scholarly journals Colliding respiratory jets as a mechanism of air exchange and pathogen transport during conversations

2021 ◽  
Vol 930 ◽  
Author(s):  
Arghyanir Giri ◽  
Neelakash Biswas ◽  
Danielle L. Chase ◽  
Nan Xue ◽  
Manouk Abkarian ◽  
...  
Keyword(s):  
Initial Phase ◽  
Short Range ◽  
Blocking Effect ◽  
Direct Numerical Simulations ◽  
Lateral Spread ◽  
High Dose ◽  
Face To Face ◽  
Pathogen Transport ◽  
Visualization Experiments ◽  
Air Exchange

Air exchange between people has emerged in the COVID-19 pandemic as the important vector for transmission of the SARS-CoV-2 virus. We study the airflow and exchange between two unmasked individuals conversing face-to-face at short range, which can potentially transfer a high dose of a pathogen, because the dilution is small when compared to long-range airborne transmission. We conduct flow visualization experiments and direct numerical simulations of colliding respiratory jets mimicking the initial phase of a conversation. The evolution and dynamics of the jets are affected by the vertical offset between the mouths of the speakers. At low offsets the head-on collision of jets results in a `blocking effect', temporarily shielding the susceptible speaker from the pathogen carrying jet, although, the lateral spread of the jets is enhanced. Sufficiently large offsets prevent the interaction of the jets. At intermediate offsets (8-10 cm for 1 m separation), jet entrainment and the inhaled breath assist the transport of the pathogen-loaded saliva droplets towards the susceptible speaker's mouth. Air exchange is expected, in spite of the blocking effect arising from the interaction of the respiratory jets from the two speakers.

PLASMA CORTICOSTEROID LEVELS AND ADRENAL ASCORBIC ACID AFTER INTRAVENOUS CORTICOTROPHIN INJECTIONS AND »STRESSFUL« STIMULI IN THE RAT

1962 ◽  
Vol 39 (4) ◽  
pp. 527-538 ◽  
Author(s):  
Pavo Hedner ◽  
Claus Rerup
Keyword(s):  
Ascorbic Acid ◽  
Abdominal Surgery ◽  
Response Curve ◽  
Significant Rise ◽  
Blocking Effect ◽  
High Dose ◽  
Ascorbic Acid Concentration ◽  
Unilateral Adrenalectomy ◽  
Subcutaneous Injections ◽  
Hypophysectomized Rats

ABSTRACT Measurements of plasma corticosteroid levels and adrenal ascorbic acid concentration in steroid blocked and hypophysectomized rats were performed. It was found that prednisolone and dexamethasone were effective in blocking endogenous corticotrophin release within 3–4 hours after subcutaneous injection. These agents also prevented completely the normally occurring rise in plasma corticoid levels after exposure of the rats to ether. Abdominal surgery (unilateral adrenalectomy) resulted in a slight but significant rise in plasma corticoid levels in spite of dexamethasone blockade. The values of adrenal ascorbic acid were not affected significantly. The blocking effect of two daily subcutaneous injections of a high dose of dexamethasone persisted for about one week after the last injection. The sensitivity of the plasma corticoid response was essentially the same in hypophysectomized and dexamethasone blocked rats. The lower part of the log dose response curve was found to be clearly non-linear in the plasma corticoid method following intravenous corticotrophin injection. As a consequence the dose level in quantitative assays of intravenously injected corticotrophin are, in our hands, of the same order as in the adrenal ascorbic acid depletion method.

scholarly journals Use of alternative consultation forms in Danish general practice in the initial phase of the COVID-19 pandemic – a qualitative study

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Tina Drud Due ◽  
Thorkil Thorsen ◽  
Julie Høgsgaard Andersen
Keyword(s):  
Patient Care ◽  
Initial Phase ◽  
Health Care Systems ◽  
Qualitative Interviews ◽  
Clinical Work ◽  
Health Issues ◽  
Short Term ◽  
Diagnostic Uncertainty ◽  
Face To Face ◽  
Care Systems

Abstract Background Attempts to manage the COVID-19 pandemic have led to radical reorganisations of health care systems worldwide. General practitioners (GPs) provide the vast majority of patient care, and knowledge of their experiences with providing care for regular health issues during a pandemic is scarce. Hence, in a Danish context we explored how GPs experienced reorganising their work in an attempt to uphold sufficient patient care while contributing to minimizing the spread of COVID-19. Further, in relation to this, we examined what guided GPs’ choices between telephone, video and face-to-face consultations. Methods This study consisted of qualitative interviews with 13 GPs. They were interviewed twice, approximately three months apart in the initial phase of the pandemic, and they took daily notes for 20 days. All interviews were audio recorded, transcribed, and inductively analysed. Results The GPs re-organised their clinical work profoundly. Most consultations were converted to video or telephone, postponed or cancelled. The use of video first rose, but soon declined, once again replaced by an increased use of face-to-face consultations. When choosing between consultation forms, the GPs took into account the need to minimise the risk of COVID-19, the central guidelines, and their own preference for face-to-face consultations. There were variations over time and between the GPs regarding which health issues were dealt with by using video and/or the telephone. For some health issues, the GPs generally deemed it acceptable to use video or telephone, postpone or cancel appointments for a short term, and in a crisis situation. They experienced relational and technical limitations with video consultation, while diagnostic uncertainty was not regarded as a prominent issue Conclusion This study demonstrates how the GPs experienced telephone and video consultations as being useful in a pandemic situation when face-to-face consultations had to be severely restricted. The GPs did, however, identify several limitations similar to those known in non-pandemic times. The weighing of pros and cons and their willingness to use these alternatives shifted and generally diminished when face-to-face consultations were once again deemed viable. In case of future pandemics, such alternatives seem valuable, at least for a short term.

Structure–desensitization relationships of angiotensin analogues in the rat isolated uterus

1985 ◽  
Vol 63 (8) ◽  
pp. 966-971 ◽  
Author(s):  
Graham J. Moore ◽  
Kevin J. Franklin ◽  
Diana M. Nystrom ◽  
Mahesh H. Goghari
Keyword(s):  
Angiotensin Ii ◽  
Initial Phase ◽  
Hydroxyl Group ◽  
High Dose ◽  
Ang Ii ◽  
Additivity Rule ◽  
Structural Determinants ◽  
First Order ◽  
Receptor Models ◽  
First Order Kinetics

The desensitizing potencies of angiotensin II (ANG II) analogues modified at positions 1, 2, 4, 7, and 8 have been examined in the rat isolated uterus assay by determining the time of recovery of the half-maximal concentration (EC50) response to angiotensin II after treatment of the tissues with a high dose (10−5 M) of each analogue for 2 min. The magnitude of the desensitization effect was substituent dependent in the following manner: position 1, sarcosine (Sar) > Asp > des-Asp; position 2, Arg > Sar; position 4, Tyr > Tyr(Me) ~ Phe; position 7, 3,4-dehydroproline (Dpr) > Pro > thioproline (Tpr) > Sar; position 8, Ile > D-Trp > Ala > Phe. The "additivity" rule applied to these structure–desensitization relationships and the most potent desensitizer, requiring 3 h for reestablishment of the EC50 response, was [Sar1,Dpr7,Ile8]-ANG II. The desensitizing potencies of these analogues did not correlate with agonist or antagonist activities and demonstrated that the angiotensin-mediated tissue desensitization process has unique structural determinants. Methylation or elimination of the tyrosine hydroxyl group of strong desensitizers virtually eliminated the desensitization effect, implicating the phenoxyl moiety in the mechanism of desensitization. The initial phase of recovery of angiotensin responsiveness after desensitization by several analogues appeared to obey first-order kinetics. The results are discussed in the contexts of both one- and two-site receptor models.

Measuring interpersonal transmission of expiratory droplet nuclei in close proximity

2021 ◽  
pp. 1420326X2110296
Author(s):  
Linzhi Fu ◽  
Peter V. Nielsen ◽  
Yi Wang ◽  
Li Liu
Keyword(s):  
Disease Transmission ◽  
Short Range ◽  
Close Contact ◽  
Measurement Techniques ◽  
Transmission Risk ◽  
Interpersonal Distance ◽  
Airborne Transmission ◽  
Face To Face ◽  
Close Proximity ◽  
Droplet Nuclei

Increasing evidence supports the significant role of short-range airborne transmission of viruses when in close contact with a source patient. A full-scale ventilated room (Cleanliness: ISO 14644–1 Class 5) and two face-to-face standing breathing thermal manikins were used to simulate a source individual and a susceptible person. Monodisperse particle generation and measurement techniques were used to evaluate the effect of virus-laden droplet nuclei size on short-range airborne transmission risk. We analysed four particle sizes (1.0, 1.5, 2.5, and 5.0 µm) to simulate the transport of exhaled droplet nuclei within an interpersonal distance of 0.5 m. The results indicated that the size distribution of airborne droplet nuclei could significantly influence transmission, with the inhalation fraction decreasing with increasing droplet nuclei size. Additionally, results showed that proximity to the source manikin could influence transmission. Inhalation fraction decreased with increasing interpersonal distance, fitting well with the 1/ d rule of droplet nuclei concentration decay. Our findings improve the understanding of the mechanism of the disease transmission.

Modeling of aircraft effects on external store ejection

2018 ◽  
Vol 233 (10) ◽  
pp. 3612-3626
Author(s):  
Mustafa Tugrul Kozak ◽  
Erdinc Nuri Yildiz ◽  
Yigit Yazicioglu ◽  
Ender Cigeroglu
Keyword(s):  
Initial Phase ◽  
Short Range ◽  
Initial Conditions ◽  
Fighter Aircraft ◽  
Clear Separation ◽  
Ejection Process ◽  
Store Separation ◽  
Rigid Body Motions ◽  
Computational Methodology ◽  
Aircraft Aerodynamics

Modern fighter aircraft, together with their interceptor roles, are utilized as aerial bomb and long-/short-range missile carriers. Separation of those external stores from aircraft is still a challenge where the external store has to clear the carrier aircraft following the ejection process. Aircraft and store aerodynamics coupled with their individual flight conditions may result in an unsafe ejection where the store may interfere with the carrier aircraft instead of a clear separation. Store ejection is the initial phase of the launching process, which dominates the separation of the store by generating the initial conditions. Any error introduced to the store separation analysis during this phase will propagate to the complete trajectory solution, which is used for determining whether the store separation is safe or not. The objective of this paper is to present a computational methodology that includes not only the store aerodynamics but also the interactions of the store with aircraft rigid body motions and deformations, together with ejector dynamics. In this study, store aerodynamics, aircraft aerodynamics, aircraft aeroelasticity, and pylon elasticity are used to characterize the ejector dynamics for determining the ejection end-of-stroke parameters.

scholarly journals Short-range and tensor correlations in $^{4}$He and $^{8}$Be studied with the antisymmetrized quasi-cluster model

2019 ◽  
Vol 2019 (6) ◽  
Author(s):  
N Itagaki ◽  
H Matsuno ◽  
Y Kanada-En’yo
Keyword(s):  
Cluster Model ◽  
Short Range ◽  
Decisive Role ◽  
Blocking Effect ◽  
Repulsive Core ◽  
Pauli Blocking ◽  
Tensor Correlation ◽  
Coherent Effects ◽  
Middle Range ◽  
Tensor Part

Abstract We apply the tensor version of the antisymmetrized quasi-cluster model (AQCM-T) to $^4\textrm{He}$ and $^8\textrm{Be}$ while focusing on the $NN$ correlations in $\alpha$ clusters. We adopt the $NN$ interactions including realistic ones containing a repulsive core for the central part in addition to the tensor part. In $^4\textrm{He}$, the $pn$ pair in the $^3D$ channel has been known to play a decisive role in the tensor correlation and the framework is capable of treating not only this channel but also the $NN$ correlations in the $^1S$ and $^3S$ channels. In $^8\textrm{Be}$, when two $\alpha$ clusters approach, the $^3D$ pair is suppressed because of the Pauli blocking effect, which also induces a decrease in the $^3S$ component through the $^3S$–$^3D$ coupling. These coherent effects result in the reduction of the attractive effect of the central-even interaction in the middle-range region and keep the distance between two $\alpha$ clusters.

Facing challenges to the permanence of people with disabilities in brazilian higher education: a study of the reality of CCJS/UFCG undergraduate courses

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Iarley Pereira de Sousa ◽  
Fábio Zoboli
Keyword(s):  
Higher Education ◽  
Human Rights ◽  
Students With Disabilities ◽  
Inclusive Education ◽  
Initial Phase ◽  
People With Disabilities ◽  
Dropout Rate ◽  
Face To Face ◽  
Data Collection Instrument ◽  
And Training

Law No. 13,409 is published, which amends the previous one, including people with disabilities among their guardians. The dropout rate of these people in higher education is 27% (Inep, 2016). The UN Declaration on human rights education and training (2012) presents the constitutive frameworks of education (accessibility, acceptability, availability, adaptability). The research hypothesis is that the CCJS / UFCG has not guided its inclusive education in these constitutive milestones and this is one of the causes for students with disabilities to have difficulties in staying in their respective courses. The Comprehensive Interview (Kaufmann, 2013) will be used as a data collection instrument, not yet applied in the field, due to the suspension of face-to-face classes, in view of the worsening of the covid-19 pandemic and the initial phase of the research.

scholarly journals Video: Colliding respiratory jets as a mechanism of air exchange and pathogen transport during conversations

2021 ◽  
Author(s):  
Arghyanir Giri ◽  
Neelakash Biswas ◽  
Danielle L. Chase ◽  
Nan Xue ◽  
Manouk Abkarian ◽  
...  
Keyword(s):  
Pathogen Transport ◽  
Air Exchange

Electron Beam Damage of Biomolecules Assessed by Energy Loss Spectroscopy

1978 ◽  
Vol 36 (3) ◽  
pp. 61-69
Author(s):  
M. Isaacson ◽  
M.L. Collins ◽  
M. Listvan
Keyword(s):  
Electron Microscopy ◽  
Radiation Damage ◽  
Structural Integrity ◽  
Analytical Electron Microscopy ◽  
High Dose ◽  
Dose Rates ◽  
Special Cases ◽  
Analytical Electron ◽  
Atom Migration ◽  
Beam Damage

Over the past five years it has become evident that radiation damage provides the fundamental limit to the study of blomolecular structure by electron microscopy. In some special cases structural determinations at very low doses can be achieved through superposition techniques to study periodic (Unwin & Henderson, 1975) and nonperiodic (Saxton & Frank, 1977) specimens. In addition, protection methods such as glucose embedding (Unwin & Henderson, 1975) and maintenance of specimen hydration at low temperatures (Taylor & Glaeser, 1976) have also shown promise. Despite these successes, the basic nature of radiation damage in the electron microscope is far from clear. In general we cannot predict exactly how different structures will behave during electron Irradiation at high dose rates. Moreover, with the rapid rise of analytical electron microscopy over the last few years, nvicroscopists are becoming concerned with questions of compositional as well as structural integrity. It is important to measure changes in elemental composition arising from atom migration in or loss from the specimen as a result of electron bombardment.

Electron-diffraction studies in synthetic polymer materials

1983 ◽  
Vol 41 ◽  
pp. 362-365
Author(s):  
D.T. Grubb
Keyword(s):  
Electron Diffraction ◽  
Synthetic Polymer ◽  
Polymer Materials ◽  
Crystallographic Structure ◽  
High Dose ◽  
Electron Dose ◽  
Dose Rates ◽  
First Case ◽  
Diffraction Patterns ◽  
The Many

Diffraction studies in polymeric and other beam sensitive materials may bring to mind the many experiments where diffracted intensity has been used as a measure of the electron dose required to destroy fine structure in the TEM. But this paper is concerned with a range of cases where the diffraction pattern itself contains the important information.In the first case, electron diffraction from paraffins, degraded polyethylene and polyethylene single crystals, all the samples are highly ordered, and their crystallographic structure is well known. The diffraction patterns fade on irradiation and may also change considerably in a-spacing, increasing the unit cell volume on irradiation. The effect is large and continuous far C94H190 paraffin and for PE, while for shorter chains to C 28H58 the change is less, levelling off at high dose, Fig.l. It is also found that the change in a-spacing increases at higher dose rates and at higher irradiation temperatures.

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