bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Hypoxia and Hyperoxia on Oxygen-Transfer Properties of the Blood of a Viviparous Snake
Authors: Herman Jay K. , Ingermann Rolf L.
Published: April 2021

Red cell oxygen affinity, red cell nucleoside triphosphate (NTP) levels and blood oxygen-carrying capacity were determined for male, nonpregnant and pregnant female, and fetal garter snakes Thamnophis elegans exposed to hypoxia (5 % oxygen) and hyperoxia (100 % oxygen). Male and nonpregnant female snakes were maintained under these conditions for up to 3 weeks and exhibited an apparent maximal change in oxygen affinity after 14 days of hypoxia and hyperoxia. Red cell NTP levels decreased and oxygen affinity increased with exposure to hypoxia, while exposure to hyperoxia promoted an increase in red cell NTP concentrations and a decrease in red cell oxygen affinity in the males. Hyperoxia-exposed nonpregnant females did not show a significant change in oxygen affinity. After 14 days of hypoxia, the pregnant females showed an increase in red cell oxygen affinity which was associated with a decrease in red cell NTP concentration and in the molar ratio of NTP/hemoglobin relative to normoxic controls. Fourteen days of hyperoxia did not result in a change in oxygen affinity of red cells from the pregnant female, but did promote a slight increase red cell NTP concentrations. The blood parameters of fetuses from females exposed to hypoxia or hyperoxia did not differ from those of normoxic control fetuses. The fetuses of females exposed to hypoxia suffered greater mortality, appeared less developed and had a lower average wet mass than the fetuses of normoxic-and hyperoxic-exposed females. Neither hypoxia nor hyperoxia altered the oxygen-carrying capacity of the blood in any group of snake.
Effects Of Antifreeze Proteins on Red Blood Cell Survival During Cryopreservation
Authors: Chao Heman , Davies Peter L. , Carpenter John F.
Published: April 2021

Antifreeze protein (AFP) types I, II and III were tested for their ability to protect red blood cells from lysis during warming, after cryopreservation in hydroxyethyl starch. All three types reduced hemolysis to 25 % of control values at similar micromolar concentrations but enhanced lysis as the AFP concentration approached millimolar levels. Site-directed mutants of type III AFP with different thermal hysteresis activities were tested for their ability to protect the cryopreserved cells from lysis. Their relative efficacy in protecting the cells correlated closely with their thermal hysteresis activity. Cryomicroscopy indicated that the protection of red cells by type III AFP and the mutant forms was due to inhibition of ice recrystallization.
Polarization Vision in Cuttlefish – A Concealed Communication Channel?
Authors: Shashar Nadav , Rutledge Phillip S. , Cronin Thomas W.
Published: April 2021

Polarization sensitivity is well documented in marine animals, but its function is not yet well understood. Of the cephalopods, squid and octopus are known to be sensitive to the orientation of polarization of incoming light. This sensitivity arises from the orthogonal orientation of neighboring photoreceptors. Electron microscopical examination of the retina of the cuttlefish Sepia officinalis L. revealed the same orthogonal structure, suggesting that cuttlefish are also sensitive to linearly polarized light. Viewing cuttlefish through an imaging polarized light analyzer revealed a prominent polarization pattern on the arms, around the eyes and on the forehead of the animals.

The polarization pattern disappeared when individuals lay camouflaged on the bottom and also during extreme aggression display, attacks on prey, copulation and egg-laying behavior in females. In behavioral experiments, the responses of cuttlefish to their images reflected from a mirror changed when the polarization patterns of the reflected images were distorted. These results suggest that cuttlefish use polarization vision and display for intraspecific recognition and communication.
Sulfide Acquisition By The Vent Worm Riftia Pachyptila Appears To Be Via Uptake Of Hs−, Rather Than H2S
Authors: Goffredi Shana K. , Childress James J. , Desaulniers Nicole T. , Lallier Francois H.
Published: April 2021

Deep-sea hydrothermal vents are home to a variety of invertebrate species, many of which host chemosynthetic bacteria in unusual symbiotic arrangements. The vent tubeworm Riftia pachyptila (Vestimentifera) relies upon internal chemolithoautotrophic bacterial symbionts to support its large size and high growth rates. Because of this, R. pachyptila must supply sulfide to the bacteria, which are far removed from the external medium. Internal ΣH2S ([H2S+HS−+S2−]) can reach very high levels in R. pachyptila (2–12 mmol l−1 in the vascular blood), most of which is bound to extracellular hemoglobins. The animal can potentially take up sulfide from the environment via H2S diffusion or via mediated uptake of HS−, or both. It was expected that H2S diffusion would be the primary sulfide acquisition mechanism, paralleling the previously demonstrated preferential uptake of CO2. Our data show, however, that the uptake of HS− is the primary mechanism used by R. pachyptila to obtain sulfide and that H2S diffusion into the worm apparently proceeds at a much slower rate than expected. This unusual mechanism may have evolved because HS− is less toxic than H2S and because HS− uptake decouples sulfide and inorganic carbon acquisition. The latter occurs via the diffusion of CO2 at very high rates due to the maintenance of an alkaline extracellular fluid pH. ΣH2S accumulation is limited, however, to sulfide that can be bound by the hemoglobins, protecting the animal from sulfide toxicity and the symbionts from sulfide inhibition of carbon fixation.
Why Do Tuna Maintain Elevated Slow Muscle Temperatures? Power Output Of Muscle Isolated From Endothermic And Ectothermic Fish
Authors: Altringham John D. , Block Barbara A.
Published: April 2021

It has been hypothesised that regional endothermy has evolved in the muscle of some tunas to enhance the locomotory performance of the fish by increasing muscle power output. Using the work loop technique, we have determined the relationship between cycle frequency and power output, over a range of temperatures, in isolated bundles of slow muscle fibres from the endothermic yellowfin tuna (Thunnus albacares) and its ectothermic relative the bonito (Sarda chiliensis). Power output in all preparations was highly temperature-dependent. A counter-current heat exchanger which could maintain a 10 °C temperature differential would typically double maximum muscle power output and the frequency at which maximum power is generated (fopt). The deep slow muscle of the tuna was able to operate at higher temperatures than slow muscle from the bonito, but was more sensitive to temperature change than more superficially located slow fibres from both tuna and bonito. This suggests that it has undergone some evolutionary specialisation for operation at higher, but relatively stable, temperatures. fopt of slow muscle was higher than the tailbeat frequency of undisturbed cruising tuna and, together with the high intrinsic power output of the slow muscle mass, suggests that cruising fish have a substantial slow muscle power reserve. This reserve should be sufficient to power significantly higher sustainable swimming speeds, presumably at lower energetic cost than if intrinsically less efficient fast fibres were recruited.
A Physiological Evaluation Of Carbon Sources For Calcification In The Octocoral Leptogorgia Virgulata (Lamarck)
Authors: Lucas Jared M. , Knapp Loren W.
Published: April 2021

The union of calcium cations with carbonate anions to form calcium carbonate (CaCO3) is a fundamentally important physiological process of many marine invertebrates, in particular the corals. In an effort to understand the sources and processes of carbon uptake and subsequent deposition as calcium carbonate, a series of studies of the incorporation of 14C-labeled compounds into spicules was undertaken using the soft coral Leptogorgia virgulata. It has been surmised for some time that dissolved inorganic carbon in sea water is used in the biomineralization process. Furthermore, it was suspected that metabolically generated CO2 is also available for calcification. As a means of testing these possible sources of carbon in spicule calcification, key enzymes or transport systems in each pathway were inhibited. First, the enzyme carbonic anhydrase was specifically inhibited using acetazolamide. Second, the active transport of bicarbonate was inhibited using DIDS (4,4′-diisothiocyanato-stilbene-2,2′-disulfonic acid). Third, CO2 generation resulting from glycolysis and the citric acid cycle was arrested using iodoacetic acid, which interferes specifically with the enzyme glyceraldehyde-3-phosphate dehydrogenase. The results indicate that dissolved CO2 is the largest source of carbon used in the formation of calcitic sclerites, followed by HCO3− from dissolved inorganic carbon. In L. virgulata, the dissolved inorganic carbon is responsible for approximately 67 % of the carbon in the sclerites. The other 33 % comes from CO2 generated by glycolysis. Two important conclusions can be drawn from this work. First, carbon for spiculogenesis comes not only from dissolved inorganic carbon in the environment but also from metabolically produced carbon dioxide. While the latter has been theorized, it has never before been demonstrated in octocorals. Second, regardless of the carbon source, the enzyme carbonic anhydrase plays a pivotal role in the physiology of spicule formation in Leptogorgia virgulata.
Light-induced and circadian changes in the compound eye of the haematophagous bug Triatoma infestans (Hemiptera: Reduviidae)
Authors: Reisenman Carolina E. , Insausti Teresita C. , Lazzari Claudio R.
Published: April 2021

We analysed dynamic changes in the ommatidial structure of the compound eyes of Triatoma infestans. This nocturnal insect possesses open-rhabdom eyes, in which a ring of six rhabdomeres from retinula cells 1–6 (R1–6) surrounds a central pair of rhabdomeres from retinula cells 7 and 8 (R7–8). Screening pigments are located in all the photoreceptors and in the primary (PPC) and secondary (SPC) pigment cells. During the day, pigments within R1–6 and the PPCs form a small ‘pupil’ above the rhabdom and pigments within R7–8 are clustered around the central rhabdomere, allowing light to reach only the central rhabdomere. At night, the ‘pupil’ widens, and pigments inside R7–8 concentrate in the proximal region of the cells, allowing light to reach the peripheral rhabdomeres. In addition, the distance between the cornea and the rhabdom decreases. These rhythmic changes adapt the sensitivity of the eye by controlling the amount of light reaching and travelling within the rhabdom. Furthermore, the rhythm persists under conditions of constant darkness (DD), i.e. it is controlled by an endogenous oscillator. Remarkably, there are differences in pigment movements between the retinula cells of a single ommatidium. The migration of pigments in R1–6 is regulated by a circadian input, while that in R7–8 is regulated by both direct light and circadian inputs. The rhythm vanishes under constant-light conditions (LL). In this species, the circadian rhythm of photonegative behaviour persists in both DD and LL conditions, suggesting that these two rhythms, in retinal morphology and visual behaviour, may be generated by different circadian oscillators.
Reactions of Salmonid Larvae to Light
Authors: Woodhead P. M. J.
Published: April 2021

The larvae of the brown trout, rainbow trout, and salmon were periodically active and negatively phototactic when illuminated. All three species exhibited a positive photo-orthokinesis, the duration of their activity being directly proportional to the log of the light intensity, over a limited range. The light threshold for the kinesis was about 0.005 m.c. but tended to be higher in many young larvae and lower in larvae of a later stage. An upper limit, although more variable, was demonstrated in some individuals, and lay between about 10 and 100 mc. in the older larvae. It is suggested that a photo-orthokinesis, coupled with a negative phototaxis, berves well to maintain the larvae within the limits of their normal habitat at this stage of development. No adaptation of the kinesis occurred after periods of up to 90 min. illumination. But larvae did exhibit a rhythm of activity, reaching peaks at intervals of about 15 min. An increase in the general level of activity, at all light intensities, occurred as the larvae grew, until they were M y active throughout an observation period. At this point the behaviour of the young fish changed, in particular the negative phototaxis was lost and the fish soon began to feed. The increase in the level of activity may be regarded as an index of development in trout and was shown to be related to the general growth of the embryo. Rainbow trout ova hatch about a week earlier than brown trout at l0° C. This does not necessarily indicate a more rapid development in the rainbow trout, Since the latter takes a week longer to achieve full activity, both species reaching this stage at about sixty days after fertilization. The behaviour of the salmon larva does not seem to be strictly comparable with that of the trout during the later sbges of developement
The Effect of A Biological Clock on the Developmental Rate of Drosophila Pupae
Authors: Harker Janet E.
Published: April 2021

A study of the course of pupal development in two strains of Drosophila melanogaster has been made in an attempt to establish the factors affecting the time of adult eclosion. The time taken to complete three stages of pupal development has been measured for pupae entering each stage at each particular hour of the day when insects were kept in 12 hr. light: 12 hr. darkness, 12 hr. bright light: 12 hr. dim light, or in continuous darkness. The duration of each stage, in both strains, is affected by the time of day, relative to the light cycle, at which the stage is entered. The duration of each stage for pupae kept in continuous darkness is affected by the time of day at which the stage is entered, relative to the light cycle to which they had been exposed as larvae. The time-interval curves for all three stages of any one strain take the same form. Because of the very wide range of developmental rates, dependent upon the time within the light cycle at which each stage begins, a population in which the larvae all pupate within a 24 hr. period will continue to produce adult flies over several days. The eclosion rhythm is a population effect and does not reflect the phasing of individuals to a dawn eclosion; the majority of adults emerge at dawn because of the summation effect of circadian rhythms of development at earlier stages.
A Multilayer Interference Reflector in the Eye of the Scallop, Pecten Maximus
Authors: Land M. F.
Published: April 2021

Animals frequently make use of highly reflecting surfaces, as for example in the tapeta of the eyes of many vertebrates, the iridophores and photophores of many marine animals, and the scales of fish. Such surfaces raise the question: how are high reflectivities, often comparable with that of polished metal, achieved using biological materials?
The Site of Release of the Diuretic Hormone in Rhodnius—A New Neurohaemal System in Insects
Authors: Maddrell S. H. P.
Published: April 2021

This investigation has sought the site of release of the diuretic hormone which appears in the haemolymph of larvae of Rhodnius shortly after they begin feeding. Material possessing diuretic activity can be extracted in high concentration from those lengths of the peripheral abdominal nerves which lie just behind the mesothoracic ganglionic mass. An electron microscope study of the mesothoracic ganglionic mass and the abdominal nerves which leave it has shown that the axons from the neurosecretory cell bodies in the ganglionic mass some of which at least have previously been shown to contain the diuretic hormone run out into the proximal lengths of the abdominal nerves where they branch. Some of the branches have been followed to neurosecretory axon endings which typically are packed with neurosecretory granules and lie immediately beneath the fibrous nerve sheath. By constricting fed insects at various positions it has been possible to show that most of the diuretic hormone is released into the region close to but behind the mesothoracic ganglionic mass. It is concluded that the release of diuretic hormone in Rhodnius is from a series of swollen neurosecretory axon endings dotted over the surface of those lengths of the peripheral abdominal nerves which lie close to the mesothoracic ganglionic mass.
Excretory role of the midgut in larvae of the tobacco horn worm, Manduca sexta (L.)*
Authors: Nijhout H.F.
Published: April 2021

Caterpillars of Manduca sexta use two distinct transport mechanisms for the excretion of dyes. One pump (Type A) has a high affinity for acid (anionic) dyes and occurs in the midgut and medial Malpighian tubules. Acid dyes accumulate rapidly in the lumen of the midgut while the Malpighian tubules appear to play only a minor role in the excretion of these dyes. The other pump (Type B) excretes basic (cationic) dyes and is located primarily in the proximal Malpighian tubules. Evidence is presented that hippuric acid competes with acid dyes for excretion by both midgut and Malpighian tubules. After the final-instar larva purges its gut the ability of the midgut and Malpighian tubules to excrete dyes gradually decreases. Sixty hours after the purge only the Malpighian tubules retain some dye excreting activity.
Applicability of hydrodynamic analyses of spermatozoan motion
Authors: Yundt A.P. , Shack W.J. , Lardner T.J.
Published: April 2021

This paper investigates the applicability of a simple hydrodynamics theory due to Gray & Hancock (1955), and extended by Brokaw (1970), to the analysis of the motions of sea urchin, rabbit, and bull spermatozoa. Experimental procedures for filming and analysing the swimming motions are presented. A detailed discussion of the agreement between the experimental and theoretical results is given, and the limitations of the theory in analysing the motion of mammalian spermatozoa are discussed.
The mechanism of plasticization of the abdominal cuticle in Rhodnius
Authors: Reynolds S.E.
Published: April 2021

The mechanism of plasticization of the abdominal cuticle in Rhodnius larvae has been investigated, using the properties of loops of cuticle under varying test conditions as a model for the behaviour of the cuticle in vivo. It is supposed that plasticization is effected by a change in the intracuticular environment. A number of model mechanisms for plasticization may be proposed, which suppose that the epidermis is capable of regulating (a) pH, (b) ionic strength, (c) Ca and/or Mg, (d) urea, within the cuticle. Analyses of cuticle ash show that models (b) and (c) are not responsible for plasticization in vivo. The levels of inorganic ions within the unplasticized cuticle are not sufficiently high to allow plasticization upon their removal. No evidence for model (d) has been found; urea does not occur in the cuticle in detectable quantities. Exact measurements of the intracuticular pH have not been achieved but staining experiments strongly suggest that a change in pH occurs within the cuticle on plasticization. This pH change is probably large enough to account for the increased extensibility shown by plasticized cuticle.
Proprioceptive motor control in fish respiration
Authors: Ballintijn C.M. , Bamford O.S.
Published: April 2021

The response of single respiratory neurones in the medulla oblongata of carp to short twitches of individual respiratory muscles were analysed. The muscle contractions were obtained through automatic electrical stimulation and could be consistently elicited in a predetermined phase relation to the ventilatory cycle. The results show that, apart from nerve cells which take part in long-term processing of proprioceptive information from several sources, neurones also exist which possess the properties of elements of a peripheral proprioceptive control loop such as tension receptor neurones, length or stretch receptor neurones and motor neurones.
Directional Hearing in the Japanese Quail (Coturnix Coturnix Japonica)
Authors: Coles R. B. , Lewis D. B. , Hill K. G. , Hutchings M. E. , Gower D. M.
Published: April 2021

The directional sensitivity of cochlear microphonics (CM) was studied in the quail by rotating a free-field sound source (pure tones, 160–10 kHz) through 360° in the horizontal plane, under anechoic conditions. Sound diffraction by the head was monitored simultaneously by a microphone at the entrance to the ipsilateral (recorded) ear canal. Pressure-field fluctuations measured by the microphone were non-directional (⩽ 4 dB) up to 4 kHz ; the maximum head shadow was 8 dB at 6·3 kHz. In comparison, the CM sensitivity underwent directional fluctuations ranging up to 25 dB for certain low, mid and high frequency bandwidths. There was noticeable variation between quail for frequencies producing maximum directional effects, although consistently poor directionality was seen near 820 Hz and to a lesser extent near 3·5 kHz. Well-defined CM directivity patterns reflected the presence of nulls (insensitive regions) at critical positions around the head and the number of nulls increased with frequency. Five major types of directivity patterns were defined using polar co-ordinates: cardioid, supercardioid, figure-of-eight, tripartite and multilobed. Such patterns were largely unrelated to head shadow effects. Blocking the ear canal contralateral to the recorded ear was shown to effectively abolish CM directionality, largely by eliminating regions of insensitivity to sound.

It is inferred that the quail ear functions as an asymmetrical pressure gradient receiver, the pressure gradient function being mediated by the interaural cavity. It is proposed that the central auditory system codes directional information by a null detecting method and computes an unambiguous (i.e. intensity independent) directional cue. This spatial cue is achieved by the difference between the directional sensitivities of the two ears, defined as the Directional Index (DI). The spatial distribution of DI values (difference pattern) demonstrated ranges and peaks which closely reflected the extent and position of nulls determined from monaural directivity functions. Large directional cues (up to 25 dB) extended throughout most of the audible spectrum of the quail and the sharpness of difference patterns increased with frequency. Primary ‘best’ directions, estimated from peaks in difference patterns, tended to move towards the front of the head at higher frequencies; rearward secondary peaks also occurred. From the properties of directional cues it is suggested that the ability of birds to localize sound need not necessarily depend on frequency; however, spatial acuity may be both frequency and direction dependent, and include the possibility of front-to-rear errors. The directional properties of bird vocalizations may need to be reassessed on the basis of the proposed mechanism for directional hearing.
Studies on Locust Rectum
Authors: Spring J. H. , Phillips J. E.
Published: April 2021

Homogenates of whole corpora cardiaca (CC) cause increases in the short-circuit current (Isc) and transepithelial electropotential difference (PD) across locust recta of 3-fold and 1·7-fold respectively, in comparison with the values for unstimulated steady-state recta. Maximum stimulation restores rectal Isc and PD to levels observed immediately after removing this organ from animals. Cyclic-AMP causes a similar maximum increase in Isc and PD; however, the response exhibits a much shorter lag time and a faster rate of rise than is observed for stimulation with CC. The addition of CC to the haemocoel side of everted rectal sacs caused whole tissue levels of cAMP in this organ to increase 3-fold. The relationship between the logarithm of CC or cAMP concentration and the increase in Iscis linear, and the decline in ΔIsc with time is also dose dependent. Small maximum increases in Isc are caused by homogenates of ventral ganglia, whole brain and rectal tissue, but the concentration of the stimulatory activity in these locust tissues is clearly three orders of magnitude lower than in CC. Inhibitors of HCO3−/H+ and Cl− transport in vertebrate systems, acetazolamide and thiocyanate, do not inhibit the stimulation of recta by CC or cAMP.
Short Communications Piezoelectric Drive for Step-By-Step Microelectrode Advancement
Authors: Peters Malte , Tetzel Hans D.
Published: April 2021

It is a common experience in working with glass-microelectrodes that penetration of a cell is performed with greatest ease if a single thrust of high velocity is applied to either the electrode or the preparation. In most cases this is accomplished by tapping on the base of the experimental set-up, or on the micromanipulator carrying the electrode. However, it is often difficult to impale small cells with this method. Various attempts have been made to overcome this difficulty by the use of electromechanical drives of high speed and spatial resolution. These include electromagnetic (Fish et al. 1971; Tomita, 1969), stepping motor (Brown & Flaming, 1977) and piezoelectric devices. Potentially, piezoelectric transducers are most suitable for these applications because of their high speed. Single elements, however, are hampered by the fact that only small excursions can be obtained at high voltages. To obtain a larger working range it is necessary to use either devices composed of many elements stacked in series or piezoelectric bender elements. There are several reports on microelectrode drives incorporating bender-elements (Lassen & Sten-Knudsen, 1968; Prazma, 1978; Tupper & Rikmenspoel, 1969) but the mechanical response to an applied electrical signal has not been documented.
Alloxazinium-Resins as Readily Available and Reusable Oxidation Catalysts
Authors: Arakawa Yukihiro , Kawahara Takayuki , Minagawa Keiji , Imada Yasushi
Published: April 2021

N5-Modified alloxazinium salts including 5-ethyl-1,3-dimethylalloxazinium and 5-ethyl-1,3-dimethyl-8-(trifluoromethyl)alloxazinium salts were readily prepared as alloxazinium-resins from the corresponding N5-unmodified ingredients via the aerobic oxidation—ion exchange protocol, previously introduced by us for the preparation of isoalloxazine analogues, and their catalysis and reusability in H2O2 oxidations were evaluated.
The association between monocyte HDL ratio and albuminuria in diabetic nephropathy
Authors: Efe Fatma Kaplan
Published: April 2021

Objectives: We aimed to investigate whether Monocyte-to-HDL ratio (MHR) had an association with albuminuria in patients with diabetic nephropathy (DN).

Methods: Diabetic patients, who had admitted to the outpatient clinic of general internal disease department between September 2017 - February 2018 and had their spot urinary albumin/creatinine ratio measured, were examined retrospectively. Patients were separated based on the presence of DN. Patients with DN were grouped as Stage-I, Stage-II and Stage-III chronic kidney disease (CKD). Groups were compared in terms of MHR. The presence of a correlation between MHR and albuminuria was investigated.

Results: MHR was found to be higher in the DN (n=85) group compared to Non- DN group. (16.2±5.5 vs. 14.3±4, p=0.037) And there was no significant difference in Stage-I, Stage-II and Stage-III CKD groups in terms of MHR. (15.2± 3.4, 16.1±6.0, 17.1±6.0, p=0.485). No significant correlation was found between MHR and albuminuria in DN and non-DN groups (p=0.634, r=0.052; p=0.553, r=-0.059).

Conclusions: DN group had higher MHR than non-nephropathy group, whereas, there was no correlation between albuminuria and MHR.

doi: https://doi.org/10.12669/pjms.37.4.3882

How to cite this:Efe FK. The association between monocyte HDL ratio and albuminuria in diabetic nephropathy. Pak J Med Sci. 2021;37(4):1128-1132.  doi: https://doi.org/10.12669/pjms.37.4.3882

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Online assessment in undergraduate medical education: Challenges and solutions from a LMIC university
Authors: Fatima Syeda Sadia , Idress Romana , Jabeed Kausar , Sabzwari Saniya , Khan Sadaf
Published: April 2021

Background and Objectives: The Covid-19 pandemic has caused large-scale disruption in almost all educational programs across the world. Planning and rapid implementation of assessment through an online format presents the next set of novel challenges that must be addressed by academic administrations across the globe.

Methods: This cross-sectional study was conducted between March to August 2020 at the Aga Khan University Medical College. Two hundred medical students of year 1 and 2 participated in the study. We describe the planning, processes, and outcomes of online assessments using video communication platforms conducted at a private university in Pakistan. Standardized protocols were written and piloted, extensive training of student, proctors and staff for preparation and conduct of online assessments were developed. Feedback was recorded after each session and suggestions were incorporated in subsequent high-stakes assessments.

Results: A total of three pilot assessments were conducted to identify issues and process refinement. Commercially available lockdown browser and ZOOM were used in the first pilot; 80% of the class was unable to launch lockdown browser and laptops required repeated reload/reboot. For the second pilot assessment, University’s VLE page & MS Teams was trailed. Issues with internet connectivity, VLE page slowdown, and suboptimal recording feature in MS Teams were identified. For the final pilot assessment, phased launching of VLE page with single test item per page was implemented with success. The students reported that attempting the online exam on VLE with ZOOM support was user friendly. Ninety percent of the class was supportive of the continuing with the online assessments.

Conclusion: In order to device an effective protocol for e-assessments conducting multiple trial runs, and incorporating feedback from all stakeholders is a necessity.

doi: https://doi.org/10.12669/pjms.37.4.3948

How to cite this:Fatima SS, Idrees R, Jabeen K, Sabzwari S, Khan S. Online assessment in undergraduate medical education: Challenges and solutions from a LMIC university. Pak J Med Sci. 2021;37(4):945-951. doi: https://doi.org/10.12669/pjms.37.4.3948

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Antithrombotic therapy in COVID-19
Authors: Saeed Sahrai , Bleie Øyvind
Published: April 2021

doi: https://doi.org/10.12669/pjms.37.4.4607

How to cite this:Saeed S, Bleie Ø. Antithrombotic therapy in COVID-19. Pak J Med Sci. 2021;37(4):931-932.   doi: https://doi.org/10.12669/pjms.37.4.4607

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
О технических изобретениях в экономике
Authors: Merkulova Yuliya
Published: April 2021

актуальность технических изобретений в экономике растёт каждый год. Эта статья объясняет сущность изобретения, его новизну, практическую значимость. Система управления множеством переменных данных потребительских показателей продукции состоит в моделировании перечня последовательностей системы, которая состоит из 6 стадий, каждаЯ стадия включает свои стадии, операции и инструменты управления данными, но они связаны и объединены в интегрированную систему с общей моделью и вносят вклад в достижение технического результата. технический результат состоит в повышении результативности, надёжности и точности выходных данных. ситуационно-стратегической продуктовой программы. координация стратегической и текущей программ, чтобы достигнуть баланса спроса и предложения приведёт к повышению не только экономической, но и социальной эффективности.
The Informational Content of High-Frequency Option Prices
Authors: Amaya Diego , Bégin Jean-François , Gauthier Geneviève
Published: April 2021

We propose the option realized variance as an observable variable to summarize the information from high-frequency option data. This variable aggregates intraday option returns from midquote prices to compute an option’s total variability for a given day, providing additional information about the jump activity in the data generating process. Using the S&P 500 index time series and options data, this paper documents the performance of this realized measure in predicting the index realized variance as well as the equity and variance risk premiums. We estimate an option pricing model and analyze its parameter estimates. Our results show that excluding high-frequency option information produces significant differences in variance jump parameters, estimated risk premiums, and option pricing errors.

This paper was accepted by Tyler Shumway, finance.
A systematic literature review of incidence and predictors of headache and migraine in survivors of haemorrhagic stroke
Authors: Jones Rachael Suzanne
Published: April 2021

Background:

Headache is a frequent symptom of stroke, but little is known about the true incidence of headache following a haemorrhagic stroke, or if there are any risk factors for experiencing stroke-related headache. A systematic literature review was undertaken to examine the burden of headache in haemorrhagic stroke.

Methods:

A systematic search of electronic databases, including MEDLINE, CINAHL, Embase, SAGE Premier, Wiley Online Library and Elsevier's ScienceDirect, with a date range of January 1990 to October 2016, for human subjects and written in English was performed. Study selection using clear criteria was undertaken, and data extraction and assessment of quality was performed.

Results:

Some five from a total of 27 studies met the selection criteria. A total of 483 participants were included. The pooled random effects model showed 0.5528 (95% CI 0.3756-0.7235) had headache at onset, and 0.3917 (95% CI 0.1156-0.7108) had long-term headaches. A pooled estimate for gender as a risk factor showed women had an odds ratio (OR) of 1.93 (95% CI 1.16-3.22).

Conclusions:

Approximately 55% of patients with intracranial haemorrhage will experience headaches at stroke onset, with a further 39% experiencing long-term headaches. Women are nearly twice as likely as men to experience headache post-intracranial haemorrhage.
Canine developmental elbow disease part 2: surgical and non-surgical management
Authors: Fernee-Hall Rosanne , Janovec Jan
Published: April 2021

Developmental elbow disease is the term encompassing several abnormalities of the elbow joint, including fragmented medial coronoid process (FCP), osteochondrosis of the humerus (OC), ununited anconeal process (UAP), cartilage injuries and incongruity of the elbow joint. These disorders are associated with varying degrees of joint instability, inflammation, and loose fragments within the joint, which result in lameness and osteoarthrosis. Treatment should ideally involve correcting the underlying causes of the disease before significant joint damage has occurred. There are many surgical options for the treatment of developmental elbow disease which aim to unload the medial compartment, replace joint surfaces and manage pain. These include the sliding humeral osteotomy, proximal abducting ulna osteotomy, joint resurfacing and joint replacement. Studies evaluating the different treatments have low case numbers, variable outcome parameters, inconsistent diagnostic criteria and short follow-up times. Non-surgical manangement should always be part of the treatment plan to manage pain and symptoms as virtually all dogs with elbow disease will go on to develop osteoathritis.
Characterization of tracers for two-color laser-induced fluorescence thermometry of liquid-phase temperature in ethanol, 2–ethylhexanoic-acid/ethanol mixtures, 1-butanol, and o-xylene
Authors: Prenting Markus Michael , Shilikhin Maksim , Dreier Thomas , Schulz Christof , Endres Torsten
Published: April 2021

The fluorescence spectra of dye solutions change their spectral signature with temperature. This effect is frequently used for temperature imaging in liquids and sprays based on two-color laser-induced fluorescence (2cLIF) measurements by simultaneously detecting the fluorescence intensity in two separate wavelength channels resulting in a temperature-sensitive ratio. In this work, we recorded temperature-dependent absorption and fluorescence spectra of solutions of five laser dyes (coumarin 152, coumarin 153, rhodamine B, pyrromethene 597, and DCM) dissolved in ethanol, a 35/65 vol.% mixture of ethanol/2-ethylhexanoic acid, ethanol/hexamethylsiloxane, o-xylene, and 1-butanol to investigate their potential as temperature tracers in evaporating and burning sprays. The dissolved tracers were excited at either 266, 355, and 532 nm (depending on the tracer) for temperatures between 296 and 393 K (depending on the solvent) and for concentrations ranging between 0.1 and 10 mg/l. Absorption and fluorescence spectra of the tracers were investigated for their temperature dependence, the magnitude of signal re-absorption, the impact of different solvents, and varying two-component solvent compositions. Based on the measured fluorescence spectra, the tracers were analyzed for their 2cLIF temperature sensitivity in the respective solvents. Coumarin 152 showed for single-component solvents the overall best spectroscopic properties for our specific measurement situation related to temperature imaging measurements in spray-flame synthesis of nanoparticles as demonstrated previously in ethanol spray flames [Exp. Fluids 61, 77 (2020)10.1007/s00348-020-2909-9].
Imaging modeling and error analysis of the star sensor under rolling shutter exposure mode
Authors: Li Yongyong , Wei Xinguo , Li Jian , Wang Gangyi
Published: April 2021

As the star sensor works under high dynamic conditions, the spot formed by the star on the imaging plane will become a tail, which directly reduces the accuracy of centroid positioning. In addition, the imaging quality of the star sensor is seriously hit by the rolling shutter effect in the rolling shutter exposure mode, which further increases positioning error. Considering the diffusion radius and the dynamic tailing of the star spot, the imaging trajectory and the energy distribution models of the star spot under the rolling shutter exposure mode are established in this paper. Furthermore, based on the purposed models, the influence of the starting positions of stars and the dispersion of star spots to the centroid positioning error are analyzed by numerical simulation respectively, from which the variation laws of the two kinds of errors are obtained. Then, the laboratory experiments are implemented to evaluate the latter error; it indicates from the experimental results that the variation of the latter error is consistent with the simulation results, which is simultaneously proved that it cannot be ignored in practical engineering application. These results can be a valuable reference for developing a high precision star sensor. The models proposed in this paper can describe the star imaging process and evaluate the centroid positioning accuracy under the roller shutter exposure mode effectively, which lays a foundation for further eliminating the rolling shutter effect in the following research and improving the dynamic performance of star sensors.
Photonic integration of Er3+:Y2SiO5 with thin-film lithium niobate by flip chip bonding
Authors: Yang Likai , Wang Sihao , Shen Mohan , Xu Yuntao , Xie Jiacheng , Tang Hong X.
Published: April 2021

Rare earth ions are known as promising candidates for building quantum light-matter interface. However, tunable photonic cavity access to rare earth ions in their desired host crystal remains challenging. Here, we demonstrate the integration of erbium doped yttrium orthosilicate (Er3+:Y2SiO5) with thin-film lithium niobate photonic circuit by plasma-activated direct flip chip bonding. Resonant coupling to erbium ions is realized by on-chip electro-optically tuned high Q lithium niobate micro-ring resonators. Fluorescence and absorption of erbium ions at 1536.48 nm are measured in the waveguides, while the collective ion-cavity cooperativity with micro-ring resonators is assessed to be 0.36. This work presents a versatile scheme for future rare earth ion integrated quantum devices.
Near-infrared monocular 3D computational polarization imaging of surfaces exhibiting nonuniform reflectance
Authors: Li Xuan , Liu Fei , Han Pingli , Zhang Shichao , Shao Xiaopeng
Published: April 2021

This paper presents a near-infrared (NIR) monocular 3D computational polarization imaging method to directly reconstruct the shape of surfaces exhibiting nonuniform reflectance. A reference gradient field is introduced to the weight constraints for globally correcting the ambiguity of the surface normal for a target with nonuniform reflectance. We experimentally demonstrated that our method can reconstruct the shape of surfaces exhibiting nonuniform reflectance in not only the near field but also the far field. Moreover, with the proposed method, the axial resolution can be kept constant even under different object distances as long as the ratio of the focal length to the object distance is fixed. The simplicity and robustness of the proposed method make it an attractive tool for the fast modeling of 3D scenes.
Two dimensional photonic crystal angle sensor design
Authors: Neil Benjamin , Chen Xu , McCann Joshua , Blair Carl , Li Ju , Zhao Chunnong , Blair David
Published: April 2021

We present a novel design for an angle sensor based on photon coupling to internal optical modes of a two dimensional photonic crystal. We show in simulation that an implementation of this design could achieve sensitivities as high as 1.61 × 106 V/rad, which in principle allows for angle measurements with a noise floor of 2.98 × 10−14 rad

/

Hz

at the photodiode noise equivalent power. We discuss the limitations of this design and predict the impact these limitations have on the sensitivity as well as the possible ways to further increase the devices sensitivity. As a proof of concept, we demonstrate experimentally a photonic crystal with an angle sensitive mode.
Precise theoretical model for quantum-dot color conversion
Authors: Xu Sheng , Yang Tao , Lin Jianyao , Shen Qiongxin , Li Jinan , Ye Yuanyuan , Wang Luanluan , Zhou Xiaojian , Chen Enguo , Ye Yun , Guo Tailiang
Published: April 2021

Quantum-dot color conversion (QDCC) is a promising technique for next-generation full-color displays, such as QD converted organic light-emitting diodes and micro light-emitting diodes. Although present QDCC research has made some progress on the experimental aspect, the optical model and corresponding mathematical expression that can lay an indispensable foundation for QDCC have not been reported yet. In this paper, we present a theoretical model for precisely describing the complete optical behavior of QDCC, including optical transmission, scattering, absorption, and conversion process. A key parameter of QDCC, called dosage factor (DoF), is defined to quantitatively express the total consumption of QDs that can be calculated as the product of film thickness and QD concentration. Theoretical relations are established between DoF and three key performance indicators of QDCC, namely the light conversion efficiency (LCE), blue light transmittance (BLT), and optical density (OD). The maximum LCE value can be predicted based on this theoretical model, as well as the relationship between the slope of the OD curve and the molar absorption coefficient of blue light. This theoretical model is verified by both simulation and experiment. Results show that the simulation and experimental data highly match the theoretical model, and the goodness of fit reaches higher than 96% for LCE, BLT, and OD. Based on this, the optimal interval of DoF is recommended that provides key guiding significance to the QDCC related experiment.
Epsilon negative-based, broadband single-polarization single-mode hollow core anti-resonant photonic crystal fiber
Authors: Liu Shidi , Zhang Liang , Tian Ming , Yang Tianyu , Dong Yuming
Published: April 2021

A broadband single-polarization single-mode (SPSM) hollow core anti-resonant photonic crystal fiber (HC-ARPCF) is proposed and analyzed by the finite element method in this paper. The HC-ARPCF design consisted of outer semicircular cladding tubes and inner circular cladding tubes. The SPSM behavior is achieved through controlling the effective material absorption loss (EML) by loading epsilon negative (ENG) material in the selected semicircular cladding tubes. Optimization of the configuration parameters is conducted to yield a large loss difference (LD) between one of the two orthogonally polarized fundamental modes and all the other unwanted modes. Therefore, only one desired mode will exist after a proper propagation distance, i.e., SPSM guidance. Specially, the optimal design provides a 288 nm (from 1408 nm to 1676 nm and from 1680 nm to 1700 nm) bandwidth in terms of 40 dB/m minimum LD (MLD) and 168 nm (from 1452 nm to 1620 nm) bandwidth in terms of 100 dB/m MLD. Furthermore, this fiber also exhibits a large effective mode area and near-zero dispersion properties over the entire operation bandwidth. The proposed HC-ARPCF may find its applications in polarization maintaining and high-power laser systems.
Jones and Stokes–Mueller analogous calculi for OAM-transforming optics
Authors: Korotkova Olga , Gbur Greg
Published: April 2021

We introduce a matrix-based approach for characterization of local interactions of optical beams with devices that result in changes of their orbital angular momentum (OAM) content. For deterministic interactions, a method similar to the Jones calculus is developed, while for interactions involving random beams and/or devices, its generalization based on the coherence-OAM matrix is suggested. Applications of the new, to the best of our knowledge, calculus to a spiral plate, a trigonometric grating, and a diffuser are considered. An alternative formulation similar to the Stokes–Mueller calculus is also outlined.
Optimal conditions for self-starting of soliton mode-locked fiber lasers with a saturable absorber
Authors: Liu Shaozhen , Chen Yu , Huang Le , Cao Tao , Qin Xuanchao , Ning Haoqing , Yan Jikun , Hu Kailin , Guo Ziyue , Peng Jiahui
Published: April 2021

With the recently developed single-shot time-stretch dispersive Fourier transform technique, we investigate the buildup process of an all-polarization-maintaining soliton mode-locked fiber laser. Considering the multi-pulse competitions and the evolution of the survived pulse, we find an optimal range of intra-cavity energy for self-starting related to the saturation energy of the employed saturable absorber. Under the conditions, one dominant pulse can build up quickly against the others, and it finally drives to single-pulse operation. The conclusions drawn here hold for other soliton mode-locked lasers.