Author Archives: Marina

What’s NOT: More About the Boolean Operator “NOT”

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Boolean Operators (AND, OR, NOT) are tools for combining search terms and are inherent part of online database searching. While experienced searchers will use Boolean Operators directly in their search strategies, even novice searchers that just enter a string of terms into a database’s search box will end up indirectly using the Boolean operator AND, as each space between words will be treated by the database as AND, thus combining each term together into a search strategy that would retrieve results that have all terms present.

Image Source: https://sru.libguides.com/english/librarybasics/booleanoperators

Most search strategies will either use just AND or a combination of both AND and OR. The third Boolean operator, NOT, is much more complicated and requires some understanding to use properly in a search.

Using the Boolean Operator NOT

The Boolean operator NOT can be used when a term or terms needs to be excluded from your search strategy.

For example, if you were interested in articles that looked at children with cancer, but you did not want articles that looked specifically at infants, you could create a search strategy like this:

cancer AND child* NOT infant*
— or —
(cancer AND child*) NOT infant*

The Problem with NOT

When using the Boolean operator NOT to exclude terms, it can become problematic when the database excludes records that contain both the term(s) you want to exclude and the term(s) you want in your search.

In the above example, not only articles about cancer in infants will be excluded from the results but it will also exclude any articles about cancer in both children and infants.

Information professionals (librarians and informationists) advise using the Boolean operator NOT with extreme caution when conducting searches. It’s better to reach out to an information professional for assistance with complex search techniques and how to best proceed with a search when there is a term you want to avoid.

Variations Across Databases

Not all databases function the same way, and using the Boolean operator NOT is no different. While most databases allow for using simply NOT to exclude terms, depending on the database or platform, you might need to use the operator AND NOT instead (Scopus), or once the search is performed use the Exclude button found within the Refine Search panel (also in Scopus).

Takeaway

The Boolean operator NOT should be used with extreme caution. It is best to consult a Librarian on its use in your search.

Chronic Stress Connection to Cancer Explained, Taking from Cancer to Fight Cancer, and More

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  • In a mice experiment, researchers from Cold Spring Harbor Laboratory got an insight into the exact nature of the connection between cancer and psychological stress. The researchers discovered that stress hormones called glucocorticoids impacted the neutrophils (white blood cells), forming structures called NETs (neutrophil extracellular traps). Usually, NETs play a positive role in immune defense in the body, but “in cancer, NETs create a metastasis-friendly environment.” The study was published in Cancer Cell.
  • Researchers at the University of Virginia Cancer Center identified a new, more efficient than existing methods, way to identify high-risk patients with acute myeloid leukemia. By measuring specific molecules in cancer cells, the new method helps identify patients at risk of poor outcomes and how well patients would respond to treatments. In the future, the technique may lead to more personalized treatments and better outcomes for patients with blood cancer. This research was published in Blood Advances.
  • Researchers from UC San Francisco (UCSF) and Northwestern University borrowed from cancer stratagems to fight cancer by using a specific mutation found in lymphoma to drastically increase the potency of normal human T cells in killing cancer cells without triggering side effects. Also, while current immunotherapies are used only against hematological cancers, the T cells engineered by Northwestern U and UCSF could kill solid tumors – “tumors derived from skin, lung and stomach in mice.” Human trials can be expected in the future. An article reporting on this research was published in Nature.
  • In a preclinical study, researchers from Columbia University and other institutions explored a molecule called Malat1, responsible for activating breast cancer dormant cells and triggering metastasis. By deleting the Malat1 gene, researchers were able to suppress cancer’s ability to metastasize. Extended to humans in the future, this research may eventually lead to better treatments and improved patient outcomes. The study was published in Nature Cancer.
  • Researchers from Vanderbilt University developed a way to kill a tumor by “disrupting its acidic “microenvironment” without harming normal tissue”. The method targets hydroxyapatite (HAP), a naturally occurring mineral also produced by some tumors. The study was published in Cancer Medicine.

Don’t Let Your Search Get Lost In Translation

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When conducting a literature search on a topic, many times the search is conducted in more than one database for more comprehensive results. And in the case of systematic reviews, such a practice is required.

Even more challenging, when it comes to systematic reviews, is that the searches in each database should be as similar to one another as possible. The process of taking an original search strategy from one database and making only necessary changes (controlled vocabulary, syntax, field codes), adapt the strategy to another database is referred to as “search translation.”

The Parts of a Search

There are several parts to complex literature searches that combine multiple elements: Boolean operators, nesting, controlled vocabulary, field codes, quotations, proximity, and special operators.

Boolean Operators

Boolean Operators (AND, OR, and NOT) are the basis of how to combine concepts to create a search.

While nearly all databases use Boolean operators in the same manner and meaning, it’s important to know when capitalization is necessary and when it is not.

Nesting

Nesting uses parentheses much in the same way they are used in Algebra — that is, whatever is inside the pair of parentheses must be done first, and from there a search (just like math), will be conducted from left-to-right.

Since nesting is about how to read and execute a search, it typically will not change between databases.

Controlled Vocabulary

Controlled vocabulary refers to the set dictionary of terms for that database, such as MeSH (Medical Subject Headings) and EmTree. MeSH is the National Library of Medicine’s controlled vocabulary, and they create the MeSH terms for PubMed. These terms may not always be identical to the MeSH terms found in MEDLINE on another platform though, and they require different identification.

Unfortunately there is no easy way to translate these terms, but using the built in databases (MeSH Database, MEDLINE Term Finder, EmTree Database, etc) you can quickly find the most closely aligned term to use.

Field Codes

Field codes are essentially the special codes for each database that tell the database where to search for that term. For example [tiab] in PubMed tells the database to search that term in the title and abstract fields only. In MEDLINE the title/abstract field code is .ti,ab, whereas in Embase it is :ti,ab.

Quotations

In order to search for a specific phrase searches must use quotations. However, depending on the database, they may require double quotations (“smart quotes”), straight quotations, or single quotations.

Proximity

Proximity operators (also called adjacency in some databases) are essentially a middle-ground between searching across an entire record and specific quotations. They allow the user to select how close they want to two terms to appear in a record. Every database uses slightly different proximity operators and syntax, and some have strict rules with how they can be used.

Special Operators

Special Operators are operators that can be added to search terms to modify what is searched. Examples of special operators are truncation and wildcards, which expand the variations of the specified term that are searched. An asterisk (*) is the common operator for truncation in many databases.

Where to Start

All the information on how to search each database according to its own rules and/or the rules of an online platform it resides on can be found in the database/platform’s Help section.

Typically, this translation of search strategies is done by a librarian manually but automated/semi-automated tools are being gradually introduced. A beta version of such tool (Query Translation) is currently available in Embase.com, the Elsevier interface of the Embase database. It will assist in “translating” PubMed searches into the Embase.com search syntax.

The tool allows entering a search term or the whole search strategy (query) and get it translated to Embase syntax.