Upper and lower limits on the stability of calving glaciers from the yield strength envelope of ice

Observations indicate that substantial changes in the dynamics of marine-terminating ice sheets and glaciers are tightly coupled to calving-induced changes in the terminus position. However, the calving process itself remains poorly understood and is not well parametrized in current numerical ice sheet models. In this study, we address this uncertainty by deriving plausible upper and lower limits for the maximum stable ice thickness at the calving face of marine-terminating glaciers, using two complementary models. The first model assumes that a combination of tensile and shear failure can render the ice cliff near the terminus unstable and/or enable pre-existing crevasses to intersect. A direct consequence of this model is that thick glaciers must terminate in deep water to stabilize the calving front, yielding a predicted maximum ice cliff height that increases with increasing water depth, consistent with observations culled from glaciers in West Greenland, Antarctica, Svalbard and Alaska. The second model considers an analogous lower limit derived by assuming that the ice is already fractured and fractures are lubricated by pore pressure. In this model, a floating ice tongue can only form when the ice entering the terminus region is relatively intact with few pre-existing, deeply penetrating crevasses.

Longstanding pigmentary changes in paediatric scalds dressed with a non-adherent siliconised dressing

The non-adherent siliconised dressing Mepitel is excellent for burns, especially in children. It provides a moist wound environment, promotes wound healing and is easy and relatively painless to use. However, surgeons should be aware that in black children its use has been associated with pigmentation abnormalities.

An educational intervention for hypertension management in older African Americans

OBJECTIVE

The purpose of this study was to assess the efficacy of a telecommunications approach to hypertension education.

METHODS

Participants (N = 83) were randomly assigned to the experimental and control groups. Experimental group participants received spiritual and hypertension-related messages via programmed telephone calls, and the control group participants received spiritual messages only. Both the experimental and control group participants received the following: printed material on hypertension-related information and regular home visits from a health educator to conduct pre-test and post-test assessments of hypertension knowledge, pill counts, and blood pressure readings.

RESULTS

There were no statistically significant improvements in hypertension knowledge. By week 4 of the intervention, there was a statistically significant decrease in systolic and diastolic blood pressure for both groups. However, there were no differences between the experimental and control groups.

DISCUSSION

There was no evidence that the telecommunications approach improved older African Americans' understanding of hypertension or its management.

Toxic shock syndrome in adult burns

Toxic shock syndrome is associated with burn injuries in children and is a cause of significant morbidity in this group. Despite multiple cases of toxic shock syndrome in adults being reported since its original description it has not been reported in adult burn patients. We report a case of toxic shock syndrome in an adult following 25% flame burns.

Determination of flumequine in channel catfish by liquid chromatography with fluorescence detection

Rapid methods are described for determination of flumequine (FLU) residues in muscle and plasma of farm-raised channel catfish (Ictalurus punctatus). FLU residues were extracted from tissues with an acidified methanol solution, and extracts were cleaned up on C18 solid-phase extraction cartridges. FLU concentrations were determined by liquid chromatography (LC) using a C18 analytical column and fluorescence detection (excitation, 325 nm; emission, 360 nm). Mean recoveries of FLU from fortified muscle were 87-94% at 5 levels ranging from 10 to 160 ppb (5 replicates per level). FLU recoveries from fortified plasma were 92-97% at 5 levels ranging from 20 to 320 ppb. Limits of detection (signal-to-noise ratio, 3:1) for the method as described were 3 and 6 ppb for muscle and plasma, respectively. Relative standard deviations (RSDs) for recoveries were < or = 12%. Live catfish were dosed with 14C-labeled or unlabeled FLU to generate incurred residues. Recoveries of 14C residues throughout extraction and cleanup were 90 and 94% for muscle and plasma, respectively. RSDs for incurred FLU at 2 levels in muscle and plasma ranged from 2 to 6%. The identity of FLU in incurred tissues was confirmed by LC/mass spectrometry.

Determination of ivermectin in salmon muscle tissue by liquid chromatography with fluorescence detection

A liquid chromatographic method was developed for determination of ivermectin B1a (IVR) extracted from raw fortified and incurred Atlantic salmon muscle tissues. The method was also used to determine fortified doramectin (DOR) in Atlantic salmon. Tissue extract was applied to C8 solid-phase extraction (SPE) column, followed by a silica SPE column. Residues in the eluate were treated with trifluoroacetic anhydride and methylimidazole to dehydrate the IVR molecule and form an aromatic fluorescent moiety with a trifluoroacetic ester. This product was subsequently treated with ammonium acetate in methanol to cleave the ester and convert the functional group back to a stable alcohol form. The analytes were determined by fluorescence with excitation at 272 nm and emission at 465 nm. A C18 Hypersil column was used for analysis with a mobile phase of acetonitrile-water (90 + 10, v/v) and an oven temperature of 65 degrees C. IVR and DOR were determined at 5 fortification levels (1, 5, 10, 20, and 40 ppb). Intra-assay absolute recoveries ranged from 75 to 89% for IVR and from 73 to 85% for DOR. Relative standard deviations (RSDs) were < 7% in all cases. The limit of detection (3 x baseline noise) was 0.25 ppb extracted from tissue. Incurred tissues had an average concentration of 32 ppb, with an RSD of 3%.

Confirmation of fluoroquinolones in catfish muscle by electrospray liquid chromatography/mass spectrometry

A multiresidue liquid chromatography/mass spectrometry (LC/MS) confirmation method for fluoroquinolones in catfish muscle was developed by using an electrospray interface. Residues of ciprofloxacin, enrofloxacin, sarafloxacin, and difloxacin were positively identified in catfish muscle fortified at 10-80 ppb as well as in incurred tissue. The extraction procedure is based on an LC method with fluorescence detection for determination of these compounds in catfish. Residues were extracted from catfish muscle with an acidic ethanol solution, and the extracts were cleaned up on a propyl sulfonic acid solid-phase extraction column. Chromatographic conditions were optimized to be compatible with the electrospray interface. Internal electrospray voltages were optimized so that 3 fragment ions, in addition to the protonated molecular ion, could be monitored for each residue. To obtain maximum sensitivity, separate MS acquisition programs were developed for ciprofloxacin/enrofloxacin and sarafloxacin/difloxacin pairs.

A bridging study between liquid chromatography and microbial inhibition assay methods for determining amoxicillin residues in catfish muscle

A bridging study was conducted to establish the correlation between a liquid chromatographic (LC) method and a microbial inhibition (MI) method for analysis of amoxicillin residues in catfish muscle. The LC procedure involved precolumn derivatization with formaldehyde followed by LC separation with fluorescence detection. The MI procedure used Bacillus stearothermophilus as the test organism and was validated in this study before the bridging investigation. The 2 methods were compared for determination of both fortified and incurred samples. No significant differences were found between the methods when all data were included in statistical computations. The linear correlation of LC means versus MI means had a slope of 0.972 and a negligible intercept (1.0 ng/g), with a correlation coefficient of 0.9962. LC was more specific and showed better sensitivity than MI for amoxicillin residues at < or = 10 ng/g. For practical purposes, values obtained by the 2 methods can be considered equivalent.

Determination off four fluoroquinolones in milk by liquid chromatography

A liquid chromatographic (LC) method with fluorescence detection is presented for the analysis of 4 fluoroquinolones; enrofloxacin (ENRO), ciprofloxacin (CIPRO), sarafloxacin (SARA), and difloxacin (DIFLX) in milk. The procedure consists of extraction of milk with acidified ethanol, isolation and retention on a cation exchange solid-phase extraction column, elution with basic methanol, and LC analysis with fluorescence detection. LC analysis is performed by isocratic elution using an acetonitrile-2% acetic acid (15 + 85) mobile phase and an Inertsil phenyl column with fluorescence detection at excitation and emission wavelengths of 278 and 450 nm, respectively. A target level of 10 ppb for each of the 4 fluoroquinolones has been established for this method. Average recovery from fortified raw milk samples (5-100 ppb each) based on a 5-point standard curve calculation was 70-90%, with relative standard deviations of < 15%.

Neurological sequelae following a high voltage electrical burn

Neurological complications secondary to electrical injury can manifest themselves either early or late. A small percentage of these patients develop delayed peripheral neuropathy. However, patients experiencing transient spinal cord symptoms have been described. We describe the development of a lower motor neurone syndrome affecting all the limbs in a patient following a significant electrical injury, which although expected to cause spinal cord necrosis showed no evidence of this on magnetic resonance imaging. The fact that neurophysiology was unable to localize the problem made this case all the more perplexing. Similar cases reported in the literature are discussed.

Unusual conchal deformity in otherwise normal ears

A case of bilateral convex conchae in otherwise normal ears is reported. As far as we are aware, such a deformity has not been reported in the literature. A technique of surgical correction by excision of a crescent of conchal cartilage is described. Relevant embryologic development of the auricle is reviewed.

Plasma/muscle ratios of sulfadimethoxine residues in channel catfish (Ictalurus punctatus)

Channel catfish (n = 84) maintained at a water temperature of 27 degrees C were used in a feeding study to determine the plasma to muscle concentration ratios of sulfadimethoxine (SDM) and 4-N-acetylsulfadimethoxine residues. Sulfadimethoxine medicated feed was provided free choice at 42 mg SDM/kg body weight once daily for 5 days and the plasma and muscle concentrations of SDM were determined at selected withdrawal times (6, 12, 24, 48, 72, and 96 hours) following the last dose. Considerable variation in total SDM tissue concentration among fish within a sampling period was observed. For fish (n = 12) at six hours post-dose, total SDM concentrations ranged from 1.4-24.8 micrograms/mL and 0.6-12.6 micrograms/g, with mean total SDM concentrations of 9.1 micrograms/mL and 5.3 micrograms/g for plasma and muscle, respectively. However, a mean plasma:muscle concentration ratio of 1.8:1 +/- 0.3:1 was obtained over all concentrations and sampling periods. The plasma:muscle 95% t distribution interval for individual fish was 1.2:1 to 2.4:1. A correlation coefficient of 0.967 was obtained for the relationship between plasma and muscle total SDM concentration among individual fish (n = 25). Results of this study indicate that plasma total SDM concentration may be used to identify samples containing violative SDM muscle residue. No fish contained total SDM muscle residues greater than the FDA tolerance (0.1 microgram/g) by 48 hours following the final dose.

Extraction and liquid chromatographic analysis of sulfadimethoxine and 4-N-acetylsulfadimethoxine residues in channel catfish (Ictalurus punctatus) muscle and plasma

A simple and rapid method was developed for the simultaneous extraction and liquid chromatographic (LC) determination of sulfadimethoxine (SDM) and 4-N-acetylsulfadimethoxine (N-acetyl SDM) in channel catfish muscle and plasma. Tissues fortified at 0, 50, 100, 200, 400, and 1000 ppb were examined. Matrix solid phase dispersion (MSPD) was used for muscle extraction. Plasma was extracted with a modified MSPD procedure in which 100 microL plasma and 400 mg C18 were blended by Vortex mixing in a disposable chromatographic column. Recovery of SDM based on radioactivity was 79% for muscle and 67% for plasma. Standard curves based on extracted fortified samples were used for quantitation of N-acetyl SDM. LC run times of 12 min were obtained using a microbore analytical column and an isocratic mobile phase of aqueous 0.017M phosphoric acid-acetonitrile at ratios of 71:29 for muscle and 73:27 for plasma extracts. Method detection limits were 26 ng SDM and 26 ng N-acetyl SDM/g muscle, and 33 ng SDM and 11 ng N-acetyl SDM/mL plasma. Intra-assay variation was < 10% for both compounds at all concentrations examined. Inter-assay variation for SDM was 13% for muscle and 14% for plasma, and for N-acetyl SDM was 11% for muscle and 10% for plasma.

Extraction and enzyme immunoassay of sulfadimethoxine residues in channel catfish (Ictalurus punctatus) muscle

Four commercially available enzyme immunoassays were evaluated for the detection of sulfadimethoxine (SDM) residues in channel catfish muscle. Matrix solid-phase dispersion (MSPD) extracts of samples (n = 60, 0.5 g) fortified with SDM at 0, 25, 50, 100, and 250 ng/g were used in all assays. Intra-assay variations for 2 MICROTITER well-based quantitative assays, SIGNAL sulfamethazine test and IDS SDM One-Step ELISA (enzyme-linked immunosorbent assay), were 5.6 and 7.7%. Interassay variations for these tests were 7.9 and 16.6%. The agreements between evaluators for 2 membrane-based, visually determined assays, CITE Sulfa Trio and EZ-SCREEN: SDM, were 77 and 95%. Performance values, as indicated by sensitivity, specificity, efficiency, and positive and negative predictive values, were 100, 92, 95, 89, and 100%, respectively for the SIGNAL test; 100, 94, 97, 92, and 100% for the IDS test; 98, 71, 82, 69, and 98% for the CITE test; and 98, 94, 96, 92, and 99% for the EZ-SCREEN assay. Eight sulfonamides cross-reacted in the SIGNAL test; EC-50 values (concentrations causing 50% inhibition of color development compared with blanks) varied from < 0.1 to 45 micrograms/mL. The EC-50 value for SDM was 0.25 microgram/mL. The CITE test cross-reacted with sulfachloropyridazine at 10 micrograms/mL. The IDS and EZ-SCREEN tests had no significant cross-reactivity with other sulfonamides. N-Acetyl SDM reacted like the parent SDM in all assays. Performance results indicated that MSPD extracts of catfish muscle may be used in these immunoassays to screen catfish muscle samples for violative levels of SDM residue.

The acquired immunodeficiency syndrome in Australia: incidence 1982-1991

OBJECTIVE

To describe the incidence of the acquired immunodeficiency syndrome (AIDS) in Australia between 1982 and 1991.

DESIGN

State and Territory Health Departments notified new diagnoses of AIDS to the National AIDS Registry. Information reported for each case included sex, date of birth, date of AIDS diagnosis, presumed mode of exposure to the human immunodeficiency virus (HIV), and illness(es) on which the diagnosis of AIDS was based.

RESULTS

To the end of March 1992, 3,160 cases of AIDS were reported as having been diagnosed between 1982 and the end of 1991. The cumulative incidence per head of population was about twice as high in New South Wales as in Australia as a whole. Over 97% of cases were in men, of whom 91% were adults or adolescents reporting homosexual contact. In women, 40% of cases were acquired through receipt of blood, blood products or tissue. The annual incidence of AIDS rose sharply until about 1988, but the annual rates of increase slowed in subsequent years. This trend was also apparent in cases acquired through sexual contact between men. In other exposure groups, numbers of cases were much smaller and trends less apparent. However, there was no indication of a similar levelling in AIDS incidence, except among blood transfusion recipients, in whom incidence may be declining.

CONCLUSION

Transmission of HIV among people with AIDS in Australia has been overwhelmingly attributed to sexual contact between men. The annual incidence of cases attributed to sexual contact between men appears to be stabilising.

Chromatographic methods for tetracycline analysis in foods

The tetracyclines have served for decades as an important class of antibiotics in food animal health and production. As such, they have also been a source of concern for residue monitoring authorities around the world. In response to this concern a number of microbial inhibition, immunoassay and bacterial receptor methods have evolved for the detection of this class of compounds in various foods of animal origin. However, these methods often lack specificity and are subject to false positive and false negative results. For these reasons a number of chromatographic methods for the separation and determination of the tetracyclines isolated from foods have been developed that are capable of identifying and quantifying individual tetracycline drugs. We present here an overview of tetracycline analytical methods, including microbial inhibition, immunoassay and receptor technologies for detection, techniques for isolation from food matrices, and thin-layer chromatographic, high-performance liquid chromatographic, gas chromatographic and mass spectrometric procedures for determination of this class of compounds. A discussion of the variables involved in such methodology and a review of method criteria are offered.

The effect of palate repair on otitis media with effusion

Cleft palate in children is very frequently associated with otitis media with effusion. In this prospective study of 150 cleft palate children aged between 2 and 18 months, the prevalence of otitis media with effusion at myringotomy before palate repair was 92 percent. Otoscopic and tympanometric follow-up assessments for 140 children indicate that there is minimal improvement in middle ear status after palate repair. The condition is persistent in 70 percent of children up to 4 years of age. Furthermore, there is no evidence that age at repair or type of cleft is influential. These findings have implications for otologic management of cleft palate children. Early routine unilateral ventilation to ensure adequate hearing but minimize the morbidity of ventilation tubes is advocated.

Beta-tubulin epitope expression in normal and malignant epithelial cells

The expression of a unique beta-tubulin isoform (class III) was monitored in squamous cell carcinoma (SCC) and normal epithelial cells using a monoclonal tubulin antibody called TuJ1. Whole tissue homogenates of SCC, normal tissue, SCC grown in nude mice, and SCC cultured cells were examined using sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot. TuJ1 antibody localization was performed using peroxidase immunostaining on paraffin sections of SCC, normal tissue, nude mouse SCC, and immunofluorescent microscopy of SCC cultured cells. The malignant tissues examined stained positive with TuJ1 and a general beta-tubulin antibody, whereas the normal tissues stained positively only for the general beta-tubulin antibody. TuJ1 epitope expression may be a useful marker for SCCs and may assist in understanding differences between normal and malignant squamous cells.

Cerebellar desmoplastic medulloblastomas. A further immunohistochemical characterization of the reticulin-free pale islands

We studied by immunohistochemistry the features of differentiation in 24 desmoplastic and 16 classic medulloblastomas (median patient ages, 18 and 6.5 years, respectively) with the use of a panel of cytoskeletal and synaptosomal markers. A distinctive pattern of immunoreactivity with a series of monoclonal antibodies (Mabs) was documented in the polar tumor cells forming the reticulin-free pale islands of the desmoplastic variant, denoting overt neuritogenesis. These comprised the following: (1) Mab Tp-NFP1A3 recognizing an epitope in the high-molecular-weight (Mr) isoform of neurofilament protein; (2) Mab AP18 to the high-Mr microtubule-associated protein 2; (3) Mab TUJ1 recognizing the class III beta-tubulin isotype (human h beta 4); and (4) Mab SY38 to synaptophysin. Immunoblot analysis confirmed the expression of h beta 4 in three medulloblastomas, yielding strong single bands in two desmoplastic medulloblastomas and a considerably weaker band in one classic medulloblastoma. Glial fibrillary acidic protein-positive tumor cells frequently formed an integral component of the pale islands. Oligodendrogliallike areas in one classic and in three desmoplastic medulloblastomas were immunopositive for the Mabs to synaptophysin, microtubule-associated protein 2, and h beta 4, indicating a neuroblastic nature. We propose that the reticulin-free structures of desmoplastic medulloblastomas constitute neoplastic foci with features of predominantly neuronal and, to a lesser degree, astroglial differentiation.

The use of the mini-tracheotomy technique in burned patients

Our experience with two patients suggests that the mini-tracheotomy is a very useful technique, and may be of great value in the treatment of sputum retention (with or without inhalation injury) in burn patients.

On the character of an distance between states in a binary switching net

Behavioral examination of binary switching net models has typically concerned itself with an examination of their cyclical character. This article considers two less frequently discussed behavioral variables--the density of "1"s in net states and the (Hamming) distance between net states. These variables are studied under fully random nets and under nets controlled at levels of internal homogeneity, forcibility or threshold. A collection of theoretical and simulated results is presented.

The hydrogen cycle in nitrogen-fixing Azotobacter chroococcum

H2 will support nitrogenase activity (C2H2 reduction) in Azotobacter chroococcum with or without added carbon substrate. Results show that H2 is metabolised to transfer electrons to nitrogenase and to the respiratory chain to produce ATP. H2-supported nitrogenase activity is most significant at low carbon substrate concentrations, but also occurs at saturating concentration. Continuous cultures of N2-fixing A. chroococcum evolved H2 from nitrogenase under O2-N2- and C-limited conditions. This H2 represented a significant proportion of nitrogenase activity. Hydrogenase activity was consistently high under C-limited conditions, but low or undetectable under O2- and N2-limitations. Pre-treatment with 40 per cent C2H2 inhibited hydrogenase activity in C-limited cultures, and H2 evolution increased under air and under Ar:O2 (4:1) mixtures. We deduce that hydrogenase : I, recycles H2 produced by nitrogenase to provide electrons and energy for N2 reduction: II, supports respiratory protection for nitrogenase under C-limited conditions, and III, does not act to prevent any inhibition of N2 reduction by H2 produced by nitrogenase. A scheme for the H2 cycle in N2-fixing A. chroococcum is proposed.