bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Affecting the Choice of Public Vs Private Healthcare Institutions for Delivery and Postnatal Care-A Study in a Rural District of Pakistan
Authors: Akhtar Sohail , Ahmed Zafar , Mehmood Asim
Published: February 2022

Maternal health is one of the most critical public health challenges in many developing countries availability of comprehensive maternal healthcare services by skilled health professionals can improve the quality of maternal health outcomes. In Pakistan, the rate of institutional delivery is lower than many other developing countries and a significant proportion of mothers seek maternal healthcare in the private health sector. There are many factors associated with utilization of maternal healthcare services including both supply side and demand side factors. The objective of this paper is to identify significant socio-economic factors affecting utilization of delivery and postnatal services in public and private healthcare facilities in district Rajanpur, Pakistan. Using multi-stage random sampling technique, 368 mothers who delivered within 6 months prior to data collection in selected basic health unit (BHU) areas were selected. Multivariate binary logistic regression was applied on primary data collected from Rajanpur district during 1st November, 2020 – 31st January, 2021. The results indicated that the household’s preference for private healthcare sector for delivery and postnatal care increases with increase in households’ education and incomes. It also showed that accessibility to healthcare facilities is significant in utilization of maternal healthcare services. Distance to healthcare facilities, cost of transport and out-of-pocket expenditure are significantly affecting the choice of healthcare institutions.
Clinical Status of Pregnancy-Induced Hypertension and Pre-Eclampsia among Sudanese Women
Authors: Osman Duaa Adil , Ahmed Aimun AE. , Khairy Salah I. , Haleem Salah Eldin Abdel Hag Abdel
Published: February 2022

Objective: The present study has been conducted with the aim of determining the clinical status of gestational hypertensive disorders in Sudan.

Methods: An analytical case-control, comparative and descriptive cross-sectional, hospital-based study was conducted at Omdurman Maternity Hospital (OMH). It included 228 cases of gestational hypertensive disorders. Data were collected through interviews, questionnaire, and admission records and analyzed statistically.

Results: The clinical status of pregnancy-induced hypertension and pre-eclampsia among Sudanese women has been estimated. Spontaneous pregnancies were 94.6% of the cases. Multigravida were 50.4% of pregnant Sudanese women presenting at OMH, 20.7% of them had a history of gestational hypertensive disorders and 18.1% had a history of miscarriage. Among the patients admitted with gestational hypertensive disorders 75% developed preeclampsia, 91% has shown non-syndromic complications and 52.2% were asymptomatic.  

Conclusion: Maternal age between 18-40 years, nulliparous primigravida or multigravida with long latency period and history of miscarriage are the commonest risk factors of hypertension complication during pregnancy, including preeclampsia, in Sudan. Significantly lower serum calcium and/or higher serum magnesium are associated with preeclampsia, syndromic HELLP is a rare association. Patient awareness is critical for early detection and prevention of disease progression.
Case Report on Hypertension in Elderly Patients
Authors: Tripathi Anjali , Kasturkar Pooja , Gomase Kavita , Gawai Jaya , Uke Trupti , Khandar Jaya , Kolhekar Sonali , Tembhare Vaishali
Published: February 2022

Introduction:  The other name of high blood pressure is hypertension. Blood pressure is the force exerted by person against wall of blood vessels. Normal value of blood pressure is 120/80 mmHg. Hypertension increases with increasing in age. It can cause various health complications like stroke, heart diseases and affect psychological health and sometimes cause death.

Clinical Findings: Chest pain, not having proper sleep, headache, irregular heart beat, loss of appetite, fatigue, anxiety, lack of coping ability.

Diagnostic Evaluation: After performing various kinds of the investigations the result is Hb% - 12.9 gm%, Total RBC Count – 4.6 millions/cumm, Total WBC count – 14500 millions/cumm, Monocytes – 2%, Granulocytes – 56%, Lymphocytes – 40%. Blood pressure – 160/100.

Therapeutic Intervention: Inj. Pantroprazole 40 mg IV x OD, Inj Emset 4 mg IV x TDS,  Inj. Levoflox 500 mg IV x OD, Tab Amlo  5 mg orally x OD, Tab Zincovit 5mg orally x OD, Tab. Orotex XT 10 mg orally xOD.

Outcome: After treatment there was improvement in my patients condition such as relief from Chest pain, Insomnia, irregular heartbeat, Headache. Increase in nutrition pattern and was and was able to cope up with the normal life stressors. The elevated blood pressure which was 160/100 was under the normal condition it was 120/80 mmHg.

Conclusion:  My Patient was admitted in Female Medicine ward no 23, AVBRH with known case of Hypertension and she had complains of Chest pain, Headache, loss of appetite, Insomnia. After getting proper treatment her condition was improved.
Critical Review on Vrushya basti: A Therapeutic Approach
Authors: Bhisikar Gautami , Parwe Shweta , Nisargandha Milind , Tikale Swati
Published: February 2022

Background: Vrushya chikitsa is one of the eight principal branches of the Ashtanga Ayurveda. The Rasayana and Vajikarana therapy promotes longevity and imparts the healthy individual's strength, complexion, and overall well-being. It deals with infertility and problems involving the body's vital reproductive fluids of Shukra dhatu. Vrushya chikitsa is also known as Vajikarana, which translates to "medication or therapy that allows a male to copulate with a woman." Vrushya chikitsa also aids in the nourishment of a person's physique. Vrushya chikitsa also helps in nourishing the body of the person. In six different Samhitas, including the Brihatrayee, Bhela Samhita, Vangasena Samhita and Bhavprakash Samhita, numerous Vrushya Basti are mentioned.

Aim: To study the vrushya basti in different Samhita.

Results: There is various vrushya basti mentioned in different Samhita, but some of studied practically, there is some unavailability of contents of vrushya basti. Due to some unavailability of contents like the meat of titir, peacock etc. vrushya basti is not possible to study.

Conclusion: There should have to check the efficacy for every vrushya basti to generate scientific evidence.
Adverse Drug Reactions in Terms of Dentistry
Authors: Dangara Yogita , Chabbra Kumar Gaurav
Published: February 2022

There is a wide range of drugs and their clinical applications that can cause adverse drug reactions (ARD) due to dose, duration, age, and gender. Drugs like ACE inhibitors, which can cause xerostomia, lichen planus, which is caused by NSAIDs and anti hypertensive drugs, ulceration, pigmentation, and osteonecrosis are not only caused by bisphosphonates but also antiangiogenic agents, and malignancy is targeted by rapamycin in the oral cavity. Changes in taste sensation, angioedema, and infection are also some of the side effects of drugs that have been reported. Immunosuppressed patients show more advanced and complex lesions. A clinician shouldn look for adverse effects of medicine.
Clinical Outcome and Laboratory Parameters in Sickle Cell Anemia Patients of Pediatric Age Group Post Hydroxyurea Therapy
Authors: Gupta Nihar , Hiwale Kishore , Vagha Sunita , Bhake Arvind , Pawar Sukanya
Published: February 2022

Background: Homozygous condition in Sickle cell disease (SCD) is called as sickle cell anemia(SCA). In sickle cell anemia patients clinically presents as hemolytic anemia, vaso-occlusive events, along with organ dysfunction and acute chest syndrome. Recently Hydroxyurea has shown promising results in treatment of sickle cell anemia. Hydroxyurea is the only approved drug by FDA which has shown disease modifying results. 

Aim: To determine the clinical outcome and laboratory parameters in SCA patients of pediatric age group post-hydroxyurea therapy.

Methods: A total of 30 patients who were diagnosed as Sickle cell anemia (SCA) patients in Sickle cell anemia OPD of Pediatric department were included in the study.

Results: Hydroxyurea therapy is expected to increase HbF% levels and improve the clinical outcome and laboratory parameters in sickle cell anemia patients of pediatric age group.
Scale‐Up and Design of a Pilot‐Plant Photobioreactor for the Continuous Culture of Spirulina platensis
Authors: Vernerey A. , Albiol J. , Lasseur C. , Gòdia F.
Published: July 2002

Scale‐up of bioreactors has the intrinsic difficulty of establishing a reliable relationship among physical parameters involved in the design of the new bioreactor and the physiology of the cultured cells. This is more critical in those cases where a more complex operation of the bioreactor is needed, such as in photobioreactors. A key issue in the operation of photobioreactors is establishing a quantification for the interaction between external illumination, internal light distribution and cell growth. In this paper an approach to the scale‐up of a photobioreactor for the culture of Spirulina platensis, based on a mathematical model describing this interaction, and the operation of a previous reactor 10 times smaller is presented. The paper describes the approach followed in the scale‐up, the analysis of different design constraints, the physical realization of the new bioreactor design, innovative use of plastic material walls to improve reactor safety, and finally the corroboration of its satisfactory operation.
Electrostatic Droplet Generation for Encapsulat ion of Somatic Tissue: Assessment of High‐Voltage Power Supply
Authors: Goosen Mattheus F. A. , Al‐Ghafri Abdullah S. , Mardi Osman El , Al‐Belushi Mohammed I. J. , Al‐Hajri Hamad A. , Mahmoud Eltag S. E. , Consolacion Evangeline C.
Published: July 2002

The production of alginate microbeads with and without somatic tissue was investigated using an electrostatic droplet generator with a custom‐made fixed (5.7 kV) and variable (0–20 kV) high‐voltage power supply. The effects of applied potential, needle size, and alginate concentration were assessed as well as the immobilization of carnation callus cells. The high‐voltage output from the power supply depended on whether the low‐voltage input was increasing or decreasing. This hysteresis effect may be due to the electrical properties of the oscillator in the high‐voltage source. While a short electrode distance and a high needle gauge were important for producing small alginate bead diameters (e.g., 100 μm), alginate concentration in the range 1–3% (w/v) was not a key factor. Somatic tissue encapsulated using 2% sodium alginate retained viability over a 2‐month culture period.
Production of Cell‐Free Xanthan Fermentation Broth by Cell Adsorption on Fibers
Authors: Yang Shang‐Tian , Lo Yang‐Ming , Chattopadhyay Devamita
Published: July 2002

Xanthan gum is a microbial polysaccharide widely used in food and oil‐drilling industries. Xanthan gum produced from the current commercial fermentation process usually contains cells and cell debris, which lower the filterability of the xanthan solution and limit its applications. The production of cell‐free xanthan gum fermentation broth is thus desirable. The feasibility of removing cells from the xanthan fermentation broth by cell adsorption to various woven fibrous materials was studied. It was found that both cotton and polyester fibers could be used to adsorb Xanthomonas campestris cells present in the fermentation broth either during batch fermentation or after the fermentation. Almost all cells were removed from the fermentation broth by adsorption to fibers. Cotton terry cloth had rough surfaces and was the preferred material for cell adsorption. Cell adsorption to cotton was faster than to polyester fibers. The adsorption kinetics can be modeled by a first‐order rate equation. The adsorption rate constants were 30–40% higher for cotton than for polyester. Cell adsorption was not efficient in the absence of xanthan gum, suggesting that the exopolysaccharide, xanthan gum, was important for efficient cell adsorption to fibers.
Position 13 analogs of the tridecapeptide mating pheromone from Saccharomyces cerevisiae: design of an iodinatable ligand for receptor binding
Authors: Liu S. , Arshava B. , Naider F. , Henry L.K. , Lee B.K. , Becker J.M.
Published: July 2002

Abstract: Analogs of the α‐factor tridecapeptide mating pheromone (WHWLQLKPGQPMY) from Saccharomyces cerevisiae in which Tyr13 was replaced with Phe, p‐F‐Phe, m‐F‐Phe, p‐NO2‐Phe, p‐NH2‐Phe or Ser were synthesized and purified to > 99% homogeneity. These analogs were bioassayed using a growth arrest assay and a gene induction assay and evaluated for their ability to compete with binding of tritiated α‐factor to its receptor Ste2p. The results showed that the phenolic OH of Tyr13 is not required for either biological activity or receptor recognition. Analogs containing fluorine, amino, nitro or a hydrogen in place of OH had 80–120% of the biological activity of the parent pheromone in the gene induction assay and had receptor affinities from nearly equal to 6‐fold lower than that of α‐factor. In contrast, substitution of Ser or Ala at position 13 resulted in a > 100‐fold decrease in receptor affinity suggesting that the aromatic ring is involved in binding to the receptor. The lack of a strict requirement for Tyr13 allowed the design of several multiple replacement analogs in which Phe or p‐F‐Phe were substituted at position 13 and Tyr was placed in other positions of the peptide. These analogs could then be iodinated and used in the development of a highly sensitive receptor‐binding assay. One potential receptor ligand [Tyr(125I)1,Nle12, Phe13]α‐factor exhibited saturable binding with a KD of 81 nm and was competed by α‐factor for binding in a whole‐cell assay. Thus a new family of radioactive ligands for the α‐factor receptor has been revealed. These ligands should be extremely useful in defining active site residues during mutagenesis and cross‐linking studies.
Association of elevated insulin‐like growth factor binding protein‐1 with insulin resistance in hyperthyroidism
Authors: Jenkins Richard C. , Valcavi Roberto , Zini Michele , Frasoldati Andrea , Heller Simon R. , Camacho‐Hubner Cecilia , Gibson J. Martin , Westwood Melissa , Ross Richard J. M.
Published: July 2002

OBJECTIVE

Insulin‐like growth factor binding‐protein‐1 (IGFBP‐1) has a role in glucose homeostasis and is present at high concentrations in hyperthyroidism. We have investigated the relationship between IGFBP‐1 concentration and glucose homeostasis in hyperthyroidism.

DESIGN

Patients and controls had intravenous glucose tolerance tests (IVGTT) and/or oral glucose tolerance tests (OGTT). Patients were tested when hyperthyroid and when euthyroid whilst the controls were tested once. The IVGTT was used to assess insulin sensitivity and the OGTT to establish that the study group had abnormal glucose tolerance. The hyperthyroid patients were treated with methimazole to restore euthyroidism.

PATIENTS

Ten patients (9 females) and 13 healthy controls (9 females) consented to the study. Ten patients and nine controls (7 females) had IVGTT. Six patients (5 females) and six controls (4 females) had OGTT.

MEASUREMENTS

Glucose, insulin, glucagon, GH and IGFBP‐1 were measured during GTT. IGF‐I, free thyroid hormones, and TSH concentrations were measured basally.

RESULTS

Hyperthyroid subjects were insulin resistant and 67% had impaired glucose tolerance. Fasting IGFBP‐1 levels were doubled in hyperthyroid subjects compared to healthy controls and correlated positively with free T4 (r = 0.84, P < 0.0001), with peak glucose during the OGTT (r = 0.68, P < 0.005) with peak insulin during the IVGTT (r = 0.51, P < 0.005) and negatively with glucose disappearance constant (r = − 0.52, P < 0.005). IGFBP‐1 was highly phosphorylated in hyperthyroid and control subjects. Fasting insulin and IGFBP‐1 levels were unrelated but IGFBP‐1 suppressed acutely during GTT in all groups. GH levels fell less in patients with hyperthyroidism than in normals during GTTs.

CONCLUSIONS

We conclude that in hyperthyroidism thyroid hormones directly increase fasting IGFBP‐1 concentration but acute regulation of IGFBP‐1 by insulin is normal and that elevated fasting phosphorylated IGFBP‐1 concentration is associated with insulin resistance.
Behavioural and cognitive associations of short stature at 5 years
Authors: Stathis SL , O’Callaghan MJ , Williams GM , Najman JM , Andersen MJ , Bor W
Published: July 2002

Objectives:To determine the extent to which childhood short stature is associated with cognitive, behavioural and chronic health problems, and whether these problems could be attributed to recognized adverse biological, psychosocial or psychological factors.

Methodology:At their first antenatal session, 8556 women were enrolled in a prospective study of pregnancy. When their children were 4 and 6 years of age, mothers completed a detailed questionnaire concerning their child’s health and behaviour. A Peabody Picture Vocabulary Test–Revised (PPVT‐R) was completed by the child at 5 years of age. Z scores were used to categorize height measurements in 3986 children. The relationship of these height categories with the child’s health, and behavioural and cognitive problems was then examined.

Results:No association was found between height and symptoms of chronic disease or behaviour problems in boys or girls. On the unadjusted analysis, mean PPVT‐R scores were significantly lower in boys with heights < 3 percentile and 3–< 10 percentile compared with study children between 10 to 90 percentile (P< 0.01). Scores were similarly significantly lower in girls with heights < 3 percentile and 3–10 percentile (P= 0.01). Even after adjusting for psychosocial and biological confounders, short stature remained a significant predictor for lower PPVT‐R scores in both boys and girls, although height only accounted for 1.1% of the variance in scores in boys and 0.5% of the variance in PPVT‐R scores in girls. Psychosocial factors had a greater role than height in determining PPVT‐R scores at 5 years of age.

Conclusions:These findings suggest a significant, though small, association between height and PPVT‐R scores at 5 years of age, independent of psychosocial disadvantage and known biological risk factors.
Preclinical pharmacology of pranlukast
Authors: Yonetomi Y. , Fujita M. , Nakagawa N. , Obata T.
Published: July 2002

Cysteinyl leukotrienes (cysLTs) exert potent biological actions through their specific receptors. They induce pathophysiological responses such as potent bronchoconstriction, mucus secretion, mucosal oedema and eosinophil infiltration. The regulation of these responses may provide a novel therapeutic approach in the treatment of allergic and inflammatory diseases. We have developed a cysLT receptor antagonist, pranlukast as one of cysLT modifiers. Preclinical pharmacology studies demonstrate that pranlukast is a potent, selective and orally active antagonist of cysLT1 receptor. Pranlukast competed with [3H]cysLTs for binding to cysLT receptors on guinea‐pig lung and nasal mucosa membranes and inhibited LTD4‐induced calcium mobilization through human cysLT1 receptors expressed on CHO cells. Oral administration of pranlukast inhibited cysLTs‐induced symptomatology in guinea‐pigs. In sensitized guinea‐pig models of asthma, pranlukast inhibited antigen‐induced early and late phase bronchoconstrictions, airway hyperresponsiveness, microvascular leakage and eosinophil infiltration into airways. Furthermore, in sensitized Brown Norway rats, pranlukast suppressed airway smooth muscle proliferation and collagen deposition characteristic of airway wall remodelling. In guinea‐pig models of allergic rhinitis, pranlukast potently blocked a biphasic nasal obstruction resistant to antihistamines, sneezing and nasal secretion induced by nasal hyperresponsiveness, suggesting the prominent efficacy of pranlukast in allergic rhinitis. From these pharmacological properties of pranlukast, it is suggested that cysLT1 receptor antagonists are useful and beneficial as a new class of antiallergic and anti‐inflammatory agents in the treatment and management of asthma and allergic rhinitis.
Role of Genetic Background in the Success of Reintroduced Peregrine Falcons
Authors: Tordoff Harrison B. , Redig Patrick T.
Published: July 2002

Abstract: Peregrine Falcons (   Falco peregrinus) of seven subspecies from four continents were bred in captivity, and approximately 1173 of their progeny were released in the midwestern United States and adjacent regions of Ontario and Manitoba in an attempt to replace the original population that was extirpated by chlorinated hydrocarbon poisoning in the 1950s. We analyzed the success of individuals of the different subspecies introduced to the Midwest. Five of the seven subspecies released have contributed to the current breeding population. Subspecies of breeding Peregrine Falcons were equally represented when breeding birds of high productivity were compared with less prolific breeders. The subspecific makeup of the breeding population did not differ significantly from that of the released population, suggesting that adaptability in this species was sufficient to override genetic differences between subspecies. Peregrines of widely different genetic stocks have thrived after release, making substantial genetic contributions to the new population.
Growth of CdTe on GaAs by electrodeposition from an aqueous electrolyte
Authors: Sircar P.
Published: July 2002

CdTe film was grown on conducting, n-type (100) GaAs single crystals by electrodeposition from an aqueous electrolyte, containing Cd and Te complexes. The CdTe film was specular and had predominantly (111) orientation, as determined from x-ray diffraction spectra.
Conversion process for passivating current shunting paths in amorphous silicon alloy solar cells
Authors: Nath P. , Hoffman K. , Vogeli C. , Ovshinsky S. R.
Published: July 2002

A process is described which provides a simple, automatic means for quickly reducing the deleterious effects of shunts in completed thin-film solar cells. The method has been used to passivate current shunting defects in large area, mass produced solar cells made from amorphous silicon alloys. In the passivation process, photovoltaic devices are exposed to an electrochemical bath which selectively converts the top surface conducting oxide to a lesser conducting state at the vicinity of shunts. The process and its utility in repairing defects will be described.
Origin of contaminants in photochemically deposited chromium films
Authors: Singmaster K. A. , Houle F. A. , Wilson R. J.
Published: July 2002

A systematic investigation of the composition of Cr films deposited by cw 257 nm photolysis of Cr(CO)6 has been performed in order to identify sources of C and O contamination. In the absence of oxygen, the films have the approximate stoichiometry CrCO, independent of light intensity (40–2900 W/cm2). Five carbonyl groups are removed by a combination of surface photochemical and spontaneous processes; the sixth cannot be desorbed in the absence of heating. Deposits grown by purely gas phase photolysis have the approximate composition Cr(CO)2. Oxygen containing species present in the cell during deposition and/or exposure to air rapidly and efficiently convert these films to Cr2O3.
Nonlinear gain caused by cavity standing wave dielectric grating as an explanation of the relationship between resonance frequency and damping rate of semiconductor diode lasers
Authors: Su Chin B.
Published: July 2002

Calculation using the recently proposed nonlinear gain caused by the cavity standing wave induced gain and index grating shows that the resonance frequency square is very nearly proportional to the modulation damping factor irrespective of cavity dimensions in semiconductor diode lasers. This is in agreement with experimental observation. Furthermore, the magnitude of the predicted damping factors is compared with measurements of V-groove lasers and mass-transport lasers. Excellent agreement is also obtained. This gives an alternative explanation of the origin of nonlinear gain other than spectral hole burning.
Piezoreflectance characterization of double-barrier resonant tunneling structures
Authors: Tober R. L. , Pamulapati J. , Oh J. E. , Bhattacharya P. K.
Published: July 2002

The piezoreflectance technique has been used to optically characterize resonant tunneling structures that utilize isolated single quantum wells. The heavy- and light-hole transitions associated with the quantum wells were prominent in the spectra of samples with barrier widths ranging from 50 to 34 Å. Their spectral positions depended not only on quantum well and barrier thicknesses, but also significantly on the amount of carrier confinement produced by barrier height. Furthermore, variations in the magnitude of impurity transitions could be observed in the spectra of different samples.
Nonlinear optical absorption in semiconductor epitaxial depletion regions
Authors: Jokerst N. M. , Garmire E.
Published: July 2002

We have observed an optically induced decrease in absorption near the band-gap energy in a single-heterostructure Schottky barrier depletion region. Photogenerated carriers created and trapped in the unbiased depletion region cause a dynamic decrease in the absorption. This depletion region electric-field absorption modulator (DREAM) exhibits nonlinear optical absorption which relies upon carrier transport induced by an electric field without an external circuit applied to the device. We demonstrate a factor of two change in absorption at peak powers of 2 mW (0.2 W/cm2).
Magnetophonon effect in GaAs Schottky gate field-effect transistors
Authors: Judd T. P. C. , Pepper M. , Hill G.
Published: July 2002

We have investigated the magnetophonon resonance in lightly doped GaAs Schottky gate field-effect transistors of different shape. It is shown that the phase and amplitude of the observed oscillations are dependent upon geometrical considerations. A model is presented in good agreement with experiment.
Warpage of GaAs-on-Si wafers and its reduction by selective growth of GaAs through a silicon shadow mask by molecular beam epitaxy
Authors: Chand N. , van der Ziel J. P. , Weiner J. S. , Sergent A. M. , Cho A. Y. , Grim K. A.
Published: July 2002

The warpage of GaAs-on-Si wafers, caused by the different thermal expansion coefficients of GaAs and Si, has been studied as a function of the GaAs thickness on 3-in.-diam Si wafers. The warpage increases from 7 to 52 μm as the GaAs layer thickness increases from 1.2 to 4.2 μm. Under vacuum clamping conditions the GaAs/Si wafers can be forced to the original flatness. By growing GaAs selectively through a Si shadow mask as islands of 1 mm×1 mm size with a periodicity of 2 mm in a 5 cm×5 cm central area of the wafer, the warpage is reduced considerably. Spatially resolved cathodoluminescence (CL) spectra indicated that the tensile strain is reduced significantly within 10 μm from the edge of the growth. Near the edge, the CL intensity is also increased indicating a reduction in nonradiative recombination at defects. The use of the Si shadow mask to obtain patterned growth is relatively simple, requiring no processing step before or after the growth, and has a great potential in the integration of GaAs and Si circuits or devices.
Direct modulation of a Nd:YAG laser by combined side and end laser diode pumping
Authors: Berger Josef , Harnagel Gary , Welch David F. , Scifres Don R. , Streifer William
Published: July 2002

A Nd:YAG laser was directly amplitude modulated by using a combination of pulsed side and cw end diode pumping. The scheme suppressed relaxation oscillations, reduced pulse delays, increased pulse energy, and avoided higher order transverse mode operation.
Coplanar vacuum photodiode for measurement of short-wavelength picosecond pulses
Authors: Bokor J. , Johnson A. M. , Simpson W. M. , Storz R. H. , Smith P. R.
Published: July 2002

We have fabricated a vacuum photodiode in a coplanar stripline geometry. This device is capable of high quantum efficiency and picosecond response time. It may be particularly useful for diagnostics of picosecond soft x rays from laser-produced plasmas.
Insulating gate InGaAs/InP field-effect transistors
Authors: Temkin H. , Chen Y. K. , Garbinski P. , Tanbun-Ek T. , Logan R. A.
Published: July 2002

Depletion mode heterostructure transistors with InGaAs channel have been fabricated by depositing the gate metallization directly on a semi-insulating Fe:InP layer grown by metalorganic chemical vapor epitaxy. The quantum well channel layer, as thin as 100 Å, shows high electron mobility of 8000 V/cm2 s at room temperature and up to 55 000 V/cm2 s at 77 K. The enhanced gate breakdown voltage results in 1 μm gate devices with transconductance of 210 mS/mm and a complete pinch-off at a low gate bias of −0.1 V. Preliminary high-frequency measurements are also discussed.
Distortion of infrared picosecond pulses after propagation in atmospheric air
Authors: Seilmeier A. , Wörner M. , Hübner H.-J. , Kaiser W.
Published: July 2002

Significant pulse distortion of infrared pulses is observed at frequencies where gaseous components of air have resonant transitions. For instance, coherent interaction with absorption lines of water vapor between 6 and 8 μm gives drastic effects after a pulse propagation as short as 80 cm. Experimental data are compared with model calculations in the small area pulse limit. A dephasing time of T2=50 ps is found for a rovibrational transition at ν̃=1576.2 cm−1 at atmospheric pressure.
Determination of minority-carrier lifetimes in p-type narrow band-gap semiconductors with two-photon absorption excitation
Authors: Loloee M. R. , Seiler D. G. , Ward G. B.
Published: July 2002

A novel method for the direct experimental determination of true minority-carrier (electron) lifetimes in p-type narrow band-gap semiconductors is presented. Specific results are given for p-InSb showing recombination involving a deep level close to midgap as the dominant recombination mechanism.
Electrical and optical properties of GaAs/AlGaAs multiple quantum wells grown on Si substrates
Authors: Mii Y. J. , Karunasiri R. P. G. , Wang K. L.
Published: July 2002

Intersubband infrared absorption and sequential resonant tunneling in GaAs/AlGaAs multiple quantum wells grown on Si substrates are reported for the first time. The observed electrical and optical properties of the multiple quantum wells on Si are comparable to similar structures grown directly on GaAs substrates. This suggests the potential application of integrating the GaAs/AlGaAs multiple quantum well devices with Si very large scale integrated circuits for long-wavelength (near 10 μm) infrared detection.
Molecular beam study of laser-induced chemical etching of Si(111) by chlorine molecules
Authors: Li Yu-Lin , Zhang Zhuang-Jian , Zheng Qi-Ke , Jin Zhong-Kao , Wu Zhen-Kai , Qin Qi-Zong
Published: July 2002

Chemical etching of Si(111) surface by chlorine molecules under 355 and 560 nm irradiation has been studied using a continuous wave supersonic molecular beam. Only two products, SiCl and SiCl2, were observed. The translational energy distributions of the gaseous products have been measured as a function of laser fluence, and can be fitted with Maxwell–Boltzmann distributions. Study on the effect of translational energy of incident chlorine molecules on the reaction rate is also presented for the first time.
Unusual low-temperature behavior of Fermi level movement at the Sb/GaAs interface
Authors: Cao Renyu , Miyano K. , Lindau I. , Spicer W. E.
Published: July 2002

The temperature dependence of the development of the Sb/GaAs electronic properties has been found to be quite small, compared to that seen with a large number of metal/GaAs interfaces studied previously. This has been correlated with the relatively small change in interface morphology due to reducing the temperature. The interface morphology and the Fermi level movement at the Sb/GaAs(110) interface were studied using photoelectron spectroscopy at room temperature and low temperature (80 K). The Sb/GaAs interface is uniform and abrupt at two temperatures. Two distinct Fermi level pinning positions are observed: 0.75 eV for n-type GaAs and 0.5 eV for p-type GaAs above the valence-band maximum independent of the temperature. The results are discussed in terms of mechanisms of Schottky barrier formation.
Subnanosecond switching of bistable tandem lasers by subpicojoule optical triggering
Authors: Öhlander Ulf , Blixt Peter , Sahlén Olof
Published: July 2002

We report on the switching-on characteristics of a bistable two-section laser diode triggered by subnanosecond optical input pulses. Minimum switching energy as a function of current bias level was measured for different input pulse wavelengths. Subnanosecond and subpicojoule switching was obtained. Estimating the input coupling to be 10%, the lowest bistable switching energy recorded was 23 fJ. The fastest recorded rise time was less than 100 ps.
High-temperature resistance behavior of Bi2Sr2CaCu2O8+y and YBa2Cu3O7−x superconductors
Authors: Bansal T. K. , Bansal Sadhana , McGreevy R. L. , Smith S. H. , Garton G.
Published: July 2002

High- and low-temperature resistance measurements have been carried out on Bi2Sr2CaCu2O8+y and YBa2Cu3O7−x in air and in vacuum. Both the ceramics exhibit a significant change in oxygen content during annealing between 350 and 450 °C. The Bi2Sr2CaCu2O8+y sample exhibits an increase in resistance with increased oxygen content resulting in deterioration of superconductivity, whereas YBa2Cu3O7−x shows improvement in superconducting behavior with increase in oxygen content. Consequently Bi2Sr2CaCu2O8+y prepared by fast cooling from the sintering temperature possesses a higher Tc , whereas slow cooling of YBa2Cu3O7−x produces a higher Tc .
Enhancement in activation efficiency for a SiF3-implanted GaAs layer by a new annealing method
Authors: Tamura Akiyoshi , Inoue Kaoru , Onuma Takeshi
Published: July 2002

We have found a new phenomenon in which the activation efficiency of a SiF3 -implanted GaAs layer is increased by the preimplant thermal treatment of the semi-insulating GaAs substrate with SiO2 encapsulant.
Separate paramagnetism and superconductivity in YBa2Cu3Oz
Authors: Tang H. B. , Ren Y. , Liu Y. L. , Yan Q. W. , Shao X. Y.
Published: July 2002

The magnetic properties of YBa2Cu3Oz with different values of z in the temperature range 1.5–300 K were measured and compared with those of DyBa2Cu3Oz and EuBa2Cu3Oz. The susceptibility data of YBa2Cu3Oz and DyBa2Cu3Oz followed the Curie–Weiss law above Tc, while those of EuBa2Cu3Oz exhibited the Van Vleck and Frank behavior [Phys. Rev. 34, 1494 (1929)] with σ=33. The paramagnetism persisted even below Tc. The effective moment per copper ion increased as the oxygen content decreased. The results suggest that the paramagnetism in YBa2Cu3Oz originates mainly from the nonsuperconducting domains of the material which have disordered oxygen vacancies or have lower oxygen content than the superconducting ones.
Linearly ramped temperature transient rapid thermal oxidation of silicon
Authors: Moslehi Mehrdad M. , Kermani Ahmad , Saraswat Krishna C.
Published: July 2002

New results on the growth kinetics of rapid thermal oxidation of Si using transient linearity ramped saw-toothed and triangular wafer temperature versus time profiles are reported. The peak wafer temperature and the heat-up/cool-down rates were varied in the ranges of 950–1200 °C and 1–200 °C/s, respectively. The grown oxides were ∼20–200 Å thick depending on the growth conditions. A comparison of the experimental data with the numerical simulation results reveals that the thin oxide steady-state dry oxidation kinetics model underestimates the thickness of oxides grown by the ramped temperature transient oxidations.
Composition dependence of superconducting properties in Bi2(Sr1−xCax)n+1CunOy (n=2, 3) thin films
Authors: Satoh T. , Yoshitake T. , Kubo Y. , Igarashi H.
Published: July 2002

Thin films of the Bi2(Sr1−xCax)n+1CunOy (n=2, 3) system were prepared on (100)MgO substrates by coevaporation of Bi2O3, Sr-Ca alloy, and Cu metal. The lattice constant of the c axis of the low Tc (∼85 K) phase (n=2) decreased with increasing Ca composition x. The superconducting transition temperatures of both the low Tc phase and high Tc (∼110 K) phase (n=3) decreased with increasing x. These tendencies indicated that both the low Tc phase and the high Tc phase have a mutual solubility between Ca and Sr atoms in this Bi system and that the Tc ’s of these two phases are related to the c-axis lattice constant.
Silicon loss and transient etch rate in selective reactive ion etching of oxide overlayers
Authors: Oehrlein G. S. , Kalish R.
Published: July 2002

Silicon dioxide to silicon etch selectivity in reactive ion etching (RIE) employing fluorocarbon gases is due to the formation of a fluorocarbon film on the substrate. This implies that etch selectivity is not achieved instantly but that the substrate will exhibit a transient etch rate and hence material loss during the film formation period. The amount of silicon lost during overetching for CF4/H2 RIE was determined by Rutherford backscattering spectrometry employing a buried marker. For standard etching conditions, about 7 nm of silicon is lost within the first minute of overetching as compared to 1.5 nm expected from steady-state etch rate data. The Si etch rate varies strongly as a function of time and decreases by a factor of greater than 10 within the first 30 s of overetching to approach a steady-state value.
Stepped-gate-oxide structure—A new approach for speed enhancement in the gate-controlled photodetector
Authors: Sun C. C. , Xu J. M.
Published: July 2002

In this letter, we report a stepped-gate-oxide structure implemented in the gate-controlled photodetector. The experimental results show that a one-order-of-magnitude enhancement in the response speed can be achieved by the use of such a structure owing to the induced transverse electrical field.
Fermi level movement at the Cs/GaAs (110) interfaces
Authors: Cao Renyu , Miyano Ken , Kendelewicz Tom , Lindau Ingolf , Spicer William E.
Published: July 2002

Fermi level (Ef ) movement and overlayer metallization at room temperature (RT) and 110 K low-temperature (LT) Cs/GaAs (110) interfaces are studied using photoemission. Initial p-type GaAs band bending is attributed to the surface donor states that originate from Cs atom chemisorption. The Ef stabilization at RT and LT is interpreted in terms of defects and the metal-induced gap states and the interplay between them. For the latter to dominate, fewer defects and establishment of overlayer metallicity are necessary.
Coherence saturation for beams of energetic photons
Authors: Csonka Paul L.
Published: July 2002

A new method is proposed to generate transversely coherent energetic photon beams. It does not rely on stimulated photon emission, therefore, is not subject to the same technological and cost limitations which affect bound-state x-ray lasers and free-electron x-ray lasers. The method leaves unchanged the photon source; it increases transverse coherence by dynamical optical means, i.e., using nonstationary optical elements. It is well suited to first-order interference experiments (e.g., x-ray holography) particularly with synchrotron radiation sources.
Superconducting phonon spectroscopy using a low-temperature scanning tunneling microscope
Authors: LeDuc H. G. , Kaiser W. J. , Hunt B. D. , Bell L. D. , Jaklevic R. C. , Youngquist M. G.
Published: July 2002

We report the first observation of phonon density of states effects in a superconductor using a low-temperature scanning tunneling microscope (STM). The phonon effects were observed using a STM spectroscopy method to measure dItunneling /dV vs V for the tunnel junction formed by the Au STM probe and a superconducting Pb sample.
Solid phase recrystallization in molecular beam deposited gallium arsenide
Authors: Kanata T. , Takakura H. , Hamakawa Y.
Published: July 2002

A series of experimental investigations on the solid phase recrystallization of molecular beam deposited gallium arsenide films on silicon dioxide/tantalum/nickel substrates has been performed. The activation energy for recrystallization is unexpectedly small (0.55 eV) in the temperature range 450–600 °C. When a thin amorphous germanium layer was grown before gallium arsenide deposition, an enhanced grain growth of gallium arsenide occurs together with anomalous germanium diffusion into the gallium arsenide layer in a semieutectic phase reaction. An enhancement of grain growth has also been observed by the utilization of a graphoepitaxy substrate having inverted pyramidal relief.
Electric field depressed emission from a Au/GaAs near-interface state
Authors: Marrakchi G. , Gavand M. , Guillot G. , Rosencher E. , Nouailhat A.
Published: July 2002

Continuous wave laser annealing was carried out on liquid phase epitaxy GaAs material. A new defect termed PL1 localized near the Au/GaAs interface was detected by deep level transient spectroscopy. This defect is related to the formation of an oxide layer at the GaAs surface during the treatment. Completely new physical behavior of this defect is observed. Deep level optical spectroscopy and deep level transient spectroscopy have shown that the emission of PL1 is depressed by the electric field. This result is discussed in view of other electric field effects.
Localized silicon etching using a laser-generated Cl source
Authors: Treyz G. V. , Scarmozzino R. , Burke R. , Osgood R. M.
Published: July 2002

Ultraviolet laser photolysis of chlorine (λ=350–360 nm) has been used to produce a microscopic atomic chlorine source. Crystalline silicon has been etched and deep through-wafer vias have been fabricated. The etching process has been modeled as a combination of diffusion from the Cl source, and recombination and etching at the silicon surface. Both experimental and theoretical results are given.
Impurity aggregation at individual dislocations in GaAs observed by means of a simultaneous electron beam induced current and cathodoluminescence technique
Authors: Eckstein M. , Jakubowicz A. , Bode M. , Habermeier H.-U.
Published: July 2002

Using simultaneous measurements of electron beam induced current and cathodoluminescence intensity it is possible to distinguish between different contributions to signal magnitude and contrast at defects. In this letter we report on the application of this technique to investigate the role of impurity aggregation and defect decoration on the recombination behavior of dislocations in GaAs. In the experiment described here we diffused copper into the crystal. We observed an increase of signal contrasts and changes in the contrast profiles. With the help of computer simulations these experimental results can be interpreted as a homogeneous decoration of dislocations, the formation of precipitates at the dislocations, and a reduced minority-carrier diffusion length in the bulk.
Origin and penetration depth of thermal degradation in InP
Authors: Sartorius B. , Pfanner K.
Published: July 2002

Thermal degradation is examined in a development stage in which local damage in the crystal lattice already exists, although the known surface deformations are not yet visible. The existence of these crystal defects is shown by means of luminescence microscopy. Depth profiles reveal that the damage is not restricted to the surface. On ‘‘dark disks,’’ e.g., a spherical spreading of the degradation by some 10 μm into the crystal volume is observed. Correlation with the position of dislocation etch pits shows that all dislocations are ‘‘decorated’’ with thermally induced defects. ‘‘Dark disks,’’ however, represent no advanced stage of degradation after having been ‘‘decorated,’’ but develop separately from a different defect type, visible as ‘‘S’’ or ‘‘flat’’ etch pits. This type of defect has not yet been taken into consideration with regard to crystal quality criteria. We suspect that thermal degradation developing from this defect type is the missing link between substrate quality and certain problems in processing and device failure.
Surface accumulation of hydrogen during capless annealing of InP
Authors: Häussler W.
Published: July 2002

InP samples, which had received a capless anneal in a phosphine/hydrogen atmosphere, were examined for hydrogen contamination by secondary-ion mass spectrometry. It is found that hydrogen accumulates at the InP surface during annealing. Annealing of Be-implanted InP leads to similar profile shapes for the Be and H atoms. Passivation of the Be acceptors, if effective at all, appears to be of only minor significance.
Leakage mechanism for tungsten/chromium metallized silicon p/n junctions
Authors: Giordano P. , Gonchond J. P. , Oberlin J. C. , Normandon P. , Basset R. , Chantre A.
Published: July 2002

The thermal stability of tungsten/chromium metallized silicon p/n junctions has been studied using several analytical techniques. A direct correlation has thus been established between junction leakage and structure. The main cause of leakage current observed after annealing at above 400 °C was found to be the generation of film-edge-induced dislocations associated with chromium disilicide formation.
Plasma-assisted epitaxial growth of InAs
Authors: Fang Sun Fei , Matsushita Koichi , Hariu Takashi
Published: July 2002

InAs layers were epitaxially grown directly on GaAs, InP, and GaSb at relatively low temperatures by plasma-assisted epitaxy (PAE) in hydrogen plasma. The electronic and crystallographic properties of PAE-InAs grown on substrates with different lattice mismatch were comparatively studied with a variable supply ratio As/In, growth temperature, and thickness of grown films. The electronic properties of PAE-InAs films comparable to those by molecular beam epitaxy (MBE) were obtained in a wide range of supply ratio, with less supply ratio, and at lower temperatures than MBE.
High-speed InP/InGaAsP metal-semiconductor field-effect transistors grown by chloride vapor phase epitaxy
Authors: Antreasyan A. , Garbinski P. A. , Mattera V. D. , Feuer M. D. , Filipe J. , Chu S. N. G.
Published: July 2002

We report the fabrication of enhancement mode InGaAsP/InP metal-semiconductor field-effect transistors having gate lengths of 2 μm. The epitaxial layers for this structure have been grown by chloride vapor phase epitaxy. The devices show extrinsic transconductances as high as 220 mS/mm, a short-circuit current gain cutoff frequency of fT=5.2 GHz, and a maximum available power gain cutoff frequency of fmax=9.5 GHz. A novel gate technology has been utilized where a lower band-gap quaternary InGaAsP layer of about 350 Å thickness is grown on the top of the InP channel layer.
Integrable optical correlator: Its temporal resolution, spectral response, and power sensitivity
Authors: Vakhshoori D. , Walker J. , Wang S. , Smith J. S. , Soccolich C. E. , Islam M. N.
Published: July 2002

A new class of optical correlator which is integrable and potentially compatible with semiconductor lasers is experimentally tested. The correlator proposed earlier (a special GaAs/AlGaAs waveguide) is shown to be broad band capable of correlating pulse trains with average power in the correlator in sub-mW range with wavelengths at least ranging from 1.06 to 1.7 μm. To show compatibility with semiconductor laser diodes the correlator device was also used to generate sum frequency signal from mixing a 400 μW cw beam of a 1.06 μm Nd:YAG laser with a 400 μW cw beam of a 1.3 μm semiconductor laser diode. The latest result shows the potential of direct measurement of optical pulses from semiconductor laser diodes at different wavelengths with a single integrable compact correlator without any mechanical translation.