9,668 research outputs found
Stratosphere aerosol and cloud measurements at McMurdo Station Antarctica during the spring of 1987
Measurements of stratospheric aerosols with balloonborne optical particle counters on 6 occasions at McMurdo Station (78 deg S) in the spring of 1986 indicated subsidence of the stratospheric sulfate layer during the time that the ozone hole was forming (Hofmann et al., 1988). Since dynamic models of ozone depletion involving upwelling in the spring polar vortex would suggest the opposite, we repeated the measurements with an increased frequency (about one sounding per week) in 1987. During 3 of the aerosol soundings in 1986, temperatures in the 15 to 20 km range were low enough (less than 80 C) for HNO3 to co-condense with water according to several theories of polar stratospheric cloud formation. However, particles were not observed with the characteristic size suggested by theory (approx. 0.5 microns). For this reason, it was proposed that polar stratospheric clouds may predominantly consist of large (approx. 5 to 50 microns) ice crystals at very low (approx. 10 sup 4- 10 sup 3 cm cubed) concentrations (Rosen et al., 1988). The particle counter employed would be relatively insensitive to these low concentrations. With the increased frequency of soundings in 1987, and adding additional size discrimination in the 1 to 2 micron region, this hypothesis could be verified if suitably low temperatures were encountered
The UW digital ozonesonde: Characteristics and flow rate calibration
During the austral springs of 1986 and 1987, a series of balloon soundings were conducted to characterize the temporal and vertical development of Antarctic ozone depletion using the electrochemical concentration cell method (ECC). An important part of this study was to perform correlative studies between ozone and aerosol particles. In order to facilitate these simultaneous measurements, a digital ozonesonde system was developed to interface with aerosol counters. The ozone measurements will be described herein. The ozonesonde modification was accomplished by converting the current output of the sonde to a frequency and adding this digital signal to the serial data stream of a Vaisala Corporation RS-80 radiosonde under microprocessor control. A number of advantages over the standard ozonesonde system currently in use are noted
Ozone profile measurements at McMurdo Station Antarctica during the spring of 1987
During the Antarctic spring of 1986, 33 ozone soundings were conducted from McMurdo Station. These data indicated that the springtime decrease in ozone occurred rapidly between the altitudes of 12 and 20 km. During 1987, these measurements were repeated with 50 soundings between 29 August and 9 November. Digital conversions of standard electrochemical cell ozonesondes were again employed. The ozonesonde pumps were individually calibrated for flow rate as the high altitude performance of these pumps have been in question. While these uncertainties are not large in the region of the ozone hole, they are significant at high altitude and apparently resulted in an underestimate of total ozone of about 7 percent (average) as compared to the Total Ozone Mapping Spectrometer (TOMS) in 1986, when the flow rate recommended by the manufacturer was used. At the upper altitudes (approx. 30 km) the flow rate may be overestimated by as much as 15 percent using recommended values (see Harder et al., The UW Digital Ozonesonde: Characteristics and Flow Rate Calibration, poster paper, this workshop). These upper level values are used in the extrapolation, at constant mixing ratio, required to complete the sounding for total ozone. The first sounding was on 29 August, prior to major ozone depletion, when 274 DU total ozone (25 DU extrapolated) was observed. By early October total ozone had decreased to the 150 DU range; it then increased during mid-October owing to motion of the vortex and returned to a value of 148 DU (29 DU extrapolated) on 27 October
Method For Obtaining Wood/Bark Adhesion Measurements on Small Samples
Using the Instron Tester, a procedure has been developed for measuring wood/bark adhesion on small samples. Using very small, specially prepared samples, wood/bark adhesion measurements were made on twenty-four hardwoods and eighteen conifers. High dormant season wood/bark adhesion in hardwoods was found to be associated with the presence of fibers in the inner bark. The procedure appears to be useful in identifying difficult-to-debark species and evaluating methods of reducing adhesion
Morphological and Bark Strength Characteristics Important to Wood/Bark Adhesion in Hardwoods
Dormant season wood/bark adhesion was determined for twenty-four hardwood species using a previously described Instron testing machine method. Wood/bark adhesion was compared, using simple and multiple correlation techniques, with bark specific gravity, inner bark strength, bark toughness, wood specific gravity, wood toughness, percent bark fibers, and percent sclereids. Wood/bark adhesion was found to be positively correlated with percent bark fibers, bark toughness, and inner bark strength. Wood/bark adhesion was negatively correlated with percent sclereids in the bark. Morphologically, it appeared that the presence of fibers increased inner bark strength, sclereids decreased inner bark strength, and inner bark strength had a major influence on wood/bark adhesion. A multiple correlation comparison employing wood toughness and inner bark strength accounted for 69% of the wood/bark adhesion encountered
Microvascular Fragments Protect Ischemic Musculocutaneous Flap Tissue from Necrosis by Improving Nutritive Tissue Perfusion and Suppressing Apoptosis
Microvascular fragments (MVF) derived from enzymatically digested adipose tissue are
functional vessel segments that have been shown to increase the survival rate of surgical flaps.
However, the underlying mechanisms have not been clarified so far. To achieve this, we raised
random-pattern musculocutaneous flaps on the back of wild-type mice and mounted them into
dorsal skinfold chambers. The flaps were injected with MVF that were freshly isolated from green
fluorescent protein-positive (GFP+
) donor mice or saline solution (control). On days 1, 3, 5, 7, and 10
after surgery, intravital fluorescence microscopy was performed for the quantitative assessment of
angiogenesis, nutritive blood perfusion, and flap necrosis. Subsequently, the flaps were analyzed
by histology and immunohistochemistry. The injection of MVF reduced necrosis of the ischemic
flap tissue by ~20%. When compared to controls, MVF-injected flaps also displayed a significantly
higher functional capillary density and number of newly formed microvessels in the transition zone,
where vital tissue bordered on necrotic tissue. Immunohistochemical analyses revealed a markedly
lower number of cleaved caspase-3+ apoptotic cells in the transition zone of MVF-injected flaps
and a significantly increased number of CD31+ microvessels in both the flaps’ base and transition
zone. Up to ~10% of these microvessels were GFP+
, proving their origin from injected MVF. These
findings demonstrate that MVF reduce flap necrosis by increasing angiogenesis, improving nutritive
tissue perfusion, and suppressing apoptosis. Hence, the injection of MVF may represent a promising
strategy to reduce ischemia-induced flap necrosis in future clinical practice
Bromelain Protects Critically Perfused Musculocutaneous Flap Tissue from Necrosis
Bromelain has previously been shown to prevent ischemia-induced necrosis in different
types of tissues. In the present study, we, therefore, evaluated for the first time, the tissue-protective
effects of bromelain in musculocutaneous flaps in mice. Adult C57BL/6N mice were randomly
assigned to a bromelain treatment group and a control group. The animals were treated daily with
intraperitoneal injections of 20 mg/kg bromelain or saline (control), starting 1 h before the flap
elevation throughout a 10-day observation period. The random-pattern musculocutaneous flaps
were raised on the backs of the animals and mounted into a dorsal skinfold chamber. Angiogenesis,
nutritive blood perfusion and flap necrosis were quantitatively analyzed by means of repeated
intravital fluorescence microscopy over 10 days after surgery. After the last microscopy, the flaps
were harvested for additional histological and immunohistochemical analyses. Bromelain reduced
necrosis of the critically perfused flap tissue by ~25%. The bromelain-treated flaps also exhibited
a significantly higher functional microvessel density and an elevated formation of newly devel oped microvessels in the transition zone between the vital and necrotic tissues when compared
to the controls. Immunohistochemical analyses demonstrated a markedly lower invasion of the
myeloperoxidase-positive neutrophilic granulocytes and a significantly reduced number of cleaved
caspase 3-positive apoptotic cells in the transition zone of bromelain-treated musculocutaneous
flaps. These findings indicate that bromelain prevents flap necrosis by maintaining nutritive tissue
perfusion and by suppressing ischemia-induced inflammation and apoptosis. Hence, bromelain may
represent a promising compound to prevent ischemia-induced flap necrosis in clinical practice
Improved Vascularization and Survival of White Compared to Brown Adipose Tissue Grafts in the Dorsal Skinfold Chamber
Fat grafting is a frequently applied procedure in plastic surgery for volume reconstruction.
Moreover, the transplantation of white adipose tissue (WAT) and brown adipose tissue (BAT) in creasingly gains interest in preclinical research for the treatment of obesity-related metabolic defects.
Therefore, we herein directly compared the vascularization capacity and survival of WAT and BAT
grafts. For this purpose, size-matched grafts isolated from the inguinal WAT pad and the interscapu lar BAT depot of C57BL/6N donor mice were syngeneically transplanted into the dorsal skinfold
chamber of recipient animals. The vascularization and survival of the grafts were analyzed by means
of intravital fluorescence microscopy, histology, and immunohistochemistry over an observation
period of 14 days. WAT grafts showed an identical microvascular architecture and functional mi crovessel density as native WAT. In contrast, BAT grafts developed an erratic microvasculature with
a significantly lower functional microvessel density when compared to native BAT. Accordingly, they
also contained a markedly lower number of CD31-positive microvessels, which was associated with
a massive loss of perilipin-positive adipocytes. These findings indicate that in contrast to WAT grafts,
BAT grafts exhibit an impaired vascularization capacity and survival, which may be due to their
higher metabolic demand. Hence, future studies should focus on the establishment of strategies to
improve the engraftment of transplanted BAT
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