D. Papadimitriou

Stem cell therapy in stroke

Abstract.Recent work has focused on cell transplantation as a therapeutic option following ischemic stroke, based on animal studies showing that cells transplanted to the brain not only survive, but also lead to functional improvement. Neural degeneration after ischemia is not selective but involves different neuronal populations, as well as glial and endothelial cell types. In models of stroke, the principal mechanism by which any improvement has been observed, has been attributed to the release of trophic factors, possibly promoting endogenous repair mechanisms, reducing cell death and stimulating neurogenesis and angiogenesis. Initial human studies indicate that stem cell therapy may be technically feasible in stroke patients, however, issues still need to be addressed for use in human subjects.

Sub-micrometre luminescent porous silicon structures using lithographically patterned substrates

Abstract Sub-micrometre area porous silicon structures were fabricated by anodization of patterned surfaces of crystalline p-type silicon, orientation (100) and resistivity 5–7 Ωcm. The mask for selective anodization was either silicon dioxide or silicon nitride, deposited onto silicon by low pressure chemical vapour deposition. The second mask was more resistant to the anodization solution (HF, ethanol and water solution) and was not dissolved during the anodization time used. When silicon dioxide was used as a mask, care was taken to stop anodization before the whole layer was removed. Patterning was done by optical lithography combined with a special process for sub-micrometre dimensions (silylation process). Dots and lines of dimensions down to 0.5 μm were produced, which exhibit strong red luminescence under UV excitation. The film thickness of the porous silicon structures in the sub-micrometre areas was smaller than the thickness in larger areas. The lateral growth of the structures under the mask was examined by scanning and transmission electron microscopy. Microphotoluminescence experiments in a confocal microscope were also used for mapping the luminescent areas.

Raman scattering and photoluminescence of nitrogenated amorphous carbon films

The structural and optical properties of nitrogenated amorphous carbon films, grown by rf-magnetron sputtering on silicon substrates, were studied by Raman and photoluminescence (PL) spectroscopy as a function of the nitrogen concentration and the substrate bias voltage Vb. For films deposited with Vb=10u2009V, the photoluminescence emission was most intense at nitrogen concentrations in the carrier gas of 25% (75% Ar), while the intensity ratio I(D)/I(G) of the Raman bands of disordered graphite (D band) and graphite (G band) partially substituted by nitrogen exhibited a minimum simultaneously observed with a minimum of G-band frequency and a maximum of G-band width. Changes in spectral characteristics of Raman scattering at a concentration of 25% (≅30u2009atu200a%) are indicative of an increase of sp3-bonded fraction and disorder. PL-enhancement coincides, in this case, with structural changes and is probably correlated to the substitution of nitrogen in the tetrahedraly bonded amorphous matrix. In the case of film...

Optical properties and new vibrational modes in carbon films

Abstract The optical properties and vibrational modes of amorphous carbon (a-C) films were studied by spectroscopic ellipsometry (SE) and Raman spectroscopy. The films were prepared by sputtering, at various energies Ei (low to high), of the argon species bombarding the film surface during deposition. The SE spectra were analysed by the Tauc–Lorentz model to describe the dielectric function e(ω) of the bulk films and to determine their optical gaps. The calculated e(ω) revealed fundamental differences in the electronic structure and C C bonding of the a-C films and can be described, in general, with two oscillators: one at ∼4xa0eV, attributed to the π→π∗ (sp2 bonds), and one in the range 10–15.5xa0eV, attributed to the average of σ→σ∗ (sp3 bonds) and high-energy (sp2 bonds) absorption. A strong optical absorption at ∼1.2xa0eV appears only in films developed with high Ei (≥130xa0eV). The Raman spectra of the a-C films show the following behavior with increasing Ei: (1) the strengths of disordered ‘D’ and graphite ‘G’ peaks are gradually reduced and finally disappear; (2) three peaks (at ∼1250, 1295 and 1330xa0cm−1) appear, reinforced at high Ei; and (3) at high Ei two well-defined peaks at ∼1556 and 2330xa0cm−1 are also detected. All of the above indicate the formation of a more ordered amorphous network with increasing Ei, and a new crystalline structure is formed at high Ei.

Micro-Raman Study of Orientation Effects of CuxSe-Crystallites on Cu-rich CuGaSe2 Thin Films

The structural properties of copper selenide (CuxSe), formed as a secondary phase on the surface of CuGaSe2 films grown under Cu-rich conditions on GaAs (100) substrates, were studied by micro-Raman spectroscopy. Raman bands at 45 and 263cm−1, observed on crystallites dispersed on the CuGaSe2 film, are in agreement with the Raman modes of CuSe and Cu2Se. Polarization- and angular-dependent micro-Raman measurements reveal that the CuxSe-crystallites are grown with a preferential orientation on the CuGaSe2 surface.

Gigantic retroperitoneal hematoma as a complication of anticoagulation therapy with heparin in therapeutic doses: a case report

IntroductionSpontaneous retroperitoneal hemorrhage is a distinct clinical entity that can present as a rare life-threatening event characterized by sudden onset of bleeding into the retroperitoneal space, occurring in association with bleeding disorders, intratumoral bleeding, or ruptures of any retroperitoneal organ or aneurysm. The spontaneous form is the most infrequent retroperitoneal hemorrhage, causing significant morbidity and representing a diagnostic challenge.Case presentationWe report the case of a patient with coronary artery disease who presented with transient ischemic attack, in whom anticoagulant therapy with heparin precipitated a massive spontaneous atraumatic retroperitoneal hemorrhage (with international normalized ratio 2.4), which was treated conservatively.ConclusionDelay in diagnosis is potentially fatal and high clinical suspicion remains crucial. Finally, it is a matter of controversy whether retroperitoneal hematomas should be surgically evacuated or conservatively treated and the final decision should be made after taking into consideration patients general condition and the possibility of permanent femoral or sciatic neuropathy due to compression syndrome.

Vasopressin and epinephrine in the treatment of cardiac arrest: an experimental study

BackgroundEpinephrine remains the drug of choice for cardiopulmonary resuscitation. The aim of the present study is to assess whether the combination of vasopressin and epinephrine, given their different mechanisms of action, provides better results than epinephrine alone in cardiopulmonary resuscitation.MethodsVentricular fibrillation was induced in 22 Landrace/Large-White piglets, which were left untreated for 8 minutes before attempted resuscitation with precordial compression, mechanical ventilation and electrical defibrillation. Animals were randomized into 2 groups during cardiopulmonary resuscitation: 11 animals who received saline as placebo (20 ml dilution, bolus) + epinephrine (0.02 mg/kg) (Epi group); and 11 animals who received vasopressin (0.4 IU/kg/20 ml dilution, bolus) + epinephrine (0.02 mg/kg) (Vaso-Epi group). Electrical defibrillation was attempted after 10 minutes of ventricular fibrillation.ResultsTen of 11 animals in the Vaso-Epi group restored spontaneous circulation in comparison to only 4 of 11 in the Epi group (p = 0.02). Aortic diastolic pressure, as well as, coronary perfusion pressure were significantly increased (p < 0.05) during cardiopulmonary resuscitation in the Vaso-Epi group.ConclusionThe administration of vasopressin in combination with epinephrine during cardiopulmonary resuscitation results in a drastic improvement in the hemodynamic parameters necessary for the return of spontaneous circulation.

Atenolol in combination with epinephrine improves the initial outcome of cardiopulmonary resuscitation in a swine model of ventricular fibrillation

STUDY OBJECTIVESnThe aim of the present study was to assess whether a beta-adrenergic blocking agent such as atenolol, administered during cardiopulmonary resuscitation, would improve initial resuscitation success.nnnMETHODSnVentricular fibrillation was induced in 20 Landrace/Large White piglets, which were left untreated for 8 minutes before attempted resuscitation with precordial compression, mechanical ventilation, and electrical defibrillation. Animals were randomized into 2 groups (10 animals each) to receive saline as placebo (20 mL dilution, bolus) + epinephrine (0.02 mg/kg) (group A) or atenolol (0.05 mg/kg per 20 mL dilution, bolus) + epinephrine (0.02 mg/kg) (group B) during cardiopulmonary resuscitation. Electrical defibrillation was attempted after 10 minutes of ventricular fibrillation.nnnRESULTSnNine animals in group B restored spontaneous circulation in comparison to only 4 in group A. Aortic systolic and diastolic pressures as well as coronary perfusion pressure were significantly increased during cardiopulmonary resuscitation in group B. Furthermore, postresuscitation heart rate of the atenolol-treated group was significantly decreased.nnnCONCLUSIONSnA beta-adrenergic blocking agent, when administered during cardiopulmonary resuscitation, significantly improves initial resuscitation success and increases blood and coronary perfusion pressures during cardiopulmonary resuscitation.

Compositional dependence of Raman scattering and photoluminescence emission in CuxGaySe2 thin films

Raman scattering and photoluminescence (PL) emission of CuxGaySe2 thin films, grown by metalorganic chemical vapor deposition (MOCVD) on GaAs (100) and by physical vapor deposition (PVD) on Glass/Mo substrates, were studied at room and low temperatures as a function of composition. Line width changes of Raman bands in the temperature range 20–300 K indicate the formation of a more disordered CuxGaySe2 phase with increasing Ga content. It is most likely that Raman bands observed at 193 and 199 cm−1 in the Ga-rich samples at low temperatures are associated with defect-related interface modes. The intensity increase of these bands and the photoluminescence intensity enhancement may be correlated to an increase in defect concentration in the Ga-rich phase. The radiative recombination in defect-rich Ga-rich samples with a higher degree of disorder apparently supports the PL emission. The observed changes are more pronounced in MOCVD than in PVD grown films.

Carbon tetrachloride modulates the rat hepatic microsomal UDP-glucuronyl transferase activity and membrane fluidity

Modulations in rat hepatic microsomal UDP-glucuronyl transferase activity have been observed during carbon tetrachloride (CCl4) poisoning, with a large decrease in the enzyme cooperativity and increase in the membrane fluidity, occurring 30 min after administration. The results strengthen the possibility that an increase in microsomal membrane fluidity may be an early key event in liver injury induced by CCl4.