builder, and it has been very difficult for me. I don't do this sort of thing EVER, but I kinda sorta know the general activity required.
I would say this, we have gained some significant sweat equity and learned a lot by fixing up this house, but I would not do this again for my personal residence. EVER.


text:
Harrowing Video of Ducks Crossing Highway
This video had me on the edge of my seat, yelling, 'What…are you CRAZY??'
It's like watching a game of Frogger…a mama duck crossing a busy Toronto highway with her baby ducklings in tow. A helicopter caught it on tape!
Subscribe to 94.3 The Point on
Did anyone else cheer when that ended?
They ALL made it. I really thought for a second a few of them were goners when some of those cars passed.
Poor little ducklings tossed around like rag dolls.
That's one crazy duck.
Would you have stopped to help the ducks if you saw them while you were driving?


text:
Move mouse over image to Zoom..
ZE-561 Antique Reproduction Bird Motif Door Plate c 1887
Tall & narrow Victorian backplate by R&E, featured in Catalog VII in 1887. Lost wax cast, it has been given an antique brass patina and lacquered to preserve its tone. Note the detailed birds design near the center of the door plate.
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text:
Wolverine Zombie by ARTofANTWatch
©2008-2017 ARTofANT
I'm not eally sure how being a zombie effects Wolverine but it can't be good.
Amazing artwork! I promoted it on facebook.com/ZombieIQ
Great work!
Scary good
He actually can't be a zombie, as he is immune to any disease Cx
it a virus made by the skrulls
You're assuming it's infection based. The original Zombie concept was magic/voodoo. And even if it is infection based he may become infected for a time until his mutant immune system catches up.
right yeah Cx didn't that point of view coming, but that's true Cx tho, would he be infected long enough to actually become a zombie?..
I think it's possible.
Then, if you think about it, the next time the Zombie Wolverine withdraws his claws (Ermahgerd, that rimed!), won't he just loose them? Lol, I mean there will not be any skin to keep them in place
Maybe. Depends on how far along the decay is but I don't think it's the skin that's a factor. All bone is held together by ligaments and moved around by muscle and tendons so at some point when his flesh totally decays, sure, he'll just fall apart. Haha.
This wolf-thing eat brains, yes-yes?
WAIT-WAIT! NOT ONLY MY-MY!!! It's too brilliant
WAIT-WAIT! NOT ONLY MY-MY!!! It's too brilliant
Reminds me of some bat man, not the Bruce Wayne kind either.
cool but would his skeleton be metal
I don't think he could actually become a zombie due to his mutant healing ability
Yeah I know Marvel had that zombie spin off but it still don't make much sense
Most people these days mostly assume a virus is the source of a zombie outbreak but that's relatively a new concept. It was originally a magical source like a ghoul or a mummy so that could easily cause a zombie Logan. Zombies in general don't really make much sense they're fun. Saying a zombie Wolvie doesn't make sense is really just being a party pooper isn't it?
I guess you have a point, I'm keeping a open mind here but I just don't really like zombie versions of awesome characters, it kinda takes away from how cool they are.
the scary part is that wolvie can live through a nuclear bomb...
really awesome work ! i really like the marvel zombies
Holy shit. X'D I think I just died a little on the inside.
This is amazing!! Well done!!
This is amazing!! Well done!!
Is this from the Marvel Zombies series?
Awesome :3
Wolverine has a healing factor, which means he's now an undead... undead i suppose.
anyway awesome drawing.
anyway awesome drawing.
Wow . . . just . . . wow


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Sbc Turbo Build Questions?
So this morning I woke up and thought a turbo'd 55 Chevy gasser would be cooler then a supercharged one, plus id make more power! And cost about the same. The problem is I don't know where to start, I'm not familiar with turbos! What parts will I all need I know for sure I need a blow through carb or at least convert one to. If I can find a good kit for 2-3 thousand awesome, if I can build something that works that is cheaper even better! The engine is a 9:2:1 flat top 355 010 4 bolt main block, stock short block, small cam its actually perfect for boost 114 lsa, vortec heads, and that's about it. I want something that will work on the stock short block but has room to grow once I build something with forged internals. Any info helps, any junk yard builds with great success I would like to hear too, budget in mind, but don't mind saving and spending 3 grand if it's worth it.
Also looking for 400-450 rwhp maybe 500 on a stock short block.
you can fab up a decent single turbo system for your budget or less, intercool it if you can, you'll probably only need about 5-10psi and with a really good tune can get away with pump premium (93 octane).
building your own blowthrough carb requires a lot of attention to detail- its not something you want to mess up, and make sure you keep a very close eye on a/f ratios and detonation when you're doing the tuning.
My goal is to keep the car as streetable as possible. 93 and possibly race gas on the weekends
I have a friend who builds turbo kits for a living. try him at his site he'll give ya the info.
Factory flat tops? The ones with the 4 eye brows.
Sts would be awesome, but I have no clue where to start.
single or twin turbo? a couple GT-40s on headers can take you a long ways. 700 hp should be no problem.keep your mixture mid 12s for safety. I think 3,000 is optimistic.
Excellent read, great insperation....I have read all zillion pages a few times now for a laugh...
I said twin turbo because that makes it very fast to spool up with reverse facing headers putting 2 little turbos out front. A single turbo is more than enough for decent boost.
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Paratransgenic control of vibriosis in shrimp aquaculture
Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/13172
Paratransgenic control of vibriosis in shrimp aquaculture
Subhadra, Bobban
Rubin, Robert
Committee Member(s)
O'Hair, Kevin
Peabody, David
Wilmer, Sibbitt
Peabody, David
Wilmer, Sibbitt
University of New Mexico. Biomedical Sciences Graduate Program
Degree Level
Infectious diseases are an increasing threat to shrimp farming industries worldwide and account for nearly $3 billion of annual economic loss. The need to devise novel approaches against these infectious agents is pressing, as traditional methods are insufficient to ward off infections. The main aim of this study was to apply paratransgenesis to control infectious agents mediating shrimp diseases. As proof-of-concept we showed that Artemia, a food source in shrimp aquaculture, internalized bacteria expressing recombinant proteins. Stable expression and retention of these marker molecules up to 10 hours after feeding with the transgenic bacteria were evident within the gut of Artemia, coincident with the time period of highest density of internalized microorganisms. Uptake of recombinant proteins by Artemia occurred during active feeding, with their rapid depletion during a non-feeding washout phase. Bioamplification of recombinant proteins through increasing trophic levels via the paratransgenic approach was then tested. For this trials were conducted aimed at delivery of recombinant proteins to larval stages of the commercial white shrimp, Litopenaeus vannamei, via direct feeding of transgenic bacteria or via feeding transgenic bacteria-engorged Artemia. In both trials, shrimp extracts showed recombinant protein accumulation during the active feeding phase and decrease during the washout period. From these studies we concluded that transgenic expression of proteins in bacteria can be detected through their paratransgenic expression in Artemia and shrimp, suggesting that this commonly employed feed organism could be applied to target infectious agents in shrimp mariculture. For this purpose we identified cecropin and melittin as effective antimicrobial peptides against vibrio species, and their combination was particularly potent without toxicity toward probiotic bacteria or algal feed organisms. Furthermore, unlike mellitin alone antibiotic resistance did not develop in Vibrio strains exposed to the cecropin/melittin mixture. Finally, the melittin gene was transduced into B.subtilis, and expression of significant levels of melittin was detected, although this was insufficient to cause detectable anti-vibrio activity. Optimization of B.subtilis expression for higher antimicrobial peptide production or employment of algal strains for anti-infectious molecule expression are key future directions for developing a paratransgenic approach as an environmentally sustainable disease mitigation strategy in marine aquaculture.
July 2011
Paratransgenesis, Shrimp diseases, Aquaculture


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Indy Audio Labs Acurus ACT 4 AV Preamp Reviewed
Dennis Burger examines the Acurus 4 from Indy Audio Labs. This 13.3-channel AV preamp supports Dolby Atmos, DTS:X, and HDMI 2.0 with HDCP 2.2. Read More
Trinnov to Show Altitude16 Prototype at ISE
At the upcoming Integrated Systems Europe (ISE) trade show in Amsterdam, Trinnov will show off a prototype of its new Altitude16 processor. Trinnov says the new mid-level processor will "inherit all the ground-breaking core technologies" of the higher-end, highly acclaimed... Read More
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Myron Ho explores Anthem's AVM 60, an 11.2-channel preamp/processor that comes fully loaded with Dolby Atmos/DTS:X support, full UHD/HDR pass-through, DTS Play-Fi whole-house music streaming, Anthem Room Correction, and more. Read More
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Dennis Burger reviews Emotiva's flagship XMC-1, a 7.2-channel AV preamp that carries an asking price of $2,499. Read More
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NAD's new Masters Series M17 is a high-performance seven-channel AV pre/pro with a modular design that helps it keep up with the changing landscape. Greg Handy puts this processor to the test. Read More
Home Theater Review's Best of 2014 Awards
Home Theater Review presents its Best of 2014 Awards. We've surveyed all the products reviewed over the past year and selected the ones we think are the most compelling. Check out our list and see if your 2014 favorites made the grade. Read More
Integra DHC-60.5 7.2-Channel A/V Preamp
In weighing the relative merits of AV receivers vs. AV separates, I think even the most staunch supporters of the latter (yours truly included) have to concede that AV preamp/processors generally lag behind their integrated brethren when it comes to... Read More
Everything You Need To Know About Home Theater AV Preamps1.0 Background
1.1 What is an AV Preamp?2.0 What Does an AV Preamp Do?
1.2 Brief History of the AV Preamp
2.1 The Role of HDMI in today's AV preamp3.0 Notable AV Preamps
2.2 Surround Sound Modes in AV preamps
2.3 Room Correction and EQ in AV preamps
1.0 Backround
1.1 What is an AV Preamp?
An AV preamp is an audio/video component that has many functions in a modern home theater system, including switching audio and video inputs, adding or processing surround sound to the audio signal path, processing or scaling video signals from sources and beyond. Unlike a traditional "receiver," an AV preamp does not have internal amplifiers. AV preamps are plugged into power amplifiers that often drive between five (5.1) and seven (7.1) speakers. They also output signal for the LFE or subwoofer channel of surround systems, which is also known as the .1, made famous in the term 5.1 or 7.1 surround.
1.2 Brief History of The AV Preamp
Born from AV and even stereo receivers, AV preamps have almost always been step-up, higher-end solutions for the needs of audiophiles and movie enthusiasts who want to create the movie or surround sound experience in their home theater or multi-channel audio systems. AV preamps or surround sound processors (SSPs) have always been used in the professional cinema world, as the need to fill large physical spaces required cienplexes to use large speakers and beefy power amplifiers.
Today, audiophiles and videophiles alike use AV preamps to achieve top of the line surround sound reproduction for sources like DVD-Audio, SACD, HD DVD, traditional DVD-Video and Blu-ray. With Blu-ray (as well as the now dead HD DVD format), AV preamps usually come packed with HDMI inputs, so that the master quality sound and 1080p video can be sent into the preamp via one copy-protected cable. Chipsets have been slow to get to market, keeping receivers and AV preamps alike somewhat behind the technological curve when it comes to AV source-switching, in contrast to the HDMI connectivity of the latest sources like Blu-ray players, as well as the latest 1080p HDTV sets.
2.0 What Does an AV Preamp Do?
• AV preamps boost the line level audio signal from analog and digital sources to levels that a power amplifier can detect and boost again to successfully power a loudspeaker.
• AV preamps accept multi-channel analog audio inputs from sources like SACD players, DVD-Audio players, HD DVD players, D-VHS decks and PCM audio from Blu-ray players.
• AV preamps process audio signals that are mono, stereo or multi-channel into a variety of surround sound modes. The user can often select these modes or can use the default mode on the preamp. AV preamps often have matrix modes that can make a stereo signal into a faux surround sound format. Yamaha was famous for these modes in their receivers in the 1980s. Advanced processing has made the matrix modes on many AV preamps to sound quite convincing. However, it is always best to have source material mastered for surround by a mixing engineer on the disc itself.
• AV preamps accept many varieties of video inputs via HDMI, DVI, component video, S-Video and often composite video sources.
• Some AV preamps come with video processing that allows the user to up-convert video sources from traditional standard-definition 480i video to higher resolutions that match the resolution of their HDTV sets such as 720p, 1080i or 1080p video. Note: up-converted video never looks as good as the native HDTV signal, even when using the highest-performance video processing, which is only found in the most expensive AV preamps. More commonly, video processing is done outside of the AV preamp, but with the rise in popularity of HDMI for both HD audio and video sources (specifically Blu-ray), more and more AV preamps are adding HD-quality video processing.
• Some AV preamps have tuners built in that can receive AM, FM, XM, Sirius or, most rarely, Internet radio.
• AV preamps are often controlled by RS-232 connectivity, which is a hard-wired control system used in the highest-end remote systems, such as Crestron, Control 4 and AMX. Other AV preamps work with RF and or IR remote control systems.
• AV preamps often come with programmable and backlit "learning" remote controls that can be used to run entire systems.
• Many AV preamps have SD or even HD video displays on the front of the component, which allow programming, source control and even previewing source material right on the front of the unit.
2.1 The Role of HDMI in Today's AV Preamp
The HDMI input is the biggest addition to AV preamps since the advent of Dolby Pro Logic surround sound in the early 1980s. HDMI is an encrypted way to send HD-quality audio and 1080p HD video via one cable from a modern source like a Blu-ray player (it's also used widely with cable boxes, HD DVD players, HD DVRs and HD game machines at varying other levels of HD resolutions, both with copy protection and without) to an AV preamp. AV installers and custom AV integrators report enthusiastically that all has not been perfect in the world of HDMI, which on the surface seems like a one-cable, copy-protected solution. Many early HDMI systems that used HDMI solely for video were so unreliable that installers would only use component video (an analog cable capable of passing up to 1080i resolutions) for their systems. Some consumers rebelled against HDMI because of the idea of computer companies forcing copy protection into their systems. However, Hollywood wasn't going to release HD content without some level of copy protection. In the case of HDMI, the copy protection is called HDCP and, like all copy protection schemes, it has been broken. Most consumers don't care, but Hollywood does, because of rampant overseas bootlegging.
HDMI to date has gone through numerous updates, leaving mainstream and audiophile manufacturers scratching their heads. Compatibility issues with different versions of HDMI are rampant and OEM manufacturers (the companies hired to actually make AV preamps for many audiophile and mainstream companies) struggle to keep up with the connectivity changes.
Handshake issues also plagued many AV preamps, as copy-protected HD sources didn't always like being connected through an AV preamp, even if the preamp only switched video. Often, an HDMI 1.3a source like a Blu-ray player wouldn't effectively connect via an AV preamp equipped with an earlier HDMI version, causing a handshake issue and passing no video. More frustratingly, HDMI handshake issues can be intermittent, causing systems to work effectively sometimes and fail to pass signal at other times.
HDMI connectors are made of plastic and do not lock in place. They break easily (albeit not as easily as S-video connectors) and can fall out of their inputs, causing system problems.
HDMI and other soft and firmware updates have been added to AV preamps, either via Ethernet connections to the Internet and or via computer updates, mostly from PCs. This has allowed many AV preamps to stay current with the laundry list of features consumers demand, as well as to keep up with the connectivity updates that come from HDMI chip-makers.
2.2 Surround Sound in AV Preamps
While most AV preamps can very effectively pass a stereo signal, most clients use them to receive surround sound material and/or convert stereo signals into faux surround sound.
Native surround sound can come from sources like DVD-Audio and SACD via a 5.1 (six analog) inputs or via digital audio inputs, say, from a DVD-Video player playing a movie using lossy surround sound formats like Dolby Digital or DTS. Native 5.1 and 7.1 surround sound can also come on an HDMI cable, along with HD video. The latest HDMI AV preamps can take this pure bit-stream HD audio information and process it into Dolby True HD or DTS HD Master Audio. This is the state of the art of surround sound at this point.
Matrix or faux surround sound modes were made popular by Yamaha in their 1980s receivers. They added delay and redirected sound to affect speakers in relatively crude ways, creating effects like "church" or "stadium," which most purists avoided. Today's matrix surround sound formats are very good, thanks to the improved software and internal processing power in AV preamps. High-end companies like Meridian have modes such as "tri-field" that can effectively expand a stereo source from a compact disc to widen the sound field to use most of the front speakers. Even audiophiles today find these matrix modes to be dramatically improved.
2.3 EQ and Room Correction in AV Preamps
One of the newest trends in AV preamps is the addition of room correction. As AV preamps have adopted more and more computing power, it is now possible for them to equalize your system to deal with acoustical anomalies in the room. Set-ups range from amazingly simple to very complex, with many needing professional calibration by an installer or acoustician.
Audyssey is at the forefront of room correction for home theater preamps. Meridian, Harman, Integra and many others offer room correction for their latest AV preamps. Many come equipped with a mic and an auto set-up that most savvy consumers can use with desirable results. Neptune Audio makes an outboard EQ and room correction model for higher-end home theater system. Wisdom Audio uses Audyssey EQs in their electronics for their ultimate-grade on-wall and in-wall speakers.
3.0 Notable AV Preamps
• Lexicon: Lexicon, owned by Harman International, is a reference-standard brand for professional AV preamps, has also made and sold some of the more important AV preamps in the history of home theater. These preamps include the Lexicon CP2, which was used to add Dolby Pro Logic to existing audiophile systems in the late 1980s and early 1990s. Another notable AV preamp from Lexicon is the MC12 HD, which is a state of the art HDMI switching audiophile preamp costing nearly $20,000.
• Fosgate: Fosgate is a brand of electronics that was well known in the world of pro audio and even car audio. They made groundbreaking preamps and surround sound processors in the Dolby Pro Logic era. The company is no longer in business today.
• Millennium: This $399 black box solution was the first consumer-grade processor to process DTS surround sound for existing AV preamps and receivers. The company is no longer in business, as most AV preamps and receivers now have these features built into them.
•Theta Casablanca: The audiophile-grade Theta Casablanca was the first high-performance AV preamp to come from a highly respected audiophile company. While riddled with early reliability problems, the Casablanca has been upgraded and stabilized to the point where it is still sold today. Theta was recently sold by its founder to ATI, which makes power amplifiers in the Los Angeles area.
• Meridian 861: The Meridian 861 is considered by many to be the best-sounding AV preamp ever built. It is also one of the most expensive AV preamps ever sold, with card configurations that can take the retail price to over $20,000. The 861 is arguably the most upgradeable AV component in high-end audio/video history, as you can upgrade an 861 from its 1994 version 1 to a current version 4 Meridian 861.
Mark Levinson No. 502: Harman's premium line just released this $35,000 AV preamp, which is designed to process and handle all of the latest features, while keeping the audiophile signal pure.


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Keep dialog input window open after button press
I have the following code which creates a button panel which links to other Mathematica scripts.
I would like to have it such that after a button press the panel remains open and active for another button press, then only closes when the done button is pressed.
menu = DialogInput[
Row[{Style["I would like to ...", FontWeight -> Bold]}],
Row[{Button["Run A", DialogReturn["1"]],
Button["Run B", DialogReturn["2"]]}],
Button[Done, DialogReturn["10"]]}]}]];
If[menu == "1", Get["/A.m"]]
If[menu == "2", Get["/B.m"]]
Any help appreciated,