Melt-quenched and as-deposited structures of amorphous selenium: a density functional/ molecular dynamics comparison.

Molecular dynamics simulations using a density functional description of energies and forces have been carried out for a model of an as-deposited (AD) surface of amorphous selenium. The deposition model assumed the annealing (at 400 K) of layers of randomly located single atoms, followed by compression to the density used in earlier melt-quenched (MQ) simulations of amorphous Se, and by further annealing. The AD and MQ structures are predominantly twofold coordinated and similar, for example in the pair distribution functions, with notable differences: the AD structures have more defects (atoms with one and three neighbours), and the ring distributions differ. These differences are also reflected in the electronic structures of the AD and MQ samples, where the increased presence of defects in the former influences the Bader charges and the edge states of the band gap. The dominance of rings found in a previous simulation of AD structures is not found.

Magma chamber evolution during the 1650 AD Kolumbo eruption provides clues about past and future volcanic activity.

Kolumbo submarine volcano lies 7 km NE of Santorini caldera and its last eruption which occurred in 1650 AD, caused damage and casualties to the nearby islands. Here a simple model of a chamber, containing silicic magma underlain by a smaller quantity of mafic magma, is utilised in order to understand the chamber behaviour during the 1650 AD eruption. Results show that in order to reproduce the duration (83-281 days) and the dense rock equivalent volume ([Formula: see text]) of the eruption, initial overpressure in the chamber should be around 10 MPa and the mafic magma should occupy up to 5% of the chamber volume. It is found that the time needed to inject mafic magma equal to 1-15% of the chamber volume varies between 1.4-13.7 ka, if the radius of the chamber is about 1500 m as inferred from tomographic images. These long recurrence times agree well with the small number of eruptions ([Formula: see text]) within a period of > 70 ka and suggest that an eruption in the near future is unlikely. Volcanic activity at Kolumbo is probably triggered by a combination of exsolved volatiles and a small but steady influx of mafic melt in the chamber.

Ab initio computer simulations of non-equilibrium radiation-induced cascades in amorphous Ge2Sb2Te5.

Ion irradiation corresponds to a process that involves the production of non-equilibrium cascades in the host material, and the atomistic modelling of such events in glasses is challenging. Here, non-equilibrium cascades in amorphous Ge2Sb2Te5 phase-change memory material have been investigated by means of first-principles molecular-dynamics simulations. A stochastic boundary-conditions approach is employed to treat the thermal nature of the cascades and drive the modelled system back to equilibrium in a natural way, while four different initial thermal-spike energies are considered. A comprehensive analysis of the cascade evolution is presented with respect to the kinetic profile and the dynamics of the cascade inside the glass structure. The modelling results show that the instantaneous maximum kinetic energy decays rapidly with time, and that the time-scale of the ballistic phase of the cascade inside the glass model is very short. The quality of the implemented approach is validated through a comparison of the calculated structure factor for the modelled glasses with experimental data from the literature. Analysis of the bonding for all the species in the glass structure highlights particular structural modifications in the connectivity of the amorphous network due to the simulated cascade.

Patterns of drug resistance among patients with tuberculous pleural effusion in Greece.

SETTING: Data on the relationship between pleural tuberculosis (TB) and anti-tuberculosis drug resistance are scarce. OBJECTIVE: To determine the patterns of drug resistance among pleural Mycobacterium tuberculosis isolates in Greece and the incidence of tuberculous pleural effusion (TPE) among patients with multidrug-resistant (MDR) or extensively drug-resistant (XDR) pulmonary TB. DESIGN: Drug susceptibility testing (DST) results recorded in the database of the National Reference Centre for Tuberculosis in Athens, Greece, over a 9-year period (2003-2011) were reviewed. Chest X-rays from hospitalised patients with pulmonary MDR/XDR-TB during the same period were also reviewed for the presence of TPE. RESULTS: Resistance to at least one first-line drug was observed in 11% of the cases (MDR-TB 3%, XDR-TB 1%), while 29% of the patients with pulmonary MDR/XDR-TB presented with TPE during the course of their disease, the majority ipsilateral to the lung lesions, which responded to guided anti-tuberculosis treatment. CONCLUSION: The prevalence of drug resistance among pleural M. tuberculosis isolates in Greece highlights the importance of DST prior to treatment selection in TPE patients. In our study population, TPE that developed in one third of the patients with pulmonary MDR/XDR-TB usually resolved with DST-guided anti-tuberculosis treatment.

Reduction of randomness in seismic noise as a short-term precursor to a volcanic eruption.

Ambient seismic noise is characterized by randomness incurred by the random position and strength of the noise sources as well as the heterogeneous properties of the medium through which it propagates. Here we use ambient noise data recorded prior to the 1996 Gjálp eruption in Iceland in order to show that a reduction of noise randomness can be a clear short-term precursor to volcanic activity. The eruption was preceded on 29 September 1996 by a Mw ~5.6 earthquake that occurred in the caldera rim of the Bárdarbunga volcano. A significant reduction of randomness started occurring 8 days before the earthquake and 10 days before the onset of the eruption. This reduction was observed even at stations more than 100 km away from the eruption site. Randomness increased to its previous levels 160 minutes after the Bárdarbunga earthquake, during which time aftershocks migrated from the Bárdarbunga caldera to a site near the Gjálp eruption fissure. We attribute this precursory reduction of randomness to the lack of higher frequencies (>1 Hz) in the noise wavefield caused by high absorption losses as hot magma ascended in the upper crust.

Encapsulation of nutraceutical monoterpenes in beta-cyclodextrin and modified starch.

The encapsulation of thymol and geraniol in beta-cyclodextrin (beta-CD) and modified starch (MS) by spray- and freeze-drying was studied. The formation of thymol/beta-CD and geraniol/beta-CD inclusion complexes was confirmed by differential scanning calorimetry (DSC). Oxidative DSC revealed that the monoterpenes enclosed in the beta-CD cavity were protected against oxidation, remaining intact in temperatures at which free monoterpenes were oxidized. Phase solubility studies showed that the inclusion complexes of thymol and geraniol with beta-CD are more soluble in water than the free molecules themselves. Furthermore, in order to evaluate the fraction of monoterpenes that can be released from their complexes with MS in aqueous media, a series of release experiments were conducted.

Early detection of subclinical HIV sensory polyneuropathy using intraepidermal nerve fibre density quantification: association with HIV stage and surrogate markers.

The linear intraepidermal nerve fibre density (IENFD) and secondary branching were evaluated from skin biopsy of both the distal calf and the proximal thigh after staining with protein gene product 9.5 in 94 individuals of an HIV outpatient cohort. Possible correlations with clinical and electrophysiological evidence of distal sensory polyneuropathy (DSP), patients' demographics, antiretroviral history and HIV surrogate markers were analysed. Reduced IENFD was recognized in the majority of this population (mean +/- standard deviation [SD] IENFD in the calf and the thigh was 3.19 +/- 1.91 and 7.07 +/- 3.5 fibres/mm, respectively). One-third of the patients with low IENFD had no clinical or electrophysiological evidence of DSP. The level of prior immunosuppression as expressed by lower nadir CD4 count, more advanced HIV stage and prior exposure to combinations of neurotoxic antiretrovirals was associated with more decreased IENFD. Increased SB was associated with symptomatic DSP.

The Bcl-2/Bax system and apoptosis in ulcerative colitis.

BACKGROUND/AIMS: Ulcerative colitis (UC) constitutes a chronic inflammatory process of the colon of unknown etiology. Current data support a pivotal role of apoptosis in the evolution of pathogenesis of UC. We performed a prospective study in order to determine the role of Bcl-2, Bax and Bcl-x in the apoptotic pathway in UC. METHODOLOGY: We included 23 patients with UC and 11 controls. Histological severity of the disease was assessed according to the Sidney classification system. Patients in the UC group were divided in 2 groups according to histological severity of the disease. The TUNEL method was used for the in situ evaluation of apoptosis. Immunohistochemical staining was used for the detection of Bax, Bcl-2, Bcl-x. For the assessment of cellular proliferation we used the monoclonal antibody Ki67. Appropriate statistical methods were applied. RESULTS: Overall 77 specimens were assessed; 57 from UC patients and 20 from controls. Bcl-2, Bax and Bcl-x were upregulated in the group of patients with UC compared to controls. Nevertheless, Bax in epithelial cells and Bcl-x in lymphocytes were downregulated in patients with moderate/severe disease (p = 0.029 and 0.04 respectively). A weak correlation between epithelial apoptosis and Bcl-x expression in lymphocytes (r = 0.31, p = 0.02) was found. An even weaker correlation was also noticed between the epithelial component apoptosis and Bax in lymphocytes (r = 0.02, p = 0.07). CONCLUSIONS: Bcl-2/Bax system does not appear to be involved in the induction of apoptosis in UC. Activation of intraepithelial lymphocytes may be associated with epithelial apoptosis or simply represent epiphenomena related to the inflammatory process.

Distal sensory polyneuropathy in HIV-positive patients in the HAART era: an entity underestimated by clinical examination.

The aim of this study was to determine the prevalence of distal sensory polyneuropathy (DSP) in our HIV-positive patients under highly active antiretroviral therapy (HAART) and to investigate correlations with clinical, laboratory and demographic factors. One hundred consecutive HIV-positive patients underwent clinical and electrophysiological evaluation for DSP. Correlations with HIV stage, CD4 count, nadir CD4 count, viral load (VL), disease duration, age, sex and type of antiretrovirals were examined. Thirty-six percent of the patients had DSP (13% clinical, 23% subclinical diagnosed by electrophysiology). The prevalence of DSP was affected in a statistically significant manner by the diagnosis of AIDS (P = 0.00033), age (P = 0.0102), nadir CD4 count (P = 0.0087) and exposure to two neurotoxic antiretrovirals (P = 0.0189). Advanced HIV stage, sex, time from diagnosis, current CD4 count and VL did not seem to affect the prevalence of DSP. Clinical examination plus electrophysiology reveals that DSP affects 36% of patients under HAART, although subclinical in 2/3 of cases. Age, severe prior immunosuppression and the combined use of zalcitabine (ddC), stavudine (d4T) and didanosine (ddI) are important risk factors.

Virtual bronchoscopy versus thin section computed tomography in evaluation of moderate and low grade stenoses: receiver operating characteristic curve analysis.

PURPOSE: To evaluate the impact of virtual bronchoscopy, under proper threshold settings, on observer level of confidence in the assessment of bronchial abnormalities producing stenoses < or = 75% compared to interpretation of thin section computed tomography (CT) images. MATERIAL AND METHODS: Sixty-five patients with fiberoptic bronchoscopy positive for tracheobronchial abnormalities were evaluated in a blinded observer study using a commercially available virtual endoscopy software package. The findings of virtual endoscopy were compared with those of fiberoptic bronchoscopy using receiver operating characteristic curves (ROCs) and other statistical tools. RESULTS: A total of 102 lesions were identified by fiberoptic bronchoscopy, with 44 of these producing bronchial stenoses < or = 75%. Concerning the latter lesions, for virtual bronchoscopy the areas under the ROCs were 0.93 and 0.96 for the two observers, respectively, while for thin section CT the corresponding values were 0.86 and 0.88; the differences observed were statistically significant. Contrary to thin section CT, virtual bronchoscopy did not show statistically significant differences from fiberoptic bronchoscopy regarding estimation of degree of stenosis. CONCLUSION: Virtual bronchoscopy under proper threshold settings has a statistically significant impact on observer performance where moderate and low-grade bronchial stenoses are concerned and gives an estimate of the degree of stenosis more precisely than thin section CT.

Cefepime versus ceftazidime for treatment of pneumonia.

Consecutive patients with pneumonia, treated with cefepime (n = 66) or ceftazidime (n = 132), were evaluated in a retrospective, observational study. There was no significant difference between the two treatment groups with respect to age, underlying diseases, acute physical and chronic health evaluation score, intensive care unit admission, presence of sepsis, community or hospital acquisition, causative organism, duration of therapy, death, cure or improvement in infection, adverse events, superinfections, presence of vancomycin-resistant enterococcus (VRE) and resistance to therapy. Post-therapy hospitalization (days) and vancomycin co-administration were significantly lower, and time to vancomycin initiation significantly higher, in the cefepime compared with the ceftazidime group. The results suggest a trend towards less resistance on therapy, less VRE, reduced vancomycin use and shorter post-therapy hospitalization in patients treated with cefepime compared with ceftazidime. The clinical outcomes for hospitalized patients treated for serious pneumonia were similar between the two groups.

The use and reported effects of mobilization with movement techniques in low back pain management; a cross-sectional descriptive survey of physiotherapists in Britain.

Manual therapy is the most commonly used approach in the management of low back pain (LBP) and encompasses a wide range of techniques. The aims of this study were to investigate the current use of mobilizations with movement (MWM) for LBP management in Britain and to inform future clinical research exploring their effects.A postal survey of a random sample of 3295 practising physiotherapists in Britain was conducted. A response rate of 72.1% (n=2357) was obtained. Of these, 48.2% (n=1136) reported treating LBP, of whom 41.1% (n=467) reported using MWMs in LBP management. Therefore, the sample applicable for analysis consisted of these 467 therapists currently treating LBP and using MWMs. Most respondents (51.4%) worked in a national health service setting. Over half of the respondents used MWMs on at least a weekly basis, with 61.9% using MWMs primarily for mechanical LBP. The most commonly reported changes seen immediately after the application of MWMs were increases in range of movement (ROM) (54.4%) and pain relief (27.5%). This was also reflected in the outcomes chosen to evaluate improvement. On average, two spinal levels were mobilized using 2-3 sets of 4-5 repetitions. The lower lumbar levels were treated more often. Most therapists indicated using a combination of other treatment approaches together with MWMs when treating LBP patients. In conclusion, this study is the first to describe the current practice of MWMs by physiotherapists in Britain, and the results will be used to inform the design of a clinical trial exploring the effects of MWMs for LBP.