Measurement of Motion beyond the Quantum Limit by Transient Amplification.

Through simultaneous but unequal electromechanical amplification and cooling processes, we create a method for a nearly noiseless pulsed measurement of mechanical motion. We use transient electromechanical amplification (TEA) to monitor a single motional quadrature with a total added noise -8.5±2.0 dB relative to the zero-point motion of the oscillator, or equivalently the quantum limit for simultaneous measurement of both mechanical quadratures. We demonstrate that TEA can be used to resolve fine structure in the phase space of a mechanical oscillator by tomographically reconstructing the density matrix of a squeezed state of motion. Without any inference or subtraction of noise, we directly observe a squeezed variance 2.8±0.3 dB below the oscillator's zero-point motion.

Laser Cooling of a Micromechanical Membrane to the Quantum Backaction Limit.

The radiation pressure of light can act to damp and cool the vibrational motion of a mechanical resonator, but even if the light field has no thermal component, shot noise still sets a limit on the minimum phonon occupation. In optomechanical sideband cooling in a cavity, the finite off-resonant Stokes scattering defined by the cavity linewidth combined with shot noise fluctuations dictates a quantum backaction limit, analogous to the Doppler limit of atomic laser cooling. In our work, we sideband cool a micromechanical membrane resonator to the quantum backaction limit. Monitoring the optical sidebands allows us to directly observe the mechanical object come to thermal equilibrium with the optical bath. This level of optomechanical coupling that overwhelms the intrinsic thermal decoherence was not reached in previous ground-state cooling demonstrations.

Reduced Sensitivity to Charge Noise in Semiconductor Spin Qubits via Symmetric Operation.

We demonstrate improved operation of exchange-coupled semiconductor quantum dots by substantially reducing the sensitivity of exchange operations to charge noise. The method involves biasing a double dot symmetrically between the charge-state anticrossings, where the derivative of the exchange energy with respect to gate voltages is minimized. Exchange remains highly tunable by adjusting the tunnel coupling. We find that this method reduces the dephasing effect of charge noise by more than a factor of 5 in comparison to operation near a charge-state anticrossing, increasing the number of observable exchange oscillations in our qubit by a similar factor. Performance also improves with exchange rate, favoring fast quantum operations.

Quantum-enabled temporal and spectral mode conversion of microwave signals.

Electromagnetic waves are ideal candidates for transmitting information in a quantum network as they can be routed rapidly and efficiently between locations using optical fibres or microwave cables. Yet linking quantum-enabled devices with cables has proved difficult because most cavity or circuit quantum electrodynamics systems used in quantum information processing can only absorb and emit signals with a specific frequency and temporal envelope. Here we show that the temporal and spectral content of microwave-frequency electromagnetic signals can be arbitrarily manipulated with a flexible aluminium drumhead embedded in a microwave circuit. The aluminium drumhead simultaneously forms a mechanical oscillator and a tunable capacitor. This device offers a way to build quantum microwave networks using separate and otherwise mismatched components. Furthermore, it will enable the preparation of non-classical states of motion by capturing non-classical microwave signals prepared by the most coherent circuit quantum electrodynamics systems.

Peripheral vascular response to potassium administration during cardiopulmonary bypass.

Potassium (K+) is often administered to patients during cardiopulmonary bypass (CPB). The effects of rapid K+ administration during CPB were studied in 30 adult patients. Each patient received one bolus dose (2, 4, 8, 12, or 16 mEq) of potassium chloride (KCl) (2 mEq/ml) during CPB. Serum K+ was significantly increased from baseline values at KCl doses of 8 mEq and larger (p less than 0.05). All increases in serum K+ returned to clinically acceptable levels within 5 minutes after the bolus. Mean arterial pressure (MAP) (torr) and total peripheral resistance (TPR) (dynes sec cm-5) changes were biphasic; after an initial transient decrease, maximal with the 16 mEq K+ bolus (MAP -21 +/- 6, TPR - 315 +/- 135), these parameters increased (8 mEq K+ bolus, MAP + 15 +/- 16, TPR + 301 +/- 90; 12 mEq K+ bolus, MAP + 43 +/- 9, TPR + 998 +/- 250; 16 mEq bolus, MAP + 51 +/- 9, TPR + 1,216 +/- 120) with a peak at 3 minutes after the bolus. Hypertension, in nine of 18 patients receiving a KCl bolus of 8 mEq or larger, was of such magnitude (range 132 to 196 torr) as to require rapid therapeutic intervention to lower blood pressure. When KCl supplementation is required on CPB and slow infusion rates seem unreasonable, bolus doses of less than 8 mEq may be administered without vascular effect.

Using claims data to monitor hospital utilization.

Controlling provider use is a continuing problem for health care insurers. This paper describes a Blue Cross and Blue Shield of Michigan system that places primary responsibility for inpatient admissions on participating hospitals and uses a dual monitoring approach. Expensive annual samples that review medical records against published criteria constitute the basic test of compliance. An inexpensive indicator is developed quarterly using automated universal claims review. Statistical methodology, costs, and savings for both monitors are described. The claims monitor uses diagnosis related group (DRG) characteristics to estimate the percentage of inappropriate utilization from historical values for the patient group.

High-tech task tracking.

The authors discuss the benefits of instituting a computerized dispatch card system to make the hospital security department more efficient and effective.

Cardiovascular effects of protamine sulfate in man.

The effect of protamine sulfate on several cardiovascular and biochemical variables was studied in man under clinical conditions. This study was performed to quantitate these effects in 15 adult patients who had undergone cardiopulmonary bypass for coronary artery bypass grafting. Protamine was administered in typical clinical doses (3 mg/kg) at typical clinical rates (total dose infused over 5 minutes). This infusion rate is greatly in excess of the 50 mg/10 min suggested in the protamine package insert. No statistically significant changes in mean arterial blood pressure, cardiac output, central venous pressure, total or ionized calcium, PaO2, PaCO2, pH, Na+, or K+ were found during or after administration of protamine sulfate. Hypotension was observed after administration of protamine to one patient, but no etiologic mechanism was apparent. Previous reports suggest cardiovascular depression by protamine in the dog, a species highly susceptible to these effects. Data obtained in man in this study do not corroborate the canine studies.

Lactoperoxidase-catalyzed oxidation of thiocyanate: polarographic study of the oxidation products.

The lactoperoxidase-catalyzed oxidation of thiocyanate (SCN-) was studied by two different polarographic techniques: direct current polarography and linear sweep voltammetry. The main oxidation product at pH 6.5, with a half-wave potential (E1/2) of -0.39 to -0.44 V, was identified as hypothiocyanite (OSCN-) ion. The E1/2 for OSCN- was not available in the literature. The identification of OSCN- was based on a close correlation between the current of the OSCN- peak and the concentration of chemically assayed OSCN-. Also the specific rates of decay of the current and that of chemically detectable OSCN- were similar, and both curves followed apparent first-order kinetics. Subsequently, the addition of a reducing agent (2-mercaptoethanol) resulted in immediate disappearance of both chemically detectable OSCN- and the OSCN- wave in the polarograms. All three components of the lactoperoxidase (LPO) system (SCN-, H2O2, and LPO) were needed to produce the OSCN- peak. Addition of excess H2O2 or H2O2-LPO to an OSCN--SCN- mixture resulted in a formation of a new peak with a characteristic peak potential (Ep) of -0.20 to -0.25 V. The generation of this new peak was associated with a simultaneous, markedly enhanced decrease of OSCN- concentration, indicating a possible reaction between H2O2 (or H2O2-LPO) and OSCN-. No equivalent reaction was obtained by the addition of buffer alone. This new peak may represent higher oxy acids of SCN- (O2SCN-, O3SCN-), formed in the oxidation of OSCN- by H2O2 or by H2O2-LPO. This type of reaction can explain why, in solutions which already contain OSCN- (e.g., in saliva), the addition of H2O2 results in the formation of highly reactive, short-lived antimicrobial products in addition to OSCN-.

Molecular analysis of membrane immunoglobulin-negative variants.

The mouse B-cell lymphoma WEHI 279.1 is a tumor which synthesizes both membrane and secreted immunoglobulin M (IgM). We have immunoselected variants which fail to express the membrane form (mIgM-); the most frequently isolated phenotype is a complete loss of both membrane expression and synthesis of the mu heavy chain within the cells. We have chosen four of these mIgM- mutants for detailed molecular investigation. One of these has suffered a large deletion which covers the region of chromosome 12 containing the expressed mu gene, but three have no detectable changes in the DNA arrangement of the mu gene. All of the mutants, including the deletion mutant, synthesize 10-30% of the wild-type level of cytoplasmic mu RNA; however, none is the appropriate size for membrane mu (mu m) or secreted mu (mu s) message. Based on our studies of the deletion mutant, which retains its nonproductively arranged allele, at least some of these RNAs may be 'sterile' transcripts from the nonproductively arranged allele. However, if all of these mRNAs derive from the other allele, they represent a substantial elevation of these sterile messages relative to the wild-type level. Furthermore, the three nondeletion mutants transcribe mu RNA at a level indistinguishable from the wild type. It is likely that their defects lie in the stability, processing, or transport of the mu RNA within the nucleus. Somatic cell hybrids between P3X and the IgM- variants produced mostly mIgM- hybrids. However, a few mIgM+ hybrids were produced, suggesting that the mu- defects may be partly complemented by the P3X fusion partner.

Use of antibiotic resistance analysis to identify nonpoint sources of fecal pollution.

A study was conducted to determine the reliability and repeatability of antibiotic resistance analysis as a method of identifying the sources of fecal pollution in surface water and groundwater. Four large sets of isolates of fecal streptococci (from 2,635 to 5,990 isolates per set) were obtained from 236 samples of human sewage and septage, cattle and poultry feces, and pristine waters. The patterns of resistance of the isolates to each of four concentrations of up to nine antibiotics were analyzed by discriminant analysis. When isolates were classified individually, the average rate of correct classification (ARCC) into four possible types (human, cattle, poultry, and wild) ranged from 64 to 78%. When the resistance patterns of all isolates from each sample were averaged and the resulting sample-level resistance patterns were classified, the ARCCs were much higher (96 to 100%). These data confirm that there are measurable and consistent differences in the antibiotic resistance patterns of fecal streptococci isolated from various sources of fecal pollution and that antibiotic resistance analysis can be used to classify and identify these sources.