Artificial Coherent States of Light by Multiphoton Interference in a Single-Photon Stream.

Coherent optical states consist of a quantum superposition of different photon number (Fock) states, but because they do not form an orthogonal basis, no photon number states can be obtained from it by linear optics. Here we demonstrate the reverse, by manipulating a random continuous single-photon stream using quantum interference in an optical Sagnac loop, we create engineered quantum states of light with tunable photon statistics, including approximate weak coherent states. We demonstrate this experimentally using a true single-photon stream produced by a semiconductor quantum dot in an optical microcavity, and show that we can obtain light with g^{(2)}(0)→1 in agreement with our theory, which can only be explained by quantum interference of at least 3 photons. The produced artificial light states are, however, much more complex than coherent states, containing quantum entanglement of photons, making them a resource for multiphoton entanglement.

Observation of the Unconventional Photon Blockade.

We observe the unconventional photon blockade effect in quantum dot cavity QED, which, in contrast to the conventional photon blockade, operates in the weak coupling regime. A single quantum dot transition is simultaneously coupled to two orthogonally polarized optical cavity modes, and by careful tuning of the input and output state of polarization, the unconventional photon blockade effect is observed. We find a minimum second-order correlation g^{(2)}(0)≈0.37, which corresponds to g^{(2)}(0)≈0.005 when corrected for detector jitter, and observe the expected polarization dependency and photon bunching and antibunching; close by in parameter space, which indicates the abrupt change from phase to amplitude squeezing.

Electro-optic polarization tuning of microcavities with a single quantum dot.

We present an oxide aperture microcavity with embedded quantum dots which utilizes a three-contact design to independently tune the quantum dot wavelength and birefringence of the cavity modes. A polarization splitting tuning of ∼5 GHz is observed. For a typical microcavity polarization splitting, the method can be used to achieve perfect polarization degeneracy that is required for many polarization-based implementations of photonic quantum gates. The embedded quantum dot wavelength can be tuned into resonance with the cavity, independent of the polarization tuning.

Purification of a single-photon nonlinearity.

Single photon nonlinearities based on a semiconductor quantum dot in an optical microcavity are a promising candidate for integrated optical quantum information processing nodes. In practice, however, the finite quantum dot lifetime and cavity-quantum dot coupling lead to reduced fidelity. Here we show that, with a nearly polarization degenerate microcavity in the weak coupling regime, polarization pre- and postselection can be used to restore high fidelity. The two orthogonally polarized transmission amplitudes interfere at the output polarizer; for special polarization angles, which depend only on the device cooperativity, this enables cancellation of light that did not interact with the quantum dot. With this, we can transform incident coherent light into a stream of strongly correlated photons with a second-order correlation value up to 40, larger than previous experimental results, even in the strong-coupling regime. This purification technique might also be useful to improve the fidelity of quantum dot based logic gates.

Frequency-domain optical probing of coherent spins in nanocrystal quantum dots.

Spin-photon interactions such as the Faraday effect provide techniques for measuring coherent spin dynamics in semiconductors. In contrast to typical ultrafast pulsed laser techniques, which measure spin dynamics in the time domain with an intense, spectrally broad probe pulse, we demonstrate a frequency-domain spin-photon resonance effect using modulated continuous-wave lasers which enables measurement of GHz-scale coherent spin dynamics in semiconductors with minimal spectral linewidth. This technique permits high-resolution spectroscopic measurements not possible with ultrafast methods. We have employed this effect to observe coherent spin dynamics in CdSe nanocrystals using standard diode lasers. By fitting the results to the expected model, we extract electron g-factors, and spin coherence and dephasing times in agreement with time-domain measurements.

Follicular expression of a human beta-cell leukaemia/lymphoma-2 (Bcl-2) transgene does not decrease atresia or increase ovulation rate in swine.

Transgenic (TG) gilts carrying a human Bcl-2 cDNA transgene driven by mouse inhibin-alpha subunit promoter were produced and evaluated to determine if ectopic expression of Bcl-2 in the ovaries would decrease the frequency of atresia in antral follicles and increase ovulation rate. Immunohistochemical analysis showed that the Bcl-2 transgene protein was expressed in granulosa and theca cells, in 86% of healthy and 54% of atretic follicles analysed in TG prepubertal and Day 50 pregnant gilts combined (n = 24). In contrast, Bcl-2 transgene protein was expressed in only 1.4% of healthy and 0% of atretic follicles in non-TG littermates (n = 13). Real-time reverse transcription-polymerase chain reaction analysis confirmed that human Bcl-2 was expressed in follicles of TG gilts. The atresia rate for the TG and non-TG groups did not differ (P > 0.05) for prepubertal (45 v. 59%) and Day 50 pregnant gilts (53 v. 52%) respectively. The mean +/- s.e.m. ovulation rate did not differ (P > 0.5) between TG (15.9 +/- 0.8, n = 12) and non-TG (16.4 +/- 0.6, n = 7) Day 50 pregnant gilts. The molecular basis of the failure of ectopic Bcl-2 expression to increase the ratio of healthy to atretic follicles is unknown, but it is possible that the activity of the mitochondrial-dependent cell death pathway was not neutralized by ectopic expression of human Bcl-2 or that other cell death pathways compensated for the decreased mitochondrial-dependent cell death.

Gender differences in coping styles and coping effectiveness in chronic obstructive pulmonary disease groups.

The purpose of this comparative study was to examine the coping styles and coping effectiveness between men and women with chronic obstructive pulmonary disease who were active in support groups for people with the disease. The entire population of the American Lung Association of Ohio, Southwestern Branch, Easy Breather's Club (n = 1103) was sent 2 mailed surveys, the Revised Jalowiec Coping Scale(1) and a demographic profile questionnaire. A total of 154 surveys were analyzed. Of this total, 43% (n = 66) were returned by men, whereas women's response was 57% (n = 88). Men were enrolled longer in pulmonary rehabilitation programs (median = 20; interquartile range = 2-28) than women (median = 4; interquartile range = 2-24). Men were noted to be more active in pulmonary rehabilitation programs, with 22% (n = 14) compared with women 14% (n = 12). Men's participation with an American Lung Association program yielded 9.4% (n = 6) in comparison with only 8% (n = 7) for women. The majority of this sample, 61% (n = 92), was not currently active. The total group used the optimistic coping style the most (M, 2.1; SD = 0.57). The total group also found the optimistic coping style to be the most effective (M, 2; SD = 0.61). No statistically significant gender differences existed for overall coping use, overall coping effectiveness, or with the 8 coping subscales. No coping differences for use or effectiveness were found to be related to participation in either a pulmonary rehabilitation program or the lung association program.

Susceptibility of murine transfer factor to dimerized ribonuclease A.

Dialyzable transfer factor was prepared from the spleens of CF1 mice actively sensitized with killed Coccidioides immitis antigen. The transfer factor was administered to normal mice either intraperitoneally or into the hind footpads. The recipient mice were tested for reactivity to the coccidioides antigen and to Candida albicans antigen by means of the footpad swelling test. The transfer factor conferred antigen-specific reactivity upon normal recipient mice when given by the intraperitoneal and footpad routes. This capacity of the transfer factor was destroyed by in vitro pretreatment with dimerized ribonuclease A, an enzyme active against double-stranded, as well as single-stranded, ribonucleic acid. In contrast, monomeric ribonuclease A, which is active against only single-stranded ribonucleic acid under the conditions used here, was without effect upon the transfer factor. These data provide evidence that murine transfer factor contains ribonucleotides that are essential for immunological activity. In addition, the data are consistent with the hypothesis, advanced by others, that the ribonucleotides may be double-stranded or uniquely looped configurations.

Transfer of delayed hypersensitivity in mice to microbial antigens with dialyzable transfer factor.

Dialyzable Lawrence-type transfer factor was prepared from the spleen cells of CF1 mice inoculated with Coccidioides immitis- and Candida albicans-killed vaccines and with live Mycobacterium tuberculosis vaccine (BCG). These preparations were shown to transfer antigen-specific cell-mediated immunity to naive mice, as measured by the delayed skin test and footpad-swelling methods. Reactivity could be demonstrated when the test antigens were given 24 h after the transfer factor, but not when they were given simultaneously. Coccidioides-specific transfer factor was shown to be sensitive to Pronase and resistant to trypsin and ribonuclease. A preparation of BCG transfer factor was sensitive to snake venom phosphodiesterase.

Delayed hypersensitivity to fungal antigens in mice. II. Molecular classes in immunogenic RNA extracts that transfer delayed hypersensitivity.

The transfer of delayed hypersensitivity to Coccidioides immitis and Candida albicans antigens with immunogenic RNA extracts was studied in a mouse model. Sensitivity was measured by skin tests and footpad swelling responses. Immunogenic RNA converted normal spleen cells in vitro so that they produced antigen-specific delayed hypersensitivity in mice that were given injections of the cells. RNase reduced the rate of, but did not abolish, in vitro interaction of immunogenic RNA extracts with lymphocytes. Immunogenic RNA transferred sensitivity on direct intraperitoneal inoculation into mice. The transfer ability was resistant to RNase preparations active against both single- and double-stranded RNA. Sedimentation gradient fractions of the immunogenic RNA were assayed by intraperitoneal injection, and converting activity was found in two fractions, greater than 33S and 6S-13S. After treatment with RNase, all activity was shifted to the less than 6S fraction. Two fractions of the immunogenic RNA in its native state (greater than 33S and 6S-13S) were also able to convert spleen cells. The data indicate that the transfer of delayed hypersensitivity by immunogenic RNA preparations is associated with RNA but may not require the intact RNA molecule.

Delayed hypersensitivity to fungal antigens in mice. II. Characterization of the active component in immunogenic RNA extracts.

In a mouse model, cell-mediated immunity to Coccidioides immitis, as assayed by the delayed hypersensitivity skin test, was transferred with whole immunogenic RNA extract and its greater than 33S and 6S-13S sedimentation fractions. Both fractions were cleaved by RNase, but the products retained their transfer activity. The greater than 33S fraction of immunogenic RNA extract was inactivated by pronase, whereas the 6S-13S fraction was resistant to the proteolytic enzyme; however, after RNase treatment the latter fraction was sensitive to pronase. This finding suggests a protective role for RNA. Dialysis of immunogenic RNA extract yielded a dialysate with a ratio of absorbance at 260 nm to that at 280 nm (A260:A280) of 1.02. Similarly, the dialysis product of RNase-treated RNA is active and has an A260:A280 ratio of 1.34. The data indicate that at least part of the active moiety of immunogenic RNA extracts is an RNA-associated, pronase-labile peptide or nucleopeptide. Furthermore, it is possible that the dialyzable transfer factor may be the same peptide or nucleopeptide cleaved from immunogenic RNA during preparation of the transfer factor.

Delayed hypersensitivity to fungal antigens in mice. I. Use of the intradermal skin and footpad swelling tests as assays of active and passive sensitization.

Mice were sensitized to Coccidioides immitis and Candida albicans antigens and tested for sensitivity by the intradermal and footpad swelling methods. In mice actively sensitized with killed antigen, antigen-specific intradermal and footpad induration responses occurred 24 and 48 hr after sensitization. Antigen-specific intradermal and footpad responses were transferred to normal mice with spleen cells from immune animals. Such responses were also transferred with normal spleen cells that had been incubated in vitro with immune RNA preparations. Histologic studies of intradermal reactions showed a mixed response of neutrophilic and mononuclear leukocytes, with slight vascular involvement compatible with delayed hypersensitivity. No intradermal or footpad responses were observed 4, 24, or 48 hr after injection in recipients of serum from actively sensitized mice. Histologic examination of skin sites in these mice revealed only a polymorphonuclear response. It is concluded that these intradermal and footpad responses are the result of delayed hypersensitivity and can be used as assays for this type of immunity in mice.

Influence of Androgen and Estrogen on Delayed Skin Test Reactivity to Candida albicans.

Recipient adult male CFW mice were passively sensitized to candida delayed skin test reactivity with splenic lymphoid cells from candida-vaccinated donor females. In recipient adult males that had been bilaterally gonadectomized as weanlings, before passive sensitization, reactivity was less than in the unilaterally gonadectomized controls. Adult males bilaterally gonadectomized as weanlings were treated with gonadal hormones during passive sensitization. 17beta-estradiol was found to decrease reactivity, whereas testosterone was found to increase reactivity. These data provide evidence that delayed skin test reactivity produced by female lymphoid cells is depressed by estrogen and is stimulated by androgen.

Influence of gonadal factors on skin test reactivity of CFW mice to Candida albicans.

Sex differences in the delayed skin test response to Candida albicans were studied in gonadectomized and control CFW mice sensitized either actively with sonically treated antigen or passively with lymphoid cells. In mice actively sensitized with antigen, the responses to candida skin testing were larger in the female. In both sexes, the skin test responses were larger in mice gonadectomized prior to sensitization than in controls of the same sex. In mice passively sensitized with male lymphoid cells, the responses to candida skin testing were essentially equal in the sexes. In both sexes, gonadectomy prior to passive sensitization with the male cells resulted in greater skin test reactivity. In mice passively sensitized with female lymphoid cells, the responses were larger in the males. In males, pre-sensitization gonadectomy resulted in smaller skin test responses, but in the females gonadectomy did not influence the responses. It is suggested that the greater skin test reactivity of the female to candida is due to a sex difference in the response of lymphoid cells to gonadal hormones. This difference may be important in the greater immune reactivity and resistance to infection which occur in the female.

Sex difference in antibody response of CFW mice to Candida albicans.

Bilaterally gonadectomized and control unilaterally gonadectomized male and female CFW mice were given a course of Candida albicans vaccine, and the agglutinating antibody response was measured. The mean titers in the control females were higher than those in the control males. Bilateral gonadectomy did not affect the mean titer in the females but in the males resulted in a significant increase in the antibody. Similar groups of mice were inoculated intraperitoneally with viable C. albicans, and 10 weeks later antibody was measured and the kidneys were cultured. There was no apparent relationship between the degree of the agglutinin response and either gonadectomy or renal candidiasis at autopsy.

Influence of gonadectomy on Candida albicans urinary tract infection in CFW mice.

Candida albicans appeared in the urine of approximately 80% of CFW mice of both sexes within 2 weeks after intraperitoneal inoculation. During a follow-up period of 10 weeks, candiduria tended to clear, but persisted in 37% of males as compared to only 16% in females. Autopsy kidney cultures yielded candida in 53% of males as compared to 25% of females. Urine cultures in both sexes when positive contained 10(3.5) to 10(4.5) candida/ml regardless of the outcome of the infection. Preinoculation gonadectomy in both sexes increased resistance to the infection but did not alter the quantitative aspects of candiduria.