From amorphous to nanocrystalline: the effect of nanograins in an amorphous matrix on the thermal conductivity of hot-wire chemical-vapor deposited silicon films.

We have measured the thermal conductivity of amorphous and nanocrystalline silicon films with varying crystalline content from 85 K to room temperature. The films were prepared by the hot-wire chemical-vapor deposition, where the crystalline volume fraction is determined by the hydrogen (H2) dilution ratio to the processing silane gas (SiH4), R = H2/SiH4. We varied R from 1 to 10, where the films transform from amorphous for R < 3 to mostly nanocrystalline for larger R. Structural analyses show that the nanograins, averaging from 2 to 9 nm in sizes with increasing R, are dispersed in the amorphous matrix. The crystalline volume fraction increases from 0 to 65% as R increases from 1 to 10. The thermal conductivities of the two amorphous silicon films are similar and consistent with the most previous reports with thicknesses no larger than a few µm deposited by a variety of techniques. The thermal conductivities of the three nanocrystalline silicon films are also similar, but are about 50-70% higher than those of their amorphous counterparts. The heat conduction in nanocrystalline silicon films can be understood as the combined contribution in both amorphous and nanocrystalline phases, where increased conduction through improved nanocrystalline percolation path outweighs increased interface scattering between silicon nanocrystals and the amorphous matrix.

Bilayer graphene grown on 4H-SiC (0001) step-free mesas.

We demonstrate the first successful growth of large-area (200 × 200 µm(2)) bilayer, Bernal stacked, epitaxial graphene (EG) on atomically flat, 4H-SiC (0001) step-free mesas (SFMs) . The use of SFMs for the growth of graphene resulted in the complete elimination of surface step-bunching typically found after EG growth on conventional nominally on-axis SiC (0001) substrates. As a result heights of EG surface features are reduced by at least a factor of 50 from the heights found on conventional substrates. Evaluation of the EG across the SFM using the Raman 2D mode indicates Bernal stacking with low and uniform compressive lattice strain of only 0.05%. The uniformity of this strain is significantly improved, which is about 13-fold decrease of strain found for EG grown on conventional nominally on-axis substrates. The magnitude of the strain approaches values for stress-free exfoliated graphene flakes. Hall transport measurements on large area bilayer samples taken as a function of temperature from 4.3 to 300 K revealed an n-type carrier mobility that increased from 1170 to 1730 cm(2) V(-1) s(-1), and a corresponding sheet carrier density that decreased from 5.0 × 10(12) cm(-2) to 3.26 × 10(12) cm(-2). The transport is believed to occur predominantly through the top EG layer with the bottom layer screening the top layer from the substrate. These results demonstrate that EG synthesized on large area, perfectly flat on-axis mesa surfaces can be used to produce Bernal-stacked bilayer EG having excellent uniformity and reduced strain and provides the perfect opportunity for significant advancement of epitaxial graphene electronics technology.

A reconstructive algorithm for plastic surgery following extensive chest wall resection.

Chest wall reconstruction following extensive resection is greatly facilitated by the use of vascularised flaps and prosthetic material. Plastic surgeons are often asked to assist with coverage of large chest wall defects. However, in addition to soft tissue coverage, we need to address other important issues such as the status of the pleural cavity, and the requirement for skeletal support. The purpose of this report is to analyse our experience, provide a reconstructive algorithm following the ablative procedure and review the literature. Two hundred chest wall resections were performed from 1975 to 2000. Defect location was divided into anterior (n = 73) lateral (n = 36) anterior-lateral (n = 36) posterior-lateral (n = 19) posterior (n = 22) and forequarter (n = 14) Average number of ribs resected was four. One hundred and fifty-eight patients (79%) required chest wall reconstruction with either prosthetic material and/or flap closure. Mesh closure was required in 85 cases (43%), being highest for lateral defects (61%), and lowest for anterior defects (31%). Vascularised flaps were needed in 112 patients (56%), more common in anterior defects (79%), and less common for the posterior-lateral defects (26%). Inpatient complication rate was 27% (43/158) following reconstruction, with a mortality of 6% (10/158). Chest wall reconstruction is common following extensive resection. This includes management of the pleural cavity, skeletal support and soft tissue coverage. A better understanding of the respiratory mechanics and local thoracoabdominal anatomy is crucial for managing these complex defects. The need for skeletal support was more prevalent in lateral and posterior-lateral defects. Flap reconstruction was required more often to cover large anterior defects, with regional flaps predominating.

Observed trends for CF3-containing compounds in background air at Cape Meares, Oregon, Point Barrow, Alaska, and Palmer Station, Antarctica.

The concentrations of CF(3)-containing compounds in archived air samples collected at Cape Meares, Oregon, from 1978 to 1997, at Point Barrow, Alaska, from 1995 to 1998, and at Palmer Station, Antarctica, from 1991 to 1997, were determined by high resolution gas chromatography and high resolution mass spectrometry. The CF(3)-containing compounds measured by this method and discussed here are: the perfluorinated compound, C(3)F(8) (FC 218); four perhalogenated compounds, CF(3)Cl (CFC 13), CF(3)CF(2)Cl (CFC 115), CF(3)CFCl(2) (CFC 114a), and CF(3)Br (Halon 1301); and three hydrofluorocompounds, CF(3)H (HFC 23), CF(3)CH(3) (HFC 143a), and CF(3)CH(2)F (HFC 134a). For four of these compounds, very few measurements have been previously reported. The atmospheric concentrations of all of the CF(3)-containing compounds continuously increased in time over the sample collection periods. From these data, the annual rates of emission into the atmosphere have been estimated. The emission rates fall into one of three distinct categories. The annual emission rates of C(3)F(8), CF(3)H, CF(3)CH(3), and CF(3)CH(2)F have continuously increased over the last two decades. That of CF(3)CFCl(2) has decreased continuously. Emission rates for CF(3)Cl, CF(3)CF(2)Cl, and CF(3)Br reached maximum levels in the late 1980s, and have been decreasing in the 1990s. The emission rates of C(3)F(8), CF(3)CH(3) and CF(3)CH(2)F were nearly zero 20 years ago but have increased rapidly during the last decade.

Thoracic reconstruction with the omentum: indications, complications, and results.

This study provides a retrospective analysis of 60 patients who underwent thoracic reconstruction with the omentum. Patients were identified by searching several databases to determine demographics, indications for surgery, operative technique, and postoperative course, including donor and recipient site morbidity. From January 1975 to May 2000, the authors harvested and transferred the omentum successfully (57 pedicled, 3 free) in 60 patients (mean age, 60 years; age range, 21-86 years) for sternal wound infections (N = 34), chest wall resections (N = 17), pectus deformities (N = 2), intrathoracic defects (N = 4), and breast reconstruction (N = 3). The omentum was used as a primary flap in 39 patients and as a salvage flap in 21 patients. Average operative time was 3.9 hours and average hospital stay was 34.3 days. Partial flap loss occurred in 7 patients, with no total flap failures. Morbidity included six abdominal wound infections and seven epigastric hernias. Mortality was 11.7%. The omentum can be harvested safely and used reliably to reconstruct varying thoracic wounds and defects. Specific indications from this series include osteoradionecrosis, chest wall tumors, massive sternal wounds, and refractory mediastinitis. Hultman CS, Culbertson JH, Jones GE, et al. Thoracic reconstruction with the omentum: indications, complications, and results.

Lack of efficacy of finasteride in postmenopausal women with androgenetic alopecia.

BACKGROUND: Finasteride, an inhibitor of type 2 5alpha-reductase, decreases serum and scalp dihydrotestosterone (DHT) by inhibiting conversion of testosterone to DHT and has been shown to be effective in men with androgenetic alopecia (AGA). The effects of finasteride in women with AGA have not been evaluated. OBJECTIVE: The purpose of this study was to evaluate the efficacy of finasteride in postmenopausal women with AGA. METHODS: In this 1-year, double-blind, placebo-controlled, randomized, multicenter trial, 137 postmenopausal women (41-60 years of age) with AGA received finasteride 1 mg/day or placebo. Efficacy was evaluated by scalp hair counts, patient and investigator assessments, assessment of global photographs by a blinded expert panel, and histologic analysis of scalp biopsy specimens. RESULTS: After 1 year of therapy, there was no significant difference in the change in hair count between the finasteride and placebo groups. Both treatment groups had significant decreases in hair count in the frontal/parietal (anterior/mid) scalp during the 1-year study period. Similarly, patient, investigator, and photographic assessments as well as scalp biopsy analysis did not demonstrate any improvement in slowing hair thinning, increasing hair growth, or improving the appearance of the hair in finasteride-treated subjects compared with the placebo group. Finasteride was generally well tolerated. CONCLUSION: In postmenopausal women with AGA, finasteride 1 mg/day taken for 12 months did not not increase hair growth or slow the progression of hair thinning.

Improvements in the detection and analysis of CF3-containing compounds in the background atmosphere by gas chromatography-high-resolution mass spectrometry.

An improved method for the gas chromatography/mass spectrometry analysis of CF3-containing compounds in air is described. This method replaces a GS-Q porous layer open tubular (PLOT) column previously used with a 30 m x 0.32 mm GS-GasPro PLOT column. For this exceedingly volatile set of compounds the GS-GasPro column provides improved peak shapes, better signal-to-noise responses and no coelution of compounds. These improvements have allowed eleven CF3-containing compounds to be detected in background air, including CF4 (FC 14), C2F6 (FC 116), CF3Cl (CFC 13), CF3H (HFC 23), CF3Br (Halon 1301), C3F8 (FC 218), CF3CF2Cl (CFC 115), CF3CHF2 (HFC 125), CF3CH3 (HFC 143a), CF3CH2F (HFC 134a), and CF3CFCl2 (CFC 114a). Three of these compounds have not been previously detected in background air, to our knowledge. Quantitative determinations for each of these compounds in the background atmosphere of Montana are also reported.

Management of the infected median sternotomy wound with muscle flaps. The Emory 20-year experience.

OBJECTIVE: The purpose of the study is to define those patient variables that contribute to morbidity and mortality of median sternotomy wound infection and the results of treatment by debridement and closure by muscle flaps. BACKGROUND: Infection of the median sternotomy wound after open heart surgery is a devastating complication associated with significant mortality. Twenty years ago, these wounds were treated with either open packing or antibiotic irrigation, with a mortality approaching 50% in some series. In 1975, the authors began treating these wounds with radical sternal debridement followed by closure using muscle or omental flaps. The mortality of sternal wound infection has dropped to < 10%. METHODS: The authors' total experience with 409 patients treated over 20 years is described in relation to flap choices, hospital days after sternal wound closure, and incidence rates of morbidity and mortality. One hundred eighty-six patients treated since January 1988 were studied to determine which patient variables had impact on rates of flap closure complications, recurrent sternal wound infection, or death. Variables included obesity, history of smoking, hypertension, diabetes, poststernotomy septicemia, internal mammary artery harvest, use of intra-aortic balloon pump, and perioperative myocardial infarction and were analyzed using chi square tests. Fisher's exact tests, and multivariable logistic regression analysis. RESULTS: The mortality rate over 20 years was 8.1% (33/49). Additional procedures for recurrent sternal wound infection were necessary in 5.1% of patients. Thirty-one patients (7.6%) required treatment for hematoma, and 11 patients (2.7%) required hernia repair. Among patients treated since 1988, variables strongly associated with mortality were septicemia (p < 0.00001), perioperative myocardial infarction (p = 0.006), and intra-aortic balloon pump (p = 0.0168). Factors associated with wound closure complications were intra-aortic balloon pump (p = 0.0287), hypertension (p = 0.0335), and history of smoking (p = 0.0741). Factors associated with recurrent infection were history of sternotomy (p = 0.008) and patients treated for sternal wound infection from 1988 to 1992 (p = 0.024). Mean hospital stay after sternal wound reconstruction declined from 18.6 days (1988-1992) to 12.4 days (1993-1996) (p = 0.005). To clarify management decisions of these difficult cases, a classification of sternal wound infection is presented. CONCLUSIONS: Using the principles of sternal wound debridement and early flap coverage, the authors have achieved a significant reduction in mortality after sternal wound infection and have reduced the mean hospital stay after sternal wound closure of these critically ill patients. Further reductions in mortality will depend on earlier detection of mediastinitis, before onset of septicemia, and ongoing improvements in the critical care of patients with multisystem organ failure.

Identification and localization of a novel cathepsin S-like proteinase in guinea pig spermatozoa.

Guinea pig spermatozoa were found to contain a novel cysteine proteinase that most closely resembled lysosomal cathepsin S. The responsible enzyme was shown to have an acrosomal localization. Like the cathepsin S of lymphocyte-rich tissues, e.g., lymph nodes and spleen, the spermatozoal enzyme digested protein substrates such as hemoglobin and Azocoll optimally at about pH 3.5 in the presence of pepstatin. No appreciable action was manifested in the range of pH 5-6 on protein substrates nor on the 7-(4-methyl)coumarylamide (NMec) derivatives of peptides commonly employed for the fluorometric assay of cathepsins B (benzyloxycarbonyl (Z)-Arg-Arg-NMec), H (Arg-NMec), and L (Z-Phe-Arg-NMec). Like spleen cathepsin S, the sperm enzyme selectively hydrolyzed Z-Phe-Arg-NMec, but its activity was uncharacteristically limited to a pH range of 3.0-3.5, where it displayed a typical high sensitivity to sulfhydryl reagents (HgCl2, mersalyl acid, iodoacetate), leupeptin, Z-Phe-Phe-CHN2, and L-trans-epoxysuccinylleucylamido(3-methyl)butane. Gossypol (a male antifertility agent) was also inhibitory. Inhibition by the mercurial sulfhydryl reagents was completely reversible with dithiothreitol. Pepstatin, a potent inhibitor of aspartic proteinases, and serine proteinase inhibitors (phenylmethylsulfonyl fluoride, benzamidine) were ineffective. Other properties displayed by the sperm extract that were uniquely characteristic of cathepsin S included stability under alkaline conditions, and a greater rate of hydrolysis when the P2-phenylalanine of the assay substrate was replaced by two aliphatic residues, as in Z-Leu-Leu-Arg-NMec.

Acidophil stem-cell pituitary adenoma in a prepubescent female. Case report.

Acidophil stem-cell pituitary adenomas account for less than 5% of pituitary tumors. Only 15 cases have previously been reported, with a mean age of occurrence of 38.7 years. A case of this unusual tumor is reported in a prepubertal girl. Clinical symptoms included prominent behavioral disturbance with associated headache and visual disturbance. There was marked elevation of serum growth hormone concentration without clinical features of growth hormone excess, suggesting that this tumor has the capacity to excrete biologically inactive hormones. The clinical and pathological features of this unusual invasive pituitary tumor are reviewed; the age spectrum for this neoplasm must be expanded to include prepubertal children.

Forehead reconstruction with a modified radial forearm flap: a case report.

Forehead reconstruction, using a radial forearm flap with opposing long arterial and venous pedicles, is presented. Advantages of this flap design are discussed.

The reverse lateral upper arm flap for elbow coverage.

Closure of soft tissue defects in the vicinity of the elbow has been attempted by numerous methods. The reverse lateral upper arm flap was conceived by applying concepts of previous work. Cadaver studies demonstrated the cutaneous territory and vascular anatomy of this region. The nature of the posterior recurrent radial artery and its perforators allows this fasciocutaneous flap to be perfused in a retrograde fashion. The flap can be used for covering various soft tissue defects around the elbow in a single stage with acceptable donor site morbidity. A case is presented in which the flap was used in a reverse flow fashion to cover an 8 X 11 cm acute cubital defect present after soft tissue release. Operative technique is discussed.

Identification, assessment, and management of children with unilateral sensorineural hearing loss.

Because some unilaterally hearing-impaired children appear to experience difficulty in communication and educational progress, it seems only appropriate to reassess the identification and management strategies that are used with these children. Accordingly, this paper presents some general information on identification, assessment, and management of children with unilateral hearing loss from the perspective of three disciplines: audiology, speech-language pathology, and psychology.

Children with unilateral sensorineural hearing loss: cognitive, academic, and social development.

Children with unilateral loss have been considered to have few, if any, communication or academic difficulties. This study was designed to evaluate the academic achievement, cognitive ability, psycholinguistic, and social skills of a group of 25 monaurally hearing-impaired compared with 25 nonhearing-impaired children. Results indicated no significant differences between the two groups on cognitive or self-concept measures. However, the unilateral group had significantly lower scores on academic tests of word recognition, spelling, and language. The unilateral group was more likely to have repeated a grade, needed special education resource help, or additional tutoring in school. Within the unilateral group, children with severe-to-profound hearing loss had significantly lower WISC-R full scale I.Q.s as compared to the group with mild-to-moderate hearing loss. The results of this study suggest that monaural deafness, especially when severe to profound, may be associated with cognitive and academic deficits, as well as secondary behavioral adjustment problems.

A dermal-fat flap for nipple reconstruction.

A refinement in technique for nipple reconstruction utilizing local tissue is described. The operation has been performed on 31 patients who have previously undergone the transverse abdominal island flap breast reconstruction. The longest follow-up is 12 months. Preliminary results appear excellent with desired nipple size and projection.

Detection of adulteration in blackberry juice concentrates and wines.

Adulteration of blackberry juice concentrates and wines with juice of sorbitol-containing fruits was detected by determining carbohydrates by high performance liquid chromatography, gas-liquid chromatography, and thin layer chromatography. Sorbitol is not fermented by yeast and can be detected in wines made from blackberry juice concentrates that contain sorbitol. High levels of sorbitol and quinic and malic acids suggest that an imported blackberry concentrate may have been adulterated with plum. Degradation of anthocyanin pigments during processing and storage limits the utility of pigment analyses in detecting adulteration.

In Vitro Effect of Bean Amylase Inhibitor on Insect Amylases 1.

The activity of a bean amylase inhibitor against amylases extracted from several insects was tested. Amylases extracted from Mediterranean flour moth larvae ( Anagasta kuhniella ), red flour beetle adults ( Tribolium castaneum ), both adults and larvae of Tribolium confusum (confused flour beetle) and yellow mealworm larvae ( Tenebrio molitor ) were inhibited while adult granary weevil ( Sitophilus granarius ) amylase was not inhibited by the bean inhibitor. The T. molitor amylase interaction with the bean inhibitor was studied further. Inhibition of the Tenebrio enzyme is expressed slowly at pH 5.4, but lowering the pH or raising the ionic strength of incubation media caused a marked increase in rate of expression of the inhibition.