Behavioral Health Care Delivery Through Street Medicine Programs in California

Mental health and substance use disorders are prevalent among people experiencing homelessness. Street Medicine can reach unhoused people who face barriers to accessing healthcare in more traditional medical settings including shelter-based clinics. However, there is little guidance on best practices for mental health and substance use treatment through Street Medicine. The aim of the study was to describe behavioral health care through Street Medicine by analyzing data from the California Street Medicine Landscape survey and follow-up qualitative interviews. Most street medicine programs utilize non-psychiatrists to diagnose and treat mental health and substance use disorders, though the capacity to provide the level of care needed varies. There is a lack of street-based psychiatric clinicians and programs have difficulty making referrals to mental health and addiction services. This report shows that Street Medicine could serve as a strategy to expand access to behavioral health care for the unhoused.

Characteristics of Homeless Temporarily-Housed in Project RoomKey During the COVID-19 Pandemic

INTRODUCTION

People experiencing unsheltered homelessness (PEUH) have higher disease burden yet limited access to healthcare. COVID-19 introduced even greater risk for PEUH aged 65+ years with an underlying chronic health condition and were temporarily housed in hotels/motels for Project RoomKey (PRK). This study aimed to characterize a PRK cohort who received primary care from a street medicine program.

METHODS

This observational case series study included a sample of 35 PRK participants receiving primary care from a street medicine team at a single site from July to September 2020. We used the HOUSED BEDS assessment tool for taking history on PEUH.

RESULTS

Participants were 63% male, 40% Hispanic/Latino/a, 40% white, 94% English-speaking, and 73% had chronic health conditions. Assessment revealed: average Homelessness (H) of 4 years; 76% had no prior social service Outreach (O); average Utilization (U) was 4 emergency department visits in prior 6-months; 68% received Salary (S) from government income; Food access or Eat (E) was commonly purchased (29%) or donated (26%); clean water to Drink (D) for 59% of participants; 86% had access to a Bathroom (B); Encampment (E) was varied and 38% reported safety concerns; Daily routine (D) showed 76% could access a telephone, 32% received social support from family; 79% reported past or current Substance use (S). No participants contracted COVID-19 during study period.

CONCLUSIONS

This study describes health and demographic characteristics of PRK participants in Southern California. Findings inform policies to continue PRK that includes onsite healthcare such as via street medicine.

From the hospital to the streets: Bringing care to the unsheltered homeless in Los Angeles

Homelessness is a neglected crisis throughout the United States. In Los Angeles (L.A.) County, nearly 59,000 residents are homeless, and the vast majority are unsheltered. An academic institution and L.A county's largest public hospital formed a partnership to launch a Street Medicine (SM) program. SM assists the inpatient team with discharge planning and builds rapport with the patient experiencing homelessness. After discharge, the SM team follows up and brings care to the patient on the streets, often developing a trusting relationship and establishing continuity of primary care. During a 12-month period, SM provided inpatient consults for 206 unsheltered homeless patients.

Prevalence of Homelessness by Gender in an Emergency Department Population in Pennsylvania

Context

According to the US Department of Housing and Urban Development, nearly 1.5 million people spend at least 1 night in an emergency shelter or transitional housing each year, and more than 500,000 people are homeless on a given night in the United States. To our knowledge, limited data exist regarding the prevalence of homelessness in ED patients by gender (male, female, and transgender).

Objective

To assess the prevalence of homelessness by gender in 3 EDs in Pennsylvania.

Methods

From May 2015 through February 2016, patients in 3 EDs were approached to take a 5-question homelessness screening survey. To participate, patients had to be aged at least 18 years, speak English, have capacity to complete the survey, be willing to participate, and not be critically ill. Frequency comparisons were made using χ2 analysis. Statistical significance was defined as P≤.05.

Results

A total of 4395 patients were included in the analysis. The mean (SD) age of the participants was 50.8 (20.5) years; 2557 (58.2%) were women and 3 (0.07%) were transgender. No difference in the rate of homelessness was observed between men and women, with 135 of 1835 men (7.4%) and 173 of 2557 women (6.8%) screening positive for homelessness (P=.472). Forty of 2557 women (1.6%) and 41 of 1835 men (2.2%) admitted they had slept outside or in an abandoned building, their car, an emergency shelter, or a hotel due to financial hardship in the past 60 days (P=.26). One transgender patient screened positive for homelessness. The mean age of participants who screened positive for homelessness was 40.9 (15.9) years.

Conclusion

No significant difference was observed in the rate of homelessness between men and women in this ED population, which defies the perception that this issue primarily affects men. Public health interventions aimed at homeless populations should consider that both men and women may be equally affected by homelessness.

Prevalence of Homelessness in the Emergency Department Setting

INTRODUCTION

According to the National Alliance to End Homelessness, the national rate of homelessness has been cited as 17.7 homeless people/10,000 people in the general population, and 24.8 homeless veterans/10,000 veterans in the general population. However, it is unknown what the prevalence of homelessness is in the emergency department (ED) setting. We set out to determine the prevalence of homelessness or at risk for homelessness in the ED setting.

METHODS

Using a five-question screening tool derived from the U.S. Department of Housing and Urban Development, Health and Human Services and the Veterans Administration definition for homelessness, we surveyed all patients meeting inclusion/exclusion criteria on scheduled shifts in one of three EDs in Northeastern Pennsylvania. To participate, subjects had to be a registered patient in the ED, be 18 years or older, speak English, have the capacity to answer survey questions, not be critically ill, be willing to participate, and not have taken the survey before. We selected two survey periods to represent seasonal variations.

RESULTS

We included 4,395 subjects in the analysis. The mean age of those who screened positive for homelessness or at risk for homelessness was 43.1 (SD 16.6). Overall, 136 (3.1%) participants screened positive for at risk for homelessness and 309 (7.0%) screened positive for homelessness. A total of 103 subjects (9.8%) screened positive for homelessness or at risk for homelessness on weekends and 312 (10.3%) on weekdays (p=0.64). The proportion of those screening positive for homelessness or at risk for homelessness varied by site: 145 (7.5%) at the trauma center, 151(9.1%) at the suburban site, and 149 (18.7%) at the center city site, p<0.001.There was no statistical significance to the difference between the trauma center and the suburban site (p=.088), but there was statistical significance between both the suburban and the trauma center when compared to the center city site (both p<0.0001). The proportion of those screening positive for homelessness in the summer months (156, 7.5%) was similar to those in the winter months (153, 6.6%), p=0.23.

CONCLUSION

In our study, the overall prevalence of homelessness or at risk for homelessness was 10.1 percent. This prevalence did not seem to vary between weekdays and weekends. Additionally, summer months had a prevalence that was as concerning as winter months. The prevalence does, however, seem to vary by institutional characteristics even in the same geographic region. Understanding the patterns of prevalence of homelessness is a step toward considering possible interventions to assist this vulnerable population.

Evaluation of the single-item self-rating adherence scale for use in routine clinical care of people living with HIV

The self-rating scale item (SRSI) is a single-item self-report adherence measure that uses adjectives in a 5-point Likert scale, from "very poor" to "excellent," to describe medication adherence over the past 4 weeks. This study investigated the SRSI in 2,399 HIV-infected patients in routine care at two outpatient primary HIV clinics. Correlations between the SRSI and four commonly used adherence items ranged from 0.37 to 0.64. Correlations of adherence barriers, such as depression and substance use, were comparable across all adherence items. General estimating equations suggested the SRSI is as good as or better than other adherence items (p's <0.001 vs. <0.001-0.99) at predicting adherence-related clinical outcomes, such as HIV viral load and CD4(+) cell count. These results and the SRSI's low patient burden suggest its routine use could be helpful for assessing adherence in clinical care and should be more widespread, particularly where more complex instruments may be impractical.

Carbohydrate-deficient glycoprotein syndrome-associated pericardial effusion treated with corticosteroids and salicylic acid

We describe an infant with a persistent pericardial effusion who was diagnosed with carbohydrate-deficient glycoprotein syndrome (CDGS)-Ia. She was born with mild dysmorphic features and common cardiac abnormalities. However, she re-presented at 2.5 months of age with a pericardial effusion. We decided to embark on a therapeutic trial of corticosteroids and salicylic acid therapy in an attempt to avoid pericardectomy. After 3 weeks of medical treatment the effusion resolved. This experience allows us to propose that medical management with corticosteroids and salicylic acid can be considered as an alternative to surgical therapy for CDGS-I patients with persistent pericardial effusions.

The development of androgen-independent prostate cancer

The normal prostate and early-stage prostate cancers depend on androgens for growth and survival, and androgen ablation therapy causes them to regress. Cancers that are not cured by surgery eventually become androgen independent, rendering anti-androgen therapy ineffective. But how does androgen independence arise? We predict that understanding the pathways that lead to the development of androgen-independent prostate cancer will pave the way to effective therapies for these, at present, untreatable cancers.

A carboxy-terminal deletion mutant of Notch1 accelerates lymphoid oncogenesis in E2A-PBX1 transgenic mice

PBX1 is a proto-oncogene that plays important roles in pattern formation during development. It was discovered as a fusion with the E2A gene after chromosomal translocations in a subset of acute leukemias. The resulting E2a-Pbx1 chimeric proteins display potent oncogenic properties that appear to require dimerization with Hox DNA binding partners. To define molecular pathways that may be impacted by E2a-Pbx1, a genetic screen consisting of neonatal retroviral infection was used to identify genes that accelerate development of T-cell tumors in E2A-PBX1 transgenic mice. Retroviral insertions in the Notch1 gene were observed in 88% of tumors arising with a shortened latency. Among these, approximately half created a Notch(IC) allele, encoding the intracellular, signaling portion of Notch1, suggesting a synergistic interaction between the Notch and E2a-Pbx1 pathways in oncogenesis. The remaining proviral insertions involving Notch1 occurred in a more 3' exon, resulting in truncating mutations that deleted the carboxy-terminal region of Notch1 containing negative regulatory sequences (Notch1(DeltaC)). In contrast to Notch(IC), forced expression of Notch1(DeltaC) in transgenic mice did not perturb thymocyte growth or differentiation. However, mice transgenic for both the E2A-PBX1 and Notch1(DeltaC) genes displayed a substantially shortened latency for tumor development compared with E2A-PBX1 single transgenic mice. These studies reveal a novel mechanism for oncogenic activation of Notch1 and demonstrate a collaborative relationship between 2 cellular oncogenes that also contribute to cell fate determination during embryonic development. (Blood. 2000;96:1906-1913)

Pim1 cooperates with E2a-Pbx1 to facilitate the progression of thymic lymphomas in transgenic mice

Mice transgenic for the leukemia oncogene E2A-PBX1 invariably develop lethal, high-grade T-cell lymphomas by 5 months of age. In this study, retroviral insertional mutagenesis was employed to identify oncogenes that cooperate with the E2A-PBX1 transgene in lymphomagenesis. Neonatal retroviral infection substantially reduced length of survival due to accelerated development of lymphomas (81 versus 130 days). The Pim1 gene was targeted by retroviral insertions in 48% of accelerated lymphomas whereas less than 5% contained activated c-Myc and none contained activated Pim2. However, Pim1 DNA rearrangements were frequently sub-stoichiometric and not present at all sites of involvement in an otherwise monoclonal lymphoma indicating that Pim1 activation occurred late in the course of lymphomagenesis. Tumor subpopulations containing activated Pim1 alleles displayed a substantial growth advantage over Pim1 negative cells following serial transfer to secondary, syngeneic recipients. Cooperative interactions were observed in intercrossed Pim1 and E2A-PBX1 transgenic mice in which all double transgenic progeny developed lethal, diffuse T lineage lymphomas by 3 months of age, whereas only 13% of E2A-PBX1 and none of Pim1 single transgenic intercross progeny developed lymphomas by 1 year. Tumors from double transgenic mice were monoclonal providing evidence that additional genetic events were required for transformation. Therefore, Pim1 and E2a-Pbx1 cooperate in T lineage lymphomagenesis but they are not sufficient and the role of Pim1 is more likely to be associated with tumor progression.

The chimeric oncoproteins E2A-PBX1 and E2A-HLF are concentrated within spherical nuclear domains

Oncogenic mutation of nuclear transcription factors often is associated with altered patterns of subcellular localization that may be of functional importance. The leukemogenic transcription factor gene E2A-PBX1 is created through fusion of the genes E2A and PBX1 as a result of t(1;19) in acute lymphoblastic leukemia. We evaluated subcellular localization patterns of E2A-PBX1 protein in transfected cells using immunofluorescence. Full-length E2A-PBX1 was exclusively nuclear and was concentrated in spherical domains denoted chimeric-E2A oncoprotein domains (CODs). In contrast, nuclear fluorescence for wild-type E2A or PBX1 proteins was diffuse. Enhanced concentrations of RNA polymerase II within many CODs and the requirement for an E2A-encoded activation domain suggested transcriptional relevance. However, in situ co-detection of nascent transcripts labeled with bromouridine failed to confirm altered transcriptional activity in relation to CODs. CODs also failed to co-localize with other proteins known to occupy functional nuclear compartments, including the transcription factor PML, the spliceosome-associated protein SC-35 and the adenovirus replication factor DBP, or with foci of DNA replication. Co-transfection of Hoxb7, a homeodomain protein capable of enhancing DNA binding by PBX1, impaired COD formation, suggesting that CODs contain E2A-PBX1 protein not associated with DNA. We conclude that, as a 'gain of function' phenomenon requiring protein elements from both E2A and PBX1, COD formation may be relevant to the biology of E2A-PBX1 in leukemogenesis.

Transient thermal lens in a ZnGeP(2) crystal

The first observations, to the authors' knowledge, of transient thermal lensing in a ZnGeP(2) crystal achieved with 2.09-µm laser excitation of 800-µs, 70-mJ pulses at 30 Hz and by burst-mode Q-switched pumping are presented. The laser power transmitted through an aperture was approximated by an adiabatic model with currently accepted values for the thermal properties of ZnGeP(2) and corresponded to focal-length changes from infinity to 10 cm during each 800-µs pulse. Similar results were seen when the crystal was operated as an optical parametric oscillator. This transient thermal lens severely limits ZnGeP(2) as a material for use in optical parametric oscillators for these modulated, high-power operating conditions.

Electrochemical determination of low blood lead concentrations with a disposable carbon microarray electrode

Lead concentrations in blood samples typical of unexposed individuals are determined by using square-wave anodic stripping voltammetry at a disposable 287-element (15-35-microns diameter) carbon microarray electrode. Analysis of a series of low Pb-containing samples (blood [Pb] = 17 to 92 micrograms/L) by standard addition gives good accuracy (average bias vs graphite furnace atomic absorption spectroscopy = -4 micrograms/L) and precision (pooled SD = 7 micrograms/L). The signal/noise ratio is improved by about an order of magnitude over that found at a single carbon disk (10 microns diameter), resulting in a detection limit (for the microarray) of 5 micrograms/L for a 60-s deposition of sample.

Electrochemical determination of low blood lead concentrations with a disposable carbon microarray electrode

Lead concentrations in blood samples typical of unexposed individuals are determined by using square-wave anodic stripping voltammetry at a disposable 287-element (15-35-microns diameter) carbon microarray electrode. Analysis of a series of low Pb-containing samples (blood [Pb] = 17 to 92 micrograms/L) by standard addition gives good accuracy (average bias vs graphite furnace atomic absorption spectroscopy = -4 micrograms/L) and precision (pooled SD = 7 micrograms/L). The signal/noise ratio is improved by about an order of magnitude over that found at a single carbon disk (10 microns diameter), resulting in a detection limit (for the microarray) of 5 micrograms/L for a 60-s deposition of sample.

A novel role for DNA photolyase: binding to DNA damaged by drugs is associated with enhanced cytotoxicity in Saccharomyces cerevisiae

DNA photolyase binds to and repairs cyclobutane pyrimidine dimers induced by UV radiation. Here we demonstrate that in the yeast Saccharomyces cerevisiae, photolyase also binds to DNA damaged by the anticancer drugs cis-diamminedichloroplatinum (cis-DDP) and nitrogen mustard (HN2) and by the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Surprisingly, mutations in photolyase were associated with resistance of yeast cells to cis-DDP, MNNG, 4-nitroquinoline oxide (4NQO), and HN2. Transformation of yeast photolyase mutants with the photolyase gene increased sensitivity to these agents. Thus, while the binding of photolyase to DNA damaged by UV radiation aids survival of the cell, binding to DNA damaged by other agents may interfere with cell survival, perhaps by making the lesions inaccessible to the nucleotide excision repair system.

Determination of lead in blood by square wave anodic stripping voltammetry at a carbon disk ultramicroelectrode

A method for blood lead ([Pb]) analysis is developed based on square wave anodic stripping voltammetry (SWASV) in an Hg(2+)-containing solution using a 10-microns-diameter carbon disk ultramicroelectrode. SWASV eliminates interference from O2 in unsparged blood-derived sample solutions, and filtration of acidified samples through nitrocellulose reduces the concentration of interfering substances, increasing the size and improving the uniformity of peak currents. Blood [Pb] values obtained by SWASV are compared with blood [Pb] values determined by graphite furnace atomic absorption spectrophotometry; good accuracy and reasonable coefficients of variation in the range 10.6-20% (average of 13.5%) are found for blood [Pb] ranging from 4 to 30 micrograms/dL. Preliminary experiments using a carbon disk microarray electrode suggest future improvements in sensitivity.

Urinary protein markers in pesticide applicators during a chlorinated hydrocarbon exposure

A previous study of 16 pesticide applicators showed that N-acetylglucosaminidase (NAG) excretion during exposure to the soil nematocide, 1,3-dichloropropene (DCP), was correlated with DCP dose and the excretion of its major metabolite, N-acetyl-S-(cis-3-chloroprop-2-enyl)-cysteine (3CNAC). Using the same urine samples, two other proteins were measured: low concentrations of albumin ("microalbuminuria," ALB) and retinol-binding protein (RBP). For each worker there were five consecutive urine collection intervals (6-8 hr each): overnight prior to exposure, morning work shift, afternoon work shift, evening after work, and overnight. Paired comparisons of each interval to baseline (first interval) for each protein excretion (creatinine corrected) did not reveal significant increases. However, amounts of renal proteins per interval, in contrast to creatinine-corrected concentrations, were more strongly correlated with each other and with 3CNAC concentrations within samples. Clear dichotomous differences in urinary protein excretion were seen for high versus low exposure (< or > 1.5 mg 3CNAC excretion/day) for NAG and RBP, but not for ALB. Based on earlier findings of a slight elevation of NAG and the minimal changes reported herein for RBP, the possible effects of short-term workplace exposure to DCP on renal protein excretion appear to be mild.

High-average-power operation of a Q-switched diode-pumped holmium laser

We have investigated high-peak- and high-average-power operation of diode-pumped, thulium-sensitized, holmium 2.1-microm lasers. Free-running laser powers of 14 W at 29 Hz have been demonstrated with 2.6% electrical efficiency. Q-switched operation produced average powers in excess of 11 W in a burst of short pulses. Preliminary optical parametric oscillator frequency conversion of the holmium laser to 4 microm is also reported.

A population study of the natural history of Wolff-Parkinson-White syndrome in Olmsted County, Minnesota, 1953-1989

BACKGROUND

Virtually all natural history studies of Wolff-Parkinson-White (WPW) syndrome have been case series and, as such, have been constrained by referral biases, skewed age and sex distributions, or brief follow-up periods. The purpose of our study was to examine the natural history, the development of arrhythmias, and the incidence of sudden death in an entire cohort of pediatric and adult WPW patients from a community-based local population.

METHODS AND RESULTS

We identified 113 residents of Olmsted County, Minnesota, during the period 1953-1989 using the centralized records-linkage system provided by the Mayo Clinic and the Rochester Epidemiology Program Project. Medical records and ECGs were reviewed to confirm the diagnosis and to establish pathway location by ECG criteria. Follow-up, via record review and telephone interview, was complete in 95% of subjects through 1990. The incidence of newly diagnosed cases was approximately four per 100,000 per year. Preexcitation was not present on the initial ECG of 22% of the cohort. Approximately 50% of the population was asymptomatic at diagnosis, with 30% subsequently having symptoms related to arrhythmia at follow-up. Two sudden cardiac deaths (SCD) occurred over 1,338 patient-years of follow-up, yielding an overall SCD rate of 0.0015 (95% confidence interval, 0.0002-0.0054) per patient-year. No SCD occurred in patients asymptomatic at diagnosis.

CONCLUSIONS

The incidence of sudden death in a local community-based population is low and suggests that electrophysiological testing should not be performed routinely in asymptomatic patients with WPW syndrome. Nevertheless, young, asymptomatic patients, particularly those < 40 years old, should return for medical follow-up should symptoms develop.

Stimulated Brillouin scattering phase conjugation of an amplified hydrogen fluoride laser beam

Optical phase conjugation through stimulated Brillouin scattering was used to correct phase aberrations on a beam that was double passed through a pulsed hydrogen fluoride laser amplifier.

Tremor at onset. Predictor of cognitive and motor outcome in Parkinson's disease?

We examined 46 male patients with idiopathic Parkinson's disease to see whether tremor at onset was as useful a predictor of benign clinical outcome as tremor predominance after several years. When we compared patients with tremor at onset (n = 27) with those whose disease began with brady-kinesia/rigidity (n = 9), or gait disorder (n = 10), we found no significant differences after a mean of 7 years in motor, cognitive, or affective status. Sixteen of the tremor-onset patients continued to have tremor predominance with minimal gait disorder after about 7 years. These tremor-predominant patients had significantly better motor outcome and somewhat better cognitive outcome than either tremor-onset patients who subsequently developed gait disorder (n = 11) or patients without tremor at onset (n = 19). Tremor predominance after several years appears to be a better predictor of a benign clinical course of Parkinson's disease than tremor at onset.

Suppression of photorefractive beam fanning using achromatic gratings

We show that achromatic grating techniques, using the 488- and 514.5-nm lines of the argon-ion laser, can suppress beam fanning while still allowing two-beam coupling to occur. The suppression is studied as a function of the ratio of the two colors used to form the achromatic grating.

Photorefractive two-beam coupling with white light

We demonstrate, for the first time to our knowledge, two-beam coupling in BaTiO(3) using white light. An achromatic grating arrangement in conjunction with a high-pressure mercury-arc lamp is used to produce the white-light fringes. The sensitivity of the coupling to source coherence, crystal orientation, and grating spacing is determined, and a comparison with two-beam coupling with monochromatic light at the same intensity is made.

Electrochemical cells for voltammetry, coulometry, and protein activity assays of small-volume biological samples

Cell designs, experimental protocols, and results for electrochemical investigation of small quantitites of biological materials under anaerobic conditions are reported. Three types of electrochemical experiments are considered: (i) cyclic voltammetry of 20- to 100-microliters samples; (ii) direct coulometry of 0.5- to 1.5-ml samples; and (iii) an electrochemically initiated protein activity assay which includes provision for analysis of gaseous reaction products and correlation with electron flux. The first two procedures are illustrated by measurement of the formal electrode potential (E0') and number of electrons transferred (n) in redox reactions of small quantities of biological and inorganic materials. The third procedure is illustrated by assaying the activity of the MoFe protein plus Fe protein complex from Azotobacter vinelandii nitrogenase for reduction of C2H2 to C2H4.

Ultranarrow linewidth waveguide excimer lasers

We have constructed a single longitudinal mode XeCl laser using microwave discharge waveguide laser technology. The pulse duration, repetition rate, and simplicity of construction associated with waveguide excimer lasers lend this system unique capabilities and a broad utility for interfacing with other excimer devices. The coherence length of the laser emission has been found to be ~6 m with a corresponding bandwidth of <22 MHz that is near the transform limit. The laser has been used to demonstrate pulsed UV Doppler velocity measurement in a simple homodyne configuration.

Isolated iron-molybdenum cofactor of nitrogenase exists in multiple forms in its oxidized and semi-reduced states

Electrochemical and EPR spectroscopic experiments demonstrate that the isolated iron-molybdenum cofactor from the molybdenum-iron protein of nitrogenase from Azotobacter vinelandii exists in multiple forms in both its oxidized and semi-reduced states. The particular forms found in either oxidation state appear to be a function of the acid/base status of the solvent, N-methylformamide. In "alkaline" N-methylformamide, a single, detectable form of iron-molybdenum cofactor is observed for both oxidized and semi-reduced states. The semi-reduced form, termed R(s-r), is the one previously recognized with an S = 3/2 EPR spectrum with apparent g values of 4.6, 3.4, 2.0. Its oxidized counterpart, termed B(ox), is characterized electrochemically by a differential pulse voltammetric reduction peak at -0.37 V versus the normal hydrogen electrode. In "acidic" solvent, two distinct, previously unrecognized redox pairs of iron-molybdenum cofactor forms exist. The two semi-reduced forms, N(s-r) and W(s-r), are characterized by EPR spectra with g = 4.5, 3.6, 2.0 and g = 4.9, 3.1, 1.9, respectively. Their oxidized counterparts, A(ox) and C(ox), have differential pulse voltammetric reduction peaks at -0.32 and -0.43 V versus the normal hydrogen electrode, respectively. Manipulations of either the isolation protocol or the sample conditions affects both the type and distribution of forms present. Each form likely corresponds to a biologically significant state of the cofactor cluster within the protein.

Diode-pumped 1.34-microm Nd(3+):YAlO(3) laser

We have pumped Nd(3+):YAlO(3) lasers with a 40-stripe, 500-mW, 807-nm diode laser. Maximum output powers at 1.34 microm of 26 mW multimode and 20 mW in a single transverse mode were achieved. The several longitudinal modes had a total spectral width of ~0.4 nm.

High-repetition-rate XeCl waveguide laser without gas flow

Operation of a microwave discharge XeCl laser at pulse-repetition rates extending to 8 kHz without flow of the laser gas is reported. Present limits on pulse-repetition rate appear to be imposed by thermally induced refractive-index gradients.

Stimulated Brillouin scattering and phase conjugation of hydrogen fluoride laser radiation

Stimulated Brillouin scattering (SBS) of hydrogen fluoride laser radiation has been demonstrated for the first reported time. A flash-lamp-pumped pulsed chemical laser, operating single-line at 2.91 microm, was used to generate backward-stimulated Brillouin scattering in high-pressure xenon gas with power reflectivities of ~50%. Intentional aberration and subsequent restoration of a high-spatial-quality beam provided evidence of phase conjugation by the SBS process.

Research on nonlinear optical materials: an assessment

The seven papers making up this assessment are based on the Workshop on Nonlinear Optical Materials held in April 1986.

Efficient phase conjugation of an ultraviolet XeF laser beam by stimulated Brillouin scattering

We report efficient, diffraction-limited, phase conjugation of an XeF (3511-A) laser beam using stimulated Brillouin scattering. Approximately 70% of the 1-GHz bandwidth-locked portion of an injection-locked XeF laser output is phase conjugated by focusing the laser beam at 5 GW/cm (2) into hexane or isopropanol.

Ultraviolet phase conjugation

We report the first known demonstration of UV phase conjugation. By use of a 15-psec, 2660-A pulse, 0.1% conjugate reflectivities were obtained through degenerate four-wave mixing in 1-mm samples of CS(2) mixtures. Although pure CS(2) did not exhibit the effect, dilution of CS(2) in several UV-transmitting solvents opened up a concentration- tunable (2450-2850 A) spectral window, allowing the optical Kerr effect to be utilized. Weaker phase conjugation at 2660 A was also observed in other Kerr media and in saturable absorber media.

A prospective study of the incidence of injury to the cranial nerves during carotid endarterectomy

In order to determine the incidence of cranial nerve injury during carotid endarterectomy, preoperative and postoperative otolaryngologic examinations were performed in a prospective series of 240 operations. Thirty patients experienced a total of 38 cranial nerve injuries, involving the recurrent laryngeal nerve in 14, the hypoglossal nerve in 13, the marginal mandibular nerve in six and the superior laryngeal nerve in five. Postoperative dysfunction affected one cranial nerve in 25 patients, two nerves in four and three nerves in one patient. Most cranial nerve injuries were asymptomatic or mild in severity, resolved in one to 12 months and probably were caused by intraoperative retraction.

On-resonant phase-conjugate reflection and amplification at 10.6 microm in inverted CO(2)

We have obtained phase-conjugate reflection and amplification with an effective reflectivity exceeding unity by redirecting the output of a TEA CO(2)-laser oscillator into its own gain medium. The intense counterpropagating waves within the laser were coupled through the saturated medium to provide the nonlinearity in a process analogous to degenerate four-wave mixing.

Absorption of pulsed CO(2)-laser radiation by SF(6) at 140 K

Measurements of absorption of pulsed CO(2) laser radiation by SF(6) at 140 K are reported. Four laser frequencies within the nu(3) absorption band were used, and the laser fluence was varied between 10(-5) and 1.0 J/cm(2). Frequency and fluence trends are discussed, and comparisons are made with room-temperature data. The results indicate that at the SF(6) ground-state band center [P(16), 10-microm line], the fluence-dependent multiple-photon-absorption cross-section curve at 140 K lies slightly above the room-temperature curve, whereas at lower frequencies the low-temperature absorption cross sections are less than 5% of the room-temperature values.

Intense high-pressure sequence-band CO2 laser

We have obtained temporally smooth, single-line megawatt output from the (0,0 degrees,2) --> [(1,0 degrees,1), (0,2 degrees,1)]1 sequence band in an 1800-Torr CO2 double-discharge laser. These lines were first observed by Reid and Siemsen in a low-pressure discharge at subwatt power outputs [Appl. Phys. Lett. 29, 250 (1976)]. The intense 10-gm region laser transitions reported here may be useful for selective molecular excitation, for nonlinear optics experiments where wavelengths of the usual C02 transitions are inappropriate, and for long-path atmospheric transmission.

Generation of single ultrashort CO(2) laser pulses in a Fabry-Perot interferometer

In a manner analogous to optical free-induction decay, we have generated ultrashort (<100 psec) intense infrared optical pulses by reflecting an abruptly terminated CO(2) laser pulse from an appropriately adjusted Fabry-Perot interferometer. Because a suitable resonantly absorbing material is not required, the scheme is applicable to any intense narrow-band laser system.