The effect of reactive plasticizer on viscoelastic and mechanical properties of solid rocket propellants based on different types of HTPB resin

Conventional plasticizers deteriorate mechanical and viscoelastic properties of the propellants due to their migration upon aging and long-term storage,which affects reliability and safety properties during exploitation.To address this issue,conventional plasticizer,dioctyl adipate(DOA),is replaced by reactive one,castor oil(CO).In addition,three different types of HTPB were used to obtain propellants with designed viscoelastic and mechanical properties.The CO increased propellants viscosity,without a significant impact on the propellant processability,regardless to the type of prepolymer.Conversely,mechanical properties were different depending on the type of resin,which were further analyzed by gel permeation chromatography(GPC).Addition of CO formed a denser polymer network and shifted T_(g) to higher values,compared to the compositions with DOA.The tensile strength of CO-containing propellants was lower at +20℃ and +50℃ compared to the reference compositions,while the strain at maximum load and strain at break were significantly increased with pronounced plastic deformation,especially for samples at -30℃.The inclusion of CO in the propellants composition gives more room for adjusting a wide range of mechanical properties.

A Cross-Sectional Study on the Impact of Operation Triple Zero (OTZ) Program on Viral Load Suppression amongst Members of the Adolescent Club in 68 Nigerian Army Reference Hospital Yaba Lagos, Nigeria

Background: In Nigeria, adolescents and young people (AYP) aged 10 - 24, comprise 22.3% of the population and with HIV prevalence of 3.5%. The AYP living with HIV enrolled at the 68 NARHY, Lagos reflects the national challenges with poor viral suppression. The OTZ program aligns with the UNAIDS 95-95-95 goals. It seeks to empower AYPLHIV to be in charge of their treatment and commit to triple zero outcomeszero missed appointments, zero missed drugs, and zero viral loads. The purpose of the study was to assess the impact of the OTZ program on viral load suppression among members of the adolescent club in 68 NARHY, Lagos. Method: A cross-sectional retrospective study to evaluate the impact of the OTZ program on the viral load of 53 AYP enrolled in the OTZ program between March 2019 to December 2019 was analyzed. The Percentage of viral load suppression before enrollment compared with 6 and 12 months after enrollment into the OTZ program. The AYP is grouped into 10 - 14, 15 - 19, and 20 - 24 years. Activities conducted were peer driven monthly meetings with the AYP during which the adolescents interacted on issues relating to improving their treatment outcomes, healthcare workers reviewed their clinical status, viral load result, provider peer counseling, and caregivers engagement to support adherence to medication and ARV refills. Results: Before OTZ, 81% aged 10 - 14 years, 75% aged 15 - 19 years, and 25% aged 20 - 24 years were virally suppressed (VL less than 1000 copies/ml). Six months after enrollment, 94% were virally suppressed95% aged 10 - 14 years, 96% aged 15 - 19 years, and 66% aged 20-24 years. Twelve months after enrollment, 96% of AYP were virally suppressed100% aged 10-14 years, 93% aged 15 - 19 years, and 100% aged 20 - 24 years. Males viral load (VL) suppression improved from 79% to 96% and 92%, while females VL suppression improved from 69% to 93% and 100% at 6 and 12 months respectively. Conclusion: The OTZ activities contributed to improved viral load suppression in the AYP of the facility.

Thermal decomposition and kinetics of plastic bonded explosives based on mixture of HMX and TATB with polymer matrices

This work describes thermal decomposition behaviour of plastic bonded explosives(PBXs) based on mixture of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX) and 2,4,6-triamino-1,3,5-trinitrobenzene(TATB)with Viton A as polymer binder. Thermal decomposition of PBXs was undertaken by applying simultaneous thermal analysis(STA) and differential scanning calorimetry(DSC) to investigate influence of the HMX amount on thermal behavior and its kinetics. Thermogravimetric analysis(TGA) indicated that the thermal decomposition of PBXs based on mixture of HMX and TATB was occurred in a three-steps. The first step was mainly due to decomposition of HMX. The second step was ascribed due to decomposition of TATB, while the third step was occurred due to decomposition of the polymer matrices. The thermal decomposition % was increased with increasing HMX amount. The kinetics related to thermal decomposition were investigated under non-isothermal for a single heating rate measurement. The variation in the activation energy of PBXs based on mixture of HMX and TATB was observed with varying the HMX amount. The kinetics from the results of TGA data at various heating rates under non-isothermal conditions were also calculated by Flynn—Wall—Ozawa(FWO) and Kissinger-Akahira-Sunose(KAS)methods. The activation energies calculated by employing FWO method were very close to those obtained by KAS method. The mean activation energy calculated by FWO and KAS methods was also a good agreement with the activation energy obtained from single heating rate measurement in the first step decomposition.

Dispersion sensitivity analysis&consistency im provement of APFSDS

The purpose of this study is to investigate and quantify some possible sources of dispersion of 120 mm APFSDS tank ammunition both experimentally and numerically.This paper aims to point out the most influential source during In-Bore Balloting Motion phase as well as in External Ballistics phase of the ammunition and quantifies its effect on dispersion.Data obtained from flight trials is critically analysed and parameters affecting dispersion such as initial yaw/pitch rates,yaw/pitch dampening,plane start angle,launch spin,clearance,centre of gravity shift,dynamic imbalance angle,cross wind,etc.are observed and,later on,studied in detail by extensive External Ballistics Monte Carlo(EBMC)simulation and Six Degree of Freedom(6-DOF)trajectory analysis.In Bore Balloting Motion simulation shows that reduction in residual spin by about 5%results in drastic56%reduction in first maximum yaw.A correlation between first maximum yaw and residual spin is observed.Results of data analysis are used in design modification for existing ammunition.Number of designs are evaluated numerically before freezing five designs for further soundings.These designs are critically assessed in terms of their comparative performance during In-bore travel&external ballistics phase.Results are validated by free flight trials for the finalised design.

Feasibility analysis of WDM links for radar applications

Active phased array antennas enhances the performance of modern radars by using multiple low power transmit/receive modules in place of a high power transmitter in conventional radars. Fully distributed phased array radars demand the distribution of various signals in radio frequency(RF) and digital domain for real time operation. This is normally achieved through complex and bulky coaxial distribution networks. In this work, we intend to tap the inherent advantages of fiber links with wavelength division multiplexed(WDM) technology and a feasibility study to adapt these links for radar applications is carried out. This is done by analysing various parameters like amplitude, delay, frequency and phase variation response of various radar waveforms over WDM links. This also includes performance evaluation of non-linear frequency modulation(NLFM) signals, known for better signal to noise ratio(SNR) to specific side lobe levels. NLFM waveforms are further analysed using pulse compression(PC) technique. Link evaluation is also carried out using a standard simulation environment and is then experimentally verified with other waveforms like RF continuous wave(CW), pulsed RF and digital signals. Synchronization signals are generated from this variable duty cycle digital signals during real time radar operation. During evaluation of digital signals, variable transient effects for different duty cycles are observed from an amplifier configuration. A suppression method is proposed to eliminate this transient effects. Further, the link delay response is investigated using different lengths of fiber spools. It can be inferred from the experimental results that WDM links are capable of handling various signals significant to radar applications.

Prevention of Maternal-to-Child Transmission of HIV: Knowledge, Attitude and Factors Influencing Active Participation among HIV-Positive Men in a Military Health Facility in Lagos, South Western Nigeria

Introduction: Traditionally, Prevention of Maternal-to-Child Transmission (PMTCT) of HIV involves women and excludes men despite their important roles. There is a need for more data on factors influencing male participation in PMTCT programs. Design: This was a cross-sectional, descriptive study of married HIV-positive men receiving care at the adult ART clinic, 68 Nigerian Army Reference Hospital Yaba. Data were collected from March 15 to April 30, 2018. Result: Out of the 366 respondents, 333 (91%) were aware that HIV can be transmitted from mother to child. However, only 43.2% correctly identified that it can be transmitted during pregnancy, while 30.2% stated during labour. Almost all of the respondents (96.4%) would also accept that their positive partners take antiretroviral treatment to protect her unborn baby, 86.9% would support non breastfeeding option after delivery, and 95.6% indicated readiness to buy formula milk for the baby. Similarly, majority believed that a pregnant woman can be tested for HIV without the permission of her partner (Mean = 1.47 ± 0.893), and that men should accompany their spouse to ANC/PMTCT clinics (Mean = 1.86 ± 0.921). Conclusion: This study revealed that despite low knowledge of PMTCT among men, there is a good level of attitude and involvement among them. We recommend further study to fully explore the impact of education on men’s participation.

Effect of firing conditions ＆ release height on terminal performance of submunitions and conditions for optimum height of release

Submunitions should exhibit optimum terminal performance at target end when released from certain pre-determined height. Selection of an optimum height of release of the submunitions depends on the terminal parameters like forward throw, remaining velocity, impact angle and flight time. In this paper,the effects of initial firing conditions and height of release on terminal performance of submunitions discussed in detail. For different height of release, the relation between range and forward throw is also established & validated for a number of firing altitude and rocket configurations.

Effect of heavy load carriage on cardiorespiratory responses with varying gradients and modes of carriage

Background: The present study was undertaken to determine the effect of different uphill and downhill gradients on cardiorespiratory and metabolic responses of soldiers while carrying heavy military loads in two different modes.Methods: Eight physically fit male soldiers with a mean age 32.0±2.0 years, a mean height of 169.5±4.9 cm, and a mean weight of 63.8±8.4 kg volunteered for this study. Each volunteer completed treadmill walking trials at a speed of 3.5 km/h while carrying no external load, 31.4 kg load in a distributed mode(existing load carriage ensembles) and compact mode(new back pack) over 5 different downhill and uphill gradients(–5%, –10%, 0%, 5%, 10%) for 6 min at each gradient. During the walking trials, heart rate(HR), oxygen uptake(VO_2), respiratory frequency(RF) and energy expenditure(EE) were determined by the process of breath-by-breath gas analysis using a K4 b2 system. The average of the last 2 min data from each 6 min walking trial for each individual was subjected to statistical analysis.Results: All parameters(HR, VO_2, RF, and EE) gradually increased with the change in gradient from downhill to level to uphill. The distributed mode showed higher values compared to compact mode for all gradients, e.g., for VO_2, there was a 10.7, 7.4, 5.1, 28.2 and 18.7% increase in the distributed mode across the 5 different gradients.Conclusions: It can be concluded from the present study that the compact mode of load carriage is more beneficial than the distributed mode in terms of cardiorespiratory responses while walking on downhill and uphill surfaces with a 31.4 kg load.

Consequence of reinforced SiC particles and post process artificial ageing on microstructure and mechanical properties of friction stir processed AA7075

Friction stir processing and post process artificial ageing was successfully carried out on AA7075 with and without reinforcement of SiC particles producing defect free processed zone with uniform distribution of filler material.Effect of SiC particle reinforcement and artificial ageing times on the microstructural modifications was characterized using optical and electron microscopy,electron backscattered diffraction and X-Ray diffraction.Hardness,impact and wear tests were carried out to investigate mechanical behaviour before and after processing.Reinforcement of SiC particles during FSP and subsequent age hardening treatment brought about nearly twofold increase in hardness and impact toughness values by the combined effect of grain refinement,Zener pinning,dispersion strengthening and precipitation hardening.Significant improvement in wear resistance in terms of wear loss was also observed after processing compared to the reference material AA7075-T6.Fractured surface of post FSP age hardened AA7075 alloy exhibited features of ductile fracture during Charpy impact test.

Is There a Future for the “Myth of Kosovo”?

The present paper aims at the exploration of the development of the political “myth of Kosovo” and its viability with respect to EU membership ambitions of Serbia. The battle of Kosovo Polje in 1389, presented as Serbian defeat, transformed itself into the founding political myth of modern Serbian nation in the 19th century and has continued to exist as such until nowadays. The “myth of Kosovo” could shift to the ideological-cultural basis of Serbian identity and religious-cultural practices in the case of successful EU integration efforts of Serbia. However, if Serbian-Kosovar dialogue fails or Serbia loses the perspective of EU membership or some crisis hits the European Union as such,“myth of Kosovo” could be instrumentalized by various Serbian actors in order to achieve their partial political aims.

Status of New HIV Infections among Infants Born of HIV Positive Mothers on Prevention of Mother to Child Transmission at Kisii Teaching and Referral Hospital, Kenya

Introduction: The goal of Prevention of Mother to child Transmission (PMTCT) is to minimize new HIV infection with PMTCT interventions which can reduce to as low as 2%. Gusii region is number 5 among counties that contribute to 65% of new HIV (Human Immunodeficiency Virus) in infections in Kenya. The study was to determine the prevalence of new HIV infections among infants (3 - 18 months) born of HIV positive mothers on PMTCT follow up at Kisii Teaching and Referral Hospital (KTRH). Method: This was a descriptive cross sectional study involving 96 infants born of HIV positive mothers on PMTCT programme at Kisii Teaching and Referral Hospital (KTRH) was conducted. The infants were between 3 to 18 months of age. The infants were investigated for their HIV status and factors associated with prevalence. The data collection was done during postnatal checkups, antiretroviral treatment follow up and immunization schedule. Data was analyzed using Statistical Package for Social Sciences (SPSS) version 20. Results: 13.5% (95% C.I = 10.1% to 16.9%) were found to be positive despite their mothers being on PMTCT program. There was no significant difference between gender and status of the infant (χ2 = 0.758, df = 1, p-value = 0.0384). Conclusion: The study confirms that there are still new HIV infections despite being followed up in the PMTCT program. The new HIV infections were associated with mixed feeding. Recommendation: Counseling on Infant feeding, use of ant-retroviral treatment and support from partners should be strengthen in the PMTCT program to ensure reduction of new HIV infections.

Evaluating the Knowledge of HIV Transmission and Prevention of Mother to Child Transmission (PMTCT) of HIV among HIV-Positive Mothers Accessing Care in Military Hospital in Lagos, Nigeria

Introduction: The prevention of mother-to-child transmission (PMTCT) plays a major role in limiting the number of children being infected by HIV. There is dearth of studies that explored the knowledge of HIV transmission and PMTCT among women living with HIV. Methods: This was a cross-sectional, descriptive study of HIV-positive mothers receiving medical care at the adult antiretroviral therapy (ART) clinic, 68 Nigeria Army Reference Hospital Yaba. A pre-tested structured questionnaire was used to collect information from the subjects concerning their socio-demographic, knowledge of HIV transmission and mother-to-child transmission of HIV and preventive measures. SPSS v23 was used for data analysis. Results: Out of the 374 participants, 282 (75.4%) were aware that HIV can be transmitted to an unborn baby from the positive mother. Of these, 240 (85.1%) were well-informed that increase mother’s viral load can increase the chances of mother-to-child transmission. 268 (95%) understood that giving of antiretroviral drugs during and after pregnancy can lower transmission risk, while 254 (90.1%) saw the use of breast milk substitutes as another prevention strategy. There was statistically significant association between the respondents’ knowledge of PMTCT and their husbands’/partners’ awareness of their HIV status. Conclusion: In conclusion, our study demonstrated a good knowledge of HIV transmission, MTCT and PMTCT among women who were receiving ART in our centre. Disclosure is a significant factor found to be associated with PMTCT knowledge. More studies can also explore if the observations in our study with women living with HIV will be comparable in similar population in different settings.

Biotoxicity of CdS/CdSe Core-Shell Nano-Structures

The cytotoxicity of hydrophobic QDs CdS/CdSe was tested assigning MTT assay on Human Embryonic Kidney cells (HEK-293), breast cancer cells (MCF-7) and Enrichlish Ascitices Cells (EAC). Approximately 65% bio-toxicity was observed in MCF-7 for the core-shell QDs. These QDs may also find effective applications in other optoelectronic devices. CdS/CdSe core-shell hetrostructure quantum dots (QDs) were generated by chemical reaction between the respective chalcogens and cadmium metal salt. Sulphur powder was utilized for CdS core preparation while selenium was extracted from an organoselenium compound to impart CdSe shell layer at a temperature between 150℃ - 200℃. So-prepared core-shell QDs showed good optical properties. The particle size was found to be in the range of 3 - 4 nm with spherical morphology and cubic crystal structure.

Generalized Method of Biparametric Sub Pixel Thermal Location

It is well-known that according the Dozier’s method, utilization of integral of Planks function in fusion of signals of two different channels of airborne radiometer makes it possible to compute such components of temperature field within one pixel as temperatures of the object and background. In the paper, the generalization of Dozier method is suggested. The suggested generalization of Dozier’s bispectral method named as biparametric method is applicable for static remote objects. In the suggested biparametric method, the measurements are carried out at the moments t1 and t2. It is assumed that the object temperature reaches quantity T(t1) and T(t2) at these moments. On the bases of operational data of scanning infrared radiometer, the square area of one pixel can be calculated in dependence of distance between object and radiometer. This makes it possible to carry out location of static objects from two basis points using serial single wavelengths measurements of radiation emitted by the sub pixel object.

Natural polysaccharides for ulcerative colitis: A general overview

Ulcerative colitis is a colonic disease characterized by the disruption of the mucosal epithelial layer and inflammation. For the treatment of this disease, various chemotherapeutic agents are available.However, the toxicities associated with chemotherapeutics greatly hamper treatment. Polysaccharide from natural resources is emerging as a potentially therapeutic substance with comparative minimum adverse effects. In this article, we are discussing polysaccharide from diverse sources(plants, edible mushrooms,and algae) which are being used in the treatment of ulcerative colitis. These polysaccharides exert their therapeutic action on ulcerative colitis through several mechanisms, including suppression of inflammatory cascades NF-κB, MAPK, IL-6/JAK2/STAT3,preventing the release of certain inflammatory mediators, modulating the intestinal microbiome, maintaining the integrity of intestinal barriers, and regulating the certain inflammatory markers. The present review compiles the role of different polysaccharides being used successfully in the management/treatment of ulcerative colitis.Special emphasis was given to explaining the biomolecular pathway.

Electroless nickel fabrication on surface modified magnesium substrates

In recent years,magnesium(Mg)has evolved as a salient material,in affiliation with electroless nickel(Ni)coating,which have found applications in automobiles,aerospace and confederate fields attributing to its excellent inherent weight sensitive properties.However,being acknowledged for its remarkable auxiliary properties like flexible machining,appreciable weight sensitivity and ability to be patently diecast into mesh constructs,magnesium is prejudiced by aeronautical standards predominantly for its inferior corrosion resistance properties.In this sense,electroless nickel plating on magnesium and its alloys has been suggested to extricate it from corrosion problem and make it more competitive in industrial and defence applications.Autocatalytic fixation of metal ions onto respective substrates accrues and alters their mechanical,electrochemical and tribological properties,destitute of any electric current aid.This proficiently identified technique is prosecuted with the assistance of a series of sequenced operations involving a prior pretreatment,which corresponds to the chemical cleaning of the substrate surface;electroless coating;and a later activation process which is a mild etching of the electroless coated surface.The susceptibility of magnesium to this methodology has advanced and propagated its exercise and applicability in aircraft,satellites and allied aeronautical fields.Contemporarily,researchers have proposed various eco-friendly and modified duplex and composite coatings which have transmuted properties of these appendages by tailoring alloy compositions and reagents employed.This review article systematically colligates various considerations and evaluations on electroless nickel applications of magnesium and its alloys and explicates how it anchors its practice in the respective domains.Furthermore,a comprehensive analysis is devised based on the pre-existing treatment methods for accomplishing the same.

Soldiers' load carriage performance in high mountains: a physiological study

Background: The present study was designed to evaluate load carriage performance at extremely high altitudes with different loads and walking speeds in terms of physiological evaluation. The degree of maximum oxygen consumption changes at high altitudes was also examined.Methods: Twelve Indian Army soldiers were acclimatized at altitudes of 3,505 m and 4,300 m. They walked for 10 minutes on a motorized treadmill at 2.5km/h and 3.5km/h speeds during carrying no loads and three magnitudes of load(10.7kg, 21.4kg, 30kg) at both altitudes. Physiological parameters such as oxygen consumption, energy expenditure, heart rate, and ventilation were recorded for each breath using a gas analyzer. The rating of perceived exertion was also noted after each load carriage session. Maximal oxygen consumption(VO2max) was measured at sea level and the two high altitudes, and respective relative workloads(% of VO2max) were calculated from oxygen consumption. Repeated measure ANOVA was applied to reveal the significant effects of the independent variables.Results: The participants had significant reductions in VO2 max with rising altitude. Marked increases in almost all physiological parameters were observed with increasing load, altitude, and speed. The soldiers expressed heavy perceived exertion levels with higher loads at 3.5km/h at the two high altitudes.Conclusions: Considering the physiological responses, expressions of perceived exertion and changes in relative work load at both of the high altitudes. Indian soldiers are advised to walk slowly with adequate rest in between their schedules and to carry not more than 32% of their body weight.

Pediatric Eye Trauma: Epidemiological, Clinical and Therapeutic Aspects at CADESSO in Donka, Guinea

Introduction: Eye trauma represents all morbid lesions on the eyeball due to external violence. In children, they are an important cause of morbidity and the leading cause of monocular blindness. The aim of this study was to determine the sociodemographic, clinical and therapeutic characteristics of eye trauma in children aged 0 to 16 at the Application Centre for the Diploma of Specialized Higher Studies in Ophthalmology (CADESSO) in Donka, Guinea. Patients and Method: This was a prospective longitudinal study with descriptive purposes from January 1 to December 31, 2019 involving 205 children victims of eye trauma. Variables related to sociodemographic, clinical and therapeutic characteristics were studied. Informed consent from patients and/or their parents was sought and obtained. The confidentiality of the files was guaranteed. The data entry was done on EPI-Info version 7 and the analysis using the Stata software. The tables were made in Excel 2010. Pearson’s Chi2 test was used for the comparison of proportions. Results: Pediatric eye trauma accounted for 9.31% of pediatric visits and 30.92% of all eye trauma cases. There was a male predominance with a sex ratio of 1.59. Age groups from 0 - 4 years;5 - 8 years and 9 - 12 were the most affected with 26.8%, 28.8% and 27.3% respectively and a decrease in the number of cases in the 13 - 16 age group (17.1%). Gambling and sports accidents accounted for 33.2%, followed by domestic accidents for 16.6% and physical injury for 8.2%. Eye contusion was the most represented at 66.3% followed by wounds of the globe 23.9% and burns at 5.9%. One hundred and twenty-six patients had received a determination of visual acuity (VA) at admission;99 were assessed at discharge and 27 were lost to follow-up. The VA ≥ 5/10th increased from 43.4% at admission to 79.8% after treatment. We had found 67% of vision ≥ 5/10 in eye bruises against 5% in eyeball wounds. Anti-inflammatories (99.5%)) were almost used. The sequelae were dominated by corneal opacities (71.9%). Conclusion: Child eye trauma is a public health problem in Guinea. The best means of care remains prevention, which must be of interest to the child and his environment.