Low-threshold, dual-passive mode locking of a large mode area Nd:GdVO(4) laser.

The all solid-state combination of a saturable Bragg mirror for amplitude modulation and a cascaded chi((2)):chi((2)) nonlinearity (phase-mismatched second harmonic crystal) as an axial-mode phase locker for continuous-wave mode locking of large mode area lasers is investigated. The dual-passive mode-locking technique generates extremely stable sub-10ps sech(2) pulses at 76MHz from a ~6W, TEM(00)-mode, diode-pumped, thermal-lens-shaped, Brewster Nd:GdVO(4) laser.

Femtosecond Ti:Sapphire Oscillator Electro-Optically Cavity Dumped at 50 kHz.

Use of a transverse KD?P Pockels cell and novel low-loss sapphire Rochon polarizer to cavity dump a hard-aperture, Kerr-lens mode-locked, Ti:sapphire oscillator is demonstrated. High-quality 90-fs pulses with energies of ~50 nJ at repetition rates of up to 50 kHz were obtained.

Malignant neoplastic disease of the parotid lymph nodes.

OBJECTIVES: To review the management and outcome of patients with malignant neoplastic disease of the parotid lymph nodes excluding those with primary salivary gland tumors. STUDY DESIGN: Retrospective review of 14 patients who had malignant parotid lymph nodes from metastatic cutaneous malignancies, direct extension from primary cutaneous malignancies, or lymphoproliferative disorders. METHODS: Charts were reviewed from three institutions and tabulated for age, gender, histopathology, treatment, and outcome. RESULTS: Fourteen patients met the criteria for study. Ten patients had neoplastic nodes from cutaneous malignancies. Seven involved squamous cell carcinoma, two were metastatic from melanoma, and one was metastatic from basal cell carcinoma. Four patients had involvement from lymphoproliferative disorders. CONCLUSIONS: Metastatic disease to the parotid nodes or direct extension to nodes from primary cutaneous malignancy demonstrates a poor prognosis in this series. Prognosis of lymphoproliferative disorder is more favorable.

Measurement of 160-fs, 248-nm pulses by two-photon fluorescence in fused-silica crystals.

Measurements of 160-fs, 248-nm ultrashort pulses are obtained through a two-photon fluorescence measurement based on the two-photon-induced color-center fluorescence in fused-silica crystals. The method proved to be reliable and advantageous in comparison with two-photon fluorescence techniques employing other materials, both solid state and gaseous.

Short-pulse amplification at 745 nm in Ti:sapphire with a continuously tunable regenerative amplifier.

We describe the design of a continuously tunable Ti:sapphire regenerative amplifier that is capable of sustaining amplification over a wavelength range from 730 nm to more than 800 nm. The amplifier cavity is tuned with a prism pair in combination with a spherical mirror. It sustains an oscillation bandwidth of 5 nm and produces a chirped output pulse energy of 1.2 mJ compressible to a duration of 140 fs at 745 nm. We present a calculation of the theoretical bandwidth.

Microbial carotenoids.

Carotenoids occur universally in photosynthetic organisms but sporadically in nonphotosynthetic bacteria and eukaryotes. The primordial carotenogenic organisms were cyanobacteria and eubacteria that carried out anoxygenic photosynthesis. The phylogeny of carotenogenic organisms is evaluated to describe groups of organisms which could serve as sources of carotenoids. Terrestrial plants, green algae, and red algae acquired stable endosymbionts (probably cyanobacteria) and have a predictable complement of carotenoids compared to prokaryotes, other algae, and higher fungi which have a more diverse array of pigments. Although carotenoids are not synthesized by animals, they are becoming known for their important role in protecting against damage by singlet oxygen and preventing chronic diseases in humans. The growth of aquaculture during the past decade as well as the biological roles of carotenoids in human disease will increase the demand for carotenoids. Microbial synthesis offers a promising method for production of carotenoids.

Post tonsillectomy hemorrhage: a ten-year retrospective study.

Tonsillectomy remains one of the most common surgical procedures performed in the world. One of the most significant complications is postoperative hemorrhage. Though most bleeding often can be controlled with local anesthesia in an office or emergency room, some patients require return to the operating room for general anesthesia to control the hemorrhage. A ten-year retrospective study was done to review patients who required return to the operating room for general anesthesia for control of hemorrhage. Variables investigated include age, gender, time of surgery, onset of hemorrhage, season of the year, and the amount of blood loss noted during initial surgery. Seven of the 756 patients (.93%) required a second general anesthesia to control hemorrhage. Seasonal and gender predilictions are noted in this study. Recent trends in tonsillectomy are reviewed. Postoperative hemorrhage creates anxiety, prolongs morbidity, and increases health care cost. Limiting this complication is clearly in the best interest of both patient and surgeon.

Singlet oxygen and peroxyl radicals regulate carotenoid biosynthesis in Phaffia rhodozyma.

Carotenoids have recently received considerable interest because of their potential in delaying or preventing degenerative diseases such as arteriosclerosis, cancer, and aging. In this study we show that the active oxygen species singlet oxygen (1O2) and peroxyl radicals differently affect carotenoid composition and biosynthesis in the yeast Phaffia rhodozyma. Photochemical generation of 1O2 with rose bengal or alpha-terthienyl induced carotenoid accumulation. In contrast, peroxyl radicals derived from t-butylhydroperoxide (tBOOH) or H2O2 decreased the content of astaxanthin and increased beta-carotene by approximately 4-fold, suggesting end product feedback regulation by astaxanthin or inhibition of biosynthetic enzymes. 14C labeling of carotenoids during oxidative stress supported the possibility of end product regulation. Carotenoids were bleached by 8 mM tBOOH within 6 h when carotenogenesis was inhibited by thymol. When treated with peroxides, a previously unreported pigment in P. rhodozyma was formed. The carotenoid had a mass of 580 Da and a molecular formula of C40H52O3. Chemical derivatizations combined with mass and absorbance spectroscopy tentatively identified the carotenoid as dehydroflexixanthin (3,1'-dihydroxy-2,3,3',4'-tetradehydro-1',2'-dihydro-beta,psi-caro tene-4-one). This study provides the first report of induction of astaxanthin biosynthesis by 1O2, probable feedback control by astaxanthin, and the oxidative degradation of astaxanthin to novel pigments in P. rhodozyma.

Closure of conchal defects. The hinged retroconchal island flap with overlying cutaneous transposition flap.

BACKGROUND: Conchal defects secondary to surgical procedures or trauma often cannot be closed primarily. OBJECTIVE: Tissue transfer for closure of defects must be tension free and not create a postauricular sulcus too shallow. METHODS: A retroconchal island flap provides such a closure. A rhomboid transposition flap used to provide closure of the donor site retains the depth of the posterior sulcus. RESULTS: The closure of the defect heals well within 4-6 weeks even in presence of scar tissue from multiple prior surgeries. CONCLUSION: The retronconchal island flap is a simple, reliable technique to close the defect of the concha without sacrificing the natural depth of the posterior sulcus.

Post tympanostomy otorrhea.

Myringotomy with placement of ventilation tubes is the most common pediatric otolaryngologic procedure in the United States. Otorrhea is generally recognized as the most common complication of this procedure. The current study is a three-year prospective evaluation of post tympanostomy otorrhea to determine what variables might be associated with otorrhea. Analysis of patients from a predominantly rural population is presented.

Intranasal melanoma.

Malignant melanoma is most commonly associated with cutaneous malignancies of sun-exposed skin, but melanoma also occurs in the mucosal surfaces of the head and neck. The symptoms of intranasal melanoma are most often associated with benign conditions that patients often ignore during the early course of the disease. Benign symptoms that persist require thorough evaluation to exclude neoplastic disease in which timely diagnosis and early treatment offers the best prognosis.

Picosecond separation and measurement of coexisting photorefractive, bound-electronic, and free-carrier grating dynamics in GaAs.

A novel transient-grating geometry, which is nondegenerate, copropagating, phase matched, and polarization sensitive, is used to isolate and measure independently the ultrafast dynamics of multiple coexisting gratings in GaAs:EL2 with a temporal resolution of <5 psec. This technique permits the measurement of the evolution of the photorefractive grating in materials with zinc blende symmetry, where the photorefractive grating is usually obscured by the stronger free-carrier and instantaneous bound-electronic gratings.

Photorefractive nonlinearities caused by the Dember space-charge field in undoped CdTe.

The photorefractive nonlinearity associated with the Dember space-charge field between electrons and holes produced by two-photon absorption is unambiguously isolated and studied in undoped CdTe by using a nondegenerate, forward-probing, polarization-sensitive, transient-grating technique with a temporal resolution of <5 ps.

Hot-carrier enhancement of photorefractive space-charge fields in zinc-blende semiconductors.

We observe an order-of-magnitude enhancement of the photorefractive effect in undoped CdTe on ~1-ps time scales that is caused by an overshoot in the two-photon-produced Dember space-charge field associated with hot-carrier transport.

Beta S-gene-cluster haplotypes in sickle cell anemia: clinical implications.

Restriction endonuclease analysis was used to detect alpha-gene deletions and to determine the haplotypes in the DNA of the beta S-gene-cluster [Benin, Central African Republic (CAR), and Senegal] in 221 patients with sickle cell anemia (SS). The clinical expression of SS was modified by the beta S-gene-cluster polymorphisms and the alpha-gene status (alpha-thalassemia-2). The overall risk of soft tissue organ failure caused by the obliterative sickle vasculopathy (including stroke, renal failure, chronic lung disease with cor pulmonale, leg ulcers, and young adult death) was increased threefold in those with a CAR haplotype and was decreased in those with a Senegalese chromosome (p = 0.003). In the presence of a Senegalese haplotype, the patient's health is better, and with the CAR haplotype it is always worse. With the Benin, it is intermediate. Acute recurrent clinical events including hospitalized sickle cell crisis, bone infarction, and infection are decreased in frequency in those with a Senegalese haplotype. The risk of most acute events including acute chest syndrome is equivalent in those with Benin or CAR haplotypes. In the United States, alpha-thalassemia-2 is co-inherited randomly among the beta S-gene-cluster haplotypes. Acute events occurring during childhood are minimally effected by this co-inheritance. The risk of soft tissue organ failure is decreased. After the age of 20 years, painful episodes of the lumbar dorsal area are increased in patients who had alpha-thalassemia-2 in association with degenerative bone disease.(ABSTRACT TRUNCATED AT 250 WORDS)