1,532 research outputs found
Size, shape, and flexibility of RNA structures
Determination of sizes and flexibilities of RNA molecules is important in
understanding the nature of packing in folded structures and in elucidating
interactions between RNA and DNA or proteins. Using the coordinates of the
structures of RNA in the Protein Data Bank we find that the size of the folded
RNA structures, measured using the radius of gyration, , follows the Flory
scaling law, namely, \AA where N is the number of
nucleotides. The shape of RNA molecules is characterized by the asphericity
and the shape parameters that are computed using the eigenvalues
of the moment of inertia tensor. From the distribution of , we find
that a large fraction of folded RNA structures are aspherical and the
distribution of values shows that RNA molecules are prolate (). The
flexibility of folded structures is characterized by the persistence length
. By fitting the distance distribution function to the worm-like
chain model we extracted the persistence length . We find that \AA. The dependence of on implies the average length of
helices should increases as the size of RNA grows. We also analyze packing in
the structures of ribosomes (30S, 50S, and 70S) in terms of , ,
, and . The 70S and the 50S subunits are more spherical compared to
most RNA molecules. The globularity in 50S is due to the presence of an
unusually large number (compared to 30S subunit) of small helices that are
stitched together by bulges and loops. Comparison of the shapes of the intact
70S ribosome and the constituent particles suggests that folding of the
individual molecules might occur prior to assembly.Comment: 28 pages, 8 figures, J. Chem. Phys. in pres
Laparoscopic intraperitoneal on-lay mesh repair for the umbilical hernia using anti-adhesive gel
Curs Chirurgie Generală al Facultăţii Stomatologie, USMF „Nicolae Testemiţanu”, Spitalul Clinic Militar Central, Chişinău, Republica Moldova, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Poziţionarea intraperitoneală a plasei chirurgicale în cadrul curei laparoscopice intraperitoneale (IPOM) impune
selectarea materialului sintetic.
Material şi metode: În clinica noastră de chirurgie (SCMC), în anii 2013-2015 au fost supuşi curei laparoscopice pentru hernie
ombilicală 10 pacienţi, 6 femei şi 4 bărbaţi. Vârsta a variat de la 20 pînă la 60 ani. Pentru protezare s-a folosit plasa din
polivinilidenftorid (PVDF) de tip „Uniflex” (Rusia), mai mare cu 5 cm decât defectul herniar pe toate dimensiunile. Pentru
prevenirea aderenţelor parieto-viscerale a fost utilizat suplimentar, compozitul antiadeziv „Mezogel” (Rusia). Fixarea plasei s-a
asigurat prin aplicarea a 5 suturi tip „ancore” transfasciale şi agrafe helicoidale neresorbabile de diametrul – 4 mm, plasate la
1cm de marginea protezei. Algometria s-a efectuat cu utilizarea scalei analog vizuale (VAS).
Rezultate: Defectul herniar a avut un diametru median de 3,9 cm. La 4 pacienţi a fost suturat defectul (diametrul = 1-3 cm)
herniar prin aplicarea suturii intracorporale. Din particularităţi intraoperatorii se menţionează: reducerea conţinutului sacului
herniar, adezioliză, controlul hemoragiei din adeziuni. Durata medie a intervenţiilor a fost de 55 min (45-65 min). În perioada
postoperatorie complicaţii nu au fost semnalate. Sindromul dolor postoperator a fost minim (VAS: 1-3); complicaţii parietale –
absente. Durata mediană de spitalizare – 3,2 zile. În perioada postoperatorie la distanţă nu s-au constatat dureri şi neuropatii,
dereglări de tranzit intestinal sau recidive herniare.
Concluzii: Cura laparoscopică a herniei ombilicale cu aplicarea protezei IPOM este o metodă fezabilă, sigură şi minim-invazivă.
Plasa şi gelul cu proprietăţi antiadezive reduce semnificativ riscul aderenţelor parieto-viscerale şi a complicaţiilor parietale,
asigurând reintegrarea socio-profesională rapidă. Avantajele expuse argumentează perspectivele utilizării tehnicii IPOM în cura
herniilor ombilicale.Introduction: In laparoscopic intraperitoneal on-lay mesh repair (IPOM) positioning of a surgical mesh requires the selection of
a synthetic material with anti-adhesive properties.
Material and methods: Within period of 2013-2015, 10 IPOM hernia repairs have been performed on the group of 10 patients
diagnosed with umbilical hernia, 6 male and 4 female. The overall age was 36.4 years (range 20-60). The PVDF monofilament
macroporous mesh has been utilized for repair. The mesh overlaped the defect with 5 cm. The combined fixation technique was
ensured by applying the “anchor” type sutures and 4 mm non-resorbable spiral tacks plaid up to 1 cm from the edge of the
prosthetic mesh. The non-adhesive composite “Mezogel” has been used to ensure the prevention of the adhesions. Algometry
was performed using visual analog scale (VAS). Results: The mean diameter of the hernia defect was 3.9 cm. In 4 cases the hernia defect (d=1-3 cm) has been closed by
applying intracorporeal suture. The intraoperative features were: reduction the hernia sac content, removal of adhesions, control
of the bleeding. The mean time of operations was 55 min. In postoperative period there no reported complications. In the
distance postoperative period were not found pain and local neuropathy, bowel disorders or hernia recurrences.
Conclusions: Laparoscopic IPOM umbilical hernia repair it is a feasible, safe and minimally-invasive procedure. Prosthesis and
gel with anti-adhesive properties significantly reduce the risk of the parieto-visceral adhesions and complications ensuring quick
socio-professional reintegration. The exposed advantages arguments the use of IPOM procedure in the umbilical hernia repair
Quantum ratchets in dissipative chaotic systems
Using the method of quantum trajectories we study a quantum chaotic
dissipative ratchet appearing for particles in a pulsed asymmetric potential in
the presence of a dissipative environment. The system is characterized by
directed transport emerging from a quantum strange attractor. This model
exhibits, in the limit of small effective Planck constant, a transition from
quantum to classical behavior, in agreement with the correspondence principle.
We also discuss parameter values suitable for implementation of the quantum
ratchet effect with cold atoms in optical lattices.Comment: Significant changes: Several text improvements and new results.
Figure 2 modified. Figure 4 adde
On Semantic Similarity in Video Retrieval
Current video retrieval efforts all found their evaluation on an
instance-based assumption, that only a single caption is relevant to a query
video and vice versa. We demonstrate that this assumption results in
performance comparisons often not indicative of models' retrieval capabilities.
We propose a move to semantic similarity video retrieval, where (i) multiple
videos/captions can be deemed equally relevant, and their relative ranking does
not affect a method's reported performance and (ii) retrieved videos/captions
are ranked by their similarity to a query. We propose several proxies to
estimate semantic similarities in large-scale retrieval datasets, without
additional annotations. Our analysis is performed on three commonly used video
retrieval datasets (MSR-VTT, YouCook2 and EPIC-KITCHENS).Comment: Accepted in CVPR 2021. Project Page: https://mwray.github.io/SSVR
Prospects for the use of the laparoscopic transabdominal pre-peritoneal approach (TAPP) in groin hernia repair
Curs Chirurgie al Facultăţii Stomatologie, USMF “Nicolae Testemiţanu”, Spitalul Clinic Militar Central, Chisinău, Republica Moldova, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Abordul laparoscopic în cura herniilor inghinale devine o metodă de elecţie pe plan mondial. Rămîne actuală
problema standardizării tehnicii chirurgicale şi optimizării rezultatelor acestui procedeu.
Material şi metode: În perioada anilor 2008-2014 în Clinică a fost efectuată cura laparoscopică a herniei inghinale la 271
pacienţi (16 – bilateral). Repartiţia herniilor conform clasificării Nyhus: tip II (n=188), tip IIIa (n=64), tip IIIb (n=18), tip IIIc (n=9),
tip IV (n=12). A fost utilizată tehnica transabdominală preperitoneală (TAPP).
Rezultate: Durata intervenţiei a constituit în medie 47,8±25,07 min, fiind mai lungă pentru herniile recidivante – 95±48,99 min
(60-180) şi bilaterale – 92,78±23,47 min (65-140). Mediana spitalizării – 3 zile, reîntoarcerea în cîmpul muncii – sub 10 zile.
Incidentele intraoperatorii au fost corectate laparoscopic. Conversia a fost efectuată la un pacient. Nu au fost constatate cazuri
de infecţie a plăgii postoperatorii. Aprecierea rezultatelor tratamentului chirurgical la distanţă a fost realizată la 223 pacienţi.
Pentru evaluarea durerii la pacienţii cu diagnosticul hernie inghinală a fost utilizată scala de evaluare numerică NRS – 11. În
perioada postoperatorie au prevalat pacienţi cu sindrom algic redus (NRS: 1-3). Algoparestezia postoperatorie persistentă a fost
diagnosticată la 4 pacienţi. Recidiva herniei a fost înregistrată la 2 pacienţi, în ambele cazuri recidiva a fost corectată
laparoscopic.
Concluzii: Experienţa noastră confirmă posibilitatea utilizării procedeului TAPP la diferite tipuri de hernie inghinală. Acumularea
experienţei permite de a lărgi indicaţiile pentru abordul laparoscopic la pacienţii cu hernii bilaterale, glisante şi recurente.
Avantajele hernioplastiei laparoscopice sunt: micşorarea sindromului algic postoperator, reintegrarea socioprofesională rapidă şi
numărul redus de complicaţii parietale.Introduction: The transabdominal pre-peritoneal procedure (TAPP) represents one of the most popular techniques used for
inguinal hernia repair. The analysis of the reported cases helps to standardize the relatively new laparoscopic technique and to
improve the overall results.
Material and methods: The group of 271 patients underwent laparoscopic hernia repair (16 bilateral) for the period 2008-2014.
According to Nyhus classification, the groin hernias were classified as type II (n=188), type IIIa (n=64), type IIIb (n=18), type IIIc
(n=9), type IV (n=12). The TAPP procedure was utilized.
Results: The mean operating time was 47.8±25.07 minutes, being statistically longer for recurrent hernias 95±48.99 min (range,
60-180) and bilateral hernias – 92.78±23.47 min (range, 65-140). The average length of hospital stay was 3 days. Patients
returned to work in an average of 10 days. The postoperative morbidity rate was 2.2%. The majority of intraoperative incidents
(intraoperative hemorrhage, n=4) were solved laparoscopically without sequelae. One case was converted to Lichtenstein
repair. Patients were evaluated at a median follow up of 24 month (range, 12-36 month). A total of 223 patients were assesssed
for long-term outcomes. Pain was assessed with Numerical Rating Scale (NRS – 11). The vast majority of post-operative
patients had minor pain manifestation of pain (NRS: 1-3). We observed 4 cases of persistent inguinal pain. The hernia
recurrence was developed in 2 patients and has been corrected via laparoscopic approach.
Conclusions: While laparoscopic hernia repair requires a lengthy learning curve, it represents safe and valid alternative to
open hernia repairs and could be effectively used for bilateral, recurrent and sliding hernias. The advantages of laparoscopic
repair include less postoperative pain, faster return to normal activities and low wound infection rate
Laparoscopic transperitoneal retromascular (sublay) mesh repair in cure of ventral hernias: first experiences
Catedra Chirurgie nr.5, Universitatea de Stat de Medicină și Farmacie „Nicolae Testemiţanu”, Spitalul Clinic Militar Central,
Chişinău, Republica Moldova, Al XIII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” și
al III-lea Congres al Societății de Endoscopie, Chirurgie miniminvazivă și Ultrasonografie ”V.M.Guțu” din Republica MoldovaIntroducere: Poziționarea laparoscopică, retromusculară (sublay) a plasei chirurgicale.
Material și metode: În clinica chirurgie Nr 5, (SCMC), în anii 2018-2019 au fost supuși curei laparoscopice pentru hernii ventrale 8
pacienți, 4 femei și 4 barbați. Vîrsta medie 25-70 ani. Pentru protezare s-a folosit plasa din polipropilen light, mai mare cu 5 cm decât
defectul herniar pe toate dimensiunile. Proteza a fost amplasată retromuscular, prin abord laparoscopic transperitoneal. Fixarea plasei
sa asigurat prin aplicarea agrafelor helicoidale nerezorbabile de ø 4 mm, plasate la 1cm de marginea protezei. Algometria sa efectuat
cu utilizarea scalei analog vizuale (VAS).
Rezultate: Defectul herniar a avut un diametru median de 3,7 cm. La toți pacienți defectul herniar a fost suturat prin aplicarea
suturii intracorporale. Din particularități intraoperatorii se menționează: reducerea conținutului sacului herniar, adezioliză, controlul
hemoragiei din adeziuni și decolarea peritoneului și tunicii retromusculare prin incizie longitudinală. Durata medie a intervențiilor a fost
de 45 min (35-65 min). În perioada postoperatorie complicații nu au fost semnalate. Sindromul dolor postoperator a fost minim (VAS
1 – 3), complicații parietale absente. Durata mediana de spitalizăre 3,1 zile. În perioada postoperatorie la distanța nu s-au constatat
dureri și neuropatii, dereglări de tranzit intestinal, recidive herniare.
Concluzii: Cura laparoscopică intraperitoneală retromusculară (sublay) a herniilor ventrale cu aplicarea protezei din polipropilen este
o metodă sigură și miniminvazivă, cu costuri reduse la consumabile. Amplasarea retromusculară a plasei exclude aderențele parietoviscerale și complicațiile parietale, asigurând reintegrarea socio-profesională rapidă. Avantajele expuse argumentează perspectivele
utilizării tehnicii laparoscopice retromusculare în cura herniilor ventrale.Introduction: Transperitoneal retromuscular sublay positioning of a surgical mesh.
Materials and methods: Within period of 2018-2019, 8 retromuscular hernia repairs have been performed on the group of 8 patients
diagnosed with ventral hernias, 4 male and 4 female. The overall age was 47,2 years (range 25 - 70). Polypropylene mesh has been
utilized for repair. The mesh overlaped the defect with 5 cm. The fixation technique was ensured by applying ø 4 mm non-resorbable
spiral tacks plaid up to 1cm from the edge of the prosthetic mesh. Algometry was performed using visual analog scale (VAS).
Results: The mean diameter of the hernia defect was 3.7 cm. In all cases the hernia defect has been closed by applying intracorporeal
suture. The intraoperative features were: reduction the hernia sac content, removal of adhesions, control of the bleeding with peritoneum
and posterior rectus are opened by a longitudinal incision. The mean time of operations was 45 min. In postoperative period there
no reported complications. In the distance postoperative period were not found pain and local neuropathy, bowel disorders, hernia
recurrences.
Conclusions: Laparoscopic transperitoneal retromuscular hernia repair is a safe and minimally-invasive procedure with low cost of
consumables. Retromuscular location of the prosthesis exclude the risk of the parietovisceral adhesions and complications ensuring
quick socio-professional reintegration. The exposed advantages argument the use of transperitoneal retromuscular procedure in the
ventral hernia repair
Teachers developing assessment for learning: impact on student achievement
While it is generally acknowledged that increased use of formative assessment (or assessment for learning) leads to higher quality learning, it is often claimed that the pressure in schools to improve the results achieved by students in externally-set tests and examinations precludes its use. This paper reports on the achievement of secondary school students who worked in classrooms where teachers made time to develop formative assessment strategies. A total of 24 teachers (2 science and 2 mathematics teachers, in each of six schools in two LEAs) were supported over a six-month period in exploring and planning their approach to formative assessment, and then, beginning in September 1999, the teachers put these plans into action with selected classes. In order to compute effect sizes, a measure of prior attainment and at least one comparison group was established for each class (typically either an equivalent class taught in the previous year by the same teacher, or a parallel class taught by another teacher). The mean effect size was 0.32
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