Development of Bioglass/PEEK Composite Coating by Cold Gas Spray for Orthopedic Implants

Cold gas spray (CGS) technology has allowed the development of biofunctional coatings composed of 45S5 and polyetheretherketone (PEEK). The combination of a bioactive glass material embedded in a polymeric matrix makes this composite an interesting material for orthopedic applications since this composite meets the biomechanical and biological requirements of an implant. In the present study, blends of bioactive glass 45S5 and PEEK powder with different granulometry and 45S5/PEEK ratio have been prepared. These mixtures of powders have been deposited onto PEEK substrates by CGS with the goal of incorporating a bioactive additive to the biocompatible polymer, which can improve the bone-implant interaction of PEEK. The deposition efficiency (DE) of the coatings has been evaluated, and from the results obtained, it was possible to conclude that DE is significantly affected by the granulometry and by the 45S5/PEEK ratio of the blends. By scanning electron microscopy (SEM) inspection, it was observed that the use of blends with high 45S5/PEEK ratio lead to the deposition of coatings with high content of 45S5. Finally, the friction behavior of the coatings was analyzed performing ball-on-disk tests and these experiments showed that the presence of glass particles has a beneficial role in the wear resistance.

Toward RGB LEDs based on rare earth-doped ZnO

By using ZnO thin films doped with Ce, Tb or Eu, deposited via radiofrequency magnetron sputtering, we have developed monochromatic (blue, green and red, respectively) light emitting devices (LEDs). The rare earth ions introduced with doping rates lower than 2% exhibit narrow and intense emission peaks due to electronic transitions in relaxation processes induced after electrical excitation. This study proves zinc oxide to be a good host for these elements, its high conductivity and optical transparency in the visible range being as well exploited as top transparent electrode. After structural characterization of the different doped layers, a device structure with intense electroluminescence is presented, modeled, and electrically and optically characterized. The different emission spectra obtained are compared in a chromatic diagram, providing a reference for future works with similar devices. The results hereby presented demonstrate three operating monochromatic LEDs, as well as a combination of the three species into another one, with a simply-designed structure compatible with current Si technology and demonstrating an integrated red-green-blue emission.

Synchronization of Optomechanical Nanobeams by Mechanical Interaction

The synchronization of coupled oscillators is a phenomenon found throughout nature. Mechanical oscillators are paradigmatic examples, but synchronizing their nanoscaled versions is challenging. We report synchronization of the mechanical dynamics of a pair of optomechanical crystal cavities that, in contrast to previous works performed in similar objects, are intercoupled with a mechanical link and support independent optical modes. In this regime they oscillate in antiphase, which is in agreement with the predictions of our numerical model that considers reactive coupling. We also show how to temporarily disable synchronization of the coupled system by actuating one of the cavities with a heating laser, so that both cavities oscillate independently. Our results can be upscaled to more than two cavities and pave the way towards realizing integrated networks of synchronized mechanical oscillators.

Memristive behaviour of Si-Al oxynitride thin films: the role of oxygen and nitrogen vacancies in the electroforming process

The resistive switching properties of silicon-aluminium oxynitride (SiAlON) based devices have been studied. Electrical transport mechanisms in both resistance states were determined, exhibiting an ohmic behaviour at low resistance and a defect-related Poole-Frenkel mechanism at high resistance. Nevertheless, some features of the Al top-electrode are generated during the initial electroforming, suggesting some material modifications. An in-depth microscopic study at the nanoscale has been performed after the electroforming process, by acquiring scanning electron microscopy and transmission electron microscopy images. The direct observation of the devices confirmed features on the top electrode with bubble-like appearance, as well as some precipitates within the SiAlON. Chemical analysis by electron energy loss spectroscopy has demonstrated that there is an out-diffusion of oxygen and nitrogen ions from the SiAlON layer towards the electrode, thus forming silicon-rich paths within the dielectric layer and indicating vacancy change to be the main mechanism in the resistive switching.

Compact focusing grating couplers for silicon horizontal slot waveguides

In this Letter, we present the design, simulation (2D and 3D), fabrication, and experimental characterization of compact and fully etched focusing gratings for a horizontal slot waveguide based on a silicon nitride layer sandwiched between amorphous silicon and a silicon-on-insulator. The measured coupling losses are about 4 dB with a 3 dB bandwidth of 38 nm. The fully etched configuration allows the fabrication in a single lithography step.

Organosilane-functionalization of nanostructured indium tin oxide films

Fabrication and organosilane-functionalization and characterization of nanostructured ITO electrodes are reported. Nanostructured ITO electrodes were obtained by electron beam evaporation, and a subsequent annealing treatment was selectively performed to modify their crystalline state. An increase in geometrical surface area in comparison with thin-film electrodes area was observed by atomic force microscopy, implying higher electroactive surface area for nanostructured ITO electrodes and thus higher detection levels. To investigate the increase in detectability, chemical organosilane-functionalization of nanostructured ITO electrodes was performed. The formation of 3-glycidoxypropyltrimethoxysilane (GOPTS) layers was detected by X-ray photoelectron spectroscopy. As an indirect method to confirm the presence of organosilane molecules on the ITO substrates, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were also carried out. Cyclic voltammograms of functionalized ITO electrodes presented lower reduction-oxidation peak currents compared with non-functionalized ITO electrodes. These results demonstrate the presence of the epoxysilane coating on the ITO surface. EIS showed that organosilane-functionalized electrodes present higher polarization resistance, acting as an electronic barrier for the electron transfer between the conductive solution and the ITO electrode. The results of these electrochemical measurements, together with the significant difference in the X-ray spectra between bare ITO and organosilane-functionalized ITO substrates, may point to a new exploitable oxide-based nanostructured material for biosensing applications. As a first step towards sensing, rapid functionalization of such substrates and their application to electrochemical analysis is tested in this work. Interestingly, oxide-based materials are highly integrable with the silicon chip technology, which would permit the easy adaptation of such sensors into lab-on-a-chip configurations, providing benefits such as reduced size and weight to facilitate on-chip integration, and leading to low-cost mass production of microanalysis systems.

ID: 30: HEPATITIS B VIRUS REACTIVATION IN AN INACTIVE CARRIER OF CHRONIC HBV AFTER THE INITIATION OF TREATMENT FOR TIBERCULOSIS

Case Presentation

A 32-year-old female with a history of chronic HBV in the inactive carrier state (HBV Surface Antigen (HBsAg) reactive, HBV Surface Antibody (anti-HBs) non-reactive, HBV Core Antibody (anti-HBc) reactive and IgM anti-HBc nonreactive) and tuberculous lymphadenitis presented to the emergency department with generalized weakness, dizziness, vomiting, and an unintentional 8 pound weight loss over the past month. She reported yellowing of the skin and light colored stools during this time. She had recently been started on Ethambutol, Levofloxacin and Capreomycin by her medical doctor for tuberculosis treatment. She denied use of any other medications or herbal supplements. She denied alcohol or illicit drug use. Her family history was unremarkable for liver disease. Physical examination was notable for scleral icterus but otherwise unremarkable. Her complete blood count and basic metabolic panel were within normal limits. HIV test was negative. Her hepatic function tests returned as follows; aspartate transaminase 1397 U/L, alanine transaminase 1234 U/L, gamma-glutamyl transpeptidase 107 IU/L, total bilirubin 2.3 mg/dL, and direct bilirubin 0.6 mg/dL. Hepatic function tests were normal 4 months prior to admission. Due to concern for drug-induced liver injury, her anti-tuberculosis medications were discontinued and she was started on intravenous N-acetyl cysteine with plans for further workup. An abdominal ultrasound revealed mild increased liver echogenicity and a polyp in the gall bladder. Hepatitis C Virus antibody was non-reactive. HBsAg was reactive, anti-HBs was non-reactive, and anti-HBc was reactive and IgM anti-HBc nonreactive. HBV DNA level was greater than 1,000,000,000 IU/mL consistent with a diagnosis of reactivation of HBV. The patient was started on tenofovir 300 mg PO daily ultimately the patient was discharged home. Follow up one month later revealed normalizing liver enzymes and an HBV DNA level of 471 IU/mL.

Discussion

HBV reactivation is diagnosed by an increase HBV DNA in chronic carrier with undetectable viral load or rise HBV DNA ≥10-fold increase in HBV DNA compared with baseline. Reactivation of HBV after starting chemotherapy or immunosuppressive medications is well described. Our case report is the first to describe HBV reactivation after starting Ethambutol, levofloxacin and Capreomycin against multidrug resistant mycobacterium tuberculosis.

Most studies reported that RIPE (Rifampin, Isoniazid, Pyrazinamide, and Ethambutol) tuberculosis therapy has shown no risk of HBV reactivation. One of the Multidrug resistant tuberculosis therapy agents which is levofloxacin can cause hepatoxicity but all previous studies did not report HBV reactivation.

Capreomycin can cause severe hepatotoxic injury especially if combined with other potential hepatotoxic, especially medications which interferes with metabolism of P450 as reported in our case with levofloxacin. That is could be explained hepatitis B reactivation after starting capreomycin, ethambutol and levofloxacin.

ID: 32: AGENESIS OF GALLBLADDER PRESENTING WITH OBSTRUCTIVE JAUNDICE

Case presentation

A 64 years old Female with no past medical or surgical history presented with yellowish discoloration of skin for two days duration associated with vague and non-radiating abdominal pain. Patient also endorses 8 pounds unintentional weight loss over the past 2–3 months.

On physical exam; scleral icterus and jaundiced skin were noted. Abdominal exam was non-significant, no rash or discoloration on inspection, abdomen is soft with no tenderness or rebound tenderness, murphy sign is negative, no organomegaly, and bowel sounds are positive upon auscultation. No renal costo-vertebral angle tenderness noted.

Laboratory testing was significant for: Alanine Aminotransferase (ALT) 448 U/L; Aspartate Aminotransferase (AST) 330 U/L, Alkaline Phosphatase (ALK) 225, Gamma-Glutamyltransferase (GGT) 530 IU/L, Leukocyte Dehydrogenase (LDH) 328 U/L, Total Protein 7.1; Albumin 4; Total Bilirubin 9.3 6 mg/dL and Direct Bilirubin 6.2 6 mg/dL. Hepatitis serology showed previously infected with Hepatitis A infection, HbA total AB+ and negative for Hepatitis B Surface Ag (HBsAg), Hepatitis B Core AB (HBcAb), Hepatitis B Surface AB (HBsAb) and Hepatitis C AB (HC ab). Tumor marker (CA 19–9) level of 27.

Imaging studies including chest X-Ray were normal without any acute cardio-pulmonary event. Abdominal-Pelvic CT scan with oral and IV contrasts showed moderate dilated intrahepatic & extra hepatic bile ducts consistent with common bile duct obstruction with no mass or stones seen. There is no liver lesion or mass. No pancreatic lesion or mass. No Gall bladder identified.

Abdominal MRCP was recommended, procedure showed intra-extra hepatic and common bile duct dilatation of maximum diameter of 1.3 cm. An ovoid filling defect was identified on distal common bile duct consistent with choledocholithiasis. No gallbladder was identified figure 1A.

Patient developed Fever 102 F with elevated WBC count of 15,000/mm3 for which she was started on IV Antibiotics empirically. Urgent ERCP was attempted and revealed marked dilatation in the region of the proximal common bile duct after contrast injection and ballooning. Proximal to the balloon there was a marked dilatation of the CBD and mild dilatation of central intra-bililary ducts. Intra-pancreatic portion of distal common bile duct is of normal caliber without filling defects. Successful extraction CBD biliary stone biliary stent placed. No gall bladder was identified figure 1B.

Patient improved over the course of one to two days with normal WBC count and normal liver enzymes. Total Bilirubin dropped to 1.5. Patient's abdominal pain resolved. She remains afebrile more than two days and was able to tolerate oral diet. Patient was discharged home and was seen one month later in gastroenterology clinic with normal liver function test.

Abstract ID: 32 Figure 1

ID: 27: K2 ABUSE SERIOUS THREAT TO NEW YORK STATE

Cannabis is one of the most commonly elicited substances abused. It is easily accessible, inexpensive, and the ultimate gateway drug. Synthetic cannabinoid has been known to be packaged under numerous trade names such as “K2, spice, AK-47, Geeked up, Smacked, and Green Giant..etc”. K2 Abuse has been rising more recently in New York State, especially among lower socioeconomic areas and among younger male individuals. Clinicians should be educated and awareness should be increased regarding patient presentation, treatment, as well as management. Although, treatment is ultimately supportive therapy, long term management to prevent future abuse is of prime importance. Death is rare but there can be serious risks associated with K2 abuse.

Case presentation

Patient is a 36-year-old male with unknown PMH who presented with bizarre behavior and anxiety. Patient was uncooperative and portraying repetitive tangential thoughts. He was found agitated, screaming “I am king of the world, and I feel good”. The patient admits to waking up this morning and smoking marijuana and his last memory since then was being in the ambulance. The patient denies any psychiatric medical history but is unable to provide any further details. The patient's family reports unusual behavior in the past few days such as religious connotations, nonsensical rantings, and repetitive thoughts causing them to contact emergency medical services. The family also admits to depressive episodes as well as suicidal ideations found in his personal written lyrics. He admits to drinking 1 pint of various types of liquor well as 6+ beers per day for >15 years. He denies any history of smoking, although he does smoke marijuana daily as per family.

On physical exam his vital signs were normal. Patient was tearful and exhibiting repetitive thoughts, despite having a somnolent general affect. The rest of the physical exam was within normal limits. Patient received intravenous crystalloid fluids, Haldol 5 mg IV, and Benzodiazepine IV. Pertinent laboratory findings is significant for elevated lactate 3.4, hypokalemia 2.2, and an elevated ammonia 53. Other laboratory findings were within normal limits. CXR and Head CT showed no significant findings and EKG was within normal limits.

Hospital course complicated with aspiration pneumonia. Patient received a full course of antibiotic therapy. Blood and urine culture showed no growth through admission. Social worker and case manager were involved and patient was offered referral to chemical dependency programs which he refused. Patient was discharged in stable condition and asked to follow up with primary care physician.

Discussion

The recreational use of synthetic cannabinoids such as K2 has been on the rise especially in younger male individuals and in lower socioeconomic status neighborhoods. In turn, the number of admissions secondary to acute intoxication has been increasing in hospitals all over the nation. More recently, since the advent of synthetic cannabinoids, there has been two reported confirmed deaths in New York City associated with K2 abuse. This can be attributed the drugs widespread accessibility. Synthetic marijuana has been legally available in the internet, local smoke shops, and even convenience stores. K2 has been advertised as the new, legal, and more cost effective way to get “high”. The popularity of this new class of drug “fad” is increasing in popularity as an alternative to marijuana and will continue to be a growing health concern.

The use of K2 and other synthetic forms of recreational substances has become an escalating problem in many institutions nationwide. Increasing awareness will allow for improved preparedness as well as provide further data on this situation. .

ID: 29: INVASIVE LIVER ABSCESS SYNDROME IN NORTH AMERICA

Case presentation

This is a 25 years old Pilipino male with no past medical history who presented with fever, rigors, fatigue and night sweats for 3 days. His symptoms progressively getting worse which made him seek medical attention. Patient travelled to Philippines five months ago which he stayed for a month.

Upon presentation, patient was febrile with Temp 104 F and tachycardic 139 BPM, BP113/76. He appeared to be diaphoretic and tachypnic on physical exam. Abdomen was soft and non-tender, no hepatomegaly or splenomegaly on palpation.

Pertinent laboratory findings included leukocytosis of 14,000 and bandemia 12, lactate of 3.6, Liver function tests – AST 62/ALT 61/ ALK 52 GGT 48 LDH 347 Total bilirubin 2.5 and direct Bilirubin 1.6 – Hepatitis serology revealed immunity against Hepatitis B (HBV). Coagulation panel and renal function were normal. Abdominal imaging revealed diffuse hepatic changes suggestive of cirrhosis and complex avascular slightly lobulated hypoechoic mass with mild posterior enhancement measuring 7.2×6.8 cm noted in the anteromedial portion of posterior segment of the right lobe (figure 1A and B).

Further tests including HIV testing, urine analysis, blood and urine cultures, Echinococcosis and Amoebic serology were none revealing. Empirical broad spectrum antibiotics with 3rd generation cephalosporin and metronidazole for possible amoebic verus pyogenic liver abscess.

After 3–4 days from admission date, he developed persistent rigors, tachycardia, and appeared to have respiratory distress which required an urgent intubation for acute respiratory failure and transferred to ICU. Urgent drainage attempted for pyogenic liver abscess. Abscess fluid culture was positive for Klebsiella pneumonia.

Patient received an intravenous ceftriaxone 2 gm daily with continuous Jackson-Pratt liver drain suction for 3–4 weeks which was curative with resolution and decrease in the size of liver abscess on repeat imaging (figure 1c).

Discussion

Klebsiella pneumoniae, a member of the Enterobacteriaceae family, is a pathogen with worldwide distribution. Most community-acquired Klebsilla pneumoniae infections cause pneumonia or urinary tract infections. Invasive liver abscess syndrome is very rare in western countries. For the past 2 decades, a distinct clinical syndrome has been emerging in Southeast Asia that is characterized by bacteremia, liver abscesses, and metastatic infections. In the past decade, few patients were diagnosed as having a liver abscess caused by K pneumoniae in two case series in the USA.

Most community-acquired Klebsilla pneumoniae infections cause pneumonia or urinary tract infections. Invasive liver abscess syndrome is very rare in western countries. Clinicians should be aware about invasive klebsiella pneumonia liver abscess especially in patients with Asian background presented with liver abscess failed the treatment with antibiotics. Treatment of invasive klebsiella pneumonia liver abscess requires dual approach medical and surgical as we approached our patient which he subsequently improved after CT-guided liver abscess drainage and four weeks of antibiotics therapy.

Abstract ID: 29 Figure 1

ID: 31: VIRAL CYTOMEGALOVIRUS IN GRANULOMATOSIS WITH POLYANGIITIS

Introduction

Cytomegalovirus (CMV) infection of the gastrointestinal (GI) tract commonly involves the esophagus, Stomach and colon. It frequently affects immune-compromised patients with Human immune deficiency (HIV), malignancy, organ transplant recipients, those on immunosuppressive medications or long standing steroid therapy. The most common symptoms include nausea, vomiting, dysphagia, odynophagia, abdominal pain, tenesmus and hematochezia. The endoscopic findings of CMV infection are variable from simple erosion, ulceration to pseudo-tumor formation. We present a rare case of CMV gastritis in an asymptomatic patient with history of Granulomatosis with Polyangiitis on immunosuppressant.

Case presentation

A 62-year-old Hispanic female with past medical history of Granulomatosis with Polyangiitis, hypertension and End Stage Renal Disease on hemodialysis, was evaluated for chronic anemia. Review of symptoms was negative for diarrhea, nausea, vomiting, abdominal pain, melena or hematochezia. Her medications included Furosemide, Amlodipine, Metoprolol, Prednisone and Cyclophosphamide. Physical exam was remarkable for pallor, normal oropharynx and negative for lymphadenopathy. Abdomen was soft, non-tender, non-distended, with normal bowel sounds. Rectal exam revealed external hemorrhoids, guaiac positive brown stools.

Pertinent laboratory data included Hemoglobin/ Hematocrit (7.9 g/dL/23.5%), Mean Corpuscular Volume of 102fL, and Serum Albumin 3.1 gm/dL. Iron studies showed normal Iron-76 mcg/dL with low total iron binding capacity (TIBC)-195. Colonoscopy was significant only for diverticulosis. Esophagogastroduodenoscopy (EGD) revealed multiple erosions in the gastric antrum along with small non-bleeding clean based ulcer (Forrest class III). Biopsy of the gastric antrum showed intra-nuclear inclusions bodies (“owl eye”) with positive immune staining for CMV antigen pathognomonic for CMV gastritis. Patient received intravenous Ganciclovir treatment for one week followed by one week of oral ValGanciclovir.

Discussion

There have been reported cases of symptomatic CMV gastritis. However, CMV gastritis in our case patient was asymptomatic. CMV infection can involve any part of the gastrointestinal tract with symptoms usually include nausea, vomiting, dysphagia, odynophagia, abdominal pain, tenesmus and hematochezia (1). It frequently affects immune-compromised patients with Human Immunodeficiency Virus, malignancy, organ transplant recipients, those on immunosuppressive medications or long standing steroid therapy but can affect immunocompetent individuals as well. CMV infection of the gastrointestinal tract commonly involves the esophagus, stomach and colon. The endoscopic findings of CMV infection are variable from simple erosion, ulceration to pseudo-tumor formation. In patients with persistent immune deficiency such as granulomatosis with polyangiitis, endoscopic evaluation is a reasonable approach to prevent potential serious complications such as gastrointestinal hemorrhage, progressive intestinal disease and death.

Structural parameters effect on the electrical and electroluminescence properties of silicon nanocrystals/SiO2 superlattices

The effect of the oxide barrier thickness (tSiO2) reduction and the Si excess ([Si]exc) increase on the electrical and electroluminescence (EL) properties of Si-rich oxynitride (SRON)/SiO2 superlattices (SLs) is investigated. The active layers of the metal-oxide-semiconductor devices were fabricated by alternated deposition of SRON and SiO2 layers on top of a Si substrate. The precipitation of the Si excess and thus formation of Si nanocrystals (NCs) within the SRON layers was achieved after an annealing treatment at 1150 °C. A structural characterization revealed a high crystalline quality of the SLs for all devices, and the evaluated NC crystalline size is in agreement with a good deposition and annealing control. We found a dramatic conductivity enhancement when the Si content is increased or the SiO2 barrier thickness is decreased, due to a larger interaction of the carrier wavefunctions from adjacent layers. EL recombination dynamics were studied, revealing radiative recombination decay times of the order of tens of microseconds. Lower lifetimes were found at higher [Si]exc, attributed to exciton confinement delocalization, whereas intermediate barrier thicknesses present the slowest decay. The electrical-to-light conversion efficiency increases monotonously at thicker barriers and smaller Si contents. We ascribe these effects mainly to free carriers, which enhance carrier transport through the SLs while strongly quenching light emission. Finally, the combination of the different results led us to conclude that tSiO2 ∼ 2 nm and [Si]exc from 12 to 15 at% are the ideal structure parameters for a balanced electro-optical response of Si NC-based SLs.

Er-doped light emitting slot waveguides monolithically integrated in a silicon photonic chip

An integrated erbium-based light emitting diode has been realized in a waveguide configuration allowing 1.54 μm light signal routing in silicon photonic circuits. This injection device is based on an asymmetric horizontal slot waveguide where the active slot material is Er(3+) in SiO2 or Er(3+) in Si-rich oxide. The active horizontal slot waveguide allows optical confinement, guiding and lateral extraction of the light for on-chip distribution. Light is then coupled through a taper section to a passive Si waveguide terminated by a grating which extracts (or inserts) the light signal for measuring purposes. We measured an optical power density in the range of tens of μW/cm(2) which follows a super-linear dependence on injected current density. When the device is biased at high current density, upon a voltage pulse (pump signal), free-carrier and space charge absorption losses become large, attenuating a probe signal by more than 60 dB/cm and thus behaving conceptually as an electro-optical modulator. The integrated device reported here is the first example, still to be optimized, of a fundamental block to realize an integrated silicon photonic circuit with monolithic integration of the light emitter.

Electrical pump & probe and injected carrier losses quantification in Er doped Si slot waveguides

Electrically driven Er(3+) doped Si slot waveguides emitting at 1530 nm are demonstrated. Two different Er(3+) doped active layers were fabricated in the slot region: a pure SiO(2) and a Si-rich oxide. Pulsed polarization driving of the waveguides was used to characterize the time response of the electroluminescence (EL) and of the signal probe transmission in 1 mm long waveguides. Injected carrier absorption losses modulate the EL signal and, since the carrier lifetime is much smaller than that of Er(3+) ions, a sharp EL peak was observed when the polarization was switched off. A time-resolved electrical pump & probe measurement in combination with lock-in amplifier techniques allowed to quantify the injected carrier absorption losses. We found an extinction ratio of 6 dB, passive propagation losses of about 4 dB/mm, and a spectral bandwidth > 25 nm at an effective d.c. power consumption of 120 μW. All these performances suggest the usage of these devices as electro-optical modulators.

[Hemodynamic effects of intravenous omeprazole in critically ill children]

INTRODUCTION

Critical patients usually have hemodynamic disturbances which may become worse by the administration of some drugs. Omeprazole is a drug used in the prophylaxis of the gastrointestinal bleeding in these patients, but its cardiovascular effects are unknown. The objective was to study the hemodynamic changes produced by intravenous omeprazole in critically ill children and to find out if there are differences between two different doses of omeprazole.

MATERIAL AND METHODS

A randomized prospective observational study was performed on 37 critically ill children aged from 1 month to 14 years of age who required prophylaxis for gastrointestinal bleeding. Of these, 19 received intravenous omeprazole 0.5mg/kg every 12 hours, and 18 received intravenous omeprazole 1mg/kg every 12 hours. Intravenous omeprazole was administered in 20 minutes by continuous infusion pump. Heart rate, systolic, diastolic and mean arterial blood pressure, central venous pressure and ECG were recorded at baseline, and at 15, 30, 60 and 120 minutes of the infusion.

RESULTS

There were no significant changes in the electrocardiogram, heart rate, blood pressure and central venous pressure. No patients required inotropic therapy modification. There were no differences between the two doses of omeprazole.

CONCLUSIONS

Intravenous omeprazole administration of 0.5mg/kg and 1mg/kg is a hemodynamically safe drug in critically ill children.

Erbium emission in MOS light emitting devices: from energy transfer to direct impact excitation

The electroluminescence (EL) at 1.54 μm of metal–oxide–semiconductor (MOS) devices withEr3C ions embedded in the silicon-rich silicon oxide (SRSO) layer has been investigated under different polarization conditions and compared with that of erbium doped SiO2 layers. EL time-resolved measurements allowed us to distinguish between two different excitation mechanisms responsible for the Er3C emission under an alternate pulsed voltage signal (APV). Energy transfer from silicon nanoclusters (Si-ncs) to Er3C is clearly observed at low-field APV excitation. We demonstrate that sequential electron and hole injection at the edges of the pulses creates excited states in Si-ncs which upon recombination transfer their energy to Er3C ions. On the contrary, direct impact excitation of Er3C by hot injected carriers starts at the Fowler–Nordheim injection threshold (above 5 MV cm(-1)) and dominates for high-field APV excitation.

Blue-green to near-IR switching electroluminescence from Si-rich silicon oxide/nitride bilayer structures

Blue-green to near-IR switching electroluminescence (EL) has been achieved in a metal-oxide-semiconductor light emitting device, where the dielectric has been replaced by a Si-rich silicon oxide/nitride bilayer structure. To form Si nanostructures, the layers were implanted with Si ions at high energy, resulting in a Si excess of 19%, and subsequently annealed at 1000 °C. Transmission electron microscopy and EL studies allowed ascribing the blue-green emission to the Si nitride related defects and the near-IR band with the emission of the Si-nanoclusters embedded into the SiO(2) layer. Charge transport analysis is reported and allows for identifying the origin of this two-wavelength switching effect.

Metal-nitride-oxide-semiconductor light-emitting devices for general lighting

The potential for application of silicon nitride-based light sources to general lighting is reported. The mechanism of current injection and transport in silicon nitride layers and silicon oxide tunnel layers is determined by electro-optical characterization of both bi- and tri-layers. It is shown that red luminescence is due to bipolar injection by direct tunneling, whereas Poole-Frenkel ionization is responsible for blue-green emission. The emission appears warm white to the eye, and the technology has potential for large-area lighting devices. A photometric study, including color rendering, color quality and luminous efficacy of radiation, measured under various AC excitation conditions, is given for a spectrum deemed promising for lighting. A correlated color temperature of 4800K was obtained using a 35% duty cycle of the AC excitation signal. Under these conditions, values for general color rendering index of 93 and luminous efficacy of radiation of 112 lm/W are demonstrated. This proof of concept demonstrates that mature silicon technology, which is extendable to low-cost, large-area lamps, can be used for general lighting purposes. Once the external quantum efficiency is improved to exceed 10%, this technique could be competitive with other energy-efficient solid-state lighting options.

DC and AC electroluminescence in silicon nanoparticles embedded in silicon-rich oxide films

Electroluminescent properties of silicon-rich oxide (SRO) films were studied using metal oxide semiconductor-(MOS)-like devices. Thin SRO films with 4 at.% of silicon excess were deposited by low pressure chemical vapour deposition followed by a thermal annealing at 1100 degrees C. Intense continuous visible and infrared luminescence has been observed when devices are reversely and forwardly bias, respectively. After an electrical stress, the continuous electroluminescence (EL) is quenched but devices show strong field-effect EL with pulsed polarization. A model based on conductive paths--across the SRO film--has been proposed to explain the EL behaviour in these devices.

Towards population inversion of electrically pumped Er ions sensitized by Si nanoclusters

This study reports the estimation of the inverted Er fraction in a system of Er doped silicon oxide sensitized by Si nanoclusters, made by magnetron sputtering. Electroluminescence was obtained from the sensitized erbium, with a power efficiency of 10(-2)%. By estimating the density of Er ions that are in the first excited state, we find that up to 20% of the total Er concentration is inverted in the best device, which is one order of magnitude higher than that achieved by optical pumping of similar materials.

Si-nanocrystal-based LEDs fabricated by ion implantation and plasma-enhanced chemical vapour deposition

An in-depth study of the physical and electrical properties of Si-nanocrystal-based MOSLEDs is presented. The active layers were fabricated with different concentrations of Si by both ion implantation and plasma-enhanced chemical vapour deposition. Devices fabricated by ion implantation exhibit a combination of direct current and field-effect luminescence under a bipolar pulsed excitation. The onset of the emission decreases with the Si excess from 6 to 3 V. The direct current emission is attributed to impact ionization and is associated with the reasonably high current levels observed in current-voltage measurements. This behaviour is in good agreement with transmission electron microscopy images that revealed a continuous and uniform Si nanocrystal distribution. The emission power efficiency is relatively low, approximately 10(-3)%, and the emission intensity exhibits fast degradation rates, as revealed from accelerated ageing experiments. Devices fabricated by chemical deposition only exhibit field-effect luminescence, whose onset decreases with the Si excess from 20 to 6 V. The absence of the continuous emission is explained by the observation of a 5 nm region free of nanocrystals, which strongly reduces the direct current through the gate. The main benefit of having this nanocrystal-free region is that tunnelling current flow assisted by nanocrystals is blocked by the SiO2 stack so that power consumption is strongly reduced, which in return increases the device power efficiency up to 0.1%. In addition, the accelerated ageing studies reveal a 50% degradation rate reduction as compared to implanted structures.

Quantum dot networks in dielectric media: from compact modeling of transport to the origin of field effect luminescence

We present a compact model of transport through a random distribution of interacting quantum dots embedded in a dielectric matrix. The model is based on a network of interconnected tunnel junctions sandwiched between two electrodes, resulting in a system of nonlinear differential equations which is numerically solved for a given time-dependent voltage applied to the gate. The capacitance matrix, electron/hole tunneling currents and the effective area of conduction between quantum dots are calculated at each integration step. The transport properties obtained from the model are successfully validated against experimental data for a silicon nanocrystal basic MOS cell, showing its potential applicability to non-volatile memories. In addition, through a simple rate equation, the calculated charge flux tunneling or impacting the nanocrystals is converted into electroluminescence. In this regard, we discuss the origin of the recently reported field effect luminescence in silicon nanocrystals. It is found that the idea of quantum-confined exciton creation through sequential injection of opposite sign carriers is in contradiction with the model and with the electron/hole tunneling time ratio obtained through the WKB approximation due to the difference in the electron and hole potential barrier heights. We show how our model of transport, along with a rate equation with the reported value for the absorption cross section for electrical excitation of silicon nanocrystals (approximately 10(-14) cm(2)), is in good agreement with experimental data obtained under pulsed excitation, without requiring further assumptions such as the formation of excitons from hole tunneling into electron-charged nanocrystals, revealing impact excitation of electrons/holes from the same substrate as the physical origin of the observed field effect luminescence.

Auger quenching-based modulation of electroluminescence from ion-implanted silicon nanocrystals

We describe high-speed control of light from silicon nanocrystals under electrical excitation. The nanocrystals are fabricated by the ion implantation of Si(+) in the 15 nm thick gate oxide of a field effect transistor at 6.5 keV. A characteristic read-peaked electroluminescence is obtained either by DC or AC gate excitation. However, AC gate excitation is found to have a frequency response that is limited by the radiative lifetimes of silicon nanocrystals, which makes impossible the direct modulation of light beyond 100 kb s(-1) rates. As a solution, we demonstrate that combined DC gate excitation along with an AC channel hot electron injection of electrons into the nanocrystals may be used to obtain a 100% deep modulation at rates of 200 Mb s(-1) and low modulating voltages. This approach may find applications in biological sensing integrated into CMOS, single-photon emitters or direct encoding of information into light from Si-nc doped with erbium systems, which exhibit net optical gain. In this respect, the main advantage compared to conventional electro-optical modulators based on plasma dispersion effects is the low power consumption (10(4) times smaller) and thus the inherent large scale of integration. A detailed electrical characterization is also given. An Si/SiO(2) barrier change from Φ(b) = 3.2 to 4.2 eV is found while the injection mechanism is changed from Fowler-Nordheim to channel hot electron, which is a clear signature of nanocrystal charging and subsequent electroluminescence quenching.

Permeation by zinc of bovine chromaffin cell calcium channels: relevance to secretion

Zn2+ increased the rate of spontaneous release of catecholamines from bovine adrenal glands. This effect was Ca2+ independent; in fact, in the absence of extracellular Ca2+, the secretory effects of Zn2+ were enhanced. At low concentrations (3-10 microM), Zn2+ enhanced the secretory responses to 10-s pulses of 100 microM 1,1-dimethyl-4-phenylpiperazinium (DMPP, a nicotinic receptor agonist) or 100 mM K+. In the presence of DMPP, secretion was increased 47% above controls and in high-K+ solutions, secretion increased 54% above control. These low concentrations of Zn2+ did not facilitate the whole-cell Ca2+ (ICa) or Ba2+ (IBa) currents in patch-clamped chromaffin cells. Higher Zn2+ concentrations inhibited the currents (IC50 values, 346 microM for ICa and 91 microM for IBa) and blocked DMPP- and K(+)-evoked secretion (IC50 values, 141 and 250 microM, respectively). Zn2+ permeated the Ca2+ channels of bovine chromaffin cells, although at a much slower rate than other divalent cations. Peak currents at 10 mM Ba2+, Ca2+, Sr2+ and Zn2+ were 991, 734, 330 and 7.4 pA, respectively. Zn2+ entry was also evidenced using the fluorescent Ca2+ probe fura-2. This was possible because Zn2+ causes an increase in fura-2 fluorescence at the isosbestic wave-length for Ca2+, i.e. 360 nm. There was a slow resting entry of Zn2+ which was accelerated by stimulation with DMPP or high-K+ solution. The entry of Zn2+ was concentration dependent, slightly antagonized by 1 mM Ca2+ and completely blocked by 5 mM Ni2+. The entry of Ca2+ evoked by depolarization with high-K+ solution was antagonized by Zn2+.(ABSTRACT TRUNCATED AT 250 WORDS)

o-Iodosobenzoic oxidation and cleavage of myosin subfragment 1

1. o-Iodosobenzoic acid (IOB) caused the formation of a disulfide bridge between SH1 and SH2 groups of myosin SF1 rendering inactive its ATPase activity. 2. IOB at high concentrations provoked fragmentation of SF1 at its tryptophan residues. 3. The main fragmentation point was located at 15 K from the amino terminus of the myosin heavy chain. 4. Actin was not fragmented by IOB. It protected SF1 tryptophans from IOB attack. 5. These results suggest a possible use of IOB as a reagent to study protein tryptophan under nondenaturing conditions.

The source of calcium for muscarinic-mediated catecholamine release from cat adrenals

1. In view of conflicting reports on the source of Ca2+ needed to trigger the secretory response to muscarinic stimulation of chromaffin cells, we have reinvestigated this problem in the cat adrenal gland perfused with oxygenated Krebs solution at 37 degrees C. Above a basal rate of secretion of 60 ng/30 s of total catecholamines, 5 s pulses of 100 microM-methacholine evoked 10-fold increases of secretion. This response was entirely mediated by muscarinic receptors, since it was blocked by submicromolar concentrations of atropine but not by d-tubocurarine. 2. Delayed application of methacholine pulses after Ca2+ removal from the Krebs solution led to a progressive decline of the secretory response with a t1/2 of 15 s. Secretion was blocked by 85% after a 60 s period of Ca2+ deprivation; extension of the external Ca2+ (Ca2+o) wash-out period up to 5 min did not further reduce the secretory response. 3. When EGTA (1 mM) was present in the 0 Ca2+ solution, the rate of decline of methacholine responses, as a function of the time of exposure to 1 mM-EGTA, was similar to that obtained with 0 Ca2+. Again, about 15-20% of the secretory response was resistant even to prolonged periods of washing out with the 0 Ca(2+)-EGTA solution. 4. The Ca2+ ionophore ionomycin (1 microM) first decreased and then accelerated the rate of decline of methacholine responses upon Ca2+o wash-out. Particularly relevant is the complete blockade of secretion when the Ca2+o wash-out is performed in the presence of this ionophore. This suggests the existence of a small intracellular functional Ca2+ store sensitive to ionomycin. 5. After abolition of the secretory response through 60 s periods of wash-out with a 0 Ca(2+)-EGTA-ionomycin solution, followed by delayed 5 s methacholine pulses after Ca2+o reintroduction, the glands instantly recovered their normal muscarinic-mediated secretory response. This suggests that upon muscarinic stimulation, Ca2+ required by the secretory machinery to trigger such response immediately comes from extracellular sources. How Ca2+o gains the cell interior so fast upon muscarinic stimulation is unknown; we have previously suggested that the muscarinic receptor in the cat chromaffin cell could be coupled to an ionophore channel which might be chemically activated by muscarinic agonists. 6. Secretory responses to 5 s pulses with 35 or 100 mM-K+ declined faster (t1/2 of 3 and 6 s, respectively) upon Ca2+o wash-out than those of methacholine.(ABSTRACT TRUNCATED AT 400 WORDS)

Voltage-dependent inactivation of catecholamine secretion evoked by brief calcium pulses in the cat adrenal medulla

1. Inactivation by voltage changes of 45Ca2+ uptake into and catecholamine release from cat adrenal glands perfused at a high rate (4 ml/min) at 37 degrees C with oxygenated Krebs-Tris solution has been studied. Experimental conditions were selected so that adrenal medullary chromaffin cells were depolarized for different time periods and with various K+ concentrations in the absence of Ca2+, prior to the application of 0.5 mM-Ca2+ for 10 s in the presence of 118 mM-K+ to test the rate of secretion (the 'Ca2+ pulse'). 2. Application of the Ca2+ pulse after perfusion with 5.9 mM-K+ led to a 100-fold increase of the basal rate of secretion. However, if the Ca2+ pulse was preceded by a 10 min period of perfusion with 118 mM-K+, the secretory response was decreased by over 80%. 3. Inactivation of secretion starts 10-30 s after high-K+ perfusion and is completed 2-5 min thereafter. Inactivation is readily reversed by perfusing the glands with normal K(+)-containing solution; the recovery phenomenon is also gradual and time-dependent, starting 30 s after repolarization and ending 300 s thereafter. 4. The rate of inactivation is much slower at 35 than at 118 mM-K+, suggesting that the process is strongly dependent on voltage. 5. Like catecholamine release, Ca2+ uptake into adrenal medullary chromaffin cells is inactivated in a voltage-dependent manner. This, together with the fact that Cd2+ blocked secretion completely and inactivation was seen equally using Ca2+ or Ba2+ as secretagogues, suggests that inactivation of a certain class of voltage-dependent Ca2+ channels is responsible for the blockade of secretion. Such channels must be slowly inactivated by voltage and highly sensitive to dihydropyridines, since (+)PN200-110 (an L-type Ca2+ channel blocker) enhanced the rate of inactivation and (+/-)Bay K 8644 (an L-type Ca2+ channel activator) prevented it, indicating that they might belong to L-subtype Ca2+ channels. 6. The effects of (+/-)Bay K 8644 (100 nM) were seen on both the voltage and time dependence of inactivation. At a moderate depolarization (35 mM-K+), the drug prevented inactivation and caused potentiation of secretion which developed gradually; at strong depolarizations (118 mM-K+), Bay K 8644 prevented the time-dependent development of inactivation. (+)PN200-110 (30 nM) did not suddenly decrease catecholamine release at the earlier times of depolarization; what the drug did was to accelerate the normal rate of inactivation induced by depolarization.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of injected glucagon or fatty acids on mitochondrial ATPase

The intraperitoneal injection of glucagon or the intravenous infusion of oleic acid provoked a rapid change in the properties of rat liver mitochondrial ATPase. When mitochondria of treated animals were isolated an increase in ATPase activity was observed as well as a modification on the response to activators and inhibitors and to the sulfhydryl reagent N-ethylmaleimide. Sensitivity to the activators dinitrophenol or bicarbonate decreased, whereas the sensitivity to inhibitors KOCN and KSCN increased, and an inhibitory effect of N-ethylmaleimide appeared. These effects gradually disappeared when mitochondrial suspensions were kept at 10 degrees C, and after approximately 5 h ATPase from mitochondria of treated and control animals behaved almost identically. If the oxidizing agent dichlorophenolindophenol was added to the isolated mitochondria the effects induced by glucagon or fatty acids immediately disappeared. The activation caused by the reducing agent dithionite on ATPase activity in mitochondria from control animals did not take place in fresh mitochondria from treated animals; however, dithionite was effective in these latter mitochondria when tested 5 h later after keeping them at 10 degrees C. The intravenous infusion of oleic acid produced a rise in the [NADH]/[NAD+] and [Total flavin]/[FAD] ratios in mitochondria, and values double as those in the controls were observed; these values gradually approached those of the control mitochondria when kept at 10 degrees C; after 24 h these ratios were the same in mitochondrial suspensions from treated and nontreated animals. These results suggest that the modification of the properties of mitochondrial ATPase induced by glucagon or fatty acids might be mediated by a change in the mitochondrial redox state.