Microswimmers and Microfluidics: Understanding and Manipulating the Locomotion of Undulatory Microswimmers

Undulatory microswimmers, such as nematodes, are of great importance to agriculture, animal and human health, and fundamental biological research. The nematode Caenorhabditis (C.) elegans is widely used as a model organism for medical studies. My work focuses on studying the locomotion of nematodes; their interactions with surfaces, fluid flow, and each other; and developing new tools to manipulate their motion for diverse applications. In the first half (chapters 2-4) of this dissertation, I investigate experimentally and theoretically the effects of flat solid surfaces, external channel flow, and other swimmers on the swimming dynamics of undulatory microswimmers. I discovered that 1) when swimming in close proximity, undulatory microswimmers synchronize their swimming gait. This synchronization is facilitated by direct collisions among the swimmers, rather than by long-range hydrodynamic interactions or deliberate actions of the swimmers; 2) undulatory micro-swimmers have a tendency to accumulate near and swim along surfaces. This behavior does not require touch sensation ability of the swimmers, and can be explained by a short-range hydrodynamic interaction between the swimmers and adjacent surface; 3) undulatory microswimmers exhibit positive rheotaxis (upstream swimming behavior) near solid surfaces. This behavior is induced by the combination of a hydrodynamic surface attraction effect and the velocity gradient of external flow near solid surfaces. These findings help explain certain intriguing behaviors of undulatory microswimmers, highlight the diverse roles of hydrodynamic forces in microswimmers\u27 life cycles, and lay the foundations for novel microswimmer manipulation methods for fundamental biological research and clinical applications. In the second half (chapters 5-7) of this dissertation, I present the design, fabrication, characterization, and applications of a few engineering devices/methods for dynamic trapping, motility measurement, motility-based sorting, and directing the motion of microswimmers. These new devices/methods enabled many studies that would be impossible or impractical with conventional methods

An Automated Microwell Platform for Large-Scale Single Cell RNA-Seq

Recent developments have enabled rapid, inexpensive RNA sequencing of thousands of individual cells from a single specimen, raising the possibility of unbiased and comprehensive expression profiling from complex tissues. Microwell arrays are a particularly attractive microfluidic platform for single cell analysis due to their scalability, cell capture efficiency, and compatibility with imaging. We report an automated microwell array platform for single cell RNA-Seq with significantly improved performance over previous implementations. We demonstrate cell capture efficiencies of >50%, compatibility with commercially available barcoded mRNA capture beads, and parallel expression profiling from thousands of individual cells. We evaluate the level of cross-contamination in our platform by both tracking fluorescent cell lysate in sealed microwells and with a human-mouse mixed species RNA-Seq experiment. Finally, we apply our system to comprehensively assess heterogeneity in gene expression of patient-derived glioma neurospheres and uncover subpopulations similar to those observed in human glioma tissue

Cultural Distance Research in Tourist Behavior - Review and Critique

Nematode Settlin

Regresijske jednadžbe za procjenu kvalitete izvedbe maksimalnog osnovnog nogometnog udarca u muškaraca i žena

Biomechanics research of soccer skills has greatly lagged behind the sport’s popularity compared to many other sports. Even for basic skills, such as the maximal instep kick, relatively few quantitative studies exist. Further, most of these fail to provide practical means to judge kick quality. The current study proposes to address this deficiency by establishing user-friendly regression equations that apply to both novice and advanced players. These allow an easy way for coaches/teachers to evaluate kick quality. The method consisted of 3D data collection (VICON system with nine high-speed cameras, 120 Hz), full-body biomechanical modeling and correlation and regression analyses of ball release speed with flexion/extension of shoulder, trunk, hip, knee and rotation of trunk as well as last stride length and body height. Twenty-four male and twenty-six female college students, equally divided into novice and advanced cohorts, participated. Results showed many of the correlations to be reliable predictors of a kick’s effectiveness. However, they are not practical since extensive use of technology and time-consuming data processing is needed. Further analyses showed multi-regressions using last stride length and body height as independent parameters to have equally reliable evaluation potential. The study concludes that, since the last two independent parameters are easy to measure, these regression equations provide an eminently practical means to evaluate the maximal instep soccer kick.U usporedbi s drugim sportovima, biomehanička istraživanja vještina u nogometu uvelike zaostaju za razinom popularnosti toga sporta u svijetu. Čak i za osnovna nogometna znanja, kao što je osnovni nogometni udarac izveden punom snagom, postoji relativno malo kvantitativnih istraživanja. Nadalje, većina tih istraživanja nije ponudila praktična rješenja za ocjenjivanje kvalitete udarca. Ovo istraživanje usmjereno je na rješavanje tih nedostataka postavljanjem praktičnih regresijskih jednadžba koje se mogu primijeniti za procjenu kvalitete izvođenja udarca početnika i naprednih nogometaša. Korištenje regresijskih jednadžba omogućit će nogometnim trenerima i profesorima tjelesne i zdravstvene kulture jednostavnu procjenu kvalitete udarca. Metoda se sastoji od prikupljanja 3D podataka (VICON sustav sa 9 visoko-frekventnih kamera, 120 Hz), biomehaničkog modeliranja cijelog tijela te korelacijskih i regresijskih analiza povezanosti početne brzine lopte nakon udarca s pregibanjem/ opružanjem ramena, trupa, kuka, koljena i s rotacijom trupa te duljinom posljednjega koraka i visinom tijela. U istraživanju su sudjelovala 24 studenta i 26 studentica koji su raspoređeni u jednake početničke i napredne grupe. Rezultati su pokazali da je velik broj korelacija bio pouzdan prediktor učinkovitosti udarca. Ipak, tolike korelacije nisu praktične budući da zahtijevaju uporabu mnogih uređaja i dugotrajnu obradu podataka. Daljnje analize pokazale su da višestruke regresije, koje se temelje na duljini posljednjega koraka i visini tijela kao nezavisnim varijablama, imaju jednak potencijal pouzdanosti za ocjenjivanja kvalitete izvođenja udarca. Budući da je duljinu posljednjega koraka i visinu tijela lako mjeriti, zaključak je ovog istraživanja da su predložene regresijske jednadžbe vrijedno praktično sredstvo za vrednovanje kvalitete maksimalnog osnovnog nogometnog udarca

SCOPE-Seq: a scalable technology for linking live cell imaging and single-cell RNA sequencing

Abstract Optically decodable beads link the identity of a sample to a measurement through an optical barcode, enabling libraries of biomolecules to be captured on beads in solution and decoded by fluorescence. This approach has been foundational to microarray, sequencing, and flow-based expression profiling technologies. We combine microfluidics with optically decodable beads and show that phenotypic analysis of living cells can be linked to single-cell sequencing. As a proof-of-concept, we demonstrate the accuracy and scalability of our tool called Single Cell Optical Phenotyping and Expression sequencing (SCOPE-Seq) to combine live cell imaging with single-cell RNA sequencing

Pouzdanost i osjetljivost pokazatelja povezanih s procjenom kardiovaskularnih funkcionalnih sposobnosti

Determining the recovery heart rate (RHR) index after various submaximal exercises is a popular and practical way for a population’s cardiovascular fitness evaluation. These evaluations are based on the regression among RHR, load intensity, and maximal oxygen uptake. However, little work has been done to 1) explore the influences of body weight and height on these tests’ reliability and sensitivity, and 2) compare the reliability among the tests. As a result, practitioners often choose tests without the appropriate criteria. This study researched the mentioned two aspects by evaluating 30 male college students via three common tests – 30 cm step test, 40 cm step test and squat-up-down test. The results showed that the reliability and sensitivity of the three tests were remarkably different. Adding body weight into the evaluation would improve both reliability and sensitivity. Considering all the influence factors, 30 cm step test was the best one. These findings suggested that applying the relative RHR index (normalized by body weight) should be considered for a population’s cardiovascular fitness evaluation in the future.Uvod Opće je poznato da razina kondicijske pripremljenosti ovisi o dobi, spolu, rasi, antropometrijskim mjerama (tjelesnoj težini i visini) te intenzitetu treninga ili vježbanja. Već desetljećima sportski znanstvenici pokušavaju pronaći pouzdane načine za njezino vrednovanje na raznim selektiranim populacijama. Kao rezultat tih istraživanja, danas postoje brojne metode za utvrđivanje stanja kondicijske pripremljenosti koje su se pokazale primjerene ili za opću populaciju ili za sportaše različite dobi. Popularan i praktičan način za procjenu kardiovaskularnih sposobnosti jest utvrđivanje indeksa frekvencije srca u oporavku (RHR) nakon različitih sub-maksimalnih optrećenja. Ove procjene temelje se na regresiji između RHR, intenziteta opterećenja i maksimalnog primitka kisika (VO2max). Ipak, vrlo malo znanstvenih istraživanja bilo je usmjereno na utvrđivanje: 1) utjecaja tjelesne težine i visine na pouzdanost i osjetljivost tih mjernih instrumenta i 2) na usporedbu koeficijenata pouzdanosti između testova. Kao posljedica toga, u praksi se izabiru i upotrebljavaju testovi bez odgovarajućih kriterija. Cilj je ove studije istražiti navedene aspekte utvrđivanjem stanja kondicijske pripremljenosti 30 studenata primjenom tri slična testa – step test na klupici visine 30 cm, step test na klupici visine 40 cm i čučnjevi. Metode Ispitanici su dobi 20,3±,2 godine, tjelesne težine 64,0±2,0 kg i visine 173,4±,9 centimetara. Svi ispitanici bili su prosječni studenti tjelesnog odgoja koji se nisu aktivno bavili sportom. Koeficijenti pouzdanosti za sve mjerne instrumente utvrđeni su formulom Thomasa i Nelsona (2001) u kojoj MSs predstavlja aritmetičku sredinu kvadrata rezultata ispitanika (varijanca pravih rezultata), a MSE aritmetičku sredinu kvadrata pogreške (varijanca pogreške ili standardna pogreška mjerenja). Sve MS vrijednosti (sume kvadrata rezultata ili zajedničke varijance rezultata) dobivene su analizom varijance (ANOVA) za svaki paralelni test. Razina značajnosti za sve testove postavljena je na razinu od 0,05. Za obradu podataka korišten je program SPSS 10 za Windowse (SPSS Inc, Chicago, IL, USA). Rezultati i rasprava Rezultati istraživanja pokazali su da su pouzdanost i objektivnost ispitivana tri testa statistički značajno različiti. Normaliziranjem rezultata s koeficijentom tjelesne težine povećala bi se i pouzdanost i osjetljivost mjernih instrumenata. Uzimajući u obzir sve faktore koji utječu na pouzdanost i osjetljivost mjernih instrumenata, pokazalo se da je najbolji od testiranih testova step test na klupici visine 30 cm. Ovi rezultati ukazuju na činjenicu da bi se relativni indeks frekvencije srca u oporavku RHR (normaliziran tjelesnom težinom ispitanika) trebao u budućnosti koristiti za utvrđivanje kardiovaskularne sposobnosti ispitanika, osobito u populacijskim mjerenjima