Stetoskopet – Tidsskriftet rett i øret.
Stetoskopet – Tidsskriftet rett i øret. Tidsskr Nor Laegeforen. 2020 Jan 14;140(1): Authors: Brean A PMID: 31948194 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Brean A Tags: Tidsskr Nor Laegeforen Source Type: research

A closed door to an open future.
ik RE PMID: 31948195 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Ørstavik RE Tags: Tidsskr Nor Laegeforen Source Type: research

Æsculap fyller 100 år.
Æsculap fyller 100 år. Tidsskr Nor Laegeforen. 2020 Jan 14;140(1): Authors: Stoltenberg C PMID: 31948196 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Stoltenberg C Tags: Tidsskr Nor Laegeforen Source Type: research

Dansens gud.
PMID: 31948197 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Dahl AA Tags: Tidsskr Nor Laegeforen Source Type: research

Polymerase gamma-relatert mitokondriesykdom.
Abstract DNA Polymerase gamma (POLG) is an enzyme that replicates and repairs mitochondrial DNA. Mutations in the gene that codes for the catalytic subunit of the enzyme, the POLG gene, are one of the most common causes of mitochondrial disease. POLG-related disorders can have overlapping phenotypes and affect a number of organ systems, and first onset may occur at any age. The disease group can serve as a paradigm for understanding mitochondrial diseases in general. PMID: 31948198 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Hikmat O, Varhaug KN, Bindoff LA Tags: Tidsskr Nor Laegeforen Source Type: research

Kikuchi's disease.
yr O PMID: 31948199 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Alnæs M, Mjelle K, Vintermyr O Tags: Tidsskr Nor Laegeforen Source Type: research

En kvinne i 40- årene som brukte vanedannende legemidler i svært høye doser.
En kvinne i 40-årene som brukte vanedannende legemidler i svært høye doser. Tidsskr Nor Laegeforen. 2020 Jan 14;140(1): Authors: Heldal AT, Aamo TO, Frost J Abstract BACKGROUND: Following a surgical procedure, a female patient in her forties was prescribed opioids (oxycodone). The prescription escalated into doses that were extremely high, and at a level beyond any experienced previously, either at the various hospital units that were involved in the treatment or in the medical literature. CASE PRESENTATION: The patient had no known history of substance abuse. After the surgica...
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Heldal AT, Aamo TO, Frost J Tags: Tidsskr Nor Laegeforen Source Type: research

Analysis of cytokines.
ke OL PMID: 31948201 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Storjord E, Hennø LT, Mollnes TE, Brekke OL Tags: Tidsskr Nor Laegeforen Source Type: research

Er seleksjonsmedisinsk praksis i Norge lovstridig?
PMID: 31948202 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Koefoed VF Tags: Tidsskr Nor Laegeforen Source Type: research

What is insomnia?
h;m M PMID: 31948203 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Engstrøm M Tags: Tidsskr Nor Laegeforen Source Type: research

Reell samhandling forebygger reinnleggelse.
PMID: 31948204 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Wyller TB Tags: Tidsskr Nor Laegeforen Source Type: research

Hva gj ør Legeforeningen for å avskaffe foretaksmodellen?
Hva gjør Legeforeningen for å avskaffe foretaksmodellen? Tidsskr Nor Laegeforen. 2020 Jan 14;140(1): Authors: Vaglum P PMID: 31948205 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Vaglum P Tags: Tidsskr Nor Laegeforen Source Type: research

B ør epilepsipasienter og pårørende informeres om risikoen for plutselig død?
Bør epilepsipasienter og pårørende informeres om risikoen for plutselig død? Tidsskr Nor Laegeforen. 2020 Jan 14;140(1): Authors: Nakken KO, Henning O PMID: 31948206 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Nakken KO, Henning O Tags: Tidsskr Nor Laegeforen Source Type: research

Omtale av leger i offentligheten – er personvernet under press?
Omtale av leger i offentligheten – er personvernet under press? Tidsskr Nor Laegeforen. 2020 Jan 14;140(1): Authors: Sondrup A PMID: 31948207 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Sondrup A Tags: Tidsskr Nor Laegeforen Source Type: research

Glymphatic MRI.
PMID: 31948208 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Ringstad G, Eide PK Tags: Tidsskr Nor Laegeforen Source Type: research

Ø. Ekeberg svarer.
Ø. Ekeberg svarer. Tidsskr Nor Laegeforen. 2020 Jan 14;140(1): Authors: Ekeberg Ø PMID: 31948209 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Ekeberg Ø Tags: Tidsskr Nor Laegeforen Source Type: research

Etiske dilemmaer ved suicidalitet.
PMID: 31948210 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Fredheim OMS, Magelssen M Tags: Tidsskr Nor Laegeforen Source Type: research

G. Hasle svarer.
PMID: 31948211 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Hasle G Tags: Tidsskr Nor Laegeforen Source Type: research

Bli ikke solbrent.
her I PMID: 31948212 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Gjersvik P, Landrø L, Roscher I Tags: Tidsskr Nor Laegeforen Source Type: research

Ikke s å kjapp med pacemaker til unge.
Ikke så kjapp med pacemaker til unge. Tidsskr Nor Laegeforen. 2020 Jan 14;140(1): Authors: Steen T PMID: 31948213 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Steen T Tags: Tidsskr Nor Laegeforen Source Type: research

A young woman with a transfusion-related pregnancy complication.
Akkök ÇA Abstract BACKGROUND: Individuals with the K0 phenotype are extremely rare. They may develop anti-Ku antibodies, which react with all antigens of the Kell blood group system, thereby leading to haemolytic transfusion reactions and haemolytic disease of the fetus and newborn. CASE PRESENTATION: A primigravida who was transfused with one unit of red blood cells due to iron deficiency anaemia developed anti-Ku antibodies. The pregnancy was closely monitored by ultrasound and antibody titres. Maternal autologous blood collection was performed twice during the last trimester as back-up in case...
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Gustavsen A, Njerve IU, Sitras V, Haugen G, Tølløfsrud PA, Akkök ÇA Tags: Tidsskr Nor Laegeforen Source Type: research

Nobelpris for oppdagelse av hvordan celler tilpasser seg skiftende oksygenniv å.
Nobelpris for oppdagelse av hvordan celler tilpasser seg skiftende oksygennivå. Tidsskr Nor Laegeforen. 2020 Jan 14;139(1): Authors: Bjørås M PMID: 31948215 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Bjørås M Tags: Tidsskr Nor Laegeforen Source Type: research

Assistert befruktning blant kvinner med epilepsi.
us MI Abstract BACKGROUND: Women with epilepsy give birth to fewer children than women without epilepsy. We wished to compare the use of assisted reproductive technology in Norwegian women who have epilepsy with Norwegian women in general. MATERIAL AND METHOD: In an international prospective registry study, the purpose of which was to identify the teratogenic effects of antiepileptic drugs, we included a total of 1510 births among Norwegian women who have epilepsy in the period 2000-2017. The women were recruited from 18 hospital neurological departments, and a protocol was completed for each pregnancy with d...
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Zaidan S, Nakken KO, Lillestølen KM, Alvestad S, Lossius MI Tags: Tidsskr Nor Laegeforen Source Type: research

Reinnleggelser ved en hjertemedisinsk avdeling.
Abstract BACKGROUND: Patient readmissions may be an indication of inappropriate patient care pathways or quality failure. The aim of the study was to determine whether we could identify improvement areas by reviewing 50 non-planned readmissions. MATERIAL AND METHOD: We reviewed 50 consecutive non-planned readmissions in the Department of Cardiology at the University Hospital of North Norway. The medical records were reviewed based on a simplified version of the '50 most recent deaths' methodology. RESULTS: Altogether 29 patients had at least one extrinsic risk factor for readmission, the most f...
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Lorentzen IC, Larsby KE, Bugge E, Lindekleiv H Tags: Tidsskr Nor Laegeforen Source Type: research

Use of video directly observed treatment for tuberculosis in Northern Norway.
Abstract BACKGROUND: In 2017, a total of 261 patients with tuberculosis were reported in Norway, whereof 90 % completed their therapy. Anti-tuberculosis drugs are administered as daily directly observed treatment (DOT) to all patients. We investigated whether this could be done by video conference. MATERIAL AND METHOD: We conducted a clinical observation study at the University Hospital of North Norway in the period 2016-2019, in which patients ≥ 16 years with tuberculosis after a minimum of two weeks of daily DOT during home visits continued their treatment through video conference (video DOT). ...
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Bendiksen R, Ovesen T, Asfeldt AM, Halvorsen DS, Gravningen K Tags: Tidsskr Nor Laegeforen Source Type: research

Matching i kasus –kontroll-studier.
Matching i kasus–kontroll-studier. Tidsskr Nor Laegeforen. 2020 Jan 14;140(1): Authors: Pripp AH PMID: 31948219 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Pripp AH Tags: Tidsskr Nor Laegeforen Source Type: research

New diagnostic criteria for insomnia and the association between insomnia, anxiety and depression.
In this study, we examine the impact of the changes in the diagnostic criteria for insomnia on the association between insomnia, anxiety and depression. MATERIAL AND METHOD: The study is based on a questionnaire survey with 68 questions that can be found on the website of the Norwegian Competence Centre for Sleep Disorders. The survey began in 2012, and our data were retrieved in 2016. The survey included validated questionnaires for insomnia, anxiety and depression: the Bergen Insomnia Scale and the Hospital Anxiety and Depression Scale (HADS). RESULTS: A total of 48 932 participants met the DSM-IV diagnost...
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Olufsen IS, Sørensen ME, Bjorvatn B Tags: Tidsskr Nor Laegeforen Source Type: research

Sudden vertigo - fateful or just fearful?
PMID: 31948221 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - January 14, 2020 Category: General Medicine Authors: Tjell C Tags: Tidsskr Nor Laegeforen Source Type: research

H åp i et håndtrykk.
Håp i et håndtrykk. Tidsskr Nor Laegeforen. 2019 Dec 20;139: Authors: Tveito K PMID: 31949316 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 20, 2019 Category: General Medicine Authors: Tveito K Tags: Tidsskr Nor Laegeforen Source Type: research

When things go wrong.
PMID: 31823565 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Vangsnes LE Tags: Tidsskr Nor Laegeforen Source Type: research

Åpent og tilgjengelig.
Åpent og tilgjengelig. Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Brean A PMID: 31823566 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Brean A Tags: Tidsskr Nor Laegeforen Source Type: research

En mann i 40- årene med akutt innsettende talevansker og ensidig lammelse.
En mann i 40-årene med akutt innsettende talevansker og ensidig lammelse. Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Jahr SH, Myro AZ, Vegge K, Campbell P Abstract BACKGROUND: Stroke has several causes and the diagnostic investigation can be challenging. Neurosyphilis occurs when Treponema pallidum infects the central nervous system, and is a rare cause of stroke. CASE PRESENTATION: A man in in his late forties with diabetes mellitus and overweight presented with headache, speech impairment and right-sided stroke symptoms. He also had cognitive impairment and psychiatric symptoms...
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Jahr SH, Myro AZ, Vegge K, Campbell P Tags: Tidsskr Nor Laegeforen Source Type: research

Simulation-based team training works.
org T PMID: 31823569 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Brattebø G, Ersdal HL, Wisborg T Tags: Tidsskr Nor Laegeforen Source Type: research

Hjemmebehandling ved lungeembolisme.
Abstract BACKGROUND: Early discharge and home treatment for pulmonary embolism patients results in fewer hospital complications and may reduce treatment costs. We wished to investigate whether it is as safe and effective as hospital treatment, and if so, how best to select patients for home treatment. MATERIAL AND METHOD: We searched the databases Embase, Ovid MEDLINE, In-Process & Other Non-Indexed Citations and the Cochrane Library for clinical trials of acute, objectively verified pulmonary embolism, where outcomes for hospital treatment and home treatment were compared. RESULTS: For a selected gr...
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Blomkvist AW, Zadig P, Christoffersen S, Kaushal S, Nordengen E, Shanmugarajah I, Ghanima W Tags: Tidsskr Nor Laegeforen Source Type: research

Gravid og med h øyt glukosenivå.
Gravid og med høyt glukosenivå. Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Gudim HB PMID: 31823571 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Gudim HB Tags: Tidsskr Nor Laegeforen Source Type: research

A failing heart.
PMID: 31823572 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Schistad ER Tags: Tidsskr Nor Laegeforen Source Type: research

Kasus –kontroll-studier.
Kasus–kontroll-studier. Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Lydersen S PMID: 31823573 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Lydersen S Tags: Tidsskr Nor Laegeforen Source Type: research

H åndens språk.
Håndens språk. Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Holck P PMID: 31823574 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Holck P Tags: Tidsskr Nor Laegeforen Source Type: research

Prevalens av diabetes blant gravide og svangerskapsutfall i Nordland og Troms 2004 –15.
Prevalens av diabetes blant gravide og svangerskapsutfall i Nordland og Troms 2004–15. Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Leeves LT, Andreasen C, Marrable S, Glasø MU, Rostad MK, Olsen IP, Bjørnerem Å Abstract BACKGROUND: The aim was to investigate the prevalence of gestational diabetes and pregnancy outcomes in women with gestational diabetes in Nordland and Troms counties. MATERIAL AND METHOD: We included all 1 067 women with type 1 diabetes, type 2 diabetes and gestational diabetes among 34 915 births at four hospitals in Nordland and Troms counties...
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Leeves LT, Andreasen C, Marrable S, Glasø MU, Rostad MK, Olsen IP, Bjørnerem Å Tags: Tidsskr Nor Laegeforen Source Type: research

Ingen m åneferd uten romfartsmedisin.
Ingen måneferd uten romfartsmedisin. Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Sæhle T PMID: 31823576 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Sæhle T Tags: Tidsskr Nor Laegeforen Source Type: research

Berekraft og bunad – aukande skilnader i norsk fødselshjelp?
Berekraft og bunad – aukande skilnader i norsk fødselshjelp? Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Engjom H PMID: 31823577 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Engjom H Tags: Tidsskr Nor Laegeforen Source Type: research

Hvordan behandle LADA-diabetes?
PMID: 31823578 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Grill V, Hals I Tags: Tidsskr Nor Laegeforen Source Type: research

Fra skyld og skam til l æring og forbedring.
Fra skyld og skam til læring og forbedring. Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Tajik AA PMID: 31823579 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Tajik AA Tags: Tidsskr Nor Laegeforen Source Type: research

Addendum til Bruk ordet fosterantallsreduksjon.
rra M PMID: 31823580 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Østborg T, Augestad LA, Barra M Tags: Tidsskr Nor Laegeforen Source Type: research

P. Gjersvik svarer.
PMID: 31823581 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Gjersvik P Tags: Tidsskr Nor Laegeforen Source Type: research

Kunnskapsbasert praksis mer dekkende enn evidensbasert medisin.
dal A PMID: 31823582 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Bjørndal A Tags: Tidsskr Nor Laegeforen Source Type: research

For lang saksbehandlingstid i enkeltsaker.
PMID: 31823583 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Homlong L, Andresen JF Tags: Tidsskr Nor Laegeforen Source Type: research

Generiske legemidler – ikke så like som vi tror?
Generiske legemidler – ikke så like som vi tror? Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Midtvedt K, Robertsen I, Åsberg A PMID: 31823584 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Midtvedt K, Robertsen I, Åsberg A Tags: Tidsskr Nor Laegeforen Source Type: research

Rettelse: Tourettes syndrom hos barn i Norge.
I, Weidle B PMID: 31823585 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Surén P, Bakken IJ, Skurtveit S, Handal M, Reichborn-Kjennerud T, Stoltenberg C, Nøstvik LI, Weidle B Tags: Tidsskr Nor Laegeforen Source Type: research

Rettelse: Hvor forskjellige kan generiske legemidler v ære?
Rettelse: Hvor forskjellige kan generiske legemidler være? Tidsskr Nor Laegeforen. 2019 Dec 10;139(18): Authors: Skovlund E PMID: 31823586 [PubMed - in process] (Source: Tidsskrift for den Norske Laegeforening)
Source: Tidsskrift for den Norske Laegeforening - December 10, 2019 Category: General Medicine Authors: Skovlund E Tags: Tidsskr Nor Laegeforen Source Type: research