Quantum transport in weakly coupled superlattices at low temperature

We report on the study of the electrical current flowing in weakly coupled superlattice (SL) structures under an applied electric field at very low temperature, i.e. in the tunneling regime. This low temperature transport is characterized by an extremely low tunneling probability between adjacent wells. Experimentally, I(V) curves at low temperature display a striking feature, i.e a plateau or null differential conductance. A theoretical model based on the evaluation of scattering rates is developed in order to understand this behaviour, exploring the different scattering mechanisms in AlGaAs alloys. The dominant interaction in usual experimental conditions such as ours is found to be the electron-ionized donors scattering. The existence of the plateau in the I(V) characteristics is physically explained by a competition between the electric field localization of the Wannier-Stark electron states in the weakly coupled quantum wells and the electric field assisted tunneling between adjacent wells. The influence of the doping concentration and profile as well as the presence of impurities inside the barrier are discussed

Platelet rich plasma following hysteroscopic adhesolysis: a randomized clinical trial

Background: Intrauterine adhesions (IUAs) is an uncommon condition that occurs after endometrial trauma, still it affects many women seeking fertility. Hystroscopic adhesolysis is the standard management procedure for IUAs, yet many concerns arise about the incidence of recurrence. This study evaluates the efficacy of Platelet rich plasma in decreasing adhesion recurrence following hystroscopic adhesolysis of severe intrauterine adhesions.Methods: A prospective randomized clinical trial held in the Endoscopy Unit of Ain Shams University Hospital, Cairo, Egypt. 160 women with grade-III intrauterine adhesions, according to American Fertility Society criteria, were randomized to either receiving 5ml platelet rich plasma injection into the uterine wall in the most affected parts of the endometrium and lining the uterine cavity by 5ml platelet rich plasma gel followed by intrauterine insertion of folley’s catheter balloon left for two weeks (study group), or only insertion of folley’s catheter balloon for two weeks with injection of placebo solution and using placebo gel (control group). Second look office hysteroscopy was performed 3 months post-operative to assess the grade of intrauterine adhesions. The primary outcome was the incidence of recurrence of intrauterine adhesions. Secondary outcomes were the post-operative improvement of menstrual duration and flow, and pregnancy rate within 1 year post-adhesolysis.Results: 70/81(86.4%) patients showed grade-I adhesions, 8/81 (9.9%) grade-II and 3/81 (3.7%) remained grade-III in the study group compared to 42/78 (53.8%) grade-I, 21/78 (26.9%) grade II and 15/78 (19.2%) grade-III in the control group (p<0.001).Conclusions: Platelet rich plasma shows better improvement of adhesion score, menses duration and menses amount following hystroscopic dissection of severe intrauterine adhesions

Preparation and Characterizations of Chitosan/Citral Nanoemulsions and their Antimicrobial Activity

Background and Objective: The antimicrobial activity of essential oils has been long recognized, however, they easily evaporate and/or decompose during preparation, owing to direct exposure to heat, pressure and light. The current study deals with the formulation and characterization of bio-based oil in water nanoemulsions and their antimicrobial activity against plant pathogens.Material and Methods: Citral oil and low molecular weight chitosan were used for preparation of nanoemulsions in the presence of sodium tripolyphosphate. Nanoemulsions were prepared by adding dropwise citral at different ratios into an aqueous solution containing chitosan, sodium tripolyphosphate and surfactant with continuous stirring and then ultrasonication. The success of formulation was confirmed by dynamic light scattering and scanning electron microscopy techniques. Physical stability and viscosity were investigated in details. The antimicrobial activity was evaluated against Erwinia carotovora, Aspergillus niger and Rhizopus stolonifer. Results and Conclusion: The nanoemulsions had a polydispersity index ranged from 0.508 to 0.614 and particle size from 27 to 1283 nm. The highest antimicrobial activity was observed with F1 formulation (EC50 = 23, 278 and 221 mg L-1, against Erwinia carotovora, Aspergillus niger and Rhizopus stolonifer, respectively). Based on the antimicrobial activity, the prepared chitosan/citral nanoemulsions can be a cost-effective way to protect crops from microbial pathogens. Because such formulations contain bioactive products, the development of resistant pathogens can be delayed.Conflict of Interest: The authors declare no conflict of interest.

Effects of soil amendment treatments on growth, yield and fruit quality of selected banana (Musa AAA) cultivars

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Banana cultivation in Sudan is restricted to the narrow strip of silt deposits along the banks of the Blue Nile and the River Nile. Hence, there is a need to expand banana cultivation in the high terrace, heavy clay soils. Banana performance in heavy clay soils is very poor, unless soil amendments are applied. Therefore, the objective of this research was to study the effects of soil amendment treatments on growth, yield and fruit quality of selected banana cultivars. The experiment was conducted in the Research Farm of the National Institute for the Promotion of Horticultural Exports, University of Gezira, during 2009-2011. Treatments consisted of three selected banana cultivars : Two introduced cultivars, namely, Grand Nain 1824 (GN) and William’s Hybrid 172 (WH) and the local cultivar Dwarf Cavendish (DC). Soil amendment treatments were : 1, 50% heavy clay (HC) + 50% loam (L); 2, 50% HC + 50% chicken manure (CM); 3, 50% HC + 25% L + 25% CM; 4, 33% HC + 33% L + 34% CM; 5, 100% HC (control). Treatments were arranged in a randomized complete block design with three replicates. Results showed that the introduced cultivars GN and WH had more vigorous vegetative growth, higher yield components, total yield and better fruit quality than the local cultivar DC. Soil amendment treatments of 50% HC + 25% L + 25% CM and 33% HC + 33% L + 34% CM resulted in the most vigorous vegetative growth, the highest yield components and total yield and the best fruit quality, followed by 50% HC + 50% L and 50% HC +50%CM, whereas the least vegetative growth, the lowest yield components, total yield and the worst fruit quality were produced by bananas grown in 100% HC (control). In order to expand banana production for the local market and export, it is recommended to amend heavy clay soils with loams and chicken manure at 33% each and grow the introduced cultivars GN and WH. &nbsp;&nbsp;&nbsp;&nbsp; تنحصر زراعة الموز في السودان على الشريط الضيق للتربة الغرينية على ضفاف النيل الأزرق ونهر النيل. هنالك حاجة ماسة للتوسع في زراعة الموز في السودان ولذلك لا بد من محاولة زراعته في الاراضي الطينية الثقيلة و التي لا تصلح لزراعة الموز إلا إذا تمت بعض المعالجات. لذلك فإن الهدف من هذا البحث هو دراسة تأثير بعض مستصلحات التربة على النمو ومكونات الإنتاج والإنتاج الكلي لثلاثة أصناف منتخبة من الموز في هذا النوع من الأراضي. أجريت التجربة في مزرعة بحوث المعهد القومي لتنمية الصادرات البستانية بجامعة الجزيرة خلال الفترة 2009-2011. اشتملت المعاملات على ثلاثة أصناف منتخبة من الموز: صنفان مستجلبان من خارج السودان وهما جراندنين 1824 (GN) وهجين وليامز172 (WH) بالإضافة إلى الصنف المحلي الكافندش القزم (DC). إشتملت مستصلحات التربة على: (1) 50% تربة طينية ثقيلة + 50% تربة غرينية ، (2) 50% تربة طينية + 50% ماروق دواجن ، (3) 50% تربة طينية + 25% تربة غرينية + 25% ماروق دواجن، (4) 33% تربة طينية + 33% تربة غرينية + 34% ماروق دواجن ، (5) 100% تربة طينية (شاهد). أستخدم تصميم القطع العشوائية الكاملة &nbsp;بثلاثة مكررات . أظهرت النتائج أن الأصناف المستجلبة من الخارج GN وWH كانت أفضل في النمو الخضري وأعلى إنتاجية وأفضل جودة للثمار من الصنف المحلي DC. معاملات مستصلحات التربة 50% تربة طينية + 25% تربة غرينية + 25% ماروق دواجن و 33% تربة طينية و33% تربة غرينية و34% ماروق دواجن أعطت أفضل نمو خضري وأعلى إنتاجية وأفضل نوعية للثمار ، تليها المعاملات 50% تربة طينية + 50% تربة غرينية و50% تربة طينية + 50% ماروق دواجن. أما زراعة الموز في الأراضي الطينية الثقيلة بدون مستصلحات أدت&nbsp; إلى أقل نمو خضري وأقل إنتاجية وأدنى نوعية للثمار. لذلك لكي يتم التوسع في زراعة الموز فى الاراضى الطينية الثقيلة للسوق المحلي والتصدير ، فإنه يوصى بإضافة&nbsp; التربة الغرينية و ماروق الدواجن بنسبة 33% لكل منهما وزراعة الأصناف المستجلبة GN و WH. &nbsp

Bioactive Paper Sensor Based on the Acetylcholinesterase for the Rapid Detection of Organophosphate and Carbamate Pesticides

In many countries, people are becoming more concerned about pesticide residues which are present in or on food and feed products. For this reason, several methods have been developed to monitor the pesticide residue levels in food samples. In this study, a bioactive paper-based sensor was developed for detection of acetylcholinesterase (AChE) inhibitors including organophosphate and carbamate pesticides. Based on the Ellman colorimetric assay, the assay strip is composed of a paper support (1×10 cm), onto which a biopolymer chitosan gel immobilized in crosslinking by glutaraldehyde with AChE and 5,5′-dithiobis(2-nitrobenzoic) acid (DTNB) and uses acetylthiocholine iodide (ATChI) as an outside reagent. The assay protocol involves introducing the sample to sensing zone via dipping of a pesticide-containing solution. Following an incubation period, the paper is placed into ATChI solution to initiate enzyme catalyzed hydrolysis of the substrate, causing a yellow color change. The absence or decrease of the yellow color indicates the levels of the AChE inhibitors. The biosensor is able to detect organophosphate and carbamate pesticides with good detection limits (methomyl=6.16×10-4 mM and profenofos=0.27 mM) and rapid response times (~5 min). The results show that the paper-based biosensor is rapid, sensitive, inexpensive, portable, disposable, and easy-to-use

Effect of nitrogen and phosphorus on growth and yield of irrigated sunflower (Helianthus annuus L.)*

&nbsp;&nbsp;&nbsp;&nbsp; Experiments were conducted in winter (2000 2001) and summer (2001) seasons at Elrahad Research Station to investigate the influe- nce of four levels of nitrogen and two levels of phosphorus on growth characters and seed yield of two sunflower cultivars, viz Rodio and Hysun 33. Experiments were arranged in a randomized complete block design with four replications. Rodio and Hysun 33 varied in their growth characters. Differences between the two cultivars. Were highly significant for plant height, leaf area index, days to 50% flowering, days to maturity, head diameter, number of seeds per head, 1000-seed weight and empty seeds percentage. The two cultivars were siY1ificantly different in their seed yield. Nitrogen application significantly increased all growth characters and seed yield of the two cultivars, in both seasons, however, it decreased days to 50% flowering and days to maturity. Nitrogen fertilizer had no significant effect on empty seeds percentage. Phosphorus application signific- antly increased leaf area index, head diameter, number of seeds per head and 1000-seed weight. However, plant height, days to maturity and percentage of empty seeds were not affected. Application of phosphorus had no significant effect on seed yield