Integrated array of 2-µm antimonide-based single-photon counting devices.

A 32x32 Sb-based Geiger-mode (GM) avalanche photodiode array, operating at 2 µm with three-dimensional imaging capability, is presented. The array is interfaced with a ROIC (readout integrated circuit) in which each pixel can detect a photon and record the arrival time. The hybridized unit for the 1000-element focal plane array, when operated at 77K with 1 V overbias range, shows an average dark count rate of 1.5 kHz. Three-dimensional range images of objects were acquired.

Near-diffraction-limited diode laser arrays by wavelength beam combining.

We demonstrate 35 W output peak power with M2 approximately 1.35 in both dimensions from a 100 element, 100 microm pitch slab-coupled optical waveguide laser diode array using wavelength beam combining.

Role of ultrasound for Down syndrome screening in advanced maternal age.

OBJECTIVE: To determine the sensitivity and false-positive rate of Down syndrome screening by use of maternal serum screen and the genetic sonogram in women > or =35 years of age. STUDY DESIGN: We searched our perinatal databases retrospectively from January 1992 to January 2000 for the following criteria: known Down syndrome fetus or newborn, advanced maternal age, and genetic sonogram from 14-24 weeks' gestation. The a priori maternal age or maternal serum screen risk was modified by likelihood ratios for ultrasound markers. Without markers the risk was reduced by 50%. The cut-off was 1:270. RESULTS: Age and maternal serum screen had a sensitivity of 90.5% and a false-positive rate of 27.1%. Age and ultrasound had a 95.2% sensitivity and 43.5% false-positive rate, whereas the combination of age, maternal serum screen, and ultrasound had a 97.6% sensitivity and a 22.0% false-positive rate. CONCLUSION: The combination of age, maternal serum screen, and ultrasound improves the sensitivity for Down syndrome detection in the advanced maternal age population.

Telesensor integrated circuits.

Progress in personal computing has recently permitted small research programs to design and simulate application-specific integrated circuits (ASICs). Inexpensive fabrication of silicon chips can then be obtained using chip foundries, and quite complex circuits can be greatly reduced in size with an accompanying increase in certain performance characteristics. Within the past 5 years it has also become possible to design ASICs which can transmit and receive radio signals and which thus may be employed in applications in which wired connections for input and output of signals are not practicable. We are currently developing research-grade prototype ASICs for the monitoring of human vital signs. In this case one or more sensors placed on an ASIC provides a signal to be transmitted a distance of 2-3 meters to a receiver/display unit. The use of ASIC telesensors provides the possibility of wireless monitoring, including long-term monitoring, with inexpensive and unencumbering devices. Their self-contained nature permits a number of potential uses in future biomedical applications as new sensors are devised which are amenable to deployment on silicon.

Vanishing gastroschisis and short-bowel syndrome.

BACKGROUND: Gastroschisis occurs in 1 of every 4000 live births resulting in a neonate with an abdominal wall defect that requires repair. Surgical correction has high survival rates. CASE: An 18-year-old primigravida had a fetus with gastroschisis detected by ultrasound performed for elevated maternal serum alpha-fetoprotein. Subsequent ultrasound found resolution of the classic sonographic features of gastroschisis and evidence of intestinal obstruction. At birth, no obvious abdominal wall defect was seen. Laparotomy was done because of clinical and radiographic evidence of bowel obstruction, and we found significant bowel loss that resulted in short-bowel syndrome. CONCLUSION: Gastroschisis diagnosed antenatally can resolve in utero causing necrosis of portions of the small and large bowels, causing short-bowel syndrome and increased morbidity and mortality.

Distribution of peltate glandular trichomes on developing leaves of peppermint.

The pattern of peltate glandular trichome initiation and ontogeny on expanding peppermint (Mentha x piperita) leaves was defined by surveying the populations of peltate glands in each of seven developmental stages within sampling areas of leaf apical, mid-, and basal zones for both abaxial and adaxial surfaces. It was shown that new peltate glands continue to form until leaf expansion ceases and that regions of active gland initiation are unevenly distributed. The distribution of gland initiation reflects the basipetal pattern of leaf maturation, with relatively immature regions at the leaf base continuing to produce oil glands long after gland production has stopped at the leaf apex. The proportion of glands in the secretory stage as a function of leaf development and the direct observations of living glands over a period of 33 h indicate that a period of only 20 to 30 h of secretory activity is required for filling of the gland storage compartment with essential oil. These findings are discussed in relation to earlier literature describing age-related changes in glandular essential oil content.

Development of peltate glandular trichomes of peppermint.

Cryofixation and conventional chemical fixation methods were employed to examine the ultrastructure of developing peltate glandular trichomes of peppermint (Mentha x piperita). Our results are discussed in relation to monoterpene production and the mechanism of essential oil secretion. Peltate glands arise as epidermal protuberances (initials) that divide asymmetrically to produce a vacuolate basal cell, a stalk cell, and a cytoplasmically dense apical cell. Further divisions of the apical cell produce a peltate trichome with one basal cell, one stalk cell, and eight glandular (secretory) disc cells. Presecretory gland cells resemble meristematic cells because they contain proplastids, small vacuoles, and large nuclei. The secretory phase coincides with the separation and filling of the sub-cuticular oil storage space, the maturation of glandular disc cell leucoplasts in which monoterpene biosynthesis is known to be initiated, and the formation of extensive smooth endoplasmic reticulum at which hydroxylation steps of the monoterpene biosynthetic pathway occur. The smooth endoplasmic reticulum of the secretory cells appears to form associations with both the leucoplasts and the plasma membrane bordering the sub-cuticular oil storage cavity, often contains densely staining material, and may be involved with the transport of the monoterpene-rich secretion product. Associated changes in the ultrastructure of the secretory stage stalk cell are also described, as is the ultrastructure of the fragile post-secretory gland for which cryofixation methods are particularly well suited for the preservation of organizational integrity.

Visualizing interfacial structure at non-common-atom heterojunctions with cross-sectional scanning tunneling microscopy.

We describe how cross-sectional scanning tunneling microscopy (STM) may be used to image the interfacial bonding across the nearly lattice-matched, non-common-atom GaSb/InAs heterojunction with atomic-scale precision. The method, which takes advantage of the length difference between interfacial and bulk bonds, appears equally applicable to AlSb/InAs and suggests how one might recover the complete structure of either heterojunction from atomic-resolution STM data.

Spectral beam combining of a broad-stripe diode laser array in an external cavity.

The outputs from an 11-element, linear diode laser array with broad stripes have been beam combined into a single beam with a beam quality of ~20x diffraction limited in the plane of the junction. This beam combining was achieved by use of a common external cavity containing a grating, which simultaneously forces each array element to operate at a different, but controlled, wavelength and forces the beams from all the elements to overlap and propagate in the same direction. The power in the combined beam was 50% of the output from the bare laser array.

Production of respirable vesicles containing live Legionella pneumophila cells by two Acanthamoeba spp.

Two Acanthamoeba species, fed at three temperatures, expelled vesicles containing living Legionella pneumophila cells. Vesicles ranged from 2.1 to 6.4 microns in diameter and theoretically could contain several hundred bacteria. Viable L. pneumophila cells were observed within vesicles which had been exposed to two cooling tower biocides for 24 h. Clusters of bacteria in vesicles were not dispersed by freeze-thawing and sonication. Such vesicles may be agents for the transmission of legionellosis associated with cooling towers, and the risk may be underestimated by plate count methods.

Monoamniotic twins: improved perinatal survival with accurate prenatal diagnosis and antenatal fetal surveillance.

OBJECTIVE: Our goal was to report our 10-year experience with monoamniotic twins and to compare that experience with cases reported in the literature. STUDY DESIGN: Records of all monoamniotic twin pregnancies managed at the University of Connecticut Health Center from March 1986 to August 1996 were reviewed. A MEDLINE search from January 1966 to August 1996 was performed, and each report was screened for accuracy of diagnosis. Only cases with umbilical cord entanglement of nonconjoined like-sex twins, the obstetrician's confirmation at delivery, or pathologic confirmation of monoamniotic placentation were included. Data collected were as follows: birth outcome, gestational age at delivery, birth weight, gender, Apgar scores, hematocrit, cord knotting, and neonatal complications. Cases from the literature were divided into those with prenatal diagnosis and those without. RESULTS: Thirteen monoamniotic pregnancies resulting in 26 infants who were born alive were managed at our center. The average gestational age at diagnosis was 16.3 weeks. All had antenatal fetal surveillance including serial sonograms and nonstress tests. The average gestational age and birth weight at delivery were 32.9 weeks and 1669 gm, respectively. Cord entanglement was noted in all cases, with knotting in 8 of 13. Two pairs of 26 newborns had evidence of twin-twin transfusion syndrome. Eight of 13 monoamniotic pregnancies were delivered because of nonreassuring results of nonstress test, two because of preterm labor, two electively because of lung maturity, and one because of intrauterine growth restriction. Two of the 26 infants died in the neonatal period, one of congenital heart disease and one of sepsis and asphyxia. The MEDLINE search revealed 96 articles with a total of 202 sets of monoamniotic twins. Comparison of cases (13 sets) with the historic control group without prenatal diagnosis (77 sets) showed a 71% reduction in relative risk of perinatal mortality. CONCLUSIONS: With accurate prenatal diagnosis, intensive fetal surveillance, and appropriately timed delivery, perinatal survival of monoamniotic twins is improved; it was 92% in this series.

Late prenatal ultrasound features of hydrometrocolpos secondary to cloacal anomaly: case reports and review of the literature.

Cloacal anomalies are extremely rare and have variable presentations. Prenatal diagnosis can be difficult especially if they present in late gestation. Here we present two cases diagnosed in the late third trimester and review the literature regarding prenatal diagnosis of cloacal anomalies.

Use of the transverse cerebellar diameter/abdominal circumference ratio in pregnancies at risk for intrauterine growth retardation.

A prospective study was conducted to evaluate the ability of the transverse cerebellar diameter/abdominal circumference ratio to identify growth-retarded fetuses. Of the cases analyzed, 48 of 87 (55%) were growth retarded by birth weight. The transverse cerebellar diameter/abdominal circumference ratio identified growth retardation with a sensitivity of 71%, specificity of 77%, positive predictive value of 79%, and negative predictive value of 68%. Fourteen growth-retarded fetuses were missed by the ratio; however, 57% of the missed cases were severely growth retarded. The transverse cerebellar diameter/abdominal circumference ratio can be useful for the assessment of fetal growth retardation; however, the ratio may be normal in cases of severe fetal growth retardation.

Transverse cerebellar diameter/abdominal circumference ratio throughout pregnancy: a gestational age-independent method to assess fetal growth.

In a prospective study of 162 patients, measurements of the transverse cerebellar diameter (TCD) and abdominal circumference (AC) were obtained between 15-38 weeks' gestation. A ratio between the TCD and AC was calculated after each examination. This ratio remained constant during gestation. The mean ratio was 13.7% (fifth and 95th percentiles of 11.9 and 15.9%, respectively); the median ratio was 13.6%. Forty-two patients had repeat measurements and the ratio did not change. This ratio is gestational age-independent; however, further investigation is needed to determine its application in the assessment of fetal growth abnormalities.

Using the same exposure factors for wet and dry casts.

This article presents laboratory and clinical findings that suggest the exposure factors for wet and dry casts should be the same and the selection of factors should be based on cast thickness rather than water content.

Polyhydramnios and obstructive renal failure: a case report and review of the literature.

Described is a pregnancy complicated by pregnancy-induced hypertension, polyhydramnios, and obstructive renal failure due to an overdistended uterus. A review of the literature disclosed that only five such cases have been reported previously. Fetal outcome was generally related to the duration of gestation at the onset of polyhydramnios.

Erect positions for "tunnel" views of the knee.

Two erect methods of radiographing the knee to produce tunnel views of the joint space are presented. Each method produces an excellent image of the intercondyloid fossa without distortion seen with some previous methods. Both erect methods are simple to perform and appear to be more comfortable for patients.

The effect of decreased developer activity on patient exposure.

Overexposing and underdeveloping a radiographic image is not a common practice, but it has been observed to occur as a result of poor processing protocols. This study discovered that, as a result of decreased developer activity, the patient exposure could be three times as great as it would be under normal conditions.

Erect position/tangential projection of the patellofemoral joint.

This paper presents an erect position, using 40 degrees knee flexion and a vertical central ray, as a simple alternative to help overcome the problems encountered with the standard "sunrise" view of the patella and patellofemoral joint.

Selecting audiovisual materials for use in radiography programs.

To select the highest quality audiovisual instructional materials for use in radiography programs, instructors must go beyond a simple subjective judgement. This article provides a method of selection that will help instructors locate and make an objective assessment of the instructional value of audiovisual materials and help insure that these materials will be of high quality and serve the learning needs of their students.