Continuous Variable Entanglement in an Optical Parametric Oscillator Based on a Nondegenerate Four Wave Mixing Process in Hot Alkali Atoms

We present the measurement of entanglement between twin beams generated with a doubly resonant optical parameter oscillator (OPO) based on four-wave mixing in hot ^{85}Rb vapor above threshold. This is the first measurement of entanglement in an OPO with a χ^{(3)} media above threshold. We reconstruct the covariance matrix for several configurations and based on a full picture of the four side band mode state, we study entanglement between all possible bipartitions. We show a robust generation of entanglement with stronger generation for a specific pair of modes. For this system, we show that atomic density is a determinant factor for the generation and loss of quantum correlations. The generation of entangled fields with an atomic OPO operating close to atomic resonance of alkali atoms enables a natural integration into quantum networks.

Efficacy of controlvit as a complementary strategy in reducing hospitalizations in patients with heart failure. Randomized clinical trial

Introduction

In patients with heart failure, the main cause of hospital admissions is due to episodes of decompensation, which are associated with an increase in the costs and resources needed for care; they have a negative impact on the quality of life and prognosis of the disease. Therefore, it is necessary to design, evaluate and implement alternatives to achieve efficient follow-up and monitoring, improving adherence to treatment and helping identify decompensation episodes that facilitate their early treatment, so new hospital admissions can be avoided. For this reason, the use of information and communication technologies (apps) is emerging as an excellent strategy for the possibility of improving coverage, real-time monitoring and timeliness of care. ControlVit® is an electronic application that allows permanent, real-time monitoring of biomedical measurements for early detection of complications.

Objective

To determine the efficacy of ControlVit® as a complementary strategy in reducing hospital admissions in patients in a heart failure program.

Methodology

A randomized, placebo-controlled, open-label clinical trial was conducted, (n=140), included patients with heart failure under controlled clinical follow-up in a structured heart failure program, into NYHA FC II–IV, capable of handling smartphones and with permanent internet connectivity. All patients were provided with educational elements, a scale and a blood pressure monitor to enter clinical data and a symptom questionnaire necessary for follow-up. The patients were randomized to 2 groups: intervention: use of ControlVit® vs. placebo, with a 6-month follow-up. The primary outcome was the difference in readmissions for heart failure between the 2 groups. Patients on the waiting list for heart transplantation or use of ventricular assist devices were excluded. All participants signed informed consent and the protocol was approved by the institutional ethics committee.

Results

A total of 140 patients were included in the study (intervention = 71, placebo = 69), with an average age of 66 years, 71% were men, the main etiology of heart failure was ischemic (60%), the main comorbidities were arterial hypertension (44%), dyslipidemia (42%), hypothyroidism (38%), chronic kidney disease (38%), and diabetes mellitus (27%). During follow-up, there were 6 deaths (3 in each group) and 17 readmissions (3 in the intervention group and 14 in the control group). After adjustment for comorbidities, HR 0.72 CI95 (0.52; 0.92), p=0.0325 was found.

Conclusion

In patients with heart failure, ControlVit® is a useful and complementary tool for follow-up, which reduces hospital admissions due to episodes of decompensation.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): German Saldarriega award.Javeriana University

Quantum Noise Correlations of an Optical Parametric Oscillator Based on a Nondegenerate Four Wave Mixing Process in Hot Alkali Atoms

We present the first measurement of two-mode squeezing between the twin beams produced by a doubly resonant optical parameter oscillator (OPO) in an above threshold operation based on parametric amplification by nondegenerate four wave mixing with rubidium (^{85}Rb). We demonstrate a maximum intensity difference squeezing of -2.7  dB (-3.5  dB corrected for losses) with a pump power of 285 mW and an output power of 12 mW for each beam, operating close to the D1 line of Rb atoms. The use of open cavities combined with the high gain media can provide a strong level of noise compression and the access to new operation regimes that could not be explored by crystal based OPOs. The spectral bandwidth of the squeezed light is broadened by the cavity dynamics, and the squeezing level is robust for strong pump powers. Stable operation was obtained up to 4 times above the threshold. Moreover, operation of the OPO close to the atomic resonances of alkali atoms allows a natural integration into quantum networks, including structures such as quantum memories.

Experimental generation of multiple quantum correlated beams from hot rubidium vapor

Quantum correlations and entanglement shared among multiple quantum modes are important for both fundamental science and the future development of quantum technologies. This development will also require an efficient quantum interface between multimode quantum light sources and atomic ensembles, which makes it necessary to implement multimode quantum light sources that match the atomic transitions. Here, we report on such a source that provides a method for generating quantum correlated beams that can be extended to a large number of modes by using multiple four-wave mixing (FWM) processes in hot rubidium vapor. Experimentally, we show that two cascaded FWM processes produce strong quantum correlations between three bright beams but not between any two of them. In addition, the intensity-difference squeezing is enhanced with the cascaded system to -7.0±0.1  dB from the -5.5±0.1/-4.5±0.1  dB squeezing obtained with only one FWM process. One of the main advantages of our system is that as the number of quantum modes increases, so does the total degree of quantum correlations. The proposed method is also immune to phase instabilities due to its phase insensitive nature, can easily be extended to multiple modes, and has potential applications in the production of multiple quantum correlated images.

Noiseless optical amplifier operating on hundreds of spatial modes

We implement a noiseless optical amplifier using a phase-sensitive four-wave mixing process in rubidium vapor. We observe performance near the quantum limit for this type of amplifier over a range of experimental parameters and show that the noise figure is always better than would be obtained with a phase-insensitive amplifier with the same gain. Additionally, we observe that the amplifier supports hundreds of spatial modes, making it possible to amplify complex two-dimensional spatial patterns with less than a 10% degradation of the input signal-to-noise ratio for gains up to 4.6. To confirm the multimode character of the amplifier, we study the noise figure as a function of spatially-varying losses. Additionally, we investigate the spatial resolution of the amplifier and show that it supports a range of spatial frequencies from 1.3 to more than 35 line pairs per millimeter.

Quantum correlated light beams from non-degenerate four-wave mixing in an atomic vapor: the D1 and D2 lines of 85Rb and 87Rb

We present experimental results showing that quantum correlated light can be produced using non-degenerate, off-resonant, four-wave mixing (4WM) on both the D1 (795 nm) and D2 (780 nm) lines of (85)Rb and (87)Rb, extending earlier work on the D1 line of (85)Rb. Using this 4WM process in a hot vapor cell to produce bright twin beams, we characterize the degree of intensity-difference noise reduction below the standard quantum limit for each of the four systems. Although each system approximates a double-lambda configuration, differences in details of the actual level structure lead to varying degrees of noise reduction. The observation of quantum correlations on light produced using all four of these systems, regardless of their substructure, suggests that it should be possible to use other systems with similar level structures in order to produce narrow frequency, non-classical beams at a particular wavelength.

Low-noise amplification of a continuous-variable quantum state

We present an experimental realization of a low-noise, phase-insensitive optical amplifier using a four-wave mixing interaction in hot Rb vapor. Performance near the quantum limit for a range of amplifier gains, including near unity, can be achieved. Such low-noise amplifiers are essential for so-called quantum cloning machines and are useful in quantum information protocols. We demonstrate that amplification and "cloning" of one half of a two-mode squeezed state is possible while preserving entanglement.

Application of structure–metabolism relationships in the identification of a selective endothelin A antagonist, BMS-193884, with favourable pharmacokinetic properties

1. Based on binding affinity, 2'-amino-N-(3,4-dimethyl-5-isoxazolyl)-4'-(2-methylpropyl)[1,1'-biphenyl]-2-sulfonamide (2) was identified as an initial lead in a programme to identify selective endothelin (ET) receptor antagonists. However, the compound was extensively metabolized in preclinical animal species and human in vitro systems due to oxidative biotransformation. 2. To optimize this structural class, the site of metabolism of 2 was determined. This allowed for focussed structure-activity and structure-metabolism studies aimed at finding more metabolically stable analogues that maintained potency. New analogues were screened for their ET binding characteristics and their stability in rat and human liver microsomes. 3. The use of the microsomal stability screen was tested by the determination of the pharmacokinetic parameters of select analogues. A good correlation was found between reduced rates of rat microsomal metabolism and reduced clearance in the rat. 4. N-(3,4-dimethyl-5-isoxazolyl)-4'-(2-oxazolyl)[1,1'-biphenyl]-2-sulfonamide (3) was identified as an analogue with improved in vitro properties and further studies revealed that the compound had improved pharmacokinetic properties. 5. N-[[2'-[[(3,4-dimethyl-5-isoxazolyl)amino]sulfonyl]-4-(2-oxazolyl)[1,1'-biphenyl]-2-yl]methyl]acetamide (4) was subsequently identified as a compound with superior in vitro properties compared with compound 3, but when tested in vivo it had a substantially increased rate of clearance. Further studies demonstrated that the clearance of this closely related structural analogue was not dictated by metabolic processes, but was mediated by transport-mediated direct biliary excretion. 6. The utility of screening for in vitro liver microsomal stability as part of the lead optimization process for compounds with metabolic liabilities was shown. It was also shown that relatively small molecular changes can dramatically change the disposition of closely related analogues and care must be used when screening for a single property.

Delocalized correlations in twin light beams with orbital angular momentum

We generate intensity-difference-squeezed Laguerre-Gauss twin beams of light carrying orbital angular momentum by using four-wave mixing in a hot atomic vapor. The conservation of orbital angular momentum in the four-wave mixing process is studied as well as the spatial distribution of the quantum correlations obtained with different configurations of orbital angular momentum. Intensity-difference squeezing of up to -6.7 dB is demonstrated with beams carrying orbital angular momentum. Delocalized spatial correlations between the twin beams are observed.

Violation of the Cauchy-Schwarz inequality in the macroscopic regime

We have observed a violation of the Cauchy-Schwarz inequality in the macroscopic regime by more than 8 standard deviations. The violation has been obtained while filtering out only the low-frequency noise of the quantum-correlated beams that results from the technical noise of the laser used to generate them. We use bright intensity-difference squeezed beams produced by four-wave mixing as the source of the correlated fields. We also demonstrate that squeezing does not necessarily imply a violation of the Cauchy-Schwarz inequality.

Generation of spatially broadband twin beams for quantum imaging

We generate spatially multimode twin beams using 4-wave mixing in a hot atomic vapor in a phase-insensitive traveling-wave amplifier configuration. The far-field coherence area measured at 3.5 MHz is shown to be much smaller than the angular bandwidth of the process and bright twin images with independently quantum-correlated subareas can be generated with little distortion. The available transverse degrees of freedom form a high-dimensional Hilbert space that we use to produce quantum-correlated twin beams with finite orbital angular momentum.

Intestinal absorption of captopril and two thioester analogs in rats and dogs

The objectives of this study were (i) to determine whether the reduced absorption of captopril from the colon of humans also occurs in rats and (ii), after confirmation of the relevance of a new rat model, to evaluate the intestinal absorption of captopril and several of its analogs. A model was developed and validated in which specific sites within the GI tract of rats were surgically implanted with a cannula such that animals could be dosed while conscious and unrestrained. The absorption of captopril after administration into the lower GI tract of rats was significantly reduced relative to the upper GI tract, which was consistent with results reported previously in humans. In rats, the absorption of the S-benzoyl thioester prodrug of captopril (SQ-25868) from the lower GI tract was substantially greater than that of captopril. However, the absorption of the S-benzoyl thioester prodrug of 4-phenyl thio-captopril (SQ-26991) from the lower GI tract was only marginally better than that of captopril. In additional studies in dogs, a 12h controlled-release formulation of SQ-25868 provided sustained blood levels of captopril while maintaining acceptable bioavailability (> 80%). Two approaches were tried, without success, to stabilize captopril in vivo: (i) complexation with zinc (SQ-26284) and (ii) use of ascorbic-acid-buffered (pH 3.5) vehicle. The zinc complex might have failed because it has very low solubility, whereas the pH-3.5-buffered vehicle was quickly neutralized within the colonic lumen in rats, and did not stabilize captopril against oxidation. Rapid neutralization might explain why the colonic bioavailability of captopril was not substantially increased when this pH-3.5-buffered vehicle was tried in humans.

Prodrugs of BMS-183920: metabolism and permeability considerations

The oral bioavailability of BMS-183920, a diacidic, potent angiotensin II receptor antagonist, is low in rats (approximately 11%). In vivo studies in bile duct-cannulated rats indicated that BMS-183920 was metabolically stable and that the low bioavailability was due to incomplete intestinal absorption. Five acyl-ester prodrugs were synthesized which were 5-15 times more permeable than BMS-183920 through Caco-2 cells. However, limited studies in rats indicated that the oral bioavailability of BMS-183920 was improved only 2-fold, in the best case. The lack of a substantial increase in bioavailability was apparently due to presystemic prodrug hydrolysis or metabolism via N-glucuronidation. Bioavailability of BMS-183920 after oral dosing of a tetrazole-ester prodrug averaged 37%, the most significant improvement within this prodrug series. Interestingly, in vitro studies indicated that the tetrazole-ester prodrug was a substrate for glucuronosyl transferase; however, its rate of bioactivation (hydrolysis) was sufficiently high to provide a substantial increase in bioavailability of BMS-183920. Therefore, while prodrug modification of BMS-183920 improved Caco-2 cell permeability and oral absorption in vivo, the relative extents of hydrolysis (bioactivation) vs metabolism of the prodrug determined whether a substantial improvement in bioavailability was achieved.

Suitability of enalapril as a probe of the dipeptide transporter system: in vitro and in vivo studies

PURPOSE

Previous in situ and in vitro studies indicated that the intestinal absorption of enalapril is a saturable carrier-mediated process via the dipeptide transporter system (DTS); however, the oral absorption of enalapril has not been reported to be a saturable process in vivo. Our objectives were to: 1) evaluate the suitability of enalapril as a probe of the DTS, and 2) compare various experimental models as they pertain to studying the DTS.

METHODS

The in vitro uptake of enalapril by rat intestinal rings and permeability across Caco-2 cells were studied as a function of concentration and in the presence of compounds that are known substrates of the DTS. The effect of enalapril on the uptake of [3H]-glycyl-L-proline (gly-L-pro) by Caco-2 cells was also examined. In vivo studies were conducted in rats (1 to 50 mg/kg) and dogs (0.06 to 6 mg/kg) to evaluate the oral absorption of enalapril over a wide dose range.

RESULTS

In vitro intestinal uptake/permeability of enalapril was not saturable nor inhibited by beta-lactam antibiotics, gly-L-pro, or SQ-29852. Moreover, a 20,000-fold molar excess of enalapril did not inhibit the uptake of [3H]-gly-L-pro by Caco-2 cells. The in vivo studies in rats and dogs did not demonstrate saturable absorption.

CONCLUSIONS

The present in vitro and in vivo results indicated that enalapril is primarily absorbed by a non-saturable, passive diffusion process and it is not a suitable model compound for studying the DTS.

Distribution of the dipeptide transporter system along the gastrointestinal tract of rats based on absorption of a stable and specific probe, SQ-29852

Peptidic drugs such as beta-lactam aminocephalosporin antibiotics (e.g., cephalexin) and the ACE inhibitors lisinopril, quinapril, and benzazepril are apparently absorbed, at least in part, by the intestinal dipeptide transporter system (DTS). Although many properties of the DTS have been elucidated, including isolation of the carrier protein, little is known about the distribution of this transporter along the gastrointestinal (GI) tract. The objectives of the present study were to (1) validate that SQ-29852 (a lysylproline ACE inhibitor) is a stable and specific probe for evaluation of the DTS in rats and (2) provide fundamental in vivo information on the distribution of the DTS along the GI tract of rats. Most of the previous studies that explored the location of the DTS typically involved either in vitro uptake or in situ disappearance of unstable or nonspecific probes. SQ-29852, on the other hand, is an ideal probe for evaluation of the DTS because it is chemically and metabolically stable and it is absorbed almost exclusively by the DTS. SQ-29852 appears to be a specific probe for the DTS because the dose-dependent reduction in absorption from about 60% to less than 8% (3 and 3000 mg/kg, respectively) suggests that at least 85% of an orally administered low dose of SQ-29852 is absorbed by a saturable process, which was shown previously to be the DTS. [14C]SQ-29852 was administered by gavage to intact rats and via an indwelling cannula in one of the following sections of the intestine: duodenum, jejunum, ileum and proximal colon (n = 4 for each site). On the basis of the recovery of [14C]SQ-29852 in urine, the DTS is apparently distributed throughout the entire GI tract of rats, including the proximal colon. The present results are consistent with previously reported results on the absorption of natural dipeptides in humans and rats and immunohistochemical evaluation in rats; however, they disagree with a recent report in humans with amoxicillin. This difference is discussed in terms of the specificity and stability of various drugs that have been used as probes of the DTS.

Evaluation of new culture media for rapid detection and isolation of salmonellae in foods

Conventional methods for Salmonella detection in foods can require up to 6 and at least 4 days. We have observed that the total analysis time can be reduced to 48 h by using Salmosyst broth as a liquid medium for both preenrichment and selective enrichment and Rambach agar (RA), a new selective plate medium. In samples of artificially contaminated ground beef Salmonella enteritidis was detected at a concentration of 0.4 CFU/g (10 CFU/25 g) by both a conventional method and the new method. Of 519 samples of foods for sale, 38 were Salmonella positive by both methods while 471 were negative. Nine samples which were negative by the conventional method were positive by the Salmosyst-RA method, while one sample positive by the first method was negative by the last. Therefore, the Salmosyst-RA method showed 97.9% sensitivity compared with the 81.2% sensitivity of the conventional method. The new method was also highly specific (98% specificity) in presumptive identification of Salmonella colonies. Furthermore, a 6-h preenrichment in Salmosyst broth has been proved sufficient for the repair of heat-injured Salmonella cells and for subsequent recovery by selective enrichment. In conclusion, the Salmosyst-RA method shows several advantages over both conventional and rapid noncultural methods: (i) only two media are required instead of the five media for conventional methods; (ii) in real time it is comparable to other rapid noncultural methods, which require 30 to 31 h; (iii) it is highly sensitive and specific; and (iv) it allows the isolation of Salmonella strains which can be characterized by appropriate phenotypic and genotypic typing methods for epidemiological investigations.