bluuebunny/crossref_metadata_2025 huggingface dataset:
AlGaAs photocathode with enhanced response at 532 nm
Authors: Wang Dong-Zhi , Zhang Yi-Jun , Li Shi-Man , Tong Ze-Hao , Tang Song , Shi Feng , Jiao Gang-Cheng , Cheng Hong-Chang , Fu Rong-Guo , Qian Yun-Sheng , Zeng Yu-Gang ,   School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China,   Science and Technology on Low-Light-Level Night Vison Laboratory, Xi’an 710065, China,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
Published: April 2024

The AlGaAs photocathode can be used in the field of underwater optical communication because of its fast response speed and adjustable spectral response range. In order to solve the problem that the low light absorption of the AlGaAs emission layer limits the improvement of its quantum efficiency, the distributed Bragg reflector (DBR) structure is used to reflect the light at a specific wavelength back to the emission layer to further increase the absorption rate, thus improving the response capability of the photocathode at 532 nm. The spectral response model of the AlGaAs photocathode with DBR structure is obtained by solving one-dimensional continuity equation. The optical model of the AlGaAs photocathode with enhanced response at 532 nm is established by the finite-difference time-domain method. The effects of the sublayer periodic pairs, the sublayer material and the thickness of emission layer and buffer layer on the absorption rate of emission layer are analyzed. The light absorption distributions of AlGaAs photocathode with and without DBR structure are compared, and the influence mechanism of DBR structure on the blue-green light absorption capacity of AlGaAs photocathode emission layer is clarified, which can provide a theoretical basis for designing its structural parameters. The results show that the DBR structure with a periodic pair of 20 and Al0.7Ga0.3As/AlAs has the best reflection effect on 532 nm light. Based on the DBR structure, when the thickness of the emission layer and buffer layer are 495 nm and 50 nm, respectively, the emission layer has the best absorption rate of 532 nm light. Furthermore, two kinds of AlGaAs photocathodes with and without DBR structure are prepared by the metal-organic chemical vapor deposition technology, and the reflectivity and profile structure of the grown samples are characterized. Then the Cs/O activation experiments are performed to compare the spectral response curves. It is found that the spectral response of the AlGaAs photocathode sample with DBR structure at 532 nm wavelength is about twice that of the sample without DBR structure.
GaSe/β-Ga2O3 heterojunction based self-powered solar-blind ultraviolet photoelectric detector
Authors: Su Ran , Xi Zhao-Ying , Li Shan , Zhang Jia-Han , Jiang Ming-Ming , Liu Zeng , Tang Wei-Hua ,   Innovation Center of Gallium Oxide Semiconductor (IC-GAO), College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China,   School of Electronic Information Engineering, Inner Mongolia University, Hohhot 010021, China,   School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China,   MIIT Key Laboratory of Aerospace Information Materials and Physics, College of Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
Published: April 2024

UV photodetectors have the advantages of high sensitivity and fast response speed. As an ultra-wide bandgap semiconductor, gallium oxide (Ga2O3) plays an extremely important role in detecting deep ultraviolet. It can form a typical type-II heterostructure with GaSe, promoting carrier separation and transport. In this work, Ga2O3 epitaxial films are grown on sapphire substrates by plasma-assisted chemical vapor deposition (PECVD). The GaSe films and GaSe/β-Ga2O3 heterojunction photodetectors are grown on gallium oxide films by Bridgeman technology. The detector has a good response to deep ultraviolet light, the dark current of the device is only 1.83 pA at 8 V, and the photocurrent reaches 6.5 nA at 254 nm. The UVC/Visible (254 nm/600 nm) has a high rejection ratio of about 354. At very small light intensities, the responsivity and detection can reach 1.49 mA/W and 6.65 × 1011 Jones, respectively. At the same time, due to the photovoltaic effect formed by the space charge region at the junction interface, the detector exhibits self-powered supply performance at zero bias voltage, and the open-circuit voltage is 0.2 V. In addition, the detector has a very good sensitivity. The device can respond quickly, whether it is irradiated with different light intensities under constant voltage, or with different voltages under constant light intensity. It can respond within milliseconds under a bias voltage of 10 V. This work demonstrates the enormous potential of heterojunctions in photoelectric detection by analyzing the photophysical and interface physical issues involved in heterojunction photodetectors, and provides a possibility for detecting the deep ultraviolet of gallium oxide.
tCFS: A new ‘CFS tracking’ paradigm reveals uniform suppression depth regardless of target complexity or salience
Authors: Alais David , Coorey Jacob , Blake Randolph , Davidson Matthew J.
Published: April 2024

When the eyes view separate and incompatible images, the brain suppresses one image and promotes the other into visual awareness. Periods of interocular suppression can be prolonged during continuous flash suppression (CFS) - when one eye views a static ‘target’ while the other views a complex dynamic stimulus. Measuring the time needed for a suppressed image to break CFS (bCFS) has been widely used to investigate unconscious processing, and the results have generated controversy regarding the scope of visual processing without awareness. Here, we address this controversy with a new ‘CFS tracking’ paradigm (tCFS) in which the suppressed monocular target steadily increases in contrast until breaking into awareness (as in bCFS) after which it decreases until it again disappears (reCFS), with this cycle continuing for many reversals. Unlike bCFS, tCFS provides a measure of suppression depth by quantifying the difference between breakthrough and suppression thresholds. tCFS confirms that: (i) breakthrough thresholds indeed differ across target types (e.g., faces vs gratings, as bCFS has shown) – but (ii) suppression depth does not vary across target types. Once the breakthrough contrast is reached for a given stimulus, all stimuli require a strikingly uniform reduction in contrast to reach the corresponding suppression threshold. This uniform suppression depth points to a single mechanism of CFS suppression, one that likely occurs early in visual processing because suppression depth was not modulated by target salience or complexity. More fundamentally, it shows that variations in bCFS thresholds alone are insufficient for inferring whether the barrier to achieving awareness exerted by interocular suppression is weaker for some categories of visual stimuli compared to others.Research on unconscious vision has proliferated recently, often employing the continuous flash suppression (CFS) method in which rapidly changing shapes viewed by one eye suppress the other eye’s image from awareness. If that suppressed image is progressively strengthened in contrast it will eventually break suppression and emerge into visible awareness. Low breakthrough thresholds are claimed to indicate unconscious processing during suppression. We introduce a method that quantifies breakthrough thresholds and suppression thresholds, thus providing a lower bound missing from previous CFS research. Comparing various image types, including those claimed to undergo unconscious processing, all images show equal suppression when both thresholds are measured. We thus find no evidence of differential unconscious processing and conclude reliance on breakthrough thresholds is misleading without considering suppression thresholds and leads to spurious claims about unconscious processing.
Chronic activation of a negative engram induces behavioral and cellular abnormalities
Authors: Jellinger Alexandra L. , Suthard Rebecca L. , Yuan Bingbing , Surets Michelle , Ruesch Evan A. , Caban Albit J. , Liu Shawn , Shpokayte Monika , Ramirez Steve
Published: April 2024

Negative memories engage a brain and body-wide stress response in humans that can alter cognition and behavior. Prolonged stress responses induce maladaptive cellular, circuit, and systems-level changes that can lead to pathological brain states and corresponding disorders in which mood and memory are affected. However, it’s unclear if repeated activation of cells processing negative memories induces similar phenotypes in mice. In this study, we used an activity-dependent tagging method to access neuronal ensembles and assess their molecular characteristics. Sequencing memory engrams in mice revealed that positive (male-to-female exposure) and negative (foot shock) cells upregulated genes linked to anti- and pro-inflammatory responses, respectively. To investigate the impact of persistent activation of negative engrams, we chemogenetically activated them in the ventral hippocampus over three months and conducted anxiety and memory-related tests. Negative engram activation increased anxiety behaviors in both 6- and 14-month-old mice, reduced spatial working memory in older mice, impaired fear extinction in younger mice, and heightened fear generalization in both age groups. Immunohistochemistry revealed changes in microglia and astrocytes, alongside GABAergic fluorescence reduction in the hippocampus. In summary, repeated activation of negative memories induces lasting cellular and behavioral abnormalities in mice, offering insights into the negative effects of rumination on human health.
Determinants of Market Participation among Smallholder Common Bean Farmers in Eswatini (Former Swaziland)
Authors: Kibirige Douglas , Singh Ajay S. , Dlamini Sicelo I. , Dlamini Delsile D. , Mavimbela N.
Published: April 2024

Purpose: Promoting small-scale farmers’ market participation is perceived to be a motivation of transforming peasantry subsistence farming to commercialization for improved rural livelihoods especially in developing countries like Eswatini. Despite efforts by the government and other stakeholders the transformation process is too slow or stagnant mostly on non-traditional export food commodities including common beans in Eswatini. The drivers of small-scale common bean farmers ‘market participation and level of market participation in Eswatini are not known, hence this study.
Objectives: The main objective of the present study is to find out the determinants of market participation among the smallholder common beans farmers in Eswatini.
Research Methods: This study used secondary data accessed from Eswatini Agricultural Development Enterprise (ESWADE) under the Smallholder Market Lead Project was used. The data was cleaned and a total of 164 common bean farmers were considered for this study. The data was analysed using descriptive statistics and Heckman two-stage selection model.
Findings: The results generated indicate that most respondents were females (63%). The results further show that there is a significant difference of 1.396 in the number of family size helping in farming between participant and non-participants. About 84.8% of the farmers depend on rain to water their beans. Gender, knowing size of land, method of watering and household farm labour size were found to be the determinants of common bean farmer’s choice and intensity of participation in the market.
Recommendation: It is recommended that farmers should consider irrigating their crops, participate fully in farming activities and know their size of land because these factors has been proven to increase the intensity of market participation of bean farmers and the government should take initiative to provide more extension officers to conduct effective training and incentives that will encourage the middle age group to participate in sugar bean farming.
Originality/ Value: This paper highlights the determinants of market participation among the smallholder common beans farmers in Eswatini as well as establishes the socio-economic characteristics of the small scale common bean farmers.
Extraneous Shocks Affecting Agribusiness Loans Default Rate in Agricultural Finance Corporation, Mount Kenya Region
Authors: Miriti M’Muruku Salesio , Kingori Gathungu Geofrey , Nkatha. Mwirigi Rael
Published: April 2024

Agro-shocks create stochastic disturbances to agribusiness performance, which spills over to the performance of credit markets. Farm loan beneficiaries domiciled in the Mount Kenya Region of the Agricultural Finance Corporation (AFC), have recorded a poor loan repayment rate of 20.33% versus 10%, which is the Central Bank of Kenya benchmark for all types of loans in Kenya. Given that agribusiness is a priority sector for addressing food and employment concerns, the performance of agri-loans is sacrosanct. This study aimed to determine the effect of extraneous shocks on the default rate of agribusiness loans disbursed by AFC in the Mount Kenya Region. The region has 11 branches with a population of 3,002 agribusiness borrowers. A sample of 300 respondents was drawn using systematic random sampling with an interval of ten. In a descriptive design using a structured questionnaire, primary data were collected on the effect of extraneous shocks on the default rate of AFC loans. To analyse the data, the Statistical Package for Social Sciences (SPSS V.27) was used. The effect of variables in predicting the default rate was estimated using regression analysis. To derive the F-statistic to test the adequacy of the regression model, ANOVA was performed. A multiple regression model was used to determine the statistical relationship between extraneous shocks and AFC loan default. The model estimates revealed that the three indicators (agroclimatic extremes, market volatility and biological hazards) of extraneous shocks explained 23.90% of the AFC loan default rate. The findings revealed that the statistical significance of the extraneous shocks was positive and significant at 5% (p values=0.00<0.05), implying that their occurrences presented performance challenges to the funded farming projects, thus plunging the loan beneficiaries into repayment challenges. The level of association of each of the indicators with the default rate is as follows: agroclimatic extremes (21.7%), market volatility (30.6%) and biological hazards (17.3%). This study contributes to the existing body of facts in agricultural finance and risk management by bringing to the fore that agro-shocks are sources of far-reaching menaces that constrain the sustainable production process further hindering the repayment of agricultural loans. The study recommends the need for strategic imperatives pointing to interventionist policies through protectionism, partnerships and the mitigation strategies to internalize the resultant negative externalities; loan actors should provide for contingencies and be alert to absorb risks emanating from shocks; penultimately, credit players should collaborate in pursuit of bespoke insurance schemes that can suitably cover farmer projects; ultimately, credit stakeholders should adopt coping strategies to cushion the societies from emerging distresses and devastating constraints.
Evaluation of Biofortified Sweet Potato Varieties for Their Growth, Yield and Economic Performance under Assam Condition
Authors: Baruah Rocktim , Pathak Nishita , Neog Manoranjan , Sarma Utpal Jyoti
Published: April 2024

An on-farm trial under Krishi Vigyan Kendra, Baksa was undertaken to evaluate the performance of two biofortified sweet potato varieties (Bhu Sona and Bhu Krishna) against a check variety Dergaon Red. The trial was conducted in eight different locations of Baksa and Dhubri district of Assam following scientific cultivation practices. Assessing the novel varieties for performance and economic return were taken as primary objectives while designing the experiment. Randomised Block Design was used to lay out the design and statistical analysis of the growth and yield characters shows significant differences between the three varieties. The variety Bhu Sona exhibited the highest vine length (214 cm), tuber length (18.6 cm), tuber weight (152.3 g), and average yield (16.7 tonnes/ha).  In some significant yield characteristics like marketable tuber yield per plant and tuber yield per plant, the two biofortified varieties were at par with each other. And with respect to days taken for harvesting from planting, Bhu Sona and Dergaon Red were at par with each other with 109.3 days. The economic analysis reflected a maximum gross income of Rs. 253500 per hectare in Bhu Sona which was 26.8% more than the check variety. The variety Bhu Krishna also exhibited a 14% increase in gross return from the check variety. The trial indicated that the cultivation of varieties Bhu Sona and Bhu Krishna is feasible under Assam conditions contributing higher economic return to the farmers.
Modelling by Generation of Poisson Distributed Numbers of First Historical Zika Outbreak in Salta, Argentina
Authors: Rosales Juan Carlos , Abad Betina
Published: April 2024

Aims/ Objectives:: In this work we describe the first historical Zika virus outbreak recorded in Salta, Argentina, in the year 2017, through Monte Carlo-type simulations using the Poisson model. Later we made comparisons with previous results.Study Design: Retrospective-descriptive studies and stochastic computational experiment analysis Place and Duration of Study: Department of Mathematic, Faculty of Exact Sciences. National University of Salta, Argentina, from March 2021 to December 2023.Methodology: Descriptive and computational experiment analysis. Parameter estimation by Maximum Likelihood and Simulation of type Monte Carlo.Results: We describe the probabilistic behavior through Monte Carlo simulations of the first historical outbreak of Zika in Salta Argentina, 2017. Based on the data of registered Zika cases, we estimate a probabilistic Poisson model with parameter\(\hat{\lambda}\) = 13:092 casesweek-1 and confidence interval 95%CI [11:889- 15:110]. Finally, by computational experiments we generate epidemic outbreaks with 20 runs. The computational experiments shows that, from a qualitative point of view, the descriptions of the outbreak are qualitatively acceptable and they were not better than the probabilistic model obtained in a previous study. However, from the statistical point of view, carrying out computational experiments of 10 comparative runs in each model, the models provide simulations of epidemic outbreaks by Zika virus, for this region of Salta, Argentina, that do not differ significantly at a confidence level of 5%.
Comprehensive Study on Macronutrient Status and Physicochemical Characteristics of Lateritic Soils of Bankura District, West Bengal, India
Authors: Nandi Nimai , Ghosh G. K. , Kundu M.C.
Published: April 2024

The present study's objective was to evaluate the content of macronutrients (N, P, K, S) in relation to some physicochemical properties of lateritic soils of Bankura district of West Bengal, India. Altogether 99 soil surface samples were collected from nine blocks namely Bankura II, Onda, Bisnupur, Barjora, Raipur, Sarenga, Bankura I, Gangajalghati, and Chatna of Bankura district of West Bengal. These soil samples were analyzed for some soil fertility parameters like particle size distribution, pH, EC, organic carbon (OC) and available macronutrients contents using standard methodology. The research area’s soils are characterized by sandy clay loam to sandy loam in texture with few samples having loamy sand texture and with soil pH raging from very strongly acidic to neutral. The EC was found to be very low (<1.0 dSm-1) indicating the safe limit for soils where OC content was ranging from low to medium. The content of available N, K of soil samples were low to medium while their content in available P was medium to high. The content of available S was deficient, medium and high for 25, 32 and 43 per cent of research area’s soils respectively. There was significant positive correlation of soil pH with available K content whereas non-significant with available S content. There was a strong and positive correlation between available N and OC levels. It will help the farmers to obtain balanced fertilizer doses for different crops and soils.
Genetic Variability for Mulberry Fruit Traits in Different Mulberry Accessions (Morus spp.)
Authors: C Sushmitha , Chikkalingaiah . , Murali K. , B. N Ahalya
Published: April 2024

The present study comprised of thirty- seven mulberry accessions. There are large differences were observed between the minimum and maximum range during rainy season and winter season. Phenotypic coefficient of variation (PCV %) was found to be higher than the respective genotypic coefficient of variation (GCV %) for all the characters denoting variability among genotypes in both the seasons. Estimates of phenotypic and genotypic coefficient of variations were high for fruit weight 105.64, 105.60%) and (70.09, 69.98 %) followed by number of seeds per fruits (58.47, 55.86%) and no. of fruits per fruits (38.45, 38.31%) in rainy season respectively. Maximum heritability was observed for fruit weight (99.92) during rainy season and in winter season PH of mulberry fruit juice recorded maximum heritability (99.93 %). Highest genetic advance was recorded for number of fruits per plant (898.09) and (790.28) during rainy and winter respectively. High heritability coupled with high genetic advance as percent of mean in respect of No. of days required for fruit formation, fruit length(cm), fruit width(cm), No. of fruits/plant, No. of fruits/plant, PH of mulberry fruit juice, Number of seeds per fruits and germination per cent of seed per fruit was observed in rainy and winter seasons.
Fungal Diversity Associated with the Hive Stored Pollen of Stingless Bees Tetragonula travancorica Shanas and Faseeh
Authors: Ramakrishna Bindu Gudi , Chellappan Mani , Kulkarni Surendra Gopal , Mathew Deepu , Thodikayil Ranjith Matta , Sudheer Shanas
Published: April 2024

The process of collecting and storing pollen by stingless bees involves a complex fermentation process, enriching it with nutrients and probiotics, making it valuable as a dietary supplement. However, the presence of mycotoxins-producing fungi in bee pollen poses health risks to humans. Thus, the study aims to characterize the fungi associated with hive-stored pollen of stingless bees. The results revealed the presence of various fungal species, including Penicillium spp. P. chrysogenum, Aspergillus flavus, and A. aculeatus. This species has a symbiotic association with hive-stored pollen and is capable of producing mycotoxins. This necessitates post-harvest processing to reduce microorganisms ensuring the safety and quality of bee-derived food products for consumer health
Comparative Analysis of Hydroponic Farming Income between Pak Choy (Brassisca chinensis L.) and Lettuce (Lactuca sativa L.)
Authors: Pryatnasari Uliya , Mursidah
Published: April 2024

The increasingly narrow area of ​​productive land, especially in big cities, makes cultivating plants using hydroponic techniques attractive and increasingly important. In hydroponic farming there is also a production income value that is different from the production of the types of vegetables that have been planted. This research aims to determine the hydroponic farming income. This research was carried out from November 2022 to January 2023. The sampling method was carried out purposive sampling or intentionally, namely at Graha Indah Farm. The data collected is primary data because this hydroponic cultivator built his own business. The research findings indicate that the hydroponic farming income at Graha Indah Farm varies significantly. Pak choy generated IDR 38,660,002.53 in the first planting season and IDR 463,920,030.36 annually, equivalent to IDR 5,799.00 m-2 year-1. Meanwhile, lettuce yielded IDR 16,183,000.83 in the first planting season and IDR 194,196,007.59 annually, equivalent to IDR 809.15 m-2 year-1. Pak choy contributed to 87.76% of the income, whereas lettuce accounted for 12.24%. Thus, it's evident that lettuce has a higher income and demand value.
Release of DNA Oligonucleotides and Their Conjugates from Controlled‐Pore Glass Under Thermolytic Conditions
Authors: Grajkowski Andrzej , Cieślak Jacek , Norris Scott , Freedberg Darón I. , Kauffman Jon S. , Duff Robert J. , Beaucage Serge L.
Published: December 2008

The sequential functionalization of long‐chain alkylamine controlled‐pore glass (CPG) with a 3‐hydroxypropyl‐(2‐cyanoethyl)thiophosphoryl linker and a dinucleoside phosphorotetrazolide leads to a uniquely engineered support for solid‐phase synthesis. Unlike conventional succinylated‐CPG supports, this support is designed to allow oligonucleotide deprotection and elimination of deprotection side‐products to proceed without release of the oligonucleotide. When needed, the DNA oligonucleotide can be thermolytically released in 2 hr under essentially neutral conditions. The modified CPG support has been successfully employed in the synthesis of both native and fully phosphorothioated DNA 20‐mers. On the basis of reversed‐phase HPLC and electrophoretic analyses, the purity of the released oligonucleotides is comparable to that of identical oligonucleotides synthesized from succinylated‐CPG supports, in terms of both shorter‐than‐full‐length oligonucleotide contaminants and overall yields. The detailed preparation of DNA oligonucleotides conjugated with exemplary reporter or functional groups, either at the 3′‐terminus or at both 3′‐ and 5′‐termini, is also described. Curr. Protoc. Nucleic Acid Chem. 35:3.17.1‐3.17.21. © 2008 by John Wiley & Sons, Inc.
Immune Mechanisms against Intracellular Pathogens
Authors: Nath Indira
Published: December 2008

Chronic infectious diseases in humans are caused by microorganisms that reside within phagocytes and epithelial cells. Host defence mechanisms against intracellular pathogens are primarily orchestrated by T lymphocytes via cytokine networks. Dysregulation of host responses lead to persistence of infection and immunopathology.
Immune System
Authors: Davies D Huw
Published: December 2008

The immune system comprises an interacting assemblage of cells and soluble molecules whose primary function is to kill invading microorganisms that may cause damage to the body. Two interdependent kinds of immune system are present in most vertebrates, which together trigger one or more different killing mechanisms according to whether the microbes live within or outside the cells of the body. An innate system, mediated by receptors which recognize uniquely microbial structures, responds rapidly to the threat of invading organisms. This underlies an adaptive system, mediated by antigen receptors on lymphocytes, which produces a more sustained and comprehensive response. Only the adaptive system, found exclusively in vertebrates, retains a memory of exposure to each microbe and ensures the system is mobilized more rapidly upon a subsequent infection by the same pathogen.

Key concepts

A rapidly mobilizable form of defence (the immune system) is required to kill microbes that breach the skin and other passive defences of the body.

Physical injury to tissues triggers inflammation which serves to mobilize the immune system and to repair tissue damage.

The innate immune system is moblized first in response to microbes and is triggered by receptors for microbial components that are not found in the body.

The innate system comprises cells such as phagocytes (macrophages, neutrophils) and natural killer cells, and soluble antimicrobial components such as complement.

The adaptive immune system is mediated by T and B lymphocytes, which are activated through the recognition of microbial components using antigen receptors.

The genes for antigen receptors are produced by a unique process of gene rearrangement that results in a vast repertoire of antigen receptors, each with a unique antigen specificity.

The repertoire of antigen receptors present in the body ensures that any invading microbe missed by the innate system can be recognized by the adaptive system.

The adaptive system uses many of the same killing (effector) mechanisms as the innate system, and is likely to have evolved only in vertebrates.

Antibodies are soluble forms of the B lymphocyte antigen receptor that are produced in large quantities during an adaptive immune response; one functionof antibodies is to bind to microbes and render them more susceptible to phagocytosis.

Because each lymphocyte has a different receptor, the adaptive system is mobilized more gradually than the innate system; however, the response is more sustained, less easily evaded by microbes, and unlike the innate system, it retains a memory of exposure to a particular microbe to ensure a more rapid response to the same microbe upon subsequent exposure.
Lymphoid Development
Authors: Gjertsen Nicole , Collazo Michelle , Kerr William G
Published: December 2008

Lymphoid cells (B cells and T cells) express antigen receptors which mediate the specific immune response. The development of lymphoid cells is tightly controlled to avoid autoreactivity and promote a diverse and useful repertoire of specificities.
Immunological Cytotoxic Factors
Authors: Pardo Julián , Anel Alberto , Regner Matthias , Froelich Christopher J
Published: December 2008

The host immune system has evolved a variety of strategies to control pathogens and tumour development. The beneficial outcome is the death of the offending cell (transformed or virus‐infected) and consequently the demise of the invading pathogen. Many of the mechanisms used by the immune system to eliminate intracellular and extracellular pathogens and transformed cells, include not only death mediators associated with cytotoxic lymphocytes, but also soluble proteins such as the complement system and the defensins, which are designed to eliminate extracellular pathogens.
Cancer Cytogenetics
Authors: Roberts Paul
Published: December 2008

The development and progression of cancer is often associated with the acquisition of nonrandom chromosome aberrations. These can produce changes in gene loci, resulting in either the deregulated expression of an oncogene, the production of a chimaeric fusion gene or inactivation of a tumour suppressor gene (TSG). Chromosome aberrations are particularly important in the diagnosis, prognosis, progression, monitoring and treatment of acute and chronic leukaemia, small round cell tumours and central nervous system tumours. Numerical chromosome changes typically result in gain or loss of a few chromosomes, but can also produce changes in ploidy. Translocations, mostly affecting oncogenes, account for the majority of disease‐specific structural chromosome aberrations, whereas deletions are more important in TSGs. Knowledge of the nature and mechanisms of action of the genes involved is important in understanding how they contribute to the genesis, promotion and progression of this complex disease.

Key concepts

Chimaeric gene fusion – the most frequent, recurrent oncogenic change usually produced via chromosome translocation. Two previously separate and independent genes are fused to form a single unique contiguous gene, and the resultant gene product has oncogenic properties.

Oncogene deregulation – juxtapositioning of an oncogene with the enhancer region of aT‐cell receptorgene or anImmunoglobulingene results in overexpression of the oncogene protein product. This is most commonly a result of a chromosome translocation.

Oncogene amplification – a selective, unscheduled increase in gene copy number enabling a cell to meet the increased transcriptional demands of neoplastic transformation. This is seen as double minutes or as a chromosome duplication.

Tumour suppressor gene inactivation – removal of the growth control functions of a TSG either by mutation or loss, after which the cell may fail to keep a cancer from developing, transforming the cell to a cancer phenotype.

Loss of heterozygosity – the key mechanism of inactivation of a TSG. At a locus heterozygous for a deleterious mutant allele and a normal allele, a deletion or other mutation in the normal allele renders the cell hemizygous or homozygous for the deleterious allele.
Dominant Traits and Diseases
Authors: Jorde Lynn B
Published: December 2008

The principles of genetic dominance and recessiveness established by Gregor Mendel in his experiments with garden peas equally apply to human genetic diseases. For dominant diseases, the inheritance of one copy of the disease allele is sufficient to produce disease. Other factors, such as incomplete penetrance, variable expression, and delayed age of onset, further influence the expression of such diseases.
Seed Germination and Reserve Mobilization
Authors: Nonogaki Hiro
Published: December 2008

When dry seeds take in water, a chain of metabolic events is initiated that results in the emergence of the radicle, thus completing germination. Thereafter, the major stored reserves within the seed are mobilized, providing nutrients to support early seedling growth.
Phenotypic and Developmental Plasticity in Plants
Authors: Kramer Elena M
Published: December 2008

Plants exhibit an astonishingly diverse capacity to respond to environmental signals in many aspects of their development. This phenotypic plasticity is an essential component of their ability to adapt to a wide range of environmental conditions and accommodate their sessile lifestyle. Developmental responses include variation in continuous characteristics, such as stomatal density or root mass, as well as discrete developmental programmes that are produced in reaction to specific stimuli. Of particular interest are the germination, photoresponsive and flowering time pathways, which integrate a wide range of information in order to tailor a plant's development to the current environment. These kinds of pathways have three fundamental components: sensory systems that receive environmental input, interface systems that translate the inputs into specific developmental responses and, lastly, the developmental pathways themselves. The genetic basis for these components is just beginning to be understood.

Key concepts

Phenotypic plasticity – The capacity of a given genotype to produce different phenotypes in different environmental conditions.

Developmental plasticity – Variation in developmental processes that is induced by different environmental conditions.

Maternal environmental effect – The ability of the mother to imprint information on her offspring, often regarding the expected environment for that offspring.
Baculovirus Insect Cell Expression System
Authors: van Oers Monique M , Vlak Just M
Published: December 2008

The baculovirus insect cell expression system is based on the use of recombinant baculoviruses (insect viruses) and their ability to produce high levels of biologically active proteins in cultured insect cells or insect larvae. These viruses have very late genes (polyhedrin, P10), which are highly expressed due to very strong promoters, but are dispensable for infectious virus formation. Deletion of these genes and replacement with foreign genes convert these viruses into expression vectors for the production of recombinant proteins. Convenient systems (bacmids) are available for engineering these baculovirus recombinants in bacteria prior to transfection into insect cells. The proteins produced can be easily purified from infected cells or their supernatants using tags and affinity chromatography. The proteins can be used for human and veterinary applications, such as vaccines and diagnostics.
Galvani, Luigi
Authors: Bresadola Marco
Published: December 2008

Luigi Galvani (1737–1798), an Italian anatomist and physician whose research on animal electricity made a significant contribution to the birth of electrophysiology.
Intellectual Disability: Genetics
Authors: Knight Samantha JL
Published: December 2008

The extent to which genetics plays a role in intelligence has long been a matter for debate. However, it is now well established that genetic effects can contribute to intellectual disability (ID), in particular, moderate to severe ID. The discovery of chromosomal rearrangements and the cloning of causal genes have both clinical and scientific value. Clinically, they help the families of those affected by providing molecular diagnoses, alleviating feelings of guilt and allowing more accurate genetic counselling. Scientifically, they provide important clues regarding the underlying biology of cognition.

Key concepts

Both intellectual ability and disability are strongly influenced by genetics.

ID is usually divided into syndromic and nonsyndromic categories.

Most recognized forms of ID are X‐chromosome linked.

Single gene mutations can cause syndromic and nonsyndromic ID.

Causative gene products can be biochemically linked, signposting functionally important processes.

Genome imbalance (aneusomy and segmental aneusomy) is a significant cause of syndromic ID.

Array comparative genomic hybridization is a powerful new technique for identifying submicroscopic genome imbalances.

Genome architecture can predispose to recurrent genomic disorders.

Clinically, the provision of a molecular diagnosis is important to families with affected members.
Predictive Genetic Testing: Emotional and Behavioural Impact
Authors: Sanderson Saskia C
Published: December 2008

Genetic tests are becoming increasingly available both clinically and commercially. It is important that the psychological impact (e.g. emotional and behavioural impact) of this emerging class of tests is understood. The evidence suggests genetic testing may have fewer adverse emotional effects than anticipated. A clear picture has not yet emerged regarding behavioural impact. However, this field is in its infancy, and there is much work still to be done. The hope is that genetic testing will be applied and communicated in effective and responsible ways that have minimal adverse emotional yet maximal positive behavioural effects, and will ultimately have a significant beneficial impact on human health.
Genetic Education of Primary Care Health Professionals in Britain
Authors: Kirk Maggie , Tonkin Emma
Published: December 2008

The drive to ensure that primary care health professionals in Britain receive appropriate genetics education has made substantial progress in recent years. The strategic initiatives that have emerged from a strong policy foundation are leading developments in education and raising awareness about the role of genetics in primary care. Although significant challenges remain, there is evidence of an evolution from justification of the place of genetics in mainstream healthcare and education, to an articulation of what genetics should be taught, and, more latterly, to a consideration of strategies in ensuring that genetics can be fully integrated into practice.
Restoration of Terrestrial Communities
Authors: Wilson Scott D
Published: December 2008

Restoration returns ecosystems that have been altered by humans to states similar to unaltered systems, especially with regard to dominant vegetation, energy flows, water capture and nutrient cycling. General themes in terrestrial restoration include the degree of alteration, the similarity of the restoration to unaltered systems, and methods for ameliorating soil and returning vegetation. Socioeconomic factors may have overriding influences on restoration strategies. Restoration is a field ripe for research, both in the synthesis of applied knowledge and as a system for experimentally addressing a broad variety of ecological topics.
Sulfur Oxidation in Prokaryotes
Authors: Dahl Christiane , Friedrich Cornelius , Kletzin Arnulf
Published: December 2008

In nature, sulfur occurs in many different oxidation states and is one of the most versatile elements in life. Reduced inorganic sulfur compounds serve either as sources for sulfur assimilation and incorporation into organic compounds or as the basis for oxidative energy‐related processes. Sulfur‐based energy transformation with concomitant mass transformations occurs almost exclusively among prokaryotes (
Archaea
and
Bacteria
). Dissimilatory sulfur oxidation in
Eukarya
is mediated by lithotrophic bacterial endosymbionts. Oxidation of reduced inorganic sulfur species by bacteria is a vital part of the global sulfur cycle and has applied importance in agriculture, waste treatment, biocorrosion and biomining. This article focuses on oxidation of reduced inorganic sulfur compounds and discusses the sulfur‐oxidizing reactions of selected phototrophic and chemotrophic prokaryotes.
Cancer Stem Cells – Basic Concepts
Authors: Hatina Jiří , Schulz Wolfgang A
Published: December 2008

There is growing evidence that tumours display a hierarchy similar to normal tissues. A small population of cancer stem cells is supposed to perpetuate tumour growth. These cells self‐renew and are highly tumourigenic upon injection into immunocompromised animals, yielding tumours largely identical to those from which they were derived. Cancer stem cells exhibit a high degree of chemoresistance due to slow cycling and constitutive expression of multiple members of the adenosine triphosphate (ATP)‐binding cassette (ABC) family of transporters. An increasing number of tumours with tumour stem cells have been identified by now, including breast, brain, colon and prostate cancers, as well as leukaemias. Detailed characterization of cancer stem cells may contribute to a better understanding of the underlying biology of the respective tumours and lead to novel curative therapies.
The Role of Biodiversity
Authors: Wilby Andrew , Hector Andy
Published: December 2008

Human activities have caused widespread loss of biodiversity raising concern about the potential impact on ecosystem processes (flows of energy and materials). A large body of recent research has shown that as species are lost from ecosystems there is, generally, a minor impact on ecosystem processes, but that this impact increases disproportionately as species diversity declines. Functional complementarity among species, due to variation in the ecological niches they occupy, appears to be the main mechanism driving this pattern. Species diversity is also usually positively related to ecosystem stability, i.e. their variation through time and the resistance and resilience to perturbation. These findings are already powerful arguments for the conservation of biodiversity, though current research aims to increase their relevance to the real world by including a more extensive range of ecosystems and processes, realistic food web structures, realistic (nonrandom) extinction scenarios and larger spatial scales.
Patch Fluorometry
Authors: Zheng Jie
Published: December 2008

Patch fluorometry is a technique aimed at correlating local conformational changes in ion channel protein with channel function. This is achieved through simultaneous recordings of fluorescence and current signals from ion channels in isolated membrane patches. The method can be applied to studies of ion channel structure–functional relationship and membrane protein dynamics.
Infrared Spectroscopy of Biological Fluids in Clinical and Diagnostic Analysis
Authors: Shaw R. Anthony , Mantsch Henry H.
Published: December 2008

The infrared (IR) spectrum of a mixture serves as the basis to quantitate its constituents, and a number of common clinical chemistry tests have proven to be feasible using this approach. This article reviews the IR spectroscopy‐based analytical methods that have been developed for consideration as clinical assays, including serum analysis, urine analysis, amniotic fluid assays for the estimation of fetal lung maturity, and others. Because of the widespread interest in the potential for in vivo measurement of blood glucose using near‐IR spectroscopy, a separate section is devoted to the analysis of glucose in whole blood.

A related technique uses the IR spectrum of biomedical specimens directly as a diagnostic tool. For example, the spectra of serum and of synovial fluid have proven to be useful in the diagnosis of metabolic disorders and arthritis respectively, without explicitly recovering their chemical composition from the spectra. Rather, characteristic spectral features and patterns have been identified as the basis to distinguish spectra corresponding to healthy patients from those corresponding to diseased patients. These and other related applications to both human and veterinary health are reviewed here. Since diagnostic spectroscopy of cells and tissues are the subject of separate reviews within this volume, the scope of the present article is restricted to analytical and diagnostic spectroscopy of biological fluids.

Issues such as ease of use, speed, reliability, sample size, and calibration stability all play important roles in governing the practical acceptability of IR spectroscopy‐based analytical methods. To provide a framework to illustrate these issues, descriptions are included for the various procedures that have been explored to successfully wed IR spectroscopy to clinical chemistry. Finally, a recent development promises to broaden the applicability of IR spectroscopy in both clinical analytical and diagnostic applications; the combination of microfluidics (laminar fluid diffusion interface) with spectroscopy of biofluids is outlined with examples illustrating the potential for this integrated technique.
Raman Spectroscopy in Analysis of Biomolecules
Authors: Niaura Gediminas
Published: December 2008

Raman spectroscopy (RS) is a vibrational spectroscopy technique based on the phenomenon of inelastic light scattering from matter (the Raman effect). It is a versatile tool for probing of biological events at the molecular level and for identification of biomolecules. The characteristic mark of modern RS is the variety of techniques used to explore the Raman effect. In this article the advantages and limitations of different methodologies including conventional Raman, resonance Raman (RR), ultraviolet resonance Raman (UVRR), surface‐enhanced Raman (SER), surface‐enhanced resonance Raman (SERR), Fourier transform Raman (FT‐Raman), micro‐Raman, time‐resolved Raman, and coherent anti‐Stokes Raman scattering (CARS) spectroscopies that can be used for analysis of structure and function of biomolecules are discussed. RR and UVRR spectroscopies are particularly important in biological applications since chromophoric groups (active centers in proteins, aromatic amino acid residues, and nucleotides), which in many cases are responsible for the function of biomolecules, can be probed selectively, by tuning the excitation wavelength to the electronic absorption transition of the chromophore. Surface‐enhanced techniques (SER and SERR) are the most sensitive, allowing RS of single biomolecules. The interpretation of the Raman spectra of biomolecules requires identification of spectra‐structure correlations. Numerous marker bands for conformation, hydrogen bonding, protonation, and hydrophobic interaction of the main constituents of biopolymers are provided and discussed.