PubMed Health⌕ Search

Biomedical subjects

G Konstantinidis

Publications and source records attributed to G Konstantinidis.

14 recordsLinked to original sources

Potassium selective chemically modified field effect transistors based on AlGaN/GaN two-dimensional electron gas heterostructures.

We investigate the use of the AlGaN/GaN high electron mobility transistor (HEMT) as a novel transducer for the development of ion-selective chemically modified HEMT sensors (ChemHEMTs). For this, polyvinyl chloride (PVC) membrane doped with ion-selective ionophores is deposited onto the area of the gate for the chemical recognition step, while the AlGaN/GaN HEMT is used as the transducer. In particular, the use of a valinocycin doped membrane with thickness of 50 microm generates a sensor with excellent analytical characteristics for the monitoring of K(+). The K(+)-ChemHEMT has sensitivity of 52.4 mV/pK(+)in the linear range of 10(-5) to 10(-2)M, while the detection limit is in the order of 3.1 x 10(-6)M. Also, the sensor shows selectivity similar to valinomycin-based ISEs, while the signal stability over time and the measurement to measurement reproducibility are very good.

Aluminum Compounds↗

Magnetic response of split-ring resonators in the far-infrared frequency regime.

We report on the fabrication, through photolithography techniques, and the detailed characterization, through direct transmission measurements, of a periodic system composed of five layers of photolithographically aligned micrometer-sized Ag split-ring resonators (SRRs). The measured transmission spectra for propagation perpendicular to the SRRs plane show a gap around 6 THz for one of the two possible polarizations of the incident electric field; this indicates the existence of a magnetic resonance, which is verified by detailed theoretical analysis. To our knowledge this is the first time that a system of more than one layer of micrometer-sized SRRs has been fabricated. The measured optical spectra of the Ag microstructure are in very good agreement with the corresponding theoretical calculations.

Journal Article↗

VR educational environments for learning in Europe.

Currently education is either class tutoring based or self-learning based using books, audio tapes, video tapes, CD-ROMs. None of the above media has been proven the best and the unique tool for education. An example presented is the creation of a virtual world in which children can learn by interacting with foreign children without leaving their environment. This approach is being implemented under a Joint Multimedia taskforce project. (VIRLAN).

Child↗

[Congenital leukemia--personal experience].

Congenital leukemia is a very rare form of acute leukemia and up to now more than 100 well documented cases have been published. Symptoms and signs of the disease may be faintly differentiated and be a differential diagnostic problem for a long period of time in comparison to other common diseases of the newborn. This is a case report on two newborns with congenital leukemia. It was an acute non-lymphoblastic leukemia in the first case, and acute lymphoblastic leukemia in the second. In both cases there were nonspecific manifestations of the disease (no weight gaining, hemorrhagic enterocolitis). In both cases polyhemotherapeutic protocols were performed. In the first case only partial remission occurred and death occurred during the hemathologic recidive of the disease. In the second case, 15 months after the diagnose of congenital leukemia has been established, complete remission is in course.

Humans↗

[Infiltration of the testes in acute lymphoblastic leukemia in childhood--personal experience].

According to various literature data testicular leukemic infiltration occurs in 5-40%, while the mean time for testicular recurrence is 36 months. Hematologic recurrence usually occurs in the interval from 1-6 months. Although testicular leukemic infiltration clinically occurs as an isolated recurrence of leukemia, it usually presents only a clearly marked spot in the general recurrence of the disease. It is a painless enlargement of one or both testes. The diagnosis is made ultrasonographically and by histopathologic examination of the biopsied testicle tissue. This paper deals with 4 patients with acute lymphoblastic leukemia and testicular recurrence. In 2 patients the testicular recurrence occurred as a part of the general recurrence of the disease, while in the other 2 at the time of testicular recurrence diagnosis, the bone marrow was regular. All 4 patients were treated with combined radiotherapy and chemotherapy, in 3 cases successfully.

Child↗

[Congenital methemoglobinemia].

This is a report on a case of inborn methemoglobinemia. The disease has been diagnosed in the first week of infant's life. At first it was assumed it was a case of inborn heart defect because of expressed generalized cyanosis, but very soon it was excluded. Values of methemoglobin were extremely high, so three days after birth hereditary methemoglobinemia was diagnosed. Our diagnosis was confirmed by disappearing of cyanosis after ascorbic acid was applied, by values of methemoglobin reductase of the infant and its father, anamnestic data revealing that mother had had temporary cyanosis during her infancy, and satisfactory clinical course of illness.

Diagnosis, Differential↗

[Adolescent mortality in Vojvodina].

The aim of the study was to determine the mortality rate of adolescents in Vojvodina and analyze the most common causes of their death. For the analysis we used the data from the Health Statistics Annual and from individual statistics reports. The observation period was between 1986 and 1988. The mean mortality rate of the adolescents in Vojvodina for that period was 6.7/100000. The leading cause of death (54.74%) was accidents (mostly traffic accidents), malignant diseases and finally cardiovascular diseases. The mortality rate was higher among older adolescents. It was 4 times higher in the outpatients compared to the inpatients and caused either by the severity of the injury and/or inadequately handled injuries. For the highest percentage of the accidents responsible were external factors among which risk behavior of the young played a significant role. The task of the society is to take appropriate measures which would reduce the role of the external factors as a cause of death.

Adolescent↗

[Drug poisoning in children in Vojvodina].

Epidemiological characteristics of acute drug poisoning in children were investigated over a period of two years (1988-1989). The total number of poisonings was 450. Among causes of poisoning psychopharmaca, especially benzodiazepine, came first (33.3%). They were followed by drugs affecting the nervous system (9.1%), usually by analgoantipyretics, and by drugs affecting the cardiovascular system (7.8%). In 10.6% of the cases poisoning was due to two or more drugs. In 12.3% of the poisonings drug was unknown. Sodium fluoride was the most frequent single cause of acute poisoning. The average age of the poisoned children was 5.1 years. Poisoning with drugs was more frequent among girls than among boys (55:45%). In more than half poisoning accidents there was no one present when poisoning occurred. A major number of poisonings were an attention-getting gesture or a suicidal attempt. There were 11 cases of repeated poisoning with the same drug.

Adolescent↗

[Acute poisoning in children in Vojvodina].

The paper deals with acute poisoning among children in Voivodina from the point of view of frequency, characteristics and regional differences. The histories of the poisoned children aged 0-16 years, who were hospitalized in all eleven in-patient clinics in Voivodina during 1985, 1986, 1988 and 1989, were analysed. Acute poisoning in children accounted for 2.4% of hospital morbidity. The most frequent causes of poisoning were medicaments (60.6%), pesticides (8.7%), ethanol (6.34%), organic solvents (5.7%) and all other substances (18.35%). Poisoning occurred more often among boys than among girls (53.47%). The average age of the poisoned was 4.7 years. The average age of the poisoned girls was significantly higher than that of the poisoned boys. Poisoning usually took place during a "game", but a major number of poisonings was suicidal. There were great regional differences as regards the course of poisoning, sex and average age of the poisoned, circumstances of poisoning and period in which it happened. The children's age and circumstances of poisoning point to the absence of preventive measures or their failure.

Acute Disease↗

[Morbidity and mortality in adolescents in Vojvodina].

Adolescents. The aim of this study was to analyze the morbidity and mortality of adolescents in SAP Vojvodina. For the analysis, data was used from the statistical yearbooks on the health protection of the population and data from individual statistical reports. The period from 1980 to 1986 was observed. In order to more easily follow the morbidity and mortality, and for a better insight into the pathology, the adolescents were divided into 2 age groups; the younger one from 10 to 14 years of age, and the older one from 15 to 19. Adolescents in Vojvodina mostly ail from respiratory diseases, illnesses of the digestive tract, and infective diseases, but a significant role in the morbidity is also taken by injuries and poisoning. Adolescents of the age group from 10 to 14 years, get sick more often. In SAP Vojvodina 156 adolescents die annually. The highest mortality is due to injuries and poisoning (16.36/1,000,000), and after that comes the mortality due to neoplasms (5.84/1,000,000), and the diseases of the respiratory and circulatory system (3.5/1,000,000). Mortality is higher in the adolescent group from 15 to 19 years of age. With this study only a partial insight was achieved into the pathology of the adolescent age group. In order to attain a full insight, it is absolutely necessary to actively and prospectively follow the health state of adolescents and the conditions of environment.

Adolescent↗

[Acute alcoholic intoxication in children in Vojvodina].

The aim of this work was to investigate the frequency and characteristics of acute ethanol poisoning in children in the territory of the Socialist Autonomous Province of Voivodina. In a retrospective study histories of poisoned children aged 0-15 years, who were hospitalized in all eleven stationary centres in Voivodina during 1985/86, were analysed. From 795 children, 52 were poisoned with ethanol (6.54%). With the exception of Novi Knezevac, where only eight cases of poisoning were recorded during the two-year period, the frequency of ethanol poisoning showed major regional differences varying from 3.03% in Zrenjanin to 11.45% in Subotica. Poisoning among boys was significantly more frequent than among girls, especially with ethanol. The average age of children poisoned with ethanol was 8.4 years i.e. almost twice that of children poisoned with other substances. The children's age and circumstances of ethanol poisoning point to the absence and failure of preventive measures.

Acute Disease↗

[Prenatal diagnosis of skeletal dysplasia: case report of a fetus with multiple anomalies].

INTRODUCTION: Skeletal anomalies are in the group of anomalies most difficult to be diagnosed antenatally. But, because of high lethality and morbidity rate as well as high possibility to be found again in the next pregnancy, they need to be systematically and actively looked for during every scan. CASE REPORT: A pregnant woman, aged 18, primigravida, was admitted to the Dept. of Obstetrics and Gynaecology because of polyhydramnios and suspected multiple fetal malformations. Fetal biparietal diameter and abdominal circumference were adequate for 33 weeks gestation, whereas all the long bones were short for the gestational age. A detailed ultrasound morphology check was impossible because of the excessive amount of amniotic fluid, but the skull, brain, lungs, spine and abdomen appeared normal. There was an impression of frontal bossing and left-sided cleft lip. A thoraco-abdominal disproportion was evident. All the extremities were short, feet were normal, and hands were not extended during the whole scan. The woman underwent an uneventful amino-drainage and three days after that she ruptured the membranes, giving birth to a live female, 2150 gr, 46 cm, Apgar score 6/7. The anomalies seen on ultrasound were confirmed after birth. After a series of dyspnea the neonate was transferred to the Dept. of Paediatrics where it underwent a series of further extensive diagnostic procedures and 37 days after birth it passed away. Postmortem examination led to the following diagnoses: Neonatus femininus eutrophicus temporis aetatis. Defectus partis memebranacei septi interventricularis. Ductus arteriosus Botalli persistence. Hypoplasia thymi. Cheliognathopalatoschisis. Low set ears. Extremitates breves. Atelectasis subtotalis pulmonis bilateralis. Foramen ovale apertum cum valvula competent. Oedema cerebri gradus maioris. DISCUSSION: Majority of fetal skeletal malformations can be relatively easily visualised during ultrasound scans and hence ultrasound is the most sensitive way of prenatal diagnosis of these anomalies. Maternal habitus, fetal position, alteration of amniotic fluid volume and gestational age can be factors that may aggravate check-ups. A prerogative for an early prenatal diagnosis of fetal skeletal anomalies is a well organized scan of each and every fetus that checks all bones, starting with the skull and finishing with hands and feet. Should an anomaly be found an extensive detailed scan by an expert should be performed, as well as karyotyping and a consultation with pediatrician/surgeon. In case of a lethal anomaly, an option of pregnancy termination should be considered and if the parents decide against it, the pregnancy should be closely monitored, with parents fully counseled about the prognosis for the child. In this case the anomaly was noted only after the 30th week of gestation and even then only because the patient came because she had some subjective difficulties because of the excessive amniotic fluid volume. On the other hand, some skeletal dysplasias can be diagnosed only in the late second, early third trimester and sometimes stay unnoticed until the end of pregnancy. This case could not be resolved definitely, for the anomalies were conclusive neither of a specific genetic syndrome, nor of an isolated skeletal dysplasia. Extensive further examination of parents as well as their families is needed in order to be able to give some information about the risks in the next pregnancy. CONCLUSION: Although skeletal anomalies are extremely difficult to diagnose antenatally, a detailed scan of a complete fetal anatomy between 20 and 32 gestational weeks with special attention given to the entire skeleton, gives certain assurance of excluding majority of major skeletal dysplasias or enables their diagnosis and further adequate plan for pregnancy management.

Abnormalities, Multiple↗

[Asphyxia and intracranial hemorrhage in high-risk neonates of various gestational ages].

The aim of this study was to compare the type and severeness of brain damage in vitally most endangered newborn infants of different gestational age. We retrospectively analyzed the records of 75 newborn infants treated and decreased at the Department of Intensive Care and Therapy of the Institute of Children's and Adolescents' Health Care in Novi Sad. Diagnoses of hypoxic-ischemic lesion and intracranial hemorrhage in the case of grade four PVH-IVH (periventricular hemorrhage-intraventricular hemorrhage) were established by ultrasonography of the brain and lumbar punction in the case of subarachnoid hemorrhage. These diagnoses were confirmed after forensic-medical expertise. The volume and degree of the damage were compared in regard to the gestational age, Apgar score and time of initial mechanical ventilation and initial parameters of the mechanical ventilation, as well as to values of acido-basic status, concentration of gases in arterialized capillary blood and type of lung damage which always occurred in these patients. In all 75 examined newborns perinatal asphyxia was the dominant etiologic factor for the course and outcome of the disease (in all patients Apgar score was 4 or less). 75% of examines were born before 32 weeks gestation and of low or very low body weight, whereas 72% had intracranial hemorrhage (periventricular-intraventricular) and hypoxic-ischemic damage of the brain parenchyma. The rest of examinees had intracranial hemorrhage or hypoxic-ischemic damage of the brain parenchyma. Although 92% of examinees received mechanical ventilation in the first 3 days of life, only 20% of newborn infants had satisfactory values of acido-basic status and gas concentrations in the blood. We concluded that in the most severe cases of perinatal asphyxia, especially in preterm newborns of low or very low body weight, both intracranial hemorrhage and hypoxic-ischemic encephalopathy develop. Damages of other organs or systems of organs, especially lungs, as a rule contribute to infaust ending.

Asphyxia Neonatorum↗