Impact of Prosopis velutina Wooton on the Composition and Diversity of Native Woody Species in a Semi-Arid Zone along the Molopo River, South Africa.

Invasive alien species represent one of the main threats to biodiversity and species extinction. This is the case for the genus Prosopis, among which Prosopis velutina is the most invasive and common tree species along the Molopo River in the North-West Province, impacting native plant communities. However, its impact on the composition and diversity of native woody species remains poorly investigated in the area. Thus, this study aimed to assess the impact of P. velutina on native woody plant composition and diversity across three sites along the Molopo River. At each site, five quadrats of 20 × 20 m2 were randomly established in invaded and adjacent uninvaded stands. A comparative methodological approach was adopted, and the woody plants in invaded and uninvaded stands with similar site conditions were sampled. The results showed that native woody species density differed significantly (p < 0.05) between invaded and uninvaded stands, except for Bray sites, where there was a marginal difference (p = 0.6). The overall native woody species density decreased by 79.7% in the invaded stand. However, non-metric multidimensional scaling (nMDS) and analysis of similarity (ANOSIM) indicated significant differences in native tree composition between invaded and uninvaded stands at all sites. In all three sites, all ecological indices had significantly lower values in invaded stands compared to uninvaded stands. The decrease in all ecological indices in invaded over uninvaded stands indicated that P. velutina invasion reduced the diversity of native woody plant species. Due to the incessant spread of P. velutina, it may become a long-term dominant species with an increasing impact on the native vegetation. Therefore, the findings of this study call for urgent management and appropriate control measures against the ongoing spread of this invader within the riparian zones of the Molopo River in North-West Province.

Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station.

Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.

Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station.

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.

Human epithelial cells exposed to functionalized multiwalled carbon nanotubes: interactions and cell surface modifications.

With the expansion of the production and applications of multiwalled carbon nanotubes (MWCNTs) in several industrial and science branches, the potential adverse effects on human health have attracted attention. Numerous studies have been conducted to evaluate how chemical functionalization may affect MWCNT effects; however, controversial data have been reported, showing either increased or reduced toxicity. In particular, the impact of carboxylation on MWCNT cytotoxicity is far from being completely understood. The aim of this work was the evaluation of the modifications induced by carboxylated-MWCNTs (MWCNTs-COOH) on cell surface and the study of cell-MWCNT-COOH interactions by means of field emission scanning electron microscope (FESEM). Human pulmonary epithelial cells (A549) were incubated with MWCNTs-COOH for different exposure times and concentrations (10 µg/mL for 1, 2, 4 h; 5, 10, 20 µg/mL for 24 h). At short incubation time, MWCNTs-COOH were easily observed associated with plasma membrane and in contact with microvilli. After 24 h exposure, FESEM analysis revealed that MWCNTs-COOH induced evident changes in the cellular surface in comparison to control cells: treated cells showed blebs, holes and a depletion of the microvilli density in association with structure modifications, such as widening and/or lengthening. In particular, an increase of cells showing holes and microvilli structure alterations was observed at 20 µg/mL concentration. FESEM analysis showed nanotube agglomerates, of different sizes, entering into the cell with two different mechanisms: inward bending of the membrane followed by nanotube sinking, and nanotube internalization directly through holes. The observed morphological microvilli modifications, induced by MWCNTs-COOH, could affect epithelial functions, such as the control of surfactant production and secretion, leading to pathological conditions, such as alveolar proteinosis. More detailed studies will be, however, necessary to examine in depth the effects induced by MWCNTs-COOH and, in particular, the timing of the MWCNT-COOH-cell interaction.

Precision Measurement of the (e

We present a measurement of the cosmic ray (e^{+}+e^{-}) flux in the range 0.5 GeV to 1 TeV based on the analysis of 10.6 million (e^{+}+e^{-}) events collected by AMS. The statistics and the resolution of AMS provide a precision measurement of the flux. The flux is smooth and reveals new and distinct information. Above 30.2 GeV, the flux can be described by a single power law with a spectral index γ=-3.170±0.008(stat+syst)±0.008(energy scale).

Electron and positron fluxes in primary cosmic rays measured with the alpha magnetic spectrometer on the international space station.

Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ∼30 GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

High statistics measurement of the positron fraction in primary cosmic rays of 0.5-500 GeV with the alpha magnetic spectrometer on the international space station.

A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above ∼200 GeV the positron fraction no longer exhibits an increase with energy.

First result from the Alpha Magnetic Spectrometer on the International Space Station: precision measurement of the positron fraction in primary cosmic rays of 0.5-350 GeV.

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

Multiple viral infections in a group of intravenous drug users: hepatitis B virus exposure is the risk factor.

OBJECTIVE: Infection with hepatotropic viruses is associated with a variable degree of liver disease, and there is evidence that more severe lesions are related to the association with another viral infection. The aim of this investigation is to establish the relationship between different viral infections occurring in the same individual and the presence and progression of liver disease. DESIGN: The study population comprises 754 intravenous (IV) drug abusers exposed to hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV) or cytomegalovirus (CMV). All individuals were followed for an average of 2 years. Liver disease was assessed by liver function tests, 99m-technetium (99mTc) liver scintigraphy, and also by liver biopsy in a subset (n = 136) of patients. The different viral patterns and presence of disease were analysed by logistic regression, and the risk factors were calculated. Contingency tables of patients with single or associated infections were drawn up to evaluate progression of liver disease. RESULTS: Association of HIV with at least one other viral infection was constant. Surface antigens of HBV (HBsAg) were always associated with HIV (n = 19); in this group, 18 patients had signs of liver disease. A past infection with HBV, as revealed by the presence of at least antibodies against the surface antigen (HBsAb) and antibodies against the core antigen of HBV (HBcAb), was detected in 463 patients (61.4%). The overall prevalence of HCV antibodies was 63.91% (n = 482). In 96.8% of the 406 patients tested, HCV-RNA was detected by reverse transcriptase polymerase chain reaction (RT-PCR). The majority of patients with high alanine transaminase (ALT) had anti-HBV antibodies in the presence of HCV (56.1%). At the end of follow-up, all of these patients showed signs of active liver disease, and scoring was significantly worse than in patients with either HBV or HCV alone. An infection/reactivation of CMV was found in patients previously exposed to HBV and with increased ALT values. CONCLUSIONS: Data emerging from this study reveal the association of HCV or CMV, or both, with a previous HBV infection, as demonstrated by HBsAb and HBcAb, and rapid progression of the disease in this group of patients. A previous HBV infection therefore appears to be an important risk factor for subsequent viral-related liver disease.

Restrictions to carbon dioxide conductance and photosynthesis in spinach leaves recovering from salt stress

Salt accumulation in spinach (Spinacia oleracea L.) leaves first inhibits photosynthesis by decreasing stomatal and mesophyll conductances to CO2 diffusion and then impairs ribulose-1, 5-bisphosphate carboxylase/oxygenase (S. Delfine, A. Alvino, M. Zacchini, F. Loreto [1998] Aust J Plant Physiol 25: 395-402). We measured gas exchange and fluorescence in spinach recovering from salt accumulation. When a 21-d salt accumulation was reversed by 2 weeks of salt-free irrigation (rewatering), stomatal and mesophyll conductances and photosynthesis partially recovered. For the first time, to our knowledge, it is shown that a reduction of mesophyll conductance can be reversed and that this may influence photosynthesis. Photosynthesis and conductances did not recover when salt drainage was restricted and Na content in the leaves was greater than 3% of the dry matter. Incomplete recovery of photosynthesis in rewatered and control leaves may be attributed to an age-related reduction of conductances. Biochemical properties were not affected by the 21-d salt accumulation. However, ribulose-1, 5-bisphosphate carboxylase/oxygenase activity and content were reduced by a 36- to 50-d salt accumulation. Photochemical efficiency was reduced only in 50-d salt-stressed leaves because of a decrease in the fraction of open photosystem II centers. A reduction in chlorophyll content and an increase in the chlorophyll a/b ratio were observed in 43- and 50-d salt-stressed leaves. Low chlorophyll affects light absorptance but is unlikely to change light partitioning between photosystems.

[Lipoma of the colon. Its clinical significance and treatment]. / Il lipoma del colon. Significato clinico e trattamento.

The authors present the observation of a case of lipoma of the transverse colon. They review the latest literature confirming the rarity of this case and its clinical importance for diagnostic and therapeutic problems that it could give.

[Blood pressure during exercise stress in young normal subjects with familial hypertension (author's transl)]. / Risposta pressoria allo sforzo di giovani normali con familiarita' ipertensiva.

The behaviour of Arterial Blood Pressure was evaluated, by treadmill stress testing, in a group of young subjects (15-30 years old) with one or two hypertensive siblings. The best fit of the interpolating slope function was used in interpretating the findings of haemodynamic data (A.B.P. during exercise). These data were analyzed in the same way in three control groups: normal subjects 15-30 years old; hypertensive patients aged 30-45; normal subjects aged 30-45. We compared function's coefficients and parameters in these selected groups. The results show no different response in the A.B.P during stress between the normal subject and the group, same aged, with hypertensive siblings. Significative differences in the function's coefficients, were found in the control hypertensive patients. The stress testing doesn't seem recommending in subjects at risk because of parenteral hypertension: no early alteration in A.B.P. seems to be unmasked during exercise stress. The males of the control normal subject show higher blood pressure exercise value than females. This different response is not present in the group with parenteral hypertension: a more strick familial resemblance in A.B.P. is suggested in female population.