Модель гибридного ракетного двигателя. Вычисления, проект и испытания

На даний час і у майбутньому ракетні двигуни будуть найголовнішими засобами виводу на орбіту космічних транспортних апаратів. В даний час найважливішою вимогою при проектуванні двигуна ракети є зменшення її вартості і максимальне збільшення енерговіддачі. Проектування ракетних двигунів - довготривалий і трудомісткий процес, метою якого є виробництво дешевого і високоякісного двигуна, що має мінімальний вплив на навколишнє середовище. Слідуючи зазначеним вимогам, Варшавський Технологічний Університет спільно з Варшавським авіаційним Інститутом розпочали програму екологічно безпечного розвитку ракетних двигунів. Експериментальний гібридний двигун ракети був розроблений і виготовлений для перевірки нової формули твердого палива. Дана стаття містить дослідження безпечної роботи двигуна з окислювачем Al/AN/HTPB, використовуючи при цьому лабораторний дослідний стенд перевірки ракетного гібридного двигуна. Основна мета цієї роботи – це проектування простого ракетного двигуна з наступною можливістю його подальшого розвитку і поліпшення.Now and in the foreseeable future rocket engine will be the most basic propulsion of space vehicle. Nowadays the most important condition in design of rocket engine is the cost reduction and increasing thrust to weight ratio as much as possible. The design of rocket engines is exhaustive and difficult process. It must produce low cost and high performance engine with minimal influence on the environment. Following these requirements, Warsaw University of Technology jointly with Institute of Aviation in Warsaw, started their own program on ecologically safe propulsion development. The experimental hybrid rocket motor has been designed and manufactured to test a new formula of solid fuel. The paper explores the performance and safety implications associated with the oxidizer enhanced Al/AN/HTPB grain by using of a laboratory scale hybrid rocket motor test stand. The main objective of this work was to design simple rocket engine that could smoothly be developed and possibly improved in the future.На данный момент и в обозримом будущем ракетные двигатели будут самыми основными двигательными установками космических транспортных средств. В настоящее время самым важным условием при проектировании двигателя ракеты является уменьшение ее стоимости и максимальное увеличение соотношения тяги к весу. Проектирование ракетных двигателей – продолжительный и трудоемкий процесс, целью которого является производство дешевого и высококачественного двигателя с минимальным влиянием на окружающую среду. Следуя указанным требованиям, Варшавский Технологический Университет совместно с Варшавским авиационным институтом начали программу экологически безопасного развития ракетных двигательных установок. Экспериментальный гибридный двигатель ракеты был разработан и изготовлен для проверки новой формулы твердого топлива. Данная статья содержит исследования безопасной работы двигателя с окислителем Al/AN/HTPB, используя при этом лабораторный испытательный стенд проверок ракетного гибридного двигателя. Основная цель этой работы состоит в проектировании простого ракетного двигателя с последующей возможностью его дальнейшего развития и улучшения

Creating diamond color centers for quantum optical applications

Nitrogen vacancy (NV) centers in diamond have distinct promise as solid-state qubits. This is because of their large dipole moment, convenient level structure and very long room-temperature coherence times. In general, a combination of ion irradiation and subsequent annealing is used to create the centers, however for the rigorous demands of quantum computing all processes need to be optimized, and decoherence due to the residual damage caused by the implantation process itself must be mitigated. To that end we have studied photoluminescence (PL) from NV$^-$, NV$^0$ and GR1 centers formed by ion implantation of 2MeV He ions over a wide range of fluences. The sample was annealed at $600^{\circ}$C to minimize residual vacancy diffusion, allowing for the concurrent analysis of PL from NV centers and irradiation induced vacancies (GR1). We find non-monotic PL intensities with increasing ion fluence, monotonic increasing PL in NV$^0$/NV$^-$ and GR1/(NV$^0$ + NV$^1$) ratios, and increasing inhomogeneous broadening of the zero-phonon lines with increasing ion fluence. All these results shed important light on the optimal formation conditions for NV qubits. We apply our findings to an off-resonant photonic quantum memory scheme using vibronic sidebands

Directing Differentiation of Pluripotent Stem Cells Toward Retinal Pigment Epithelium Lineage

Development of efficient and reproducible conditions for directed differentiation of pluripotent stem cells into specific cell types is important not only to understand early human development but also to enable more practical applications, such as in vitro disease modeling, drug discovery, and cell therapies. The differentiation of stem cells to retinal pigment epithelium (RPE) in particular holds promise as a source of cells for therapeutic replacement in age-related macular degeneration. Here we show development of an efficient method for deriving homogeneous RPE populations in a period of 45 days using an adherent, monolayer system and defined xeno-free media and matrices. The method utilizes sequential inhibition and activation of the Activin and bone morphogenetic protein signaling pathways and can be applied to both human embryonic stem cells and induced pluripotent stem cells as the starting population. In addition, we use whole genome transcript analysis to characterize cells at different stages of differentiation that provides further understanding of the developmental dynamics and fate specification of RPE. We show that with the described method, RPE develop through stages consistent with their formation during embryonic development. This characterization- together with the absence of steps involving embryoid bodies, three-dimensional culture, or manual dissections, which are common features of other protocols-makes this process very attractive for use in research as well as for clinical applications. SIGNIFICANCE: This report describes a novel method of directed differentiation to generate retinal pigment epithelium (RPE) cells from pluripotent stem cells. The employed method is based on adherent monolayer culture using xeno-free conditions and manipulation of the Activin and bone morphogenetic protein signaling pathway using small molecules and recombinant proteins. Whole genome microarray analysis was performed to characterize the differentiation process and understand the developmental path of RPE generation in vitro. This method can be applied for generation of RPE for research as well as for clinical applications

Газометанный \ газокислородный ракетный двигатель. Проектирование и разработка

Хімічні ракетні двигуни – є і будуть у майбутньому найбільш широко використовуваними рушіями для транспортування на орбіту Землі. Інформаційна потреба технологій, постійно зростаюче число супутників, які необхідно виводити на орбіту змушує виробників ракетної техніки будувати двигуни з більш широким діапазоном тяги і кращою якістю роботи. З іншого боку, для мінімізації впливу на навколишнє середовище в космічній промисловості, передбачається використання екологічнобезпечних видів палива. Одним з видів палива, що є екологічнобезпечним і гарантує якісну роботу, є метан. Це паливо знаходиться в області інтересів всесвітньої ракетної галузі. Однак, на сьогоднішній день, лише кілька двигунів, що використовують метан пройшли повну перевірку, що вказує на широку область можливих удосконалень цієї техніки.Головна мета статті полягає в тому, щоб проаналізувати можливість використання метану як палива для ракетних двигунів. Авторами з використанням методів чисельної газової динаміки (CFD) проведені обчислення експериментального ракетного двигуна. Проведений аналіз є основою для проектування експериментального зразка. Експериментальне дослідження роботи нового двигуна проведено з метою підтвердження правильності обчислень. У майбутньому планується випробовування системи охолодження двигуна, що буде завершенням даного проекту.Chemical rocket engines are still and will be in the foreseeable future the most widely used means of propulsion systems in transportation into the earth's orbit. What is more, information technologies need more and more satellites constellations to be replenished. This forces the rocket industry to build rocket engines with wider range of thrust and better performance. On the other hand, in order to minimize the influence on the environment, ecologically-safe propellants are considered to be used in space industry [1]. One of propellants, which is ecologically-safe and guarantees good overall performance is methane. This fuel is in area of interests of world's rocket industry. However, till today only a few methane rocket engines were tested, so it seems to be a wide area of possible improvements in this field. The main aim of the paper will be to analyze the possibility of using methane as a fuel for the rocket engine. The authors made the computations of a model rocket engine, fueled by methane, using CFD method. The analysis stands as the basis for the design of a model rocket engine. Experimental research to check the calculations’ validity as well as testing of its cooling system will complete the design.Химические ракетные двигатели являются и будут в обозримом будущем, наиболее широко используемыми двигательными установками для транспортирования на орбиту Земли. Информационная потребность технологий, постоянно растущее число спутников, которые необходимо выводить на орбиту, вынуждает производителей ракетной техники строить двигатели с более широким диапазоном тяги и лучшим качеством работы. С другой стороны, для минимизации влияния на окружающую среду в космической промышленности, предполагается использование экологически безопасных видов топлива. Одним из видов топлива, которое является экологически-безопасным и гарантирует качественную работу, является метан. Это топливо находится в области интересов всемирной ракетной отрасли. Однако, на сегодняшний день, лишь несколько двигателей, использующих метан, прошли полную проверку, что указывает на широкую область возможных усовершенствований этой техники. Главная цель статьи состоит в том, чтобы проанализировать возможность использования метана как топлива для ракетных двигателей. Авторами с использованием методов численной газовой динамики (CFD) проведены вычисления экспериментального ракетного двигателя. Проведенный анализ является основой для проектирования экспериментального образца. Экспериментальное исследование работы нового двигателя проведено с целью подтверждения правильности вычислений. В будущем планируется испытание системы охлаждения двигательной установки, которое будет являться завершением данного проекта

Towards high-speed optical quantum memories

Quantum memories, capable of controllably storing and releasing a photon, are a crucial component for quantum computers and quantum communications. So far, quantum memories have operated with bandwidths that limit data rates to MHz. Here we report the coherent storage and retrieval of sub-nanosecond low intensity light pulses with spectral bandwidths exceeding 1 GHz in cesium vapor. The novel memory interaction takes place via a far off-resonant two-photon transition in which the memory bandwidth is dynamically generated by a strong control field. This allows for an increase in data rates by a factor of almost 1000 compared to existing quantum memories. The memory works with a total efficiency of 15% and its coherence is demonstrated by directly interfering the stored and retrieved pulses. Coherence times in hot atomic vapors are on the order of microsecond - the expected storage time limit for this memory.Comment: 13 pages, 5 figure

Measuring phonon dephasing with ultrafast pulses using Raman spectral interference

A technique to measure the decoherence time of optical phonons in a solid is presented. Phonons are excited with a pair of time-delayed 80 fs near infrared pulses via spontaneous transient Raman scattering. The spectral fringe visibility of the resulting Raman pulse pair, as a function of time delay, is used to measure the phonon dephasing time. The method avoids the need to use either narrow band or few femtosecond pulses and is useful for low phonon excitations. The dephasing time of phonons created in bulk diamond is measured to be τ=6.8 ps (Δν=1.56 cm-1). ©2008 The American Physical Society

IGF-I activates caspases 3/7, 8 and 9 but does not induce cell death in colorectal cancer cells

Background: Colorectal cancer is the third most common cancer in the western world. Chemotherapy is often ineffective to treat the advanced colorectal cancers due to the chemoresistance. A major contributor to chemo-resistance is tumour-derived inhibition or avoidance of apoptosis. Insulin-like growth factor I (IGF-I) has been known to play a prominent role in colorectal cancer development and progression. The role of IGF-I in cancer cell apoptosis is not completely understood.Methods: Using three colorectal cancer cell lines and one muscle cell line, associations between IGF-I and activities of caspase 3/7, 8 and 9 have been examined; the role of insulin-like growth factor I receptor (IGF-IR) in the caspase activation has been investigated.Results: The results show that exogenous IGF-I significantly increases activity of caspases 3/7, 8 and 9 in all cell lines used; blocking IGF-I receptor reduce IGF-I-induced caspase activation. Further studies demonstrate that IGF-I induced caspase activation does not result in cell death. This is the first report to show that while IGF-I activates caspases 3/7, 8 and 9 it does not cause colorectal cancer cell death.Conclusion: The study suggests that caspase activation is not synonymous with apoptosis and that activation of caspases may not necessarily induce cell death

Relationships between hypoxia markers and the leptin system, estrogen receptors in human primary and metastatic breast cancer: effects of preoperative chemotherapy

<p>Abstract</p> <p>Background</p> <p>Tumor hypoxia is marked by enhanced expression of hypoxia-inducible factor-α (HIF-1α) and glucose transporter-1 (Glut-1). Hypoxic conditions have also been associated with overexpression of angiogenic factors, such as leptin. The aim of our study was to analyze the relationships between hypoxia markers HIF-1α, Glut-1, leptin, leptin receptor (ObR) and other breast cancer biomarkers in primary and metastatic breast cancer in patients treated or untreated with preoperative chemotherapy.</p> <p>Methods</p> <p>The expression of different biomarkers was examined by immunohistochemistry in 116 primary breast cancers and 65 lymph node metastases. Forty five of these samples were obtained form patients who received preoperative chemotherapy and 71 from untreated patients.</p> <p>Results</p> <p>In primary tumors without preoperative chemotherapy, HIF-1α and Glut-1 were positively correlated (p = 0.02, r = 0.437). HIF-1α in primary and metastatic tumors without preoperative therapy positively correlated with leptin (p < 0.0001, r = 0.532; p = 0.013, r = 0.533, respectively) and ObR (p = 0.002, r = 0.319; p = 0.083, r = 0.387, respectively). Hypoxia markers HIF-1α and Glut-1 were negatively associated with estrogen receptor alpha (ERα) and positively correlated with estrogen receptor beta (ERβ). In this group of tumors, a positive correlation between Glut-1 and proliferation marker Ki-67 (p = 0.017, r = 0.433) was noted. The associations between HIF-1α and Glut-1, HIF-1α and leptin, HIF-1α and ERα as well as Glut-1 and ERβ were lost following preoperative chemotherapy.</p> <p>Conclusions</p> <p>Intratumoral hypoxia in breast cancer is marked by coordinated expression of such markers as HIF-1α, Glut-1, leptin and ObR. The relationships among these proteins can be altered by preoperative chemotherapy.</p

Stromelysin-3 over-expression enhances tumourigenesis in MCF-7 and MDA-MB-231 breast cancer cell lines: involvement of the IGF-1 signalling pathway

BACKGROUND: Stromelysin-3 (ST-3) is over-expressed in the majority of human carcinomas including breast carcinoma. Due to its known effect in promoting tumour formation, but its impeding effect on metastasis, a dual role of ST-3 in tumour progression, depending on the cellular grade of dedifferentiation, was hypothesized. METHODS: The present study was designed to investigate the influence of ST-3 in vivo and in vitro on the oestrogen-dependent, non-invasive MCF-7 breast carcinoma cell line as well as on the oestrogen-independent, invasive MDA-MB-231 breast carcinoma cell line. Therefore an orthotopic human xenograft tumour model in nude mice, as well as a 3D matrigel cell culture system, were employed. RESULTS: Using both in vitro and in vivo techniques, we have demonstrated that over-expression of ST-3 in MCF-7 and MDA-MB-231 cells leads to both increased cell numbers and tumour volumes. This observation was dependent upon the presence of growth factors. In particular, the enhanced proliferative capacity was in MCF-7/ST-3 completely and in MDA-MB-231/ST-3 cells partially dependent on the IGF-1 signalling pathway. Microarray analysis of ST-3 over-expressing cells revealed that in addition to cell proliferation, further biological processes seemed to be affected, such as cell motility and stress response. The MAPK-pathway as well as the Wnt and PI3-kinase pathways, appear to also play a potential role. Furthermore, we have demonstrated that breast cancer cell lines of different differentiation status, as well as the non-tumourigenic cell line MCF-10A, have a comparable capability to induce endogenous ST-3 expression in fibroblasts. CONCLUSION: These data reveal that ST-3 is capable of enhancing tumourigenesis in highly differentiated "early stage" breast cancer cell lines as well as in further progressed breast cancer cell lines that have already undergone epithelial-mesenchymal transition. We propose that ST-3 induction in tumour fibroblasts leads to the stimulation of the IGF-1R pathway in carcinoma cells, thus enhancing their proliferative capacity. In addition, further different cellular processes seem to be activated by ST-3, possibly accounting for the dual role of ST-3 in tumour progression and metastasis