bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental alteration of litter sex ratios in a mammal
Authors: Cameron Elissa Z , Lemons Patrick R , Bateman Philip W , Bennett Nigel C
Published: November 2007

Adaptive theory predicts that mothers would be advantaged by adjusting the sex ratio of their offspring in relation to their offspring's future reproductive success. Studies investigating sex ratio variation in mammals, including humans, have obtained notoriously inconsistent results, except when maternal condition is measured around conception. Several mechanisms for sex ratio adjustment have been proposed. Here, we test the hypothesis that glucose concentrations around conception influence sex ratios. The change in glucose levels resulted in a change in sex ratios, with more daughters being born to females with experimentally lowered glucose, and with the change in glucose levels being more predictive than the glucose levels
per se
. We provide evidence for a mechanism, which, in tandem with other mechanisms, could explain observed sex ratio variation in mammals.
Water sorption isotherms of freeze‐dried milk products: applicability of linear and non‐linear regression analysis in modelling
Authors: Jouppila Kirsi , Roos Yrjó H.
Published: November 2007

Summary  Water sorption of various freeze‐dried milk products was modelled using several water sorption isotherm models, most of which proved to be applicable. Sorption models were fitted to experimental data using linear and non‐linear regression analysis. Both methods gave almost the same prediction of water sorption when the model had a good fit. The GAB model was considered to be the most applicable in predicting water sorption in practical applications, as the use of one universal model is desirable. Time‐dependent changes, e.g. lactose crystallization above glass transition, were taken into account in the water sorption modelling. Water contents and relative humidities which allowed changes in physico‐chemical properties were not included in the modelling, because of unsteady amounts of sorbed water.
A differential scanning calorimetry study of wheat grain cooking
Authors: Stapley Andrew G. F. , Gladden Lynn F. , Fryer Peter J.
Published: November 2007

Summary  A number of commercial processes involve whole grain cooking. In this study, differential scanning calorimetry (DSC) scans were taken of whole wheat grains that had been boiled or steamed for various times at either 100 d̀C or 120 d̀C. Scans were also taken of raw grains that had been soaked and equilibrated to different moisture contents. Raw grains showed peak temperatures to be dependent on moisture content, in close agreement with literature data for wheat starch/water mixtures. The two cooking methods showed different behaviour, which can be explained with reference to magnetic resonance imaging (MRI) (Stapley et al., 1997). For steamed grains with high moisture contents at longer cooking times, part of the DSC endotherm was below the cooking temperature, and conversion occurred in the cooker. DSC endotherms of steamed grains showed a clearly denned onset temperature, c. 6d̀C above the steam temperature, due to the release of latent heat. MRI shows partially boiled grains to have a high moisture content in the outer regions and an inner core of lower moisture content. The peak temperatures observed by DSC were similar to those expected of soaked grains with the same moisture contents as that of the core. It is postulated that the inner core contains unconverted starch, and that conversion has been achieved in the outer regions. The specific heat capacity for each grain was also measured, and correlated well with moisture content, but was not strongly influenced by the grain treatment.
The extractable β‐carotene content of Guku (Bidens pilosa) leaves after cooking, drying and storage
Authors: Benhura Mudadi A. N. , Chitsiku Irene C.
Published: November 2007

Summary  The β‐carotene content of young tender leaves of Guku (Bidens pilosa) was found to be 64 μg g‐1 in fresh samples. The extractable β‐carotene content of Guku leaves boiled for 20 min was 31% greater than that in leaves blanched for 1 min. Boiling for up to 60 min resulted in a 6% decrease of β‐carotene compared with the concentration in blanched leaves. Drying in the sun and in the shade resulted in losses of β‐carotene of 92% and 93% respectively. After 6 days of refrigeration of unblanched leaves, about 38% of the β‐carotene was lost. There was no appreciable change in the levels of β‐carotene after the blanched leaves had been kept frozen at ‐18d̀C for 5 weeks. Blanched mature leaves had 62% more β‐carotene than young leaves.
Effect of production factors and ripening conditions on the characteristics of Serra cheese
Authors: Macedo Angela C. , Malcata F. Xavier , Oliveira Jorge C.
Published: November 2007

Summary  The individual and interactive effects of four production factors (amount of vegetable rennet, temperature of coagulation, pressing and salting of the fresh cheese) and two ripening factors (temperature and relative humidity) on microbiological, physico‐chemical, biochemical, textural and sensory characteristics of Serra cheese were simultaneously studied using a 2vi6‐1 factorial design. Highly significant effects of salting and ripening relative humidity upon the characteristics of the cheese were detected. Addition of salt to the surface of the fresh cheese reduced microbial growth, water activity, moisture and lactic acid contents, proteolysis, lipolysis, aroma and softness of the cheese. Conversely, increase of the relative humidity during ripening increased these charactereristics. Pressing had no statistically significant effect on cheese characteristics.
The applicability of the GAB model to food water sorption isotherms
Authors: Lewicki Piotr P.
Published: November 2007

Summary  The fitting ability of the GAB equation has been analysed. It has been shown that the GAB model describes well sigmoidal type isotherms when parameters are kept in the following regions: 0.24 7lt; k ≤ 1 and 5.67 ≤ c ≤ ∞. Outside these regions the isotherm is either no longer sigmoidal or the monolayer capacity is estimated with the error larger than ± 15.5%. Moreover, keeping constants in the above regions fulfils the requirements of the BET model.
Modulation of neuropeptide Y and Y1 receptor expression in the amygdala by fluctuations in the brain content of neuroactive steroids during ethanol drinking discontinuation in Y1R/LacZ transgenic mice
Authors: Eva Carola , Mele Paolo , Collura Devis , Nai Antonella , Pisu Maria Giuseppina , Serra Mariangela , Biggio Giovanni
Published: November 2007

Previous studies have shown that GABAergic neuroactive steroids increase Y1 receptor (Y1R) gene expression in the amygdala of Y1R/LacZ transgenic mice, harbouring the murine Y1R gene promoter linked to a LacZ reporter gene. As ethanol is known to increase GABAergic neuroactive steroids, we investigated the relationship between fluctuations in the brain content of neuroactive steroids induced by chronic voluntary ethanol consumption or ethanol discontinuation and both the level of neuropeptide Y (NPY) immunoreactivity and Y1R gene expression in the amygdala of Y1R/LacZ transgenic mice. Ethanol discontinuation (48 h) after voluntary consumption of consecutive solutions of 3%, 6%, 10% and 20% (v/v) ethanol over 4 weeks produced an anxiety‐like behaviour as measured by elevated plus maze. Voluntary ethanol intake increased the cerebrocortical concentration of the progesterone metabolite 3α‐hydroxy‐5α‐pregnan‐20‐one (3α,5α‐TH PROG) that returned to control level 48 h after discontinuation of ethanol intake. Ethanol discontinuation significantly decreased NPY immunoreactivity and concomitantly increased Y1R/LacZ transgene expression in the amygdala, whereas chronic ethanol intake failed to affect these parameters. The 5α‐reductase inhibitor finasteride prevented both the increase in the cerebrocortical concentration of 3α,5α‐TH PROG apparent after 4 weeks of ethanol intake and the changes in NPY immunoreactivity and transgene expression induced by ethanol discontinuation. Data suggest that 3α,5α‐TH PROG plays an important role in the changes in NPY–Y1R signalling in the amygdala during ethanol discontinuation.
Influence of climate change on the abundance, distribution and phenology of woodland bird species in temperate regions
Authors: LEECH D. I. , CRICK H. Q. P.
Published: November 2007

There is now overwhelming evidence that an increase in the concentration of greenhouse gases in the Earth's atmosphere has caused global temperatures to increase by 0.6 °C since 1900 and further increases of between 1.4 and 5.8 °C are predicted over the next century. Changes in climatic conditions have already influenced the demography, phenology and distribution of a wide range of plant and animal taxa. This review focuses on the impacts, both observed and potential, of climate change on birds breeding in temperate woodlands of the Western Palaearctic, a significant proportion of which are currently declining. Changes in ambient temperatures and patterns of precipitation may have direct and indirect effects on the survival rates and productivity of bird species, thus influencing population sizes. For some species or populations, the timing of events such as egg‐laying and return from the wintering grounds is also changing in relation to shifts in the peak of food availability during the breeding season. The degree to which different individuals are able to track these temporal changes will have a significant bearing on population sizes and distributions in the future. Unless active management steps are taken, the relatively low dispersal rates of tree species may lead to a decrease in the total area of some woodland habitat types as losses at the southern edge of the range are likely to occur much more quickly than expansion at the northern edge. In addition, the dispersal rates of many woodland birds are themselves low, which could affect their ability to move to new habitat patches if currently occupied areas become unsuitable. Thus, woodland birds may be particularly susceptible to the impacts of climate change.
Reduced Postoperative Atrial Fibrillation Using Multidrug Prophylaxis
Authors: Ott Richard A. , Gutfinger Dan E. , Alimadadian Hossein , Miller Mark , Selvan Arthur , Weinberg David , Hlapcich Wendy L. , Tanner Teresa M.
Published: November 2007

Abstract Background: Atrial fibrillation (AFIB) is the most common complication following coronary artery bypass grafting (CABG). Despite three decades of recognition, efforts to reduce the high incidence reported (15%‐30%) have been largely unsuccessful. Reasons for postoperative AFlB are likely multifactorial. As a result, we defined a multidrug prophylaxis based on agents known to be individually effective. This method was applied prospectively to a series of consecutive CABG patients with the goal of reducing the incidence of new‐onset postoperative AFIB. Methods: Isolated CABG with cardiopulmonary bypass was performed on 517 consecutive patients. A rapid recovery protocol emphasizing AFlB multidrug prophylaxis was applied to all patients. All patients received 10 μg of triiodothyronine intraoperatively when the clamp on the aorta was released. Immediately following CABG, parenteral magnesium was administered to assure a serum magnesium > 2.2 mEq/dL. Thyroxine 200 μg was administered parenterally to all patients on postoperative days 1 and 2. Metoprolol (25 mg to 100 mg/day) was begun on all patients after ex‐tubation provided: heart rate > 85 beats/min and systolic blood pressure > 130 mmHg. Parenteral procainamide (12 mg/kg) loading dose, followed by a maintenance dose (2 mg/min), was used for patients who developed premature atrial contractions (> l/min), nonsustained supraventricular tachycardia, or any episodes of atrial fibrillation. All patients also received postoperative digitalization, steroids, and aggressive diuresis. Results: The 30‐day operative mortality was 3.7%. The overall incidence of new‐onset postoperative AFlB was 10.3% (53 patients). There was no major difference in operative mortality (7.5% vs 3.2%, p = 0.231, Parsonnet risk score, or intraoperative variables between AFlB patients and the non‐AFIB patients. Patients presenting with a preoperative acute myocar‐dial infarction (p < 0.051, left main stenosis 2 70% (p < 0.011, and advanced age 2 70 years (p < 0.05) were at increased risk of developing AFIB. The length of stay for patients with AFlB was 9.9 2 9.6 days versus 5.9 2 5.2 days (p < 0.001). Conclusion: Application of a multidrug prophylaxis can reduce postoperative AFlB to a low incidence. Identification of associated clinical features can help predict patients at risk for postoperative AFIB. Additional strategies to target postoperative AFlB may include treatment at the earliest recognition of atrial rhythm instability.
Chronic Aortic Dissection (DeBakey Type II) with Infective Thrombus in the False Channel
Authors: Matsubayashi Keiji , Ueda Yuichi , Ogino Hitoshi , Sugita Takaaki , Yoshimura Shinichiro
Published: November 2007

Abstract A 68‐year‐old man with a DeBakey type II chronic aortic dissection developed bacteremia secondary to a urinary tract infection with the Serratia species. This resulted in an infected thrombus in the false channel and a subsequent rupture of the ascending aorta. An emergency resection of the ascending aorta and a Dacron graft interposition were performed. The patient suffered from severe neurological insufficiency and died of pneumonia 6 months postoperatively. The optimal operation time and surgical options of an infected aortic dissection should be determined.
Comparison of Intermittent Warm and Cold Blood Perfusion During Hypothermic Myocardial Preservation on Functional and Metabolic Recovery
Authors: Masters Thomas N. , Robicsek Francis , Fokin Alexander A. , Cook Joseph W. , Gong Geoffrey , Jenkins Sceria , Rice Harold , Dobbins Charles , Parker Regina
Published: November 2007

Abstract Numerous techniques are used to maintain intraoperative heart viability. The studies presented here evaluated heart function and metabolism after various periods of preservation up to 4 hours with intermittent warm and cold blood perfusion. Using a heterotopic heart model cooled to 10°C and maintained for 1, 2, 3, and 4 hours, various preservation techniques were compared. Changes in myocardial metabolism were determined from substrate uptakes and biopsy samples of the left ventricular muscle for high‐energy phosphates. Preservation techniques included: (1) sustained hypothermia, (2) 1 or 2 hours of sustained warm blood perfusion with fibrillation, (3) intermittent cold blood perfusion during 2, 3, and 4 hours of preservation, (4) intermittent warm blood perfusion during 2, 3, and 4 hours of preservation and (5) a control group (no preservation). Normothermic fibrillation had no effect on postpreservation functional or metabolic parameters. Sustained hypothermia reduced functional recovery proportional to the length of ischemia. The cold intermittent procedures maintained function and metabolism better than sustained hypothermia, while warm intermittent preservation maintained function and metabolism at control levels throughout the recovery period for all preservation techniques. Changes in ATP mirrored the functional changes. Creatine phosphate (CP) was markedly reduced during heart isolation and preservation and exceeded the control by 100% during reperfusion. For operative procedures of 2 hours or less, functional and metabolic recovery was not affected by the various preservation methods applied. Warm intermittent perfusion during hypothermic preservation offered the best protection for the myocardium. The warming cycles during hypothermia may provide some degree of preconditioning and protect the myocardium during reperfusion.
Coronary‐Coronary Bypass Using the Internal Thoracic Artery: A Sparing Procedure of the Arterial Conduit
Authors: Hirotani Takashi , Kameda Tadashi , Kumamoto Takayuki , Shirota Shogo , Yamano Mototsugu
Published: November 2007

Abstract Background: The internal thoracic artery (ITA) is well known to be the best conduit for coronary artery bypass grafting. However, the bilateral use of IT As remains limited because in situ right IT As (RITAs) do not possess an adequate length to be directed to the posterolateral myocardium. We thus considered using free ITAs for conduits between the two segments of the same coronary artery. Methods: From March 1997 to May 1999, 17 patients underwent coronary‐coronary bypass grafting (C‐CBG) using free ITAs. Early operative results were analyzed. C‐CBG was indicated when the right ITA had an inadequate length or when a distal part of the ITA was left unused. Results: No patient died after C‐CBG and none have experienced angina since C‐CBG (mean follow‐up period 27.3 ± 19.8 months). Postoperative angiography was performed in all subjects at discharge. Only one coronary‐coronary bypass graft was occluded, the other grafts were patent, and there were no stenotic changes. Bilateral ITAs were used in 75% of the patients undergoing CABG during the period of this study. Conclusions: C‐CBG can expand the use of bilateral ITAs and can provide an alternative method for revascularization of the posterolateral myocardium.
An Effective Technique to Correct Anterior Mitral Leaflet Prolapse
Authors: Alfieri Ottavio , Maisano Francesco
Published: November 2007

Abstract Up to one‐third of the patients with degenerative mitral valve disease and severe mitral regurgitation have anterior mitral valve prolapse due to chordal rupture or elongation. Surgical treatment of such a condition is often technically demanding and not infrequently associated with suboptimal results. Techniques used to treat anterior leaflet prolapse include chordal transfer, chordal shortening, artificial chordae, and anterior leaflet resection or plication. Each of these strategies has potential shortcomings, and there is considerable controversy concerning the durability of anterior leaflet prolapse repairs using these techniques. The “edge‐to‐edge” technique, a simple and effective method of correcting anterior mitral leaflet prolapse is described.
Surgical Techniques for the Repair of Anterior Mitral Leaflet Prolapse
Authors: Duran Carlos M.G.
Published: November 2007

Abstract Myxomatous disease is the leading cause of mitral valve regurgitation in the developed world. Although posterior mitral leaflet (PML) prolapse is the most common cause of regurgitation and of repair, lesions of the anterior mitral leaflet (AML) are often considered beyond the possibilities of repair. The surgical anatomy and pathology of the AML and a precise terminology for the location of the lesions are described. The surgical maneuvers for comrnissural prolapse, chordal shortening, chordal replacement, leaflet resection, and annuloplasty are also described. The advantages and limitations of each maneuver are discussed. It is concluded that a flexible approach to the repair of the AML is necessary to adapt the best technique for each type of lesion. No particular technique can be applied systematically to all lesions. It is the author's contention that the majority of AML lesions can be repaired safely.
Climates Create Cultures
Authors: Van de Vliert Evert
Published: November 2007

The circumstances in which societies adapt their cultural values and practices to cold, temperate, and hot climates include the availability of money to cope with climate. Country‐level studies have shown that feeling good, doing good, altruistic volunteering, intrinsic work motivation, cooperative enculturation, and democratic leadership are least prevalent in poorer countries with more demanding climates, moderately prevalent in poor and rich countries with temperate climates, and most prevalent in richer countries with more demanding climates. The common denominator is that inhabitants of lower‐income countries in more demanding climates emphasize survival values at the expense of self‐expression values, whereas the inhabitants of higher‐income countries in more demanding climates emphasize self‐expression values at the expense of survival values. These findings have practical implications for the cultural consequences of global warming and economic growth, and for the effectiveness of financing for human development.
The role of superoxide dismutase in the susceptibility of bean leaves to ozone injury
Authors: Chanway C. P. , Runeckles V. C.
Published: November 2007

The primary leaves of bush bean plants pretreated daily with very low levels of ozone (0.02 or 0.05 ppm) pass through stages of varying susceptibility to a subsequent acute dose. This variation in response can only partly be accounted for by stomatal behaviour. Present studies indicate that the levels of the oxyradical scavenger, superoxide dismutase (SOD), assayed in leaf homogenates, appear to play no role in the phenomenon. No observed changes in the levels of extracted SOD following various low ozone pretreatment regimes could be related to changes in susceptibility to acute injury, in comparisons with control plants maintained in charcoal-filtered air prior to acute fumigation. The only significant increases in SOD levels which appeared to be directly related to ozone exposure occurred simultaneously with the appearance of visible symptoms of injury from either the cumulative chronic or acute ozone exposures.
Lathyrus macrorhizus: influence des facteurs stationnels sur la floraison in situ
Authors: Bricage Pierre
Published: November 2007

Flowering in Lathyrus macrorhizus takes place the whole year round, irrespective of photoperiod. Minimum flower production often occurs at the end of a spell of continuously decreasing air temperatures and is always preceded by a heavy rain period; the length of time following the end of this period is inversely proportional to air temperature. Maximum flower production often occurs at the end of a spell of continuously increasing air temperatures and is always preceded by a period of drought. It is suggested that flowering cycles correspond with cycles of metabolic activity in tubers, depending on respiratory gas exchanges and on temperatures. [Journal translation]
Les bruyères in vitro. III. Dynamisme de la croissance rythmique chez l’Erica × darleyensis. Étude du développement des feuilles et des entre-noeuds
Authors: Viémont Jean-Daniel
Published: November 2007

Erica × darleyensis grown in vitro and under proper conditions has a rhythmic growth. The length of limbs and internodes of 145 branches was measured. After analysis, the results have led to a model. An attempt to interpret the architecture of a single branch in vitro is proposed.
Ultrastructure of thick-walled hyphae of Glomus fasciculatum in old roots of white clover (Trifolium repens)
Authors: Lim Loon Lui , Cole A. L. J. , Fineran B. A.
Published: November 2007

Transmission electron microscopy reveals many thick-walled intercellular and intracellular arbuscular trunk hyphae in old roots of white clover. Wall thickness varies among hyphae, from those enclosed by only a primary wall to those in which various layers of secondary wall material occur. The total thickness of the wall usually lies between 1 and 2 μm. The secondary wall shows a lamellar organization and occasionally may almost completely obliterate the protoplast. In some walls, closely packed lamellae form dark-staining bands separated by lighter staining bands of wider spaced lamellae. Cytochemical staining indicates that the primary and secondary walls contain polysaccharide material. Several thick-walled hyphae show broken layers in the outermost regions overlying deeper layers of uninterrupted wall. The ruptured wall appears to have been caused by local expansion of the hypha during the phase of extensive secondary wall thickening. It is suggested that the thick-walled hyphae may provide propagative structures on disintegration of the host cortex. Another hypothesis is that these hyphal walls might provide a pathway for apoplastic transport. Solutions contained in mature tissues of the root might move via the walls for utilization by the endophyte in those regions of the root where the growing hyphae are more active metabolically.
Seed cones of Metasequoia milleri from the Middle Eocene of southern British Columbia
Authors: Basinger James F.
Published: November 2007

Permineralized ovulate cones of Metasequoia milleri Rothwell and Basinger (Taxodiaceae) are preserved in silicified peats of the Middle Eocene Allenby Formation near Princeton, B.C., Canada. Cones are about 17 mm wide and 25 mm long and are borne terminally on sparsely leaved stalks or peduncles. Twenty to 30 cone scales are arranged decussately on the cone axis. Externally, cone scales are broadly hexagonal and labiate in appearance owing to a medial cleft. Several ovules, with micropyles directed toward the cone axis, are attached to the adaxial surface of the cone scale. Seeds are 3–4 mm wide and about 5 mm long, with two lateral wings each approximately equal in size to the central seed body. Anatomical similarity to and close association with pollen cones and vegetative remains of M. milleri indicate that all organs belong to a single species. The vegetative body and pollen cones of M. milleri differ in few respects from those of living Metasequoia glyptostroboides Hu and Cheng. The seed cones of M. milleri cannot be distinguished from those of the living species. The close resemblance of the two species indicates evolutionary near stasis, at least structurally, throughout the Tertiary.
MODELING AND OPTIMIZATION OF ZONE-BASED REGISTRATION FOR MOBILE COMMUNICATION NETWORK
Authors: BAEK JANG-HYUN , KIM KYUNG-HEE , SICKER DOUGLAS C.
Published: November 2007

An efficient mobility management for mobile stations plays an important role in mobile communication networks. Two basic operations of mobility management are location registration and paging. A zone-based registration (ZBR) is implemented in most of the mobile communication networks and we consider the mobility management scheme that combines a zone-based registration and a selective paging (SP). We propose a new analytical model that can reflect the characteristics of the ZBR smoothly where location areas of the ZBR are set up so that regions such as roads, bridges, rivers and mountains, where there is relatively little traffic, will constitute their boundaries. We adopt a revised 2-dimensional random walk mobility model to consider such characteristics. In addition, we propose a more efficient division scheme of location area for 2-step selective paging. We evaluate the performance of the mobility management scheme using our mobility model to determine the optimal size of a location area that will result in the minimum signaling traffic on radio channels. Numerical results are provided to demonstrate that our mobility model is useful to evaluate the ZBR more exactly. The results of this study can be used effectively in analyzing and comparing the performances of various mobility management schemes.
Hybrid Organic/Inorganic Transistors Utilizing an Indenofluorene Derivative as Emitter
Authors: Serbena José P. , Hümmelgen Ivo A. , Hadizab Tayebeh , Wang Zhi Y.
Published: November 2007

The molecular semiconductors are widely used on a great diversity of electronic and optoelectronic devices. The incorporation of molecular semiconductors to semiconductor- metal-semiconductor transistors (SMS) simplified the required production technology and, more importantly, allowed the construction of devices in vertical architecture with nearly ideal common-base current gains. In this work we present the results of the construction of SMS transistors utilizing an organic semiconductor, an indenofluorene derivative (DPIF), as emitter. The base and collector are respectively tin (Sn) and p- doped silicon (Si-p). The devices were electrically characterized at three-terminal measurements and were operated in common-base and common-emitter modes, revealing a permeable- base characteristic. The base thickness was varied in order to investigate the influence on the device performance. High current gain (~1) was obtained in common-base mode, and in common-emitter mode a current gain of 120 was achieved for a base thickness of 23 nm.
Design, Fabrication and Performance of Microdevices for Infrared Detection Applications
Authors: de Souza Michelly S. , Pires M. P. , Souza P. L. , Vieira G. S. , Gebhard T. , Unterrainer K. , Lopes A. J.
Published: November 2007

We report on the development of microdevices for mid and far- infrared detection, based on semiconductor structures of InGaAs/InAlAs and GaAs/AlGaAs multi-quantum wells using intraband transitions. The materials were grown by metalorganic vapor phase epitaxy and processed as n-i-n devices by microelectronic techniques. A light coupling scheme was applied, using waveguide geometry with 45o incidence at the edge. The two types of detectors were characterized in terms of dark current and photocurrent, showing peaks at 4.3 and 9.6μm, respectively.
CMOS Active-Pixel Structure for Eye-Aberration Detection
Authors: Furtado A. S. , de Lima Monteiro D. W.
Published: November 2007

For ophthalmic instrumentation, the development of new applicationspecific image sensors can be aided by standard microelectronics technologies. The detector must be capable of sensing very low light levels, without being corrupted by noise effects, yielding a high signal-tonoise ratio (SNR). This paper presents the results of an alternative pixel structure fabricated in standard 1.6μm n-well CMOS technology for future integration in a wavefront sensor for the detection of aberrations in the human eye.
Coupling of a CMOS Optical Sensor to a Micromachined Deformable Mirror with an Adaline Neural Method
Authors: de Lima Monteiro D. W. , Ferriera Antonio I. , Teixeria Frederico B. , Melo Joao G. , Vdovin Gleb
Published: November 2007

We report on the preliminary results of an Adaline neural method for the coupling of a custom CMOS wavefront sensor to a micromachined adaptive mirror. The algorithm does not rely on a fixed basis matrix -as opposed to traditional methods-, offers excellent immunity to round-off errors and admits real-time input adaptability to speed up computations.
High Viscosity Sensing Using a Love Wave Acoustic Platform Combined with a PDMS Microfludic Chip
Authors: Raimbault V. , Rebière D. , Dejous C. , Guirardel M. , Conedera V. , Pistré J.
Published: November 2007

This paper exhibits a microsensor solution to allow Love wave acoustic oscillators working under highly viscous liquid environments. Microfluidic techniques are employed to limit attenuation caused by viscous coupling using a poly(dimethylsiloxane) (PDMS) chip bonded on the Love wave device. Fabrication of PDMS chips is detailed. Several microfluidic chip geometries have been realized. Liquid flows of aqueous glycerol solutions up to 0.939 Pa.s (939cP, 98% glycerol) have been tested. Thanks to insertion losses diminution, we were able to observe the Newtonian to Maxwellian behaviour transition in an oscillator mode. Modelisation using the classical perturbation theory is discussed.
Design, Fabrication ABD Testing of Inexpensive Diffractive Optical Elements
Authors: Filho Dirceu S. , Cirino Giuseppe , Pizolato José C. , Neto Luiz G. , Verdonck Patrick
Published: November 2007

In this work diffractive optical elements were designed using the Iterative Fourier Transform Algorithm, developed and refined for using in Diffractive Optical Elements and lithographic mask design. The Iterative Fourier Transform Algorithm was run with Matlab tools. The designs were implemented using lithographic masks produced on transparencies through a commercial, low cost off-set process. These masks were used to perform optical lithography on glass substrates. Final tuning by plasma etching was necessary to obtain well performing diffractive optical elements.
A Proposed Process to Fabricate Strain Gauge Directly Over the Sensor Substrate by Serigraphic Method
Authors: de Lima Bruno L. , Rodrigues da Silva Ana N. , Morimoto N.
Published: November 2007

The main goal of this work is to characterize the strain gauges fabricated by serigraphic method aiming at its application in pressure sensors and load cells. The strain gauges are fabricated by serigraphic method: 316 L stainless steel and aluminum substrates in order to determine fabrication. The strain gauges fabricated over the aluminum substrate showed low sensibility due mainly to the low sheet resistance of the used paste A gauge factor between 2.8 and 14.6 were obtained for strain gauges fabricated over 316 L stainless steel substrates. It was observed a direct dependence of the gauge factor and the sheet resistance of the paste used to fabricate the strain gauge. A study was carried out in order to determine the dependence of the sensibility and electrical resistance with the thickness of resistive film using the serigraphic pastes which resulted in the best gauge factor(related to the number of serigraphic steps).It was verified that the electrical resistance increases with the number of sintering cycles.
Young's Modulus of a-SiC:H Determined by the Resonant Frequency of Thermally Driven Cantilevers
Authors: Rehder G. , Carreño M. N.
Published: November 2007

This paper describes the determination of the Young's modulus of a-SiC:H films deposited by PECVD at low temperatures (300{degree sign}C) using thermally driven cantilevers. Hydrogenated amorphous silicon carbide (a- SiC:H) cantilevers fabricated by bulk micromachining of silicon substrate are thermally actuated by induced Joule effect to determine their frequency of resonance. The geometric feature of the cantilever along with the material density and Young's modulus are a function of the resonant frequency. Cantilevers of 500 μm in length showed resonant frequencies ranging from 6.9 to 7.7 kHz which relates to a Young's modulus from 343 to 477 GPa with an average of 410 GPa that is similar to crystalline SiC reported in the literature.
UV Bandpass Optical Filter for Microspectometers
Authors: Correia J. H. , Emadi A. R. , Wolffenbuttel R. F.
Published: November 2007

This paper describes the design and modeling of a UV bandpass optical filter for microspectrometers. The materials used for fabricating the multilayer UV filter are: silicon dioxide (SiO2), titanium dioxide (TiO2) and yttrium oxide (Y2O3). The optical filter shows a bandpass response wavelength in the range 230-280 nm, with a transmittance higher than 80%. Such a device is extremely suitable for optical detection of biological molecules with optical absorption or/and fluorescence in the UV spectral range. This UV optical filter can be built using post- processing after integrated-circuit and UV photodiode fabrication in a bipolar or CMOS technology. The dielectric multi-layer stack can be deposited on top of the UV photodiode after the standard technology process has been completed. The number of layers was optimized for 11 with all layers of a thickness acceptable for reproducible fabrication. The materials used for fabricating the UV filter are silicon compatible. Applications presented are in DNA solutions (to measure the optical density of these solutions at 260 nm) and in the detection of a gas flame in the presence of ambient light based on the different emission spectra in the UV.
Modeling of Advanced Semiconductor Devices
Authors: Ungersboeck Enzo , Sverdlov Viktor , Kosina Hans , Selberherr Siegfried
Published: November 2007

Aggressive downscaling of modern semiconductor devices forces development engineers to question the validity of existing modeling approaches. Models for carrier transport have to be considered which are applicable on the transition into the quantum regime. An overview of semiclassical current transport models and their enhancements used for the simulation of nanoelectronic devices is given. Emphasis is put on arising modeling challenges in the existing and future technology nodes. Electron mobility analysis of ultra-scaled, strained field-effect transistors is presented in detail.
Fermi Pinning in Metal-Oxide-Semiconductor Structures Results from Low Oxygen Content at the Metal-Oxide Interface
Authors: Fonseca L. R. , Knizhnik A. A. , Gavrikov A. V. , Iskandarova I. M. , Bagatur'yants A. A. , Potapkin B. V.
Published: November 2007

The selection of a proper metal for replacement of polycrystalline silicon as the metal gate in future generation transistors has been hampered by pinning of the metal Fermi level at the metal/dielectric interface. Using monoclinic hafnia and zirconia as the gate dielectric we compare two different metal gate/gate dielectric interface structures where the oxygen affinity of the metal gate is either low or high under normal processing conditions. We show that for the metal gate with high oxygen affinity (molybdenum) the metal Fermi pinning is weaker than for the metal gate with low oxygen affinity (platinum). Through first principles calculations this behavior is explained as the result of an oxygen-rich interface for the former and a reduced interface for the latter. Based on these observations we propose a general model for Fermi pinning at the metal/metal oxide interface as mainly caused by low levels of interfacial oxygen. Such red uced interfaces may result from processing conditions as well as by the metal gate low affinity for oxygen.
Evaluation of Triple-Gate FinFETS with High-k Dielectrics and TiN Gate Materials Under Analog Operation
Authors: Pavanello M. A. , Martino João A. , Simoen Eddy , Rooyackers R. , Collaert N. , Claeys Cor
Published: November 2007

This work presents the analog performance of nMOS and pMOS triple-gate FinFETs with high-k dielectrics, TiN gate material and undoped body from DC measurements. Different fin widths and devices with and without halo implantation are explored. No halo FinFETs can achieve extremely large gain at similar channel length and improved unity gain frequency. The FinFETs with channel length of 110 nm achieved an intrinsic gain of 25 dB. Extremely large Early voltages have been measured on long channel nMOS and pMOS with relatively wide fins compared to the results usually reported in the literature. The large Early voltage obtained suggests the devices are in the onset of volume inversion phenomena due to the low doping level of the device body.
Analysis of Silicon Thickness Reduction on Analog Parameters of GC GAA SOI Transitors Operating up to 300{degree sign}C
Authors: dos Santos Carolina D. , Pavanello M. A. , Martino João A.
Published: November 2007

This paper analyzes the impact of silicon film thickness reduction in some analog parameters of Gate-All-Around (GAA) transistors using the graded-channel (GC) architecture. The study was done at high temperatures (up to 300{degree sign}C) through two- dimensional simulations. As the silicon film is reduced an improvement on the Early voltage was observed. However, for GC GAA devices this improvement is more pronounced at room temperature than at high temperatures. The output swing voltage (VOS) was also studied and it decreases while reducing the silicon thickness. Regarding the GC GAA the VOS is larger than conventional GAA in 50 nm thick transistors.
Series Resistance Influence on the Linear Kink Effect in Twin-Gate Partially Depleted SOI nMOSFETS
Authors: Agopian Paula G. , Martino João A. , Simoen Eddy , Claeys Cor
Published: November 2007

This work elaborates on the influence of the series resistance on the linear kink effect (LKE) in twin-gate partially depleted (PD) Silicon-on-Insulator (SOI) nMOSFETs. The study is based on two-dimensional numerical simulations and is validated by experimental results. A relationship between the total resistance and the apparent mobility degradation factor is reported, showing that the twin-gate structure and a conventional SOI transistor with an external resistance both present a similar LKE reduction. The asymmetric behavior of the body potential with the interchange of the master and slave transistor of the twin-gate structure will be also shown.
Design and Simulation of a Thyristor Surge Protective Device for Telecommunication Systems
Authors: de Orio R. L. , Swart J. , Marzano W.
Published: November 2007

This paper describes the design of a thyristor surge protective device (TSPD) for telecommunication equipments based on electrical simulations carried out with ATLAS from SILVACO. The influence of the device doping and geometry on the breakover voltage, switching and holding current and on the on-state voltage drop has been analyzed. It has been shown that the TSPD voltage capability is dependent on the breakdown voltage of the p-n (substrate) junction. Also, it has been observed that pregion doping concentration and emitter geometry have both a great impact on the on-state device operation. A TSPD with breakover voltage of 297 V, holding current of 38.5 mA and on-state voltage drop of 6.7 V at a current of 1 A has been demonstrated.
Polarization Dependence of Photocurrent in InAs/InGaAs/InP Quantum-Dot Infared Photodetectors
Authors: Souza P. L. , Gebhard T. , Schrey F. F. , Strasser G. , Unterrainer K. , Pires M. P. , Landi S. M. , Villas-Boas J. M. , Studart N.
Published: November 2007

Through polarization dependence measurements of photocurrent together with theoretical calculations we were able to identify different intersubband transitions in InAs/InGaAs/InP quantum dot structures for mid infrared photodetectors. Photocurrent for normal incidence was observed but stronger signals are detected for TM polarization of the incident light, revealing a certain extent of a 2D behavior.
High Magnetic Field as a Tool to Study Resonant Sequential Tunneling in Multi-Quantum Wells
Authors: Vieira G. S. , Guimarães P. S.
Published: November 2007

We report magneto-tunneling measurements in doped GaAs/AlGaAs multi-quantum wells which show evidence of a significant magnetic field induced reduction of low energy electron scattering mechanisms. Using such phenomenon we show how a high magnetic field can be used to determine precisely the biases for the best resonant tunneling condition in a multi-quantum well structure. We propose the use of this effect as a tool to validate heterostructure design models and software.
Image Recognition Task Based on Decoupled Single-Electron Hamming Networks
Authors: Guimaraes J. G. , du Pin Calmon A. , da Costa José C.
Published: November 2007

This paper presents a black and white image recogniton task implemented using a decoupled single-electron (SET) Hamming neural network. For the first time, more than 18000 single-electron transistors are used in such a task. This network allows a more practical hardware implementation. Simulation results for various temperatures are presented. A vector clustering task is simulated using SIMON. Robustness against random offset charges, as well as dynamic behavior are evaluated.
Signal Classifier Based on a Single-Electron Stochastic Associative Memory
Authors: do Carmo H. C. , Guimaraes J. G. , da Costa José C.
Published: November 2007

This paper presents a classifier system based on a stochastic associative memory using single-electron basic circuits. This memory can stochastically extract, from a set of stored reference patterns, the one that is most similar pattern to a given input pattern. Simulations are carried out to demonstrate the functionality of the system.
Impact of the Nitrogen Concentration of sub-1.3 nm gate Oxides on 65 nm Technology Transistor Parameters
Authors: Rotondaro A. L. , Laaksonen R. T. , Singh S. P.
Published: November 2007

The nitrogen concentration of ultrathin gate oxides (sub-1.3 nm) was varied in a wide range (from 13 % to 23 %). The threshold voltage and the channel carrier mobility of advanced 65 nm technology CMOSFET transistors fabricated with these oxides were analyzed. It was observed that increasing the nitrogen concentration in the gate oxide results in a negative shift of the threshold voltage for both NMOS and PMOS devices and a degradation of the hole mobility. It was also observed that p-channel transistors are more sensitive to the nitrogen concentration of the gate oxide than n-channel transistors.
Study of TiO2 and SiO2/TiO2 as Gate Dielectric Maaterials
Authors: Albertin K. F. , Valle M. A. , Pereyra I.
Published: November 2007

MOS capacitors with TiO2 and TiO2/SiO2 dielectric layer were fabricated and characterized. TiO2 films where physical characterized by Rutherford Backscattering, Fourier Transform Infrared Spectroscopy and Elipsometry measurements. Capacitance-voltage (1MHz) and current-voltage measurements were utilized to obtain, the effective dielectric constant, effective oxide thickness (EOT), leakage current density and interface quality. The results show that the obtained TiO2 films present a dielectric constant of approximately 40, a good interface quality with silicon and a leakage current density, of 70 mA/cm2 for VG = 1V, acceptable for high performance logic circuits and low power circuits fabrication, indicating that this material is a viable substitute for current dielectric layers in order to prevent tunneling currents. The results for SiO2 (6nm) /TiO2(58nm) layer show a reduction of 3 orders of magnitude in leakage current density and an effec tive dielectric constant of 20, also viable to substitute the usual dielectric material in CMOS fabrication.
p-Type δ-Doped Layers in GaAs Isolated by He+ Bombardment
Authors: Boudinov H. , Pesenti G. C. , Danilov I. , Zvonkov B N.
Published: November 2007

Ion implantation is an essential process for production of modern III-V compound semiconductor devices and circuits and has been proven as a successful method to convert a conductive layer into a highly resistive one. Due to its simplicity, precise depth control and compatibility with planar technologies, ion implantation is a potential alternative for mesa etching. Selective masking of the semiconductor surface with photoresist followed by ion irradiation is an efficient and practical way to isolate closely spaced devices. Irradiation of GaAs by ions results in resistivity increase as a consequence of free carrier removal by trapping at defects introduced by the irradiation. Delta-doping is a well known technique which spatially confines the dopants to one atomic layer during epitaxial growth of semiconductor materials. In the present work a dose dependence of sheet resistance of delta- doped GaAs structures, irradiated by He+ ions, was inve stigated. It was found that a threshold dose for electrical isolation of the structures was determined by the energy of ions and by the concentration of initial doping.
MEIS Study of Sb Implantation in O or N pre-implanted Si(001) and SIMOX
Authors: Dalponte M. , Boudinov H. , Goncharova L. V. , Garfunkel E. , Gustafsson T.
Published: November 2007

Medium energy ion scattering (MEIS) was used to study distribution of ion-implanted Sb dopant in Si with excess vacancies and SIMOX substrates and the effects of thermal treatments. Extra vacancies in Si were generated by N or O pre-implantations at high temperature. Effects related to the different chemical nature of the pre-implanted species are expected under these conditions. Different Sb annealing behavior and distribution were observed for O and N pre-implanted Si. The oxygen containing samples (SIMOX and O pre-implanted Si) presented higher substitutionality after long annealing times. The nitrogen pre- implanted Si presented the lowest amount of segregated Sb and more uniform dopant distribution. Both pre-implanted samples, N and O, had a large dopant loss to the atmosphere during annealing.