1. A transcritical vapor compression system comprising:
a fluid circuit circulating a refrigerant in a closed loop, said fluid circuit having operably disposed therein, in serial order, a first compressor, an intercooler, a second compressor with a variable capacity, a first heat exchanger, an expansion device and a second heat exchanger wherein said first compressor compresses the refrigerant from a low pressure to an intermediate pressure, said second compressor compresses the refrigerant from the intermediate pressure to a supercritical pressure, said first heat exchanger is positioned in a high pressure side of said fluid circuit and said second heat exchanger is positioned in a low pressure side of said fluid circuit, said expansion device reducing the pressure of the refrigerant from a supercritical pressure to a relatively lower pressure; and
means for cooling the refrigerant within one of said compressors.
2. The system of claim 1 wherein said cooling means comprises a third heat exchanger in fluid communication with a housing of said one compressor.
3. The system of claim 2 wherein said housing of said one compressor includes an internal conduit, said third heat exchanger being configured to circulate a fluid medium through said internal conduit of said housing.
4. The system of claim 3 wherein said fluid medium comprises one of oil, water, and forced air.
5. The system of claim 1 further comprising a controller electrically connected to said second compressor and operable to vary a capacity of said second compressor.
6. The system of claim 5 wherein said controller comprises a means for regulating the pressure of the refrigerant in said first heat exchanger.
7. The system of claim 5 wherein the temperature and pressure of the refrigerant at an inlet of said first compressor is substantially unchanged by variations in the capacity of said second compressor.
8. The system of claim 5 wherein said intercooler is configured to maintain a substantially constant refrigerant temperature at an inlet of said second compressor while the capacity of said second compressor varies.
9. The system of claim 8 wherein the intermediate pressure varies with variations in the capacity of said second compressor.
10. The system of claim 1 wherein said cooling means comprises a means for circulating the refrigerant through a housing of said one compressor.
11. The system of claim 10 wherein said cooling means comprises a second expansion device in fluid communication with said housing of said one compressor.
12. The system of claim 10 wherein said cooling means comprises a flash gas vessel in fluid communication with said housing of said one compressor.
13-21. (canceled)
22. A transcritical vapor compression system comprising:
a fluid circuit circulating a refrigerant in a closed loop, said fluid circuit having operably disposed therein, in serial order, a first compressor, a second compressor, a first heat exchanger, an expansion device and a second heat exchanger wherein said first compressor compresses the refrigerant from a low pressure to an intermediate pressure, said second compressor compresses the refrigerant from the intermediate pressure to a supercritical pressure; and
means for cooling the refrigerant within one of said compressors.
23. The system of claim 22 wherein said first heat exchanger is positioned in a high pressure side of said fluid circuit and said second heat exchanger is positioned in a low pressure side of said fluid circuit, said expansion device reducing the pressure of the refrigerant from a supercritical pressure to a relatively lower pressure.
24. The system of claim 22 wherein said second compressor has a variable capacity.
25. The system of claim 22 further comprising an intercooler disposed between said first compressor and said second compressor in said fluid circuit.
26. The system of claim 22 wherein said cooling means comprises a means for regulating the pressure of the refrigerant in said first heat exchanger.
27. The system of claim 22 wherein said cooling means comprises a means for circulating the refrigerant through a housing of said one compressor.
28. The system of claim 27 wherein said cooling means comprises a second expansion device in fluid communication with said housing of said one compressor.
29. The system of claim 27 wherein said cooling means comprises a flash gas vessel in fluid communication with said housing of said one compressor.
30-34. (canceled)
35. A method of controlling a transcritical vapor compression system, said method comprising:
providing a fluid circuit circulating a refrigerant in a closed loop, the fluid circuit having operably disposed therein, in serial order, a first compressor, an intercooler, a second compressor, a first heat exchanger, an expansion device and a second heat exchanger;
compressing the refrigerant from a low pressure to an intermediate pressure in said first compressor;
compressing the refrigerant from the intermediate pressure to a supercritical pressure in the second compressor;
decreasing a temperature of the refrigerant in the first heat exchanger;
passing the refrigerant through the expansion device and reducing the pressure of the refrigerant in the expansion device; and
selectively cooling the refrigerant within one of the compressor.
36. A method of controlling a transcritical vapor compression system, said method comprising:
providing a fluid circuit circulating a refrigerant in a closed loop, the fluid circuit having operably disposed therein, in serial order, a first compressor, an intercooler, a second compressor, a first heat exchanger, an expansion device and a second heat exchanger;
compressing the refrigerant from a low pressure to an intermediate pressure in said first compressor;
compressing the refrigerant from the intermediate pressure to a supercritical pressure in the second compressor;
decreasing a temperature of the refrigerant in the first heat exchanger;
passing the refrigerant through the expansion device and reducing the pressure of the refrigerant in the expansion device; and
selectively cooling the refrigerant between said compressors.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for assaying sperm motility in a forward direction and density of active sperm in a semen sample comprising
(A) placing the sample in a sample reservoir,
(B) allowing sperm in the sample to migrate from the sample reservoir into and along a microchannel that confines the sperm to single-direction movement within the channel toward a downstream collection region, and
(C) measuring the rate of migration and the flux of sperm through the microchannel.
2. The method of claim 1, wherein the microchannel has width and depth dimensions each in the range of 10 to 100 \u03bcm.
3. The method of claim 2, wherein said microchannel has a known length, said downstream collection region includes a collection reservoir with a known volume, and step (C) includes
(C1) measuring the change in concentration of cells present in the collection reservoir as a function of time,
(C2) determining from step (C1), and the volume of said collection reservoir, the density of active sperm in said sample as a function of time, and
(C3) determining from step (C1), the average rate of migration of sperm through said microchannel in a downstream direction.
4. The method of claim 3, wherein
step (C1) includes generating a time-dependent function whose slope approximates the change in number of cells present in the collection reservoir per unit of time, and whose intercept approximates the time to first appearance of sperm in said collection reservoir,
step (C2) includes comparing said function with one or more standard functions generated with semen samples of different known sperm counts and rates of forward progression, and
step (C3) includes determining from said intercept, the average rate of travel in a forward direction of said sperm.
5. The method of claim 3, which further includes labeling said sample with a fluorescent reporter, and step (C1) includes measuring fluorescence emission in the collection reservoir.
6. The method of claim 5, wherein said labeling includes exposing sperm to a fluorescence reporter having a cleavable ester group that promotes uptake of the reporter into sperm in an uncharged state, and inhibits efflux of the reporter from sperm in a charged, cleaved-ester state.
7. The method of claim 3, wherein step (C!) includes measuring cell-dependent absorption or light scattering in the collection reservoir.
8. The method of claim 1, wherein step wherein the width of said microchannel is such as to limit sperm movement along said microchannel to single file, and step (C) includes
(C1) detecting individual sperm as they migrate past a detection zone in the microchannel, in an upstream to downstream direction,
(C2) counting the number of sperm that migrate past the detection zone, and
(C3) determining the rate of migration of individual sperm through said detection zone.
9. The method of claim 8, wherein the width of said microchannel is between about 15-40 \u03bcm.
10. The method of claim 8, wherein said detection zone is defined by a pair of adjacent, axially spaced detectors, and step (C) additionally includes correlating signals received from each detector to enhance the signal-to-noise ratio for each detection event.
11. The method of claim 8, wherein said detection zone is defined by a pair of adjacent, axially spaced detectors, and step (C3) additionally includes using the time interval between signals received from said detectors to determine the rate of migration of sperm within the microchannel.
12. The method of claim 8, which further includes labeling said sample with a fluorescent reporter, and step (C1) includes measuring the fluorescence of sperm migration through the detection zone.
13. The method of claim 12, wherein said labeling includes exposing sperm to a fluorescence reporter having a cleavable ester group that allows uptake of the reporter into sperm in a substantially uncharged state, but inhibits efflux of the reporter from sperm in a charged, cleaved-ester state.
14. The method of claim 8, wherein step (C!) includes measuring cell-dependent absorption or light scattering in the collection reservoir.
15. The method of claim 8, which further includes labeling said sperm with a magnetic or conductive-metal particles, and step (C1) includes measuring an electrical signal (i) generated by a circuit element placed adjacent the detection zone, and (ii) characteristic of a sperm labeled with magnetic or conductive-metal particles passing through the detection zone.
16. The method of claim 15, wherein step (C3) includes determining the rate of migration of a sperm passing through said detection zone from the rate of change of signal characteristics generated by the circuit element.
17-32. (canceled)