Femtosecond resolution of soft mode dynamics in structural phase transitions.

The microscopic pathway along which ions or molecules in a crystal move during a structural phase transition can often be described in terms of a collective vibrational mode of the lattice. In many cases, this mode, called a "soft" phonon mode because of its characteristically low frequency near the phase transition temperature, is difficult to characterize through conventional frequency-domain spectroscopies such as light or neutron scattering. A femtosecond time-domain analog of light-scattering spectroscopy called impulsive stimulated Raman scattering (ISRS) has been used to examine the soft modes of two perovskite ferroelectric crystals. The low-frequency lattice dynamics of KNbO(3) and BaTiO(3) are clarified in a manner that permits critical evaluation of microscopic models for their ferroelectric transitions. The results illustrate the advantages of ISRS over conventional Raman spectroscopy of low-frequency, heavily damped soft modes.

A state secret: the closely guarded report of a hospital inquiry.

Two hundred years ago, Cork Street Fever Hospital was built by charitable subscription. Seven years after becoming a public-private partnership in 1937, its administration was subjected to a Sworn Inquiry. Why the Inquiry was held and why the Inspector's Report was never published are the questions addressed in this paper.

A large outbreak of salmonellosis and its economic cost.

In the summer of 1989, a large outbreak of gastroenteritis occurred in persons attending a barbeque. An investigation was carried out to determine the cause, institute control measures, and to estimate the costs involved in the outbreak. Epidemiological investigation revealed that chicken served at the barbeque was the pecant food, which was confirmed by microbiological investigation. Prompt institution of control measures resulted in early containment of secondary spread. Nevertheless, the total cost of the outbreak amounted to 77,995 pounds. The economic impact of this outbreak was therefore considerable.

Lummer-Gehrcke interferometer modified for the spectroscopy of thin dielectric films.

The obsolete Lummer-Gehrcke interferometer is reexamined, and it is shown how, with a few simple modifications, this instrument can be used to study the optical properties of thin, solid, dielectric films. In particular, the thickness, the wavelength dispersion, and the absorption spectrum of the film can all be obtained simultaneously. In the case of anisotropic films, the polarization dependence of these parameters is obtained very conveniently. The modified interferometer allows continuous monitoring of the above parameters in situ during growth.

Bistable configurations of the microchannel spatial light modulator.

The performance of two MSLM configurations that can be used to achieve optically bistable operation is discussed. The operating criteria for each mode are investigated, and the results are presented.

Physician role conflict and resulting career changes. Gender and generational differences.

OBJECTIVE: To evaluate gender and generational differences both in the prevalence of role conflict and in resulting career changes among married physicians with children. STUDY DESIGN: Cross-sectional survey. PARTICIPANTS: We sent a survey to equal numbers of licensed male and female physicians (1,412 total) in a Southern California county; of the 964 delivered questionnaires, 656 (68%) were returned completed. Our sample includes 415 currently married physicians with children, 64% male and 36% female. MEASUREMENTS AND MAIN RESULTS: The prevalence of perceived role conflict, or career changes for marriage, and of career changes for children were evaluated. Types of career changes were also evaluated. More female than male physicians (87% vs 62%, p < .001) and more younger than older female physicians (93% vs 80%, p < .01) and male physicians (79% vs 54%, p < .001) experienced at least moderate levels of role conflict. Younger female and male physicians did not differ in their rates of career change for marriage (57% vs 49%), but female physicians from both age cohorts were more likely than their male peers to have made career changes for their children (85% vs 35%, p < .001). Younger male physicians were twice as likely as their older peers to have made a career change for marriage (49% vs 28%, p < .001) or children (51% vs 25%, p < .001). The most common type of career change made for marriage or children was a decrease in work hours. CONCLUSIONS: Most physicians experience role conflict, and many adjust their careers in response. Flexible career options may enable physicians to combine professional and family roles more effectively.

Oblique-cut LiNbO(3) microchannel spatial light modulator.

Significant improvements in the spatial resolution, framing speed, optical quality, and space-domain image-processing capabilities of the microchannel spatial light modulator have been realized by employing oblique-cut rather than z-cut LiNbO(3) crystals, high-strip-current (250-microA) microchannel plates, and an acceleration grid in the gap of the device. In particular, a prototype device employing a 330-microm-thick, optimum-cut (rotated 55 degrees from the z axis) LiNbO(3) crystal exhibited a framing rate in excess of 30 Hz with full modulation depth and a spatial resolution of ~1.9 cycles/mm at 50% contrast (~10 cycles/mm at 10% contrast). Additionally, four-level to two-level intensity image conversion, contrast reversal, contrast enhancement, edge enhancement, and the binary-level operations AND, NAND, OR, NOR, XOR, and NXOR have been demonstrated by operating the device in its space-domain image-processing mode.

Simple closed-loop system for real-time optical phase measurement.

A simple closed-loop system for estimating optical phase, called an interference phase loop, is presented. In this system the output intensity from an elementary interferometric phase sensor (e.g., Zernike phase contrast, homodyne, heterodyne, polarization, or shearing interferometer) is detected and used to drive a phase modulator in the path of the wavefront being measured. It is shown theoretically and experimentally that with large gain this configuration ignores amplitude fluctuations and unambiguously estimates phase at high speed over a dynamic range of multiple-pi radians. When self-interference (e.g., Zernike phase contrast) is employed, monochromatic light is not required.

Technique for real-time high-resolution adaptive phase compensation.

An "all-optical" approach for the realization of adaptive optical systems potentially containing in excess of a million spatial-resolution elements is reported. A phase-measurement and -compensation technique called an interference phase loop is employed in conjunction with a monolithic optically addressed spatial light modulator (SLM). Wave-front phase compensation and shaping, and the ability to ignore amplitude fluctuations and compensate phase in real time over multiple pi radians of dynamic range, were demonstrated in two discrete-channel laboratory test systems containing one and nineteen resolution elements. All-optical phase compensation with a monolithic SLM was also successfully demonstrated.

Spatial light modulators for optical information processing: introduction by the feature editors.

Some twenty-five papers (including two Letters to the Editor) in this 15 November 1989 issue of Applied Optics consider the technology and use of spatial light modulators. This brief introduction reviews the field.

Amplified reflection through anisotropic four-wave mixing in BaTiO(3).

We have demonstrated cw non-phase-conjugate amplified reflection in single-crystal BaTiO(3) using anisotropic four-wave mixing. We show that the reflected beam is polarized orthogonally to the readout beam and that it is a true reflection of the image beam, not a phase conjugate. The maximum reflectivity measured was approximately 200%.

Perianal appearances associated with constipation.

The perianal appearances were studied prospectively of 136 constipated children (mean age 3.9 years, 67 boys, 69 girls). Anal dilatation, fissures, tags, warts, perianal oedema, redness, blueness, and veins were recorded. It was noted whether dilatation occurred immediately or at 30 and 60 seconds with the buttocks minimally separated, and on subsequent firm lateral traction of the buttocks. The degree of faecal loading was assessed in all children. Anal dilatation was found in 24 (18%) and first appeared on lateral traction in eight (6%). In three quarters of the children with dilatation faecal loading or perianal signs were present. Fissures were found in 35 (26%) children and tags in seven (5%). Perianal redness was more likely to be associated with fissures, and blueness with dilatation. We conclude that there are no pathognomonic perianal signs in childhood constipation and that the technique of anal examination should be standardised.

Prednisolone and salbutamol in the hospital treatment of acute asthma.

The use of oral prednisolone (2 mg/kg) to treat children admitted to hospital with acute asthma was assessed in a placebo controlled study. Children were further randomised to receive either 0.15 mg/kg salbutamol every 30 minutes for the first three hours of admission, or 5 mg salbutamol every one to four hours as needed. Treatment was double blind and the assessor was unaware of the nebuliser regimen given. Children were examined before and after treatment with salbutamol on arrival and reassessed four hours after admission. Seventy children completed the study. Seventeen (46%) of 37 children receiving prednisolone and six (9%) of 33 receiving placebo were fit for discharge after four hours of treatment. There was no significant difference between the two nebuliser regimens. Clinical parameters indicative of asthma severity were improved in all groups. Between group comparisons at reassessment showed higher peak flows in those receiving prednisolone and nebulisers every 30 minutes but differences were not significant for other parameters. Objective parameters indicating steroid efficacy over placebo were minimal. Despite this, those receiving prednisolone were more readily identifiable as being fit for discharge within four hours of treatment.

Audit strategies to reduce hospital admissions for acute asthma.

An eightfold rise in hospital admissions for acute asthma from 1971-85 prompted two studies to audit the admissions policy at the Royal Alexandra Hospital. In the first study the on call senior house officer (SHO) was replaced by an experienced registrar and over a four month period 53 children out of 158 were sent home from the receiving room compared with six out of 39 seen by the SHOs. In the second study an SHO training programme was established together with a home treatment package. Over a 12 month period the on call SHOs assessed 687 children with acute asthma; 229 (43.5%) were deemed fit to be sent home. Only seven of these were readmitted within one week. Diary symptom score cards filled in by parents indicated that children sent home without admission fared no worse at home than those admitted and then discharged for the two weeks after leaving hospital. The development of strategies to improve assessment and immediate management in the hospital receiving room can reduce hospital admissions for acute asthma, allowing more children to be safely managed in the community.

Use of budesonide in severe asthmatics aged 1-3 years.

The treatment of severe asthmatics aged 1-3 years with budesonide administered via Nebuhaler and Laerdal facemask was assessed in a six month, double blind, placebo controlled study. Patients were randomised to budesonide (n = 20) or placebo (n = 20) treatment. Daily symptom scores were recorded by parents and clinic visits occurred every six weeks. Cough scores improved significantly with budesonide: nocturnal and daytime cough scores (0-2) fell by a mean (SEM) of 0.4 (0.2) and 0.5 (0.2); while with placebo the nocturnal score increased by 0.1 (0.2) and daytime score was unchanged at 0.0 (0.2). All other data showed improvements for active over placebo treatment. Thirteen children in each group completed six months' treatment. Parents of 25 of these found the delivery system convenient and easy to use. While blinded to treatment it was assessed to be beneficial in nine of 13 receiving budesonide and four of 13 receiving placebo. The Nebuhaler and facemask is an acceptable delivery system for long term asthma treatment. Symptoms are significantly reduced when it is used to give 400-800 micrograms budesonide/day to children aged 1-3 years who cannot use other delivery systems.

Marital and parental satisfaction of married physicians with children.

OBJECTIVE: To evaluate personal and professional factors associated with marital and parental satisfaction of physicians. STUDY DESIGN: Cross-sectional study. PARTICIPANTS: A survey was sent to equal numbers of licensed male and female physicians in a Southern California county. Of 964 delivered questionnaires, 656 (68%) were returned completed. Our sample includes 415 currently married physicians with children, 64% male and 36% female. MEASUREMENTS AND MAIN RESULTS: Ratings of marital and parental satisfaction were measured on a 5-point Likert scale, 5 being extremely satisfied. Prevalence of work and home life factors was also evaluated. The mean score for marital satisfaction was 3.92 (range 1.75-5.0). Approximately half of the physicians reported high levels of marital satisfaction (63% of male physicians and 45% of female physicians). The gender difference disappeared after adjusting for age differences. Two factors were associated with high marital satisfaction: a supportive spouse (odds ratio [OR] 10.37; 95% confidence interval [CI] 2.66, 40.08) and role conflict (OR 0.61; 95% CI 0.42, 0.88). The mean score for parental satisfaction was 3. 43 (range 1.0-5.0), and approximately two thirds of both male and female physicians reported at least moderate levels of parental satisfaction. The major factors associated with parental satisfaction were a supportive spouse (OR 2.24; 95% CI 1.32, 3.80), role conflict (OR 0.35; 95% CI 0.23, 0.53), salaried practice setting (OR 2.14; 95% CI 1.21, 3.81), marriage to a spouse working in a profession (OR 2.14; 95% CI 1.21, 3.81), and marriage to a spouse working as a homemaker (OR 2.33; 95% CI 1.20, 4.56). Number of hours worked was not found to be related to either satisfaction score, but rather to an intervening variable, role conflict. CONCLUSIONS: For physicians with children, our study indicates that minimizing the level of role conflict and having a supportive spouse are associated with higher levels of marital and parental satisfaction. Working in salaried positions and marriage to a spouse who is either working in a profession or who is a stay-at-home parent are also related to high parental satisfaction.

Computer-generated multiple-phase-level holograms by use of color-printer techniques.

High-efficiency phase-only computer-generated holograms (CGH's) were produced expediently and inexpensively by a color-encoded discrete-phase-level process. Computer-generated-hologram gray levels were mapped to color with a high-resolution color printer, and color was mapped to phase by a broad-spectral-sensitivity high-resolution black-and-white film. Experimental results illustrating colorto optical-density and color-to-phase mapping are presented for Kodak 649F film. A variety of optical interconnection elements exhibiting high diffraction efficiencies and high contrast ratios for both on- and off-axis performance were fabricated by this technique. Typical experimental results are presented.

Charge-transfer-plate spatial light modulators.

Charge-transfer-plate spatial light modulators (CTPSLM's) are a class of devices that employ chargetransfer plates as the interface between the charge-generation element and the light-modulation element. Both optically addressed and electrically addressed devices have been built. Chargegenerating elements for the optically addressed devices include photoconductors, photodiode and phototransistor arrays, optoelectronic integrated circuit chips, and photocathode-microchannel-plate assemblies. For electrically addressed devices, electron guns, very large-scale integrated circuits, thin-film transistors, and matrix electrodes are among the possible charge-generation elements. Lightmodulation elements used in CTPSLM's include liquid crystals, electro-optic organic and inorganic crystals, polymers, deformable membrane mirrors, oil films, multilayer dielectric films, and electroluminescent films. In principle, all combinations of charge-generation elements and light-modulating elements are possible. This paper explores the fundamental performance limitations of CTP technology, and describes the design, operation, and applications of five different CTPSLM's (three based on membrane-mirror technology and two on liquid-crystal technology).

Microchannel spatial light modulator.

A sensitive, high-speed, optically addressed spatial light modulator is being developed for real-time optical dataprocessing applications involving low-level-control light signals. This device is expected to have a sensitivity of better than 10(-3) microJ/cm(2), a framing rate of about 1 kHz, and a spatial resolution of approximately 20 line pairs/mm. The time response, sensitivity, spatial resolution, and other operating characteristics are being studied in a first-generation device; preliminary results are reported.